NOVEL COMPOUND HAVING EFFECT OF PROMOTING NEURON DIFFERENTIATION

Abstract: A novel cystacycline derivative provided according to the present invention has a novel neuron differentiation promoting activity and is thus useful as a medicament for the treatment of central and peripheral nervous system disorders and the like.

Description: Technical Field The present invention relates to novel compounds having a neuron differentiation promoting activity and pharmaceutical use thereof. Background Art Neurotrophic factors are proteinaceous compounds that participate in differentiation induction of neurons and in maintainance of the existence and survival of nerve cells. Nerve growth factors (hereinafter often abbreviated as NGF) are known to be representative of such compounds (Ann. Neuro., 10, 499-503 (1981)). It is manifested that NGF is deeply involved in the differentiation, existence maintenance and repair of neurons in both the central and peripheral nervous systems. Damages of nerves caused by aging, internal and external factors often develop pathological symptoms. Such damages are found to cause, in the central nervous system, Alzheimer's disease, dementia induced by cerebro-vascular disorders, disturbance of consciousness due to cerebral contusion, tremor or muscle rigidity by Parkinson's disease, etc. It is also known that damages in the peripheral nervous system are induced by amyotrophic lateral sclerosis, spinal muscle atrophy, motor function disturbances due to neuron damages accompanied by accidents, etc., and that neuropathies are induced by diabetes mellitus, uremia, vitamin B1 or B12 deficiency, chronic liver disease, sarcoidosis, amyloidosis, hypothyrea, cancer, angiopathy, Sjögren symptoms, immunopathy accompanied by infections, hereditary disease, physical compression, drugs (carcinostatic agents, tuberculostatic agents, anti-epileptic agents, etc.) or intoxication (arsenic, thallium, carbon disulfide, etc.); in more detail, see RINSHO KENSA (Clinical Test), 40, 760-766 (1996). It was the recognition in the art that when neurons suffer irreversible damages from these disorders, it is difficult to regenerate and repair the damaged neurons. However, on the hypothesis that neuropathy could be treated if the neurotrophic factors act on neurons, development of neurotrophic factors as medicaments against neuropathy has been initiated (Science, 264, 772-774 (1994)). For instance, clinical trial of NGF is in progress against Alzheimer's disease, neural damages or spinal injuries. NGF is a series of proteins having approximately 50,000 molecular weight. For the treatment of neuropathy, it generally takes a long period of time. For these reasons, it is difficult to develop efficient administration and pharmaceutical formulation. Gene therapy namely induction of NGF gene, is also another choice for the treatment but its therapeutic effect is yet unclear. It is known that when NGF is present, PC 12 cells - which are the established cell line cloned from rat adrenal medulla pheochromocytoma - terminate cell proliferation and differentiate into neuron-like cells with neurites. This procedure enables to screen an effective substance having a NGF-like neuron differentiation promoting activity. For example, antibiotic staurosporin was found to have the PC 12 cell differentiation promoting activity (SHINKEI KAGAKU, 26, 200-220 (1987)). A similar differentiation promoting activity was recently observed in a biological active compound NK175203 (hereinafter referred to as cystacyclin) which was produced from Streptomyces sp. NK175203 strain FERM BP-4372 (WO 95/31992). However, the toxicity and pharmacokinetics of staurosporin in vivo make its application as a medicament difficult. It has thus been strongly desired to develop a low molecular weight compound that exhibits a neuron differentiation promoting activity, is low toxic and is readily prepared synthetically. Disclosure of Invention The present inventors have made extensive investigations on cystacycline derivatives and as a result, have found novel compounds represented by general formula (I) and pharmacologically acceptable salts thereof. The present invention has thus been accomplished. The present invention relates to the following compounds and compositions comprising the same. 1) A ketone derivative of formula [1]: wherein: A D is an unsubstituted or substituted aromatic hydrocarbon, said substituted aromatic hydrocarbon comprising 1 to 6, preferably 1 to 3 substituents selected from the group consisting of a (C 1 -C 4 ) alkyl, halogen, hydroxy, (C 1 -C 4 ) alkyloxy, amino, mono- or di (C 1 -C 4 )alkylamino, thiol, carboxy, (C 1 -C 4 )alkyloxycarbonyl, (C 1 -C 5 )acyloxy, (C 1 -C 5 )acylthio, (C 1 -C 5 )acylamino, cyano and trifluoromethyl; an unsubstituted or substituted aromatic heterocyclic ring or saturated heterocyclic ring, said substituted aromatic heterocyclic ring or saturated heterocyclic ring comprising 1 to 6, preferably 1 to 3 substituents selected from the group consisting of a (C 1 -C 4 ) alkyl, halogen, hydroxy, (C 1 -C 4 ) alkyloxy, amino, mono- or dl (C 1 -C 4 )alkylamino, thiol, carboxy, (C 1 -C 4 )alkyloxycarbonyl, (C 1 -C 5 )acyloxy, (C 1 -C 5 )acylthio, (C 1 -C 5 )acylamino, cyano and trifluoromethyl; B D is hydrogen or an unsubstituted aliphatic hydrocarbon group having 1 to 4 carbon atoms; X D is O, S, SO, SO 2 or NH; Y D is a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 6 carbon atoms, wherein said substituted aliphatic hydrocarbon group may contain 1 to 6, preferably 1 to 4 substituents and the substituents are selected from: carboxy; COOR1, wherein R1 is a substituted or unsubstituted alkyl or alkenyl having 1 to 4 carbon atoms wherein said alkyl or alkenyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino; CONR2R3, wherein each of R2 and R3 , which may be the same or different and independently represents hydrogen or an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino; COW, wherein W Is a saturated heterocyclic ring which may be unsubstituted or substituted with carboxy or a group derived therefrom or, amino or a group derived therefrom; NR4R5 , wherein each of R4 and R5 , which may be the same or different and independently represents hydrogen, an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetyalmino, or an unsubstituted or substituted acyl having 1 to 5 carbon atoms wherein said acyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino; hydroxy; and OCOR15, wherein R 15 is an alkyl having 1 to 4 carbon atoms; or an unsubstituted aromatic hydrocarbon group or monocyclic aromatic heterocyclic ring having 3 to 6 carbon atoms; Z D is carboxy, COOR7 , wherein R7 is an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino; CONR8R9 wherein each of R8 and R9 , which may be the some or different and independently represents hydrogen or an unsubstituted or substituted olkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino; COW, wherein W is a saturated heterocyclic ring which may be unsubstituted or substituted with carboxy or a group derived therefrom, or amino or a group derived therefrom, a substituted alkyl or alkenyl having 1 to 4 carbon atoms, wherein said alkyl or alkenyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino; or a pharmacologically acceptable salt thereof. 2) A ketone derivative of formula [1] or a pharmacologically acceptable salt thereof, according to 1) above, wherein: X D is S, O, or SO; Y D is an aliphatic hydrocarbon group having 1 to 6 carbon atoms, wherein at least one hydrogen is substituted with a substituent as defined in claim 1 for the aliphatic hydrocarbon group of Y D ; and, Z D is carboxy, COOR7, wherein R7 is an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino, CONR8R9 wherein each of R8 and R9 , which may be the same or different and independently represents hydrogen or an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino, COW, wherein W is a saturated heterocyclic ring which may be unsubstituted or substituted with carboxy or a group derived therefrom, or amino or a group derived therefrom. 3) A ketone derivative of formula [1] or a pharmacologically acceptable salt thereof, according to 1) above, wherein: A D is an unsubstituted or substituted benzene ring wherein, when substituted, 1 to 3 hydrogen atoms are substituted with an unsubstituted alkyl group having 1 to 4 carbon atoms, a halogen, an alkoxy having 1 to 4 carbon atoms or trifluoromethyl; B D is hydrogen or an aliphatic hydrocarbon group having 1 to 4 carbon atoms: X D is S, O, or SO; Y D is an aliphatic hydrocarbon group having 1 to 6 carbon atoms, wherein at least one hydrogen is substituted with a substituent as defined In claim 1 for the aliphatic hydrocarbon group of Y D ; and Z D is carboxy, COOR7 , wherein R7 is an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acelyloxy, acetylthio, cyano and acetylamino, CONR8R9 wherein each of R8 and R9 , which may be the same or different and Independently represents hydrogen or an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino. 4) A ketone derivative of formula [1] or a pharmacologically acceptable salt thereof, according to 3) above, wherein: A D is an unsubstituted or substituted benzene ring, wherein, when substituted, 1 to 3 hydrogen atoms are substituted with methyl, methoxy, methoxycarbonyl, nitro, cyano, a halogen or trifluoromethyl; B D is hydrogen or an alkyl having 1 to 4 carbon atoms; X D is S; Y D is an aliphatic hydrocarbon group having 1 to 6 carbon atoms, wherein at least two hydrogen atoms are substituted with carboxy; COOR1', wherein R1' is an alkyl or alkenyl having 1 to 4 carbon atoms; NHCOR 14 , wherein R 14 is an alkyl having 1 to 4 carbon atoms which hydrogen may optionally be substituted with fluorine; hydroxy; or OCOR 15, wherein R 15 is an alkyl having 1 to 4 carbon atoms; Z D is carboxy, COOR7' , wherein R7' is an alkyl having 1 to 4 carbon atoms or CH 2 OR10', wherein R10' is hydrogen or an acyl having 1 to 5 carbon atoms. 