Cyclohexapeptide compounds, processes for their production and their use as a pharmaceutical

A cyclohexapeptide compound of general formula (I), wherein R1 is C1–C20 alkyl; C9–C20 alkenyl; C9–C20 alkoxyphenyl; an aryl group selected from: phenyl, biphenyl, terphenyl and naphthyl; C1–C12 alkylphenyl, C2–C12 alkenylphenyl, C1–C12 alkoxyphenyl; linoleoyl; palmitoyl; 12-methylmyristoyl; 10,12-dimethylmyristoyl; or —COC6H4(p)OC8H17, R1 and R3 are independently —OH; —CN; —CH2NH2; —N3; aryl; substituted aryl; heterocyclyl and substituted heterocyclic with 1–3 of the same or different heteroatoms; aminoalkylamino; mono or di-substituted linear or cyclic aminoalkylamino; —OR, wherein, R is C1–C12 alkyl; substituted alkyl of the type —(CH2)n—X, where n is 1–5 and X is Cl, Br, I, COOY, CN, NH2 or a heterocyclic and where Y is C1–C6 linear or branched alkyl; C2–C12-alkenyl; aryl; fused aryl; substituted aryl; a heterocyclic containing 1–3 heteroatoms; mono or di-substituted aminoalkyl; or a hydroxy protecting group; and R3 may additionally be imidazolyl; R2 and R4 are independently —H or —OH; R5 is —H or —CH3, R6 is —H, —CH3 or —CH2CONH2. R7 is —H, —CH3 or —OH. R8 and R9 are independently —H or —CH2-Sec.amine in which the sec.amine is attached to —CH2 through its N linkage; and its pharmaceutically acceptable salts. The compounds are useful as antifungal agents.

This application is a 371 of PCT/EP00/06769 filed Jul. 15, 2000.

Novel cyclohexapeptide compounds, processes for their production and their use as a pharmaceutical.

The present invention relates to cyclohexapeptide compounds belonging to the echinocandin class having a substituent group at the ornithine-5, homotyrosine-4 and ortho position of the phenolic hydroxy of the homotyrosine unit, and pharmaceutically acceptable salts thereof. The present invention further relates to processes for the preparation of the novel cyclohexapeptide compounds, to the use of the compounds and their pharmaceutically acceptable salts as pharmaceuticals, in particular to their use in the treatment of fungal infections, and to pharmaceutical compositions comprising the novel compounds or a pharmaceutically acceptable salt thereof.

The search for new and effective antifungal agents has been intensified by the increase in immunological diseases and aggressive immunosuppressive chemotherapy. Present therapeutic options for the treatment of fungal infections are limited to compounds in two classes, the polyenes and the azoles. Due to an increase in the number of isolates, which are resistant to conventional antifungal agents, there presently exists a need for new antifungal and anti-pneumocystis agents. Because there are limited numbers of antifungal agents available for the treatment of life-threatening fungal infections and because resistance may further limit the utility of the newer azoles, there is an urgent need for new antifungal agents with a different mode of action.

Accordingly, the present invention provides novel antifungal cyclohexapeptide compounds represented by general formula I as shown below:

To the nitrogen atom of the secondary amine are attached the same or different groups selected from: C1–C12alkyl, C2–C12alkenyl, aryl, substituted aryl, alkylaryl and substituted alkylaryl, or the nitrogen atom of the secondary amine is part of a heterocyclic group, optionally substituted by one or more of: C1–C6alkyl, C2–C6alkenyl, aryl, amino, nitro and halogen, or a fused heterocyclic group, whereby the heterocyclic group in each case contains 1–3 of the same or different heteroatoms.

In a preferred first embodiment, R1is —OH or —OR and R3is —OH, —OR or imidazolyl, wherein R in each case is C1–C12alkyl, substituted alkyl of the type —(CH2)n—X, where n is 1–5, X is Cl, Br, I, COOY, CN, NH2or a heterocyclic and Y is a C1–C6linear or branched alkyl; C2–CO2-alkenyl; aryl; fused aryl; substituted aryl; a heterocyclic containing 1–3 heteroatoms; mono or di-substituted aminoalkyl; or a hydroxy protecting group.

Ideally in the first embodiment R8and/or R9is —CH2-secondary amine.

In an alternative preferred embodiment R1is 12-methylmyristoyl, R1and R3are independently —OH, —CN, —CH2NH2, —N3, aryl, substituted aryl, a heterocyclyl or a substituted heterocyclyl, having the heterocyclyl in each case 1–3 of the same or different heteroatoms, aminoalkylamino, or mono or di-substituted linear or cyclic aminoalkylamino, R2and R4are both —OH, R5and R7are both —CH3, R6is —H, and R8and R9are both —H.

The compounds provided by this invention are semi-synthetic cyclic hexapeptides derived from cyclic peptides, which are produced by culturing various microorganisms. A number of cyclic peptides are known in the literature, including mulundocandin, sporiofungin, echinocandin B and aculeacin.

These cyclic hexapeptides have closely related structures with some modification of the cyclic peptide and/or the N-acyl fatty acid chain. For example mulundocandin has a methyl-myristoyl side chain, aculeacin A has a palmitoyl side chain, echinocandin B has a linoleoyl side chain and pneumocandin Ao has a di-methylmyristoyl side chain. The naturally occurring cyclic hexapeptides of the echinocandin class have a labile C—O bond and C—N bond at the ornithine-5 position as disclosed in U.S. Pat. No. 5,378,804 issued Jan. 3, 1995.

According to the present invention there are further provided processes for the preparation of novel cyclohexapeptide compounds of general formula I above.

The invention is described herein using the terms defined below unless otherwise specified.

Throughout the specification and appended claims, a given chemical formula or name shall encompass all optical and stereoisomers as well as racemic mixtures where such isomers and mixtures exist.

As used herein, the term “C1–C12alkyl” refers to a straight or branched alkyl chain having from one to twelve carbon atoms. Typical C1–C12alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, t-butyl, pentyl, hexyl, octyl, nonyl, decyl, undecyl, dodecyl and the like