5) A ketone derivative of formula [1] or a pharmacologically acceptable salt thereof, according to 4) above, wherein: A D is an unsubstituted benzene ring or a benzene ring substituted with methyl or methoxy; B D is hydrogen; X D is S; Y D is 2-acetylamino-2-carboxyethyl, 2-acetylamino-2-methoxycarbonylethyl or 2-acetylaminoethyl; and, Z D is carboxy, methoxycarbonyl, acetoxymethyl or hydroxymethyl. 6) A pharmaceutical composition comprising as an effective ingredient a ketone derivative of formula [1] according to 1) through 5) above, or a pharmacologically acceptable salt thereof. 7) A composition according to 6) above for the treatment of central nervous disorders. 8) A composition according to 6) above for the treatment of peripheral nervous disorders. 9) A composition according to 6) above for promoting nerve cell differentiation. Best Mode for Carrying Out the Invention The compounds of the present invention represented by formula (I) exhibit a neuron differentiation promoting activity and can be used as medicaments for the treatment of nerve disturbances in the central and peripheral nervous systems. The compounds of the present invention will be described below in more detail. In the ketone derivative of the present invention represented by general formula [1], the unsubstituted or substituted aromatic hydrocarbon ring, aromatic heterocyclic ring or saturated heterocyclic ring shown by A D is exemplified by a benzene, 1-naphthalene, 2-naphthalene, thiophene, furan, pyrrole, imidazole, oxazole, pyrazole, isoxazole, pyridine, pyrazine, indane, quinoline, isoquinoline, quinazoline, coumarine, pyrrolidine, piperidine or piperazine ring, preferably a benzene ring and a monocyclic aromatic heterocyclic ring, more preferably a benzene ring. These rings may be unsubstituted or substituted. When substituted, 1 to 6, preferably 1 to 3 substituents may be present on each ring. Examples of the substituents include an alkyl having 1 to 4 carbon atoms, a halogen, hydroxy, an alkyloxy having 1 to 4 carbon atoms, amino, a monoalkylamino or dialkylamino having 1 to 4 carbon atoms, thiol, carboxy, an alkyloxycarbonyl having 1 to 4 carbon atoms, an acyloxy having 1 to 5 carbon atoms, an acylthio having 1 to 5 carbon atoms, an acylamino having 1 to 5 carbon atoms, cyano and trifluoromethyl. Examples of the halogen are bromine, chlorine and fluorine. Examples of the alkyl having 1 to 4 carbon atoms and the alkyl moiety in the acyl having 1 to 5 carbon atoms are the same as those given for A. Preferred examples of A D are those unsubstituted, or those substituted with methyl, methoxy, methoxycarbonyl, nitro, cyano, a halogen or trifluoromethyl, for 1 to 3 hydrogen atoms. In the ketone derivatives of general formula [1], the unsubstituted aliphatic group B D having 1 to 4 carbon atoms refers to an alkyl or alkenyl having 1 to 4 carbon atoms which may optionally be substituted. Examples of the alkyl group are methyl, ethyl, n-propyl, n-butyl, isopropyl, cyclopropyl and tert-butyl. Examples of the alkenyl are vinyl, 2-propenyl, isopropenyl and 2-butenyl. Preferably, the aliphatic hydrocarbon group is exemplified by methyl, ethyl, n-propyl and isopropyl, more preferably methyl. In the ketone derivatives of the present invention represented by formula [1], X D is preferably S, 0 or SO, most preferably S. In Y D in the ketone derivatives represented by general formula [1], the straight or branched aliphatic hydrocarbon group having 1 to 6 carbon atoms includes an alkyl or an alkenyl. Examples of the alkyl are methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, isopropyl and tert-butyl. Examples of the alkenyl are vinyl, 2-propenyl, isopropenyl and 2-butenyl. Preferably the aliphatic group is an alkyl having 1 to 4 carbon atoms, more preferably ethyl. The aliphatic hydrocarbon group may be unsubstituted or substituted. Where the aliphatic hydrocarbon group is substituted, the group may contain, e.g., 1 to 6, preferably 1 to 4 substituents. As such substituents, there are carboxy or a group derived therefrom, amino or a group derived therefrom and, hydroxy or a group derived therefrom. The aromatic hydrocarbon ring or monocyclic aromatic heterocyclic ring having 3 to 6 carbon atoms refers to an aromatic hydrocarbon ring such as a benzene ring and a aromatic heterocyclic ring such as a 5- or 6-membered ring containing nitrogen, oxygen or sulfur. Where the aromatic hydrocarbon ring or aromatic heterocyclic ring is substituted, examples of such substituents are the same as those given for the aliphatic hydrocarbon group. The group derived from carboxy includes a functional group of carboxy, such as an esterified or amidated carboxy group, cyano, hydroxymethyl or aminomethyl formed by reducing these functional groups, and functional groups derived therefrom by modification like acylation or alkylation of the functional groups. Preferably, the carboxy and the group derived therefrom include carboxy, COOR1 (wherein R1 is an unsubstituted or substituted alkyl or alkenyl having 1 to 4 carbon atoms), CONR2R3 (wherein each of R2 and R3, which may be different or the same, independently represents hydrogen or a substituted or unsubstituted alkyl having 1 to 4 carbon atoms) and COW (W is an unsubstituted or substituted heterocyclic ring). Herein, the alkyl shown by R1 in COOR1 may be straight, branched or cyclic. Examples of the alkyl moiety are methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, tert-butyl and cyclobutyl, preferably methyl, ethyl, and n-propyl, more preferably methyl. Examples of the alkenyl are vinyl, 2-propenyl, isopropenyl and 2-butenyl. Where the alkyl or alkenyl is substituted, e.g., 1 to 6, preferably 1 to 3 substituents may be present. Examples of the substituents are a halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino. Examples of the halogen are the same as defined for A. Preferably, the alkyl for R1 is unsubstituted. Where the alkyl shown by R2 or R3 and its substituent(s) are substituted, examples of such substituents are the same as those defined for R1. Preferably W represents a saturated heterocyclic ring, more preferably, an azetidine, piperidine, pyrrolidine, piperazine or morpholine ring. These heterocyclic rings may be coupled to carbonyl via carbon or nitrogen, preferably to carbonyl via nitrogen. Where the heterocyclic ring is substituted, 1 to 4, preferably 1 to 2 substituents may be present on each ring. Examples of the substituents are carboxy or a group derived therefrom and amino or a group derived therefrom. Examples of these substituents are as defined in the specification. The group derived from amino is a group shown by NR4R5 (wherein each of R4 and R5, which may be different or the same, independently represents hydrogen, an unsubstituted or substituted alkyl having 1 to 4 carbon atoms or an unsubstituted or substituted acyl having 1 to 5 carbon atoms). In the group shown by NR4R5, the alkyl moiety for R4 and R5 and the substituents where the alkyl is substituted are the same as those defined for R1. The acyl for R4 and R5 may be straight, branched, cyclic, saturated or unsaturated. Representative examples of the acyl are acetyl, propionyl, acroyl, propioloyl, n-butyryl, isobutyryl, crotonoyl, valeryl, isovaleryl and pivaloyl. Where the acyl is substituted, examples of the substituents are the same as those defined for R1. Preferably, the amino-derived group is NHCOR14 (wherein R14 is an alkyl having 1 to 4 carbon atoms in which hydrogen(s) may be substituted with fluorine(s); examples of the alkyl are the same as those given for R1). The number of fluorine atoms which may be substituted is 1 to 9, preferably 1 to 7. Most preferably, R14 is methyl. Example of the group derived from hydroxy is OCOR15 (wherein R15 is an alkyl having 1 to 4 carbon atoms and examples of the alkyl are the same as those defined for R1). Z D in the ketone derivatives [1] of the present invention represents carboxy or a group derived therefrom, an unsubstituted or substituted alkyl or alkenyl having 1 to 4 carbon atoms. Examples of the group derived from carboxy are the same as defined above. Examples of the alkyl and alkenyl, and the substituents where the alkyl or alkenyl is substituted are the same as those defined for A D . Preferred examples of Z D include carboxy, COOR7 (wherein R7 is an unsubstituted or substituted alkyl having 1 to 4 carbon atoms), CONR8R9 (wherein each of R8 and R9, which may be different or the same, independently represents hydrogen or a substituted or unsubstituted alkyl having 1 to 4 carbon atoms). Examples of the alkyl moiety shown by R7, R8, and R9 and the substituents when the alkyl moiety is substituted are the same as those defined for R1. More preferred examples of Z D are carboxy, COOR7' (wherein R7' is an alkyl having 1 to 4 carbon atoms) and CH 2 OR10' (wherein R10' is hydrogen, an unsubstituted or substituted acyl having 1 to 5 carbon atoms). Examples of R7' are the same as those given for R1. Examples of the acyl moiety in R10' are the same as those given for R4, most preferably, carboxy, methoxycarbonyl, hydroxymethyl and acetyloxymethyl. Representative examples of the compounds in accordance with the present invention are listed below. (1D) 3-{(2R)-2-acetylamino-2-carboxyethylthio}-methyl-4-oxo-1-n-pentanoic acid; (2D) 3-{(2R)-2-acetylamino-2-methoxycarbonylethylthio)methyl-4-oxo-1-n-pentanoic acid; (3D) trans-2-[(2R)-2-acetylamino-2-methoxycarbonylethylthio)methyl-3-ethoxycarbonyl-1-cyclobutanone; (4D) trans-2-{(2R)-2-acetylamino-2-carboxyethylthio}methyl-3-oxo-1-cyclobutanecarboxylic acid; (5D) 2-(2,3-dihydroxy-n-propyl)thiomethyl-3-acetoxymethyl-1-cyclobutanone; (6D) 2-{(2R)-2-acetylamino-2-carboxyethylthio)-methyl-3-oxo-1-cyclohexanecarboxylic acid; (7D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-phenylbutyric acid; (8D) 3-[(2R)-(2-acetylamino-2-methoxycarbonyl)-ethylthio]methyl-4-oxo-4-phenylbutyric acid; (9D) 3-[(2R)-(2-acetylamino-2-methoxycarbonyl)-ethylthio]methyl-4- (4-methoxyphenyl) -4-oxobutyric acid; (10D) 3-{2-(acetylamino)ethylthio)methyl-4-(4-methoxyphenyl)-4-oxobutyric acid; (11D) 3-{2- (acetylamino)ethylthio}methyl-4-oxo-4-phenylbutyric acid; (12D) 3-(2-{acetylamino)ethylthio}methyl-4-(4-methylphenyl)-3-oxobutyric acid; (13D) 3-{(2R)-(2-acetylamino-2-methoxycarbonyl)-ethylthio}methyl-4- (4-methylphenyl) -3-oxobutyric acid; (14D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-(4-trifluoromethylphenyl)butyric acid; (15D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-(2-trifluoromethylphenyl)butyric acid; (16D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-(3-trifluoromethylphenyl)butyric acid; (17D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-(3-pyridyl)butyric acid; (18D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-(2-pyridyl)butyric acid; (19D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-(4-pyridyl)butyric acid; (20D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-(1-naphthyl)-4-oxobutyric acid; (21D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-(2-naphthyl)-4-oxobutyric acid; (22D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-(1-piperidyl)butyric acid; (23D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-(4-methyl-1-piperazinyl)-4-oxobutyric acid; (24D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-(4-phenyl-1-piperazinyl)butyric acid; (25D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-(2-furyl)-4-oxobutyric acid; (26D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-(3-furyl)-4-oxobutyric acid; (27D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-(2-thienyl)butyric acid; (28D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4-(3-thienyl) butyric acid; (29D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-oxo-4- (2-pyrrolyl)butyric acid; (30D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthiolmethyl-4-oxo-4-(3-pyrrolyl)butyric acid; (31D) 3-[(2R)-(2-acetylamino-2-carboxy)-ethylthio]methyl-4-(2-imidazolyl)-4-oxobutyric acid; (32D) 3-[(2R)-(2-acetylamino-2-methoxycarbanyl)-ethylthio)methyl-4-oxo-4-(3-pyridyl)butyric acid; (38D) 4-[(2R)-{(2-acetylamino-2-carboxy)-ethylthio)lmethyl-5-oxo-5-phenylpentanoic acid The compounds of the present invention may also be present in the form of stereoisomers such as geometrical isomers and mixtures thereof, diastereoisomers and mixtures thereof, optical isomers and racemic isomers. The compounds of the present invention cover all of these stereoisomers and mixtures thereof. The compounds of the present invention may optionally be present in the form of pharmacologically acceptable salts thereof. Examples of such salts are salts with acids including inorganic salts such as hydrochlorides, sulfates, phosphates, and Group IIIA salts, e.g., aluminum salts, etc.; and organic salts such as p-toluenesulfonates. As salts with bases, there are salts with alkali metals such as sodium or potassium, salts with alkaline earth metals such as calcium, and organic salts with methylamine, ethylenediamine, etc. These pharmacologically acceptable salts of the compounds of the present invention may be prepared by known methods. Hereinafter representative processes for preparing the compounds of the present invention are shown below but are not deemed to be limited to these processes only. The compounds of the present invention shown below and intermediates thereof may be isolated by conventional means of extraction, recrystallization, chromatography and the like. The compounds of general formula [1] wherein X D is S, O or NH are prepared by reacting ketone derivatives (the carbonyl at the 1-position may be protected appropriately; hereinafter simply referred to as reactive derivatives) represented by general formula [2D]: (wherein U is a splitting-off group and, A' D , B' D and Z' D have the same significance as defined in A D , B D and Z D but where the group contains a functional group, the functional group may be protected suitably), with compounds of general formula [3D]: HX D 2 - Y' D (wherein X D 2 is S, O or NH and Y' D has the same significance as defined for Y D but where it contains a functional group, the functional group may be properly protected), and when required, removing the protective group. Preferred examples of the reactive derivatives described above are compounds of general formulas [4D], [5D], [6D], [7D] and [8D]. In the formulas above, R16 is an aliphatic group having 1 to 10 carbon atoms, such as an alkyl, an alkenyl or an aryl. These groups may be substituted or unsubstituted. Where a substituent(s) are a functional group(s), the functional groups may be appropriately protected with protective groups. Each of R17 and R18, which may be the same or different, independently represents an alkyl having 1 to 4 carbon atoms or R17 and R18 are combined together to form a piperazine ring or a pyrrolidine ring. A' D , B' D and Z' D have the same significance as defined above. R16 and Z' D may also be combined together to form a γ-butyrolactone ring. Examples of the compounds of general formulas [4D], [5D], [6D], [7D] and [8D] are shown below. (a) 4-acetyl-γ-butyrolactone (b) 3-methylidene-4-oxo-1-n-pentanoic acid (c) trans-2,3-bis(acetoxymethyl)-1-cyclobutanone (d) 3-acetoxymethyl-2-methylidene-1-cyclobutanone (e) 3-ethoxycarbonyl-2-methanesulfoxymethyl-1-cyclobutanone (f) 3-ethoxycarbonyl-2-methylidene-1-cyclobutanone (g) 2-[(2,3-O-isopropylidene)propylsulfonyl]-methyl-3-oxo-1-cyclohexanecarboxylic acid (h) 2-methylidene-3-oxo-1-cyclohexanecarboxylic acid (i) 4-oxo-4-phenyl-3-(1-piperidyl)methylbutyric acid (j) 4-oxo-4-(3-pyridyl)-3-(1-piperidyl)methylbutyric acid (p) 4- (1-piperidyl) methyl-5-oxo-5-phenylpentanoic acid In the compounds of formula [3D] wherein X D is S, the compounds of formula [3D] include the following: (q) (2R)-2-acetylamino-2-carboxyethanethiol (r) (2R)-2-acetylamino-2-methoxycarbonylethanethiol (s) 2,3-dihydroxypropane-1-thiol (alpha-thioglycerine) For conducting the above reaction, any condensation process may be used so long as the compounds of formula [2D] can be condensed with the compounds of formula [3D]. The reaction is carried out generally in an organic solvent, water or a mixture thereof. As the organic solvent there may be employed an aromatic hydrocarbon such as benzene, toluene, etc.; an alcohol such as methanol, ethanol, etc.; an ether such as tetrahydrofuran, diethyl ether, etc.; a halogenated hydrocarbon such as methylene chloride, chloroform, etc.; a ketone such as acetone, methyl ethyl ketone, etc.; an aprotic polar solvent such as dimethyl sulfoxide, dimethylformamide, etc. Preferred examples of the solvent to be used are an ether such as tetrahydrofuran or diethyl ether, a halogenated hydrocarbon such as methylene chloride or chloroform, a ketone such as acetone or methyl ethyl ketone, an aprotic polar solvent such as dimethyl sulfoxide or dimethylformamide an alcohol such as methanol or ethanol, or a mixture of such solvent and water. The reaction proceeds generally in the presence of an acid or a base or in the absence or any catalyst, preferably under basic conditions. Where no catalyst is used, the reaction may sometimes proceed with heating. Reactants used to make the reaction system are an inorganic base such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium hydride, etc., or an organic base such as triethylamine, 1,8-diazabicyclo[5.4.0]-undeca-7-ene, etc. These reactants are employed in an amount of approximately 0.1 to 20-fold mols, preferably approximately 0.5 to 5-fold mols. The reaction temperature is not particularly limited so that the reaction may be carried out under cooling, at ambient temperature or with heating. Preferably, the reaction is performed at a temperature between -20°C and 130°C. Where the condensation is performed in the absence of a catalyst, the temperature is preferably between 30°C and 200°C. The compounds of formula [2D] may be reacted with the compounds of formula [3D] in an equimolar amount. Practically, the compounds of formula [3D] may be used in an excess amount, e.g., 1 to 2-fold mols. The reaction is performed in 0.1 to 200 hours, preferably 0.1 to 72 hours. The compounds of formula [1D] wherein X D is SO 2 may be prepared by oxidizing the compounds of formula [1D] wherein X D is S. The oxidizing agent suitable for use in the oxidation includes an organic peracid such as m-chloroperbenzoic acid, etc., an inorganic oxidizing agent such as permanganate, chromic acid, ruthenium tetroxide, etc., hydrogen peroxide, an organic peroxide, etc., preferably an organic peracid such as m-chloroperbenzoic acid. The compounds of formula [1D] wherein X D is SO may be prepared by oxidizing the compounds of formula [1D] wherein X D is S. The oxidizing agent suitable for use in the oxidation includes an organic peracid such as m-chloroperbenzoic acid, etc., an inorganic oxidizing agent such as manganese dioxide, chromic acid, ruthenium tetroxide, etc., hydrogen peroxide, an organic peroxide, a halogen type oxidizing agent such as periodic acid, etc. For example, Compound (a) and Compound (b) described above may be prepared as follows. Compound (a) is known and may be prepared, e.g., by the method described in Bull. Chem. Soc. Jpn., 32, 1282 (1959). Compound (b) is also known and may be prepared, e.g., by the process disclosed in Japanese Patent KOKOKU Showa 37-5911. Compound (b) may be prepared by maintaining Compound (a) under acidic or basic conditions. Reactants used for the above reaction are an inorganic base such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium hydride, etc., an organic base such as triethylamine, 1,8-diazabicyclo[5.4.0]-undeca-7-ene, etc., an in-organic acid such as hydrochloric acid, sulfuric acid, etc., and an organic acid such as p-toluenesulfonic acid, preferably an organic base such as triethylamine, 1,8-diazabicyclo[5.4.0]-undeca-7-ene or an inorganic acid such as sulfuric acid. Compounds (c) and (d) can be prepared as follows. Compound (c) analogues are known and described in, e.g., Tetrahedron Lett., 6453 (1989) and Compound (c) itself can be readily prepared by the process described therein. Compound (d) can be prepared by maintaining Compound (c) under basic conditions. Reactants that may be advantageously used for the reaction are an inorganic base such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium hydride, etc., and an organic base such as triethylamine, 1,8-diazabicyclo[5.4.0]-undeca-7-ene, etc., preferably an organic base such as triethylamine or 1,8-diazabicyclo[5.4.0]-undeca-7-ene. Compounds (e) and (f) may be prepared as follows. Compound (e-1) is known and may be prepared, e.g., by the process described J. Org. Chem., 53, 3841 (1988). To convert Compound (e-1) to Compound (e) and then Compound (f), the process described in J. Org. Chem., 53, 611 (1988) is applied by appropriate modification. That is, Compound (e-2) can be prepared by treating Compound (e-1) with a base and treating the anions generated with formaldehyde. As the base, there may be used LDA, n-butyl lithium, KHMDS, sodium hydride, etc., preferably LDA. Formaldehyde is preferably reacted as a monomer after cracking of its polymer. Compound (e) can be prepared by mesylation of Compound (e-2) in a conventional manner. More specifically, Compound (e-2) is reacted with mesyl chloride as a reactant in methylene chloride, while ice-cooling, in the presence of triethylamine as a base. Then Compound (f) can be produced via Compound (e) spontaneously under the same system at a time. Compounds (g) and (h) may be prepared as follows. Compound (g-1) and Compound (g-2), which are known by literature and commercially available, are subjected to Diels-Alder reaction in a conventional manner to give Compound (g-3). Compound (g-3) is converted into Compound (g-4) through the reduction with lithium aluminum hydride and the removal of silyl 5 protective group. The allyl alcohol moiety in Compound (g-4) is oxidized with manganese dioxide in a conventional manner. The hydroxy groups of resulting Compound (g-5) is acetylated in acetic anhydride-pyridine as a reactant followed by the reduction of the double bond in the ring with palladium-carbon. Compound (g-6) can thus be readily prepared. The reaction of Compound (g-6) to give Compound (g-7) can be performed under conditions similar to those used to condense the compounds of formula [2D] and the compounds of formula [3D]. In this reaction, alpha-thioglycerine is employed as the compound of formula [3D]. Next, the 1,2-diol group of Compound (g-7) is protected with a protective group such as an acetal, a ketal or an ortho-ester. Preferably, Compound (g-7) is reacted with acetone or its activated derivative in the presence of an acid catalyst to give Compound (g-8), where the 1,2-diol is protected with the isopropylidene. Subsequently, the acetyl is removed by alkaline hydrolysis in a conventional manner to give Compound (g-9). The sulfide of Compound (g-9) is oxidized to the sulfone. Thus, Compound (g-10) is prepared. The reaction is carried out under such conditions that are similar to those used for the oxidation but the hydroxy is not oxidized. Where the hydroxy is oxidized to COOH, Compound (g) can be prepared in one step. Compound (g) can be prepared by oxidizing the hydroxy with an oxidizing agent. The oxidizing agent that can be used includes an inorganic acid such as a permanganate, chromic acid, etc., preferably chromic acid. Compound (h) can be prepared by maintaining Compound (g) under basic conditions similar to those used to condense the compounds of formula [2D] and the compounds of formula [3D], without adding the compounds of formula [3D] to the reaction system. Reactants that may be advantageously used for the reaction are an inorganic base such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, etc., and an organic base such as triethylamine, 1,8-diazabicyclo[5.4.0]-undeca-7-ene, etc., preferably an organic base such as triethylamine. Compound (i) is known and may be prepared, e.g., by the process described in J. Chem. Soc. (C), 2308 (1967). Compound (j) may be prepared by reacting the corresponding aldehyde with an acrylic acid derivative in the presence of a catalyst such as sodium cyanide or 3-benzyl-5-(2-hydroxyethyl)-4-methylthiazolium chloride, etc. (Chem. Ber., 109, 289, 541 (1976)) and then subjecting the reaction product to Mannich reaction. Compound (p) can be prepared by subjecting known 5-oxo-5-phenylpentanoic acid to Mannich reaction. Compounds (q) and (s) are commercially available from, e.g., Tokyo Kasei K.K. Compound (r) can be readily prepared by heating Compound (q) in methanol in the presence of an acid catalyst. As the acidic catalyst, there are an in-organic acid such as hydrochloric acid, sulfuric acid, etc., an organic acid such as p-toluenesulfonic acid, or a Lewis acid such as boron fluoride etherate, etc., preferably an organic acid such as p-toluenesulfonic acid. Hereinafter the pharmaceutical properties of the compounds of the present invention will be described in more detail. The compounds of the present invention and pharmacologically acceptable salts thereof are found to exhibit a potent neuron differentiation promoting activity. Therefore, the compositions comprising as the active ingredient the compounds of the present invention and pharmacologically acceptable salts thereof are effective for promoting or accelerating the neuron differentiation and can thus be used as medicaments for the treatment of central and peripheral nervous disorders. Where the compounds of the present invention and pharmacologically acceptable salts thereof are used as the neuron differentiation accelerator, the composition may be used in the form of pharmaceutical preparations such as injection, drop, granules, tablets, granulates, fine particles, powders, capsules, liquid, inhalation, suppositories, eye lotion, plaster, ointment, spray, etc., singly or in combination with pharmaceutically acceptable additives such as carriers, excipient, diluents, dissolution aids, etc. The route for administration may be chosen from oral and parenteral administration (systemic and local administration). The compound of the present invention or a pharmacologically acceptable salt thereof contained in the pharmaceutical composition varies depending upon the form of the preparation but preferably in an amount of 0.1 to 100 wt%. A dose is determined depending upon age, sex, body weight, conditions of the patient and purpose of treatment, etc., but generally in a range of approximately 0.001 to 5000 mg/kg/day. Next, the processes for preparing the compounds of the present invention or pharmacologically acceptable salts thereof and the neuron differentiation accelerating activity will be described below in more detail with reference to the following Examples. Example 1 Preparation of 3-{(2R)-2-acetylamino-2-carboxyethylthio}methyl-4-oxo-1-n-pentanoic acid (Compound 1D) Compound (a) (256.3 mg, 2.00 mmols) was dissolved in tetrahydrofuran (3 ml) and 1,8-diazabicyclo[5.4.0]-undeca-7-ene (609 mg, 4.00 mmols) was added to the solution. The mixture was reacted overnight at room temperature. After Amberlist-15 (3 g) was added to the reaction mixture, the mixture was stirred for 5 minutes. Then the resin was filtered off. The filtrate was concentrated in vacuo. The residue was purified by silica gel column chromatography (40 ml, hexane : ethyl acetate = 3 : 2 to 1 : 1) to fractionate the fraction containing Compound (b). The fraction was concentrated in vacuo. The residue obtained was dissolved in tetrahydrofuran (3 ml). N-Acetyl-L-cysteine (107.7 mg, 0.66 mmol) and triethylamine (265.1 mg, 2.62 mmols) were added to the solution. After stirring at room temperature overnight, the reaction solution was concentrated in vacuo. The residue was purified by silica gel column chromatography (40 ml, methylene chloride : methanol = 10 : 1 to 2 : 1). The objective fraction was concentrated in vacuo and dissolved in tetrahydrofuran (3 ml) and methanol (1 ml). Amberlist-15 (2 g) was added to the solution. After stirring the mixture for 3 minutes, the resin was filtered off and the filtrate was concentrated in vacuo. The residue was purified by silica gel column chromatography (40 ml, methylene chloride : methanol = 10 : 1) to give Compound (1D) (40.9 mg, yield: 7%). 1H-NMR (200 MHz, DMSO-d6)) δ : 1.86 (3H, s), 2.18 (3H, s), 2.4 -2.6 (2H, m), 2.7 - 3.0 (4H, m), 3.05 (1H, m), 4.38 (1H, ddd, J=B.1, 8.1, 5.1Hz), 8.24 (1H, d, J=8.1Hz) MS (FAB, POS) m/z : 292 (M+H)+ In a manner similar to the above procedures, 3-{(2R)-2-acetylamino-2-methoxycarbonylethylthio)methyl-4-oxo-1-n-pentanoic acid (Compound 2D) may be prepared. 1H-NMR (200 MHz, DMSO-d6) δ : 1.86 (3H, s), 2.17 (3H, s), 2.4 - 2.7 (2H, m), 2.7 - 3.0 (4H, m), 3.04 (1H, m), 3.65 (3H, s), 4.46 (1H, ddd, J=8.1, 8.1, 5.7Hz), 8.39 (1H, d, J=8.1Hz) MS (FAB, POS) m/z : 306 (M+H)+ Example 2 Preparation of trans-2-{(2R)-2-acetylamino-2-methoxycarbonylethylthio}methyl-3-ethoxycarbonyl-1-cyclobutanone (Compound 3D) (1) Preparation of trans-2-hydroxymethyl-3-ethoxycarbonyl-1-cyclobutanone (Compound e-2) Under ice cooling, diisopropylamine (0.296 g, 2.92 mmols) was added to a solution of n-butyl lithium (1.59 M/hexane solution, 2.79 mmols) in tetrahydrofuran (8 ml) and the mixture was stirred for 10 minutes. After cooling to -78°C, a solution of 3-ethoxycarbonyl-1-cyclobutanone (Compound e-1) (355.4 mg, 2.50 mmols) in tetrahydrofuran (3 ml) was dropwise added to the mixture, which was then stirred for 15 minutes. After the temperature was once elevated to 0°C, the mixture was stirred for 15 minutes and again cooled to -78°C. Hexamethylphosphoramide (535.8 mg, 2.99 mmols) was added to the system. After stirring for 5 minutes, a solution obtained by trapping formaldehyde subjected to cracking at 160°C and trapped in diethyl ether of -78°C was poured into the system through a needle. The reaction was terminated by adding hydrochloric acid and the insoluble matters were filtered off. The filtrate was concentrated in vacuo. The residue was purified by silica gel column chromatography (50 ml, hexane : diethyl ether = 1 : 1 to 1 : 2) to give Compound (e-2) (50.7 mg, yield: 12%). 1H-NMR (60 MHz, CDCl3) δ : 1.30 (3H, t, J=7Hz), 2.17 (1H, br), 3.23 (2H, m), 3.6 - 4.0 (4H, m), 4.20 (2H, q, J=7Hz) (2) Preparation of 2-methylidene-3-ethoxycarbonyl-1-cyclobutanone (Compound f) Compound (e-2) was dissolved in methylene chloride (2 ml). Under ice cooling, triethylamine (60.1 mg, 0.59 mmol) and mesyl chloride (36.7 mg, 0.32 mmol) were added to the solution. The mixture was stirred for 30 minutes under the same conditions. Water and diethyl ether were added to the system for separation. The resulting organic layer was washed with water and then with saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate and concentrated in vacuo to give Compound (f) (40.3 mg, yield: 96%). 1H-NMR (60 MHz, CDCl3) δ : 1.33 (3H, t, J=7Hz), 3.30 (1H, dd, J=15Hz, 8Hz), 3.40 (1H, dd, J=15.6Hz), 4.00 (1H, m), 4.40 (2H, q, J=7Hz), 5.50 (1H, m), 6.03 (1H, m) (3) Preparation of trans-2-{(2R)-2-acetylamino-2-methoxycarbonylethylthio}methyl-3-ethoxycarbonyl-1-cyclobutanone (Compound 3D) Compound (f) (40.3 mg, 0.26 mmol) was dissolved in methylene chloride (2 ml). Under ice cooling, N-acetyl-L-cysteine (46.1 mg, 0.26 mmol) and triethylamine (10.9 mg, 0.11 mmol) were added to the solution. The mixture was stirred for an hour under the same conditions. The reaction solution was concentrated and the residue was purified by silica gel column chromatography (20 ml, methylene chloride : methanol = 40 : 1) and Sephadex LH-20 (10 ml, eluted with methanol) to give Compound (3D) (27.4 mg, yield: 36.4%). 1H-NMR (200 MHz, CDCl3) δ : 1.31 (3H, t, J=7.4Hz), 2.07 (3H, s), 2.80 (2H, m), 3.0 - 3.5 (5H, m), 3.78 (3H, s), 3.84 (1H, m), 4.24 (2H, dd, J=7.0, 1.7Hz), 4.83 (1H, dt, J=7.6, 4.9Hz), 6.46 (1H, brs, J=6.3Hz) MS (FAB, POS) m/z : 332 (M+H)+ Example 3 Preparation of trans-2-{(2R)-2-acetylamino-2-carboxyethylthio}methyl-3-oxo-1-cyclobutanecarboxylic acid (Compound 4D) After 3N hydrochloric acid aqueous solution (4 ml) was added to Compound (3) (17.4 mg, 0.05 mmol), the mixture was stirred at room temperature overnight. The reaction solution was concentrated in vacuo. The residue obtained was purified twice by Sephadex LH-20 (100 ml and 200 ml, eluted with methanol) and twice by silica gel column chromatography (2 ml, methylene chloride : methanol = 20 : 1 to 2 : 1) to give Compound (4D) (6.0 mg, yield: 40%). 1H-NMR (200 MHz, CD30D) δ : 2.01 (3H, 2.80 - 4.0 (8H, m), 4.60 (1H, m) MS (FAB, POS) m/z : 290 (M+H)+ Example 4 Preparation of trans-3-acetoxymethyl-2-(2,3-dihydroxypropylthio)methyl-1-cyclobutanone (Compound 5D) (1) Preparation of 3-acetoxymethyl-2-methylidene-1-cyclobutanone (Compound d) After tetrahydrofuran (3 ml) and 1,8-diazabicyclo[5.4.0]-undeca-7-ene (25.5 mg, 0.168 mmol) was added to Compound (c) (30 mg, 0.14 mmol), the mixture was stirred at room temperature for an hour. The reaction solution was purified by silica gel column chromatography (10 ml, hexane : ethyl acetate = 2 : 1) to give Compound (d) (23 mg, yield: 95.5%). 1H-NMR (60 MHz, CDCl3) δ : 2.00 (3H, s), 2.65 - 3.30 (3H, m), 4.33 (2H, m), 5.30 (1H, d, J=4.1Hz), 5.80 (1H, d, J=4.1Hz) (2) Preparation of trans-3-acetoxymethyl-2-(2,3-dihydroxypropylthio)methyl-1-cyclobutanone (Compound 5D) Compound (d) (23 mg, 0.133 mmol) was dissolved in acetone (1 ml) and a solution of alpha-thioglycerin (11 ul, 0.133 mmol) in methanol (1 ml) was added to the solution. The mixture was stirred at room temperature for an hour. The reaction solution was concentrated. The residue obtained was purified by silica gel column chromatography (20 ml, dichloromethane : methanol = 20 : 1) to give Compound (5D) (19 mg, yield: 51.3%). 1H-NMR (200 MHz, CDCl3) δ : 2.07, 2.10 (3H, sx2), 2.45 - 3.45 (8H, m), 3.50 - 3.90 (3H, m), 4.33 (2H, m) Example 5 Preparation of 2-{(2R)-2-acetylamino-2-carboxyethylthio}methyl-3-oxo-1-cyclohexanecarboxylic acid (Compound 6D) (1) Preparation of 4.5-dimethoxycarbonyl-3-trimethylsiloxy-1-cyclohexene (Compound g-3) Compound (g-1) (589 mg, 4.09 mmols) and Compound (g-2) (588 mg, 4.09 mmols) were dissolved in benzene. The reaction was carried out at 150°C for 5 hours. After the reaction solution was concentrated, the residue was purified by silica gel column chromatography (80 ml, hexane : ethyl acetate = 5 : 1 to 3 : 1) to give Compound (g-3) (875 mg, yield: 74.6%). 1H-NMR (200 MHz, CDCl3) δ : 0.05 - 0.12 (9H, m), 1.95 - 2.20 (1H, m), 2.70 - 2.94 (1H, m), 2.95 - 3.19 (1H, m), 3.68 (3H, m), 3.70 (3H, s), 4.50 (1H, m), 5.50 - 5.90 (2H, m) (2) Preparation of 4,5-bis(hydroxymethyl)-3-hydroxy-1-cyclohexene (Compound g-4) Lithium borohydride was suspended in anhydrous tetrahydrofuran (25 ml). Under ice cooling, a solution of Compound (g-3) (875 mg, 3.05 mmols) in anhydrous tetrahydrofuran (4 ml) was dropwise added to the suspension. The reaction was carried out for 2 hours. Then water (0.196 ml), 15% sodium hydroxide aqueous solution (0.196 ml) and water (0.59 ml) were added to the mixture. Stirring was further continued. After the suspension was filtered, the filtrate was concentrated. The residue was purified by silica gel column chromatography (20 ml, methylene chloride : methanol = 20 : 1) to give Compound (g-4) (340 mg, 70.5%). Preparation of 5,6-bis(hydroxymethyl)-2-cyclohexan-1-one (Compound g-5) Compound (g-4) (320 mg, 2.02 mmols) was dissolved in acetone (20 ml). Manganese dioxide (1400 mg) was gradually added to the solution. After the reaction, the precipitates were filtered off. The filtrate was concentrated and the residue was purified by silica gel column chromatography (40 ml, methylene chloride : methanol = 10 : 1) to give Compound (g-5) (205 mg, 61.1%). 1H-NMR (200 MHz, CDCl3) δ : 2.30 - 2.60 (4H, m), 3.65 (2H, m), 3.76 (1H, dd, J=3.67Hz, 11.08Hz), 4.10 (1H, dd, J=3.67Hz, 11.08Hz), 5.98 (1H, dt, J=2.12Hz, 12.13Hz), 7.08 (1H, m) (4) Preparation of 2,3-bis(acetoxymethyl)-1-cyclohexanone (Compound g-6) Pyridine (10 ml) and acetic anhydride (3 ml) were added to Compound (g-5) (205 mg, 1.31 mmol). The mixture was reacted at room temperature for 2 hours. After the reaction solution was concentrated, the residue was subjected to silica gel column chromatography (20 ml, hexane : ethyl acetate = 1 : 1). The fraction was concentrated and the concentrate was dissolved in ethanol (20 ml). Palladium-carbon (50% hydrated) (50 mg) was added to the solution. The reaction was carried out at room temperature overnight in hydrogen atmosphere. The catalyst was filtered off and the filtrate was concentrated. The residue was purified by silica gel column chromatography (30 ml, methylene chloride : methanol = 20 : 1) to give Compound (g-6)- (175 mg, 73.0%). 1H-NMR (200 MHz, CDCl3) δ : 1.70 (2H, m), 1.89 - 2.20 (3H, m), 2.02 (3H, s), 2.08 (3H, s), 4.13 (2H, m), 4.38 (2H, m) (5) Preparation of 3-acetoxymethyl-2-[2,3-(dihydroxy}propylthio]methyl-1-cyclohexanone (Compound g-7) 2,3-Bis(acetoxymethyl)-1-cyclohexanone (Compound g-6) (200 mg, 0.826 mmol) was dissolved in acetone (3 ml). A solution of alpha-thioglycerin (89.2 mg, 0.826 mmol) in methanol (1 ml) and 1N sodium hydroxide (0.826 ml) were added to the solution. The mixture was stirred at room temperature for an hour. Silica gel (1 g) was added to the reaction mixture. After concentration, the residue was purified by silica gel column chromatography (30 ml, dichloromethane : methanol = 20 : 1) to give Compound (g-7) (175 mg, yield: 73.0%). MS (FAB, POS) m/z: 291 (M+H)+ (6) Preparation of 3-acetoxymethyl-2-[(2,3-O-isopropylidene)propylthiolmethyl-1-cyclohexanone (Compound g-8) Compound (g-7) (170 mg, 0.586 mmol) was dissolved in anhydrous acetone (1.5 ml), p-Toluenesulfonic acid monohydrate (11 mg, 0.06 mmol), dimethoxypropane (0.34 ml, 1.76 mmol) were added to the solution. The mixture was stirred at room temperature for 30 minutes. After water (2 ml) was added to the reaction mixture and the pH was adjusted to 7.0 with saturated hydrogensodium carbonate, the mixture was extracted three times with ethyl acetate (5 ml). The organic layer was washed with saturated sodium chloride aqueous solution (5 ml), dried over anhydrous sodium sulfate and concentrated to give Compound (g-8) (191 mg, yield: 98.7%). 1H-NMR (200 MHz, CDCl3) δ : 1.30 (3H, s), 1.39 (3H, s), 1.52 - 2.15 (5H, m), 2.03 (3H, s), 2.20 - 3.05 (7H, m), 3.67 (1H, m), 3.82 - 4.29 (4H, m) (7) Preparation of 3-hydroxymethyl-2-[(2,3-O-isopropylidene)propylthiolmethyl-1-cyclohexanone (Compound g-9) Compound (g-8) (191 mg, 0.578 mmol) was dissolved in methanol (2 ml). Under ice cooling, water (0.2 ml) and 1N sodium hydroxide (0.57 ml) were added to the solution. The mixture was stirred for 15 minutes while ice cooling. By adding 1N hydrochloric acid to the reaction mixture, the pH was adjusted to 6.8. Silica gel (500 mg) was added to the system. The mixture was then concentrated and the residue was purified by silica gel column chromatography (20 ml, dichloromethane : methanol = 30 : 1) to give Compound (g-9) (155 mg, yield: 93.1%). MS (FAB, POS-) m/z: 289 (M+H)+ (8) Preparation of 3-hydroxymethyl-2-([2RS)-(2,3-O-isopropylidene)propylsulfonyl]methyl-1-cyclohexanone (Compound g-10) Compound (g-9) (155 mg, 0.538 mmol) was dissolved in dichloromethane (2 ml). Under ice cooling, a dichloromethane solution (5 ml) of m-chloroperbenzoic acid (232 mg, purity 80%, 1.07 mmol) was added to the solution. After the reaction mixture was filtered, water (4 ml) and 20% sodium hydrogen sulfite (0.17 ml) were added to the filtrate. Saturated sodium hydrogen carbonate was added to the mixture until the pH of the aqueous layer became 7.0. After the aqueous layer was extracted twice with dichloromethane (10 ml), the dichloromethane layer was washed with saturated sodium chloride aqueous solution (15 ml), dried over anhydrous sodium sulfate and concentrated. The residue was purified by silica gel column chromatography (18 ml, hexane : ethyl acetate = 1 : 3) to give Compound (g-10) (151 mg, yield: 87.7%). MS (FAB, POS) m/z: 321 (M+H)+ (9) Preparation of 2-[(2,3-O-isopropylidene)-propylsulfonyl]methyl-3-oxo-1-cyclohexanecarboxylic acid (Compound g ) Compound (g-10) (151 mg, 0.47 mmol) was dissolved in acetone (9 ml). Jones reagent was added to the solution until the solution turned orange. The mixture was stirred at room temperature for 10 minutes. Thereafter, 2-propanol was added to the reaction mixture until it turned green. The mixture was concentrated and water (5 ml) was added to the concentrate. The resulting solution was extracted 3 times with dichloromethane (5 ml). The dichloromethane layer was washed with saturated sodium chloride aqueous solution (10 ml), dried over anhydrous sodium sulfate and then concentrated to give Compound (g) (88.6 mg, yield: 56.4%). MS (ESI, NEG) m/z: 333 (M-H)- (10) Preparation of 2-{(2R)-2-acetylamino-2-carboxyethylthio}methyl-3-oxo-1-cyclohexanecarboxylic acid Compound 6D) Compound (g) (88.6 mg, 0.265 mmol) was dissolved in acetone (3 ml). N-Acetyl-L-cysteine (43.2 mg, 0.265 mmol),1N sodium hydroxide (0.78 ml, 0.795 mmol) and methanol (1 ml) were added to the solution. The mixture was stirred for 2 hour at room temperature. After the pH of the mixture was adjusted to 6.8 with 1N hydrochloric acid, the residue was purified by Sephadex LH-20 (200 ml, 80% hydrated methanol) to give the sodium salt (57.7 mg, yield: 60.3%) of Compound (6D). 1H-NMR (200 MHz, D20) δ : 1.52 - 2.18 (4H, m), 2.00 (3H, s), 2.27 - 3.22 (8H, m), 4.28 (1H, dd, J=4.03Hz, 8.34Hz) MS (ESI, NEG) m/z : 361 (M-Na)- Example 6 Preparation of 3-[(2R)-(2-acetylamino-2-carboxy)ethylthio]methyl-4-oxo-4-phenylbutyric acid (Compound 7D) N-Acetyl-L-cysteine (39 mg, 0.24 mmol) and ethanol (4 ml) were added to 4-oxo-3-(1-piperidinyl)methyl-4-phenylbutyric acid (66 mg, 0.24 mmol). The mixture was heated to reflux for 2 hours. After the reaction mixture was concentrated in vacuo, water (5 ml) and ethyl acetate (B ml) were added to the residue. The pH of the aqueous layer was adjusted to 2.0 with 1N hydrochloric acid followed by liquid-liquid separation. The mixture was extracted twice with ethyl acetate (8 ml). The collected ethyl acetate layers were washed with saturated sodium chloride aqueous solution (5 ml), dried over anhydrous sodium sulfate and then concentrated in vacuo. The residue was purified by silica gel column chromatography (20 ml, chloroform : methanol = 20 : 1) to give Compound (7D) (45 mg, yield: 53.1%). 1H-NMR (60 MHz, CD30D) δ : 2.19 (1.5H, s), 2.20 (1.5H, s), 2.50 - 3.30 (6H, m), 4.16 (1H, m), 4.58 (1H, m), 7.55 (3H, m), 8.00 (2H, m) MS (FAB, POS) m/z : 354 (M+H)+ Example 7 Preparation of 3-[(2R)-(2-acetylamino-2-methoxycarbonyl)ethylthio]methyl-4-oxo-4-phenylbutyric acid (Compound 8D) N-Acetyl-L-cysteine methyl ester (66.3 mg, 0.37 mmol) and ethanol (4 ml) were successively added to 4-oxo-3-(1-piperidyl)methyl-4-phenylbutyric acid (103 mg, 0.37 mmol). The mixture was heated to reflux for an hour. The reaction mixture was purified in a manner similar to Example 6 to give Compound (8D) (116 mg, yield: 84.5%). 1H-NMR (60 MHz, CDCl3 δ : 2.01 (1.5H, s), 2.03 (1.5H, s), 2.48 - 3.16 (6H, m), 3.70 (1.5H, s), 3.73 (1H, s), 4.17 (1H, m), 4.85 (1H, m), 6.70 (1H, m), 7.52 (3H, m), 7.90 (2H, m) MS (FAB, POS) m/z : 368 (M+H)+ Example 8 Preparation of 3-[(2R)-(2-acetylamino-2-methoxycarbonyl)ethylthiolmethyl-4-(4-methoxyphenyl)-4-oxobutyric acid (Compound 9D) N-Acetyl-L-cysteine methyl ester (66.3 mg, 0.37 mmol) and ethanol (3 ml) were added to 4-(4-methoxyphenyl)-4-oxo-3-(1-piperidyl)methyl-butyric acid (109 mg, 0.37 mmol). The mixture was heated to reflux for 2 hours. Purification was performed in a manner similar to Example 6 to give Compound (9D) (110 mg, yield: 73.4%). 1H-NMR (200 MHz, CDCl3) δ : 1.98 (1.5H, s), 2.05 (1.5H, s), 2.68 (2H, m), 2.90 (4H, m), 3.69 (1.5H, s), 3.72 (1.5H, s), 3.89 (3H, s), 4.02 (1H, m), 4.80 (1H, m), 6.48 - 6.72 (1H, m), 6.98 (2H, d, J=8.92Hz), 7.40 (1H, brs), 7.98 (2H, dd, J=3.3Hz, 8.92Hz) MS (FAB, POS) m/z : 398 (M+H)+ Example 9 Preparation of 3-{2-(acetylamino)ethylthiolmethyl-4-(4-methoxyphenyl)-4-oxobutyric acid (Compound 10D) N-Acetyl-L-cysteamine (45 mg, 0.37 mmol) and ethanol (3 ml) were added to 4-(4-methoxyphenyl)-4-oxo-3-(1-piperidyl)methyl-4-phenylbutyric acid (109 mg, 0.37 mmol). The mixture was heated to reflux for 2 hours. Purification was performed in a manner similar to Example 6 to give Compound (10D) (93 mg, yield: 72%). 1H-NMR (200 MHz, CDCl3) δ : 1.98 (1.5H, s), 2.58 - 2.76 (4H, m), 2.90 (2H, m), 3.39 (2H, m), 3.89 (3H, m), 4.07 (1H, m), 6.12. (1H, t, J=4.68Hz), 6.60 (1H, brs), 6.95 (2H, d, J=8.9Hz), 7.98 (2H, d, J=8.9Hz) MS (FAB, POS) m/z : 340 (M+H)+ Example 10 Preparation of 3-{2-(acetylamino)ethylthio}methyl-4-oxo-4-phenylbutyric acid (Compound 11D) N-Acetyl-L-cysteamine (45 mg, 0.37 mmol) and ethanol (3 ml) were added to 4-oxo-4-phenyl-3-(1-piperidyl)methylbutyric acid (103 mg, 0.37 mmol). The mixture was heated to reflux for 2 hours. Purification was performed in a manner similar to Example 6 to give Compound (11D) (83 mg, yield: 71.7%). 1H-NMR (200 MHz, CDCl3) δ : 1.97 (3H, s), 2.58 - 2.78 (4H, m), 2.90 (2H, m), 3.48 (2H, m), 4.11 (1H, m), 6.25 (1H, t, J=5.21Hz), 7.50 (3H, m), 7.98 (2H, m), 8.05 (1H, brs) MS (FAB, POS) m/z : 310 (M+H)+ Example 11 Preparation of 3-{2-(acetylamino)ethylthio}methyl-4-(4-mathylphenyl)-4-oxobutyric acid (Compound 12D) N-Acetyl-L-cysteamine (57 mg, 0.47 mmol) and ethanol (3 ml) were added to 4-(4-methylphenyl)-4-oxo-3-(1-piperidyl)methylbutyric acid (131 mg, 0.47 mmol). The mixture was heated to reflux. Purification was performed in a manner similar to Example 6 to give Compound (12D) (114 mg, yield: 73.6%). 1H-NMR (60 MHz, CDCl3) δ : 2.30 (3H, s), 2.70 (3H, s), 2.76 - 3.30 (4H, m), 3.30 - 4.15 (4H, m), 4.33 (1H, m), 6.70 (1H, t, J=6.0Hz), 7.50 (2H, d, J=9.2Hz), 7.80 (1H, brs), 8.16 (2H, d, J=9.2Hz) MS (FAB, POS) m/z : 382 (M+H)+ Example 12 Preparation of 3-{(2R)-(2-acetylamino-2-methoxycarbonyl)ethylthio}methyl-4-(4-methylphenyl)-4-oxobutyric acid (Compound 13D) N-Acetyl-L-cysteine methyl ester (92 mg, 0.52 mmol) and ethanol (3 ml) were added to 4-(4-methylphenyl)-4-oxo-3-(1-piperidyl)methylbutyric acid (142 mg, 0.52 mmol). The mixture was heated to reflux for 2 hours. Purification was performed in a manner similar to Example 6 to give Compound (13D) (126 mg, yield: 63.5%). 1H-NMR (60 MHz, CDCl3) δ : 2.30 (3H, s), 2.38 (1.5H, s), 2.80 (3H, s), 2.98 - 3.60 (6H, m), 4.01 (1.5H, s), 4.10 (1.5H, s), 4.40 (1H, m), 5.14 (1H, m), 7.02 (1H, m), 7.41 (1H, brs), 7.52 (2H, d, J=8.5Hz), 8.17 (2H, d, J=8.5Hz) MS (FAB, POS) m/z : 324 (M+H)+ Example 13 Preparation of 3-[(2R)-(2-acetylamino-2-methoxycarbonyl)ethylthio]methyl-4-oxo-4-(3-pyridyl)butyric acid (Compound 32D) (1) Preparation of methyl 4-oxo-4-(3-pyridyl)butyrate (Compound 32D-A) In nitrogen atmosphere, a solution of 3-pyridinecarboxyaldehyde (10.7 g, 100 mmols) in anhydrous dimethylformamide (20 ml) was dropwise added to a solution of sodium cyanide (2.44 g, 50 mmols) at 30°C in anhydrous dimethylformamide (80 ml) over 30 minutes. After stirring for 30 minutes, a solution of methyl acrylate (8.6 g, 100 mmols) in anhydrous dimethylformamide (80 ml) was dropwise added to the reaction mixture over an hour followed by stirring for 3 hours at 30°C. Acetic acid (0.66 ml) and water (30 ml) were added to the reaction solution. After stirring for 10 minutes, the mixture was concentrated in vacuo. Water (360 ml) and chloroform (300 ml x 3) were added to the residue for separation. The resultant organic phase was washed with saturated sodium chloride aqueous solution (300 ml), dried over anhydrous sodium sulfate and concentrated in vacuo. The residue was purified by silica gel column chromatography (650 ml, hexane : ethyl acetate = 1 : 1 - 1 : 2) to give Compound (32D-A) (7.87 g, yield: 40.7%). (2) Preparation of 4-oxo-4-(3-pyridyl)butyric acid (Compound 32D-B) Compound (32D-A) (5.04 g, 26.11 mmols) was dissolved in methanol (60 ml). After 1N sodium hydroxide aqueous solution (32 ml) was added to the solution, the mixture was stirred for 3 hours at room temperature. Then, 2N hydrochloric acid (16 ml) was added to the reaction mixture followed by concentration in vacuo. The residue was purified by silica gel column chromatography (250 ml, chloroform : methanol : acetic acid = 20 : 1 : 0.5) to give Compound (32D-B) (3.13 g, yield: 66.9%). 1H-NMR (200 MHz, CD3OD) δ : 2.72 (3H, t, J=6.5Hz), 3.33 (3H, t, J=6.5Hz), 7.59 (1H, m), 8.42 (1H, m), 8.73 (1H, m), 9.14 (1H, m) MS (FAB, POS) m/z : 180 (M+H)+ (3) Preparation of 4-oxo-4-(3-pyridyl)-3-(1-piperidyl)methylbutyric acid (Compound 32D-C) Piperidine (140 mg, 1.64 mmol) and 37% formalin (0.133 ml, 1.64 mmol) were added to Compound (32D-B) (246 mg, 1.37 mmol). The mixture was stirred at 100°C for 2 hours. Silica gel (1.8 g) was added to the reaction solution. After concentration, the residue was purified by silica gel column chromatography (30 ml, chloroform : methanol : acetic acid = 10 : 1 : 0.5 to 10 : 5 : 3) to give Compound (32D-C) (300 mg, yield: 79%). 1H-NMR (200 MHz, CDCl3) δ : 1.45 - 1.80 (6H, m), 2.30 - 3.15 (8H, m), 4.28 (1H, m), 7.46 (1H, dd, J=4.7Hz, 8.0Hz), 8.00 (1H, brs), 8.37 (1H, dt, J=2.0Hz, 8.0Hz), 8.78 (1H, dd, J=1.6Hz, J=4.8Hz), 9.28 (1H, d, J=1.6Hz) (4) Preparation of 3-[(2R)-(2-acetylamino-2-methoxycarbonyl)ethylthiolmethyl-4-oxo-4-(3-pyridyl)butyric acid (Compound 32D) N-Acetyl-L-cysteine methyl ester (96.2 mg, 0.54 mmol.) was added to a solution of Compound (32D-C) (150 ml, 0.54 mmol) in ethanol (3 ml). The mixture was heated to reflux for 2 hours. The reaction mixture was concentrated. The residue was purified by silica gel column chromatography (30 ml, chloroform : methanol : acetic acid = 20 : 1 : 0.5) to give Compound (32D) (89 mg, yield: 44.7%). 1H-NMR (200 MHz, CDCl3) δ : 1.98 (1.5H, s), 2.01 (1.5H, s), 2.70 (2H, m), 2.93 (4H, m), 3.68 (1.5H, s), 3.71 (1.5H, s), 4.06 (1H, m), 4.79 (1H, m), 6.80 (1H, m), 7.20 (1H, m, NH), 7.49 (1H, m), 8.35 (1H, m), 8.75 (1H, d, J-3.9Hz), 9.24 (1H, s), 1.048 (1H, brs) MS (FAB, POS) m/z : 369 (M+H)+ Example 14 Preparation of 4-[(2R)-{(2-acetylamino-2-carboxy)-ethylthio}]methyl-5-oxo-5-phenylpentanoic acid (Compound 38D) (1) Preparation of 4-(1-piperazinyl)methyl-5-oxo-5-phenylpentanoic acid (Compound 38D-A) 4-Benzoylbutyric acid (1000.9 mg, 5.21 mmols) was suspended in a formalin aqueous solution (507 mg, 6.25 mmols) and piperidine (532 mg, 6.25 mmols). The reaction was carried out at 100°C for 3 hours and a half. Piperidine (517 mg, 6.07 mmols) was added thereto and the mixture was heated to 100°C for further 3 hours. After air-cooling to room temperature, the reaction mixture was concentrated in vacuo. The residue was purified by silica gel column chromatography (100 ml, dichloromethane : methanol =10 : 1 to 5 : 1) to give Compound (38D-A) (1500.8 mg, yield: 99%). 1H-NMR (200 MHz, CDCl3) δ : 1.2 - 1.8 (8H, m), 2.10 (1H, m), 2.42 (1H, m), 2.5 - 3.0 (4H, m), 3.16 (1H, dd, J=2.0Hz, 12.7Hz), 3.38 (4H, m), 3.16 (1H, dd, J=2.0Hz, 12.7Hz), 3.38 (1H, dd, J=8.1Hz, 12.5Hz), 4.37 (1H, m), 7.2 - 7.4 (2H, m), 7.46 (1H, t, J=7.4Hz), 8.41 (2H, d, J=7.2Hz), 9.30 (1H, br). MS (FAB, POS) m/z : 290 (M+H)+ (2) Preparation of 4-[(2R)-{(2-acetylamino-2-carboxylethylthio}]methyl-5-oxo-5-phenylpentanoic acid (Compound 38D) Compound (38D-A) (576.0 mg, 1.99 mmol) and (R)-N-acetylcysteine (324.7 mg, 1.99 mmol) were dissolved in ethanol (5 ml). The solution was heated to reflux for 4 hours. After air-cooling, the mixture was concentrated in vacuo. The residue was purified by silica gel column chromatography (100 ml, chloroform : methanol = 10 : 1 to 3 : 1) to give Compound (38D) (417.4 mg, yield: 57%). 1H-NMR (200 MHz, DMSO-d6) δ : 1.7 - 2.0 (2H, m), 1.83 (3H, d, J=2Hz), 2.20 (2H, t, J=7.3Hz), 2.6 - 3.0 (4H, m), 3.86 (1H, m), 4.33 (1H, dt, J=4.8Hz, 7.4Hz), 7.5 - 7.7 (3H, m), 8.00 (2H, dd, J=7.0Hz, 2.2Hz), 8.09 (1H, d, J-7.3Hz). MS (FAB, NEG) m/z : 366 (M-H)+ Test Example 1 Neuron-like neurite extension effect of the compounds of this invention on PC12 cells The effect of the compounds of the invention was examined by a modification of the method of Green et al., Ann. Rev. Neurosci., 3, 353, 1980, and evaluated in terms of morphological change of PC12 cells and a level of the change. That is, PC12 cells were inoculated on Dulbecco-modified Eagle's medium supplemented with 10% calf fetal serum and 10% equine serum in approximately 100,000 cells/ml. The cells were incubated at 37°C overnight in 5% CO 2 using collagen-coated 96 well multiplates. Morphological change of the cells was microscopically observed one day after the test compound was added to each well under this conditions. The minimum effective dose (MED, g/ml) of each compound on PC12 cells that caused neuron-like neurite extension is shown in Table 2 below. Minimum effective dose to cause neuron-like neurite extension on PC12 cells Compound No . MED (g/ml) 1D 25 2D 13 3D 0.8 4D 13 5D 50 6D 50 7D 13 8D 6.3 9D 50 10D 100 11D 13 12D 13 13D 13 32D 3.1 38D 6.3 Industrial Applicability The compounds of the present invention or pharmacologically acceptable salts thereof exhibit a potent neuron differentiation accelerating activity. The pharmaceutical compositions comprising these compounds or pharmacologically acceptable salts thereof are thus useful as neuron differentiation accelerators and effectively applicable as medicaments for the treatment of central or nervous system disorders.

Claims: A ketone derivative of formula [1]: wherein: A D is an unsubstituted or substituted aromatic hydrocarbon, said substituted aromatic hydrocarbon comprising 1 to 6, preferably 1 to 3 substituents selected from the group consisting of a (C 1 -C 4 ) alkyl, halogen, hydroxy, (C 1 -C 4 ) alkyloxy, amino, mono- or di (C 1 -C 4 )alkylamino, thiol, carboxy, (C 1 -C 4 )alkyloxycarbonyl, (C 1 -C 5 )acyloxy, (C 1 -C 5 )acylthio, (C 1 -C 5 )acylamino, cyano and trifluoromethyl; an unsubstituted or substituted aromatic heterocyclic ring or saturated heterocyclic ring, said substituted aromatic heterocyclic ring or saturated heterocyclic ring comprising 1 to 6, preferably 1 to 3 substituents selected from the group consisting of a (C 1 -C 4 ) alkyl, halogen, hydroxy, (C 1 -C 4 ) alkyloxy, amino, mono- or di (C 1 -C 4 )alkylamino, thiol, carboxy, (C 1 -C 4 )alkyloxycarbonyl, (C 1 -C 5 )acyloxy, (C 1 -C 5 )acylthio, (C 1 -C 5 )acylamino, cyano and trifluoromethyl; B D is hydrogen or an unsubstituted aliphatic hydrocarbon group having 1 to 4 carbon atoms; X D is O, S, SO, SO 2 or NH; Y D is a substituted or unsubstituted aliphatic hydrocarbon group having to 6 carbon atoms, wherein said substituted aliphatic hydrocarbon group may contain 1 to 6, preferably 1 to 4 substituents and the substituents are selected from: carboxy; COOR1, wherein R1 is a substituted or unsubstituted alkyl or alkenyl having 1 to 4 carbon atoms wherein said alkyl or alkenyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino; CONR2R3, wherein each of R2 and R3 , which may be the same or different and independently represents hydrogen or an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetytthio, cyano and acetylamino; COW, wherein W is a saturated heterocyclic ring which may be unsubstituted or substituted with carboxy or a group derived therefrom or, amino or a group derived therefrom; NR4R5 , wherein each of R4 and R5 , which may be the same or different and independently represents hydrogen, an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetyalmino, or an unsubstituted or substituted acyl having 1 to 5 carbon atoms wherein said acyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, ocetyloxy, acetytthio, cyano and acetylamino; hydroxy; and OCOR15, wherein R 15 is on alkyl having 1 to 4 carbon atoms; or an unsubstituted aromatic hydrocarbon group or monocyclic aromatic heterocyclic ring having 3 to 6 carbon atoms; Z D is carboxy, COOR7 , wherein R7 is an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acelyloxy, acetyfthio, cyano and acetylamino; CONR8R9 wherein each of R8 and R9 , which may be the some or different and independently represents hydrogen or on unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, ocetyloxy, ocetylthio, cyano and ocetylamino; COW, wherein W is a saturated heterocyclic ring which may be unsubstituted or substituted with carboxy or a group derived therefrom, or amino or a group derived therefrom, a substituted alkyl or alkenyl having 1 to 4 carbon atoms, wherein said alkyl or alkenyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino; or a pharmacologically acceptable sort thereof. A ketone derivative of formula [1] or a pharmacologically acceptable salt thereof, according to claim 1, wherein: X D is S, O, or SO; Y D is an aliphatic hydrocarbon group having 1 to 6 carbon atoms, wherein at least one hydrogen is substituted with a substituent as defined in claim 1 for the aliphatic hydrocarbon group of Y D ; and. Z D is corboxy, COOR7 , wherein R7 is an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetytthio, cyano and acetylamino, CONR8R9 wherein each of R8 and R9 , which may be the some or different and independently represents hydrogen or on unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, ocetyloxy, acetytthio, cyano and acetylamino, COW, wherein W is a saturated heterocyclic ring which may be unsubstituted or substituted with carboxy or a group derived therefrom, or amino or a group derived therefrom. A ketone derivative of formula [1] or a pharmacologically acceptable salt thereof, according to claim 1, wherein: A D is an unsubstituted or substituted benzene ring wherein, when substituted, 1 to 3 hydrogen atoms are substituted with an unsubstiiuted alkyl group having 1 to 4 carbon atoms, a halogen, an alkoxy having 1 to 4 carbon atoms or trifluoromethyl; B D is hydrogen or an aliphatic hydrocarbon group having 1 to 4 carbon atoms: X D is S, O, or SO; Y D is an aliphatic hydrocarbon group having 1 to 6 carbon atoms, wherein at least one hydrogen is substituted with a substituent as defined in claim 1 for the aliphatic hydrocarbon group of Y D ; and Z D is carboxy, COOR7 , wherein R7 is an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably 1 to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino, CONR8R9 wherein each of R8 and R9 , which may be the same or different and independently represents hydrogen or an unsubstituted or substituted alkyl having 1 to 4 carbon atoms wherein said alkyl may be substituted with 1 to 6, preferably to 3 substituents and the substituents are selected from halogen, hydroxy, thiol, carboxy, methoxycarbonyl, acetyloxy, acetylthio, cyano and acetylamino. A ketone derivative of formula [1] or a pharmacologically acceptable salt thereof, according to claim 3, wherein: A D is an unsubstituted or substituted benzene ring, wherein, when substituted, 1 to 3 hydrogen atoms are substituted with methyl, methoxy, methoxycarbonyl, nitro, cyano, a halogen or trifluoromethyl; B D is hydrogen or an alkyl having 1 to 4 carbon atoms; X D is S; Y D is an aliphatic hydrocarbon group having 1 to 6 carbon atoms, wherein at least two hydrogen atoms are substituted with carboxy; COOR1' , wherein R1' is an alkyl or alkenyl having to 4 carbon atoms; NHCOR14 , wherein R14 is an alkyl having 1 to 4 carbon atoms which hydrogen may optionally be substituted with fluorine; hydroxy; or OCOR 15, wherein R 15 is an alkyl having 1 to 4 carbon atoms; Z D is carboxy, COOR 7' , wherein R 7' is an alkyl having 1 to 4 carbon atoms or CH 2 OR10', wherein R10' is hydrogen or an acyl having 1 to 5 carbon atoms. A ketone derivative of formula [1] or a pharmacologically acceptable salt thereof, according to claim 4, wherein: A D is an unsubstituted benzene ring or a benzene ring substituted with methyl or methoxy; B D is hydrogen; X D is S; Y D is 2-acetylamino-2-carboxyethyl, 2-acetylamino-2-methoxycarbonylethyl or 2-acetylaminoethyl; and, Z D is carboxy, methoxycarbonyl, acetoxymethyl or hydroxymethyl. A pharmaceutical composition comprising as an effective ingredient a ketone derivative of formula [1] according to any one of claims 1 through 5, or a pharmacologically acceptable soft thereof. A composition according to claim 6 for the treatment of central nervous disorders. A composition according to claim 6 for the treatment of peripheral nervous disorders. A composition according to claim 6 for promoting nerve cell differentiation.

Inventors: HARADA TAKASHI, KUWAHARA ATSUSHI, MORINO TOMIO, NAGAI MASASHI, NISHIKIORI TAKAAKI, SAITO SEIICHI, SATO TAKAMICHI, TOMIYOSHI TSUGIO, HARADA, TAKASHI, KUWAHARA, ATSUSHI, MORINO, TOMIO, NAGAI, MASASHI, NISHIKIORI, TAKAAKI, SAITO, SEIICHI, SATO, TAKAMICHI, TOMIYOSHI, TSUGIO
Applicants: NIPPON KAYAKU KK, NIPPON KAYAKU KABUSHIKI KAISHA
Application year: 1998
Main classification: C07C229
IPC codes: C07D205, C07D307, C07D207, C07D295, C07D213, C07C229, C07C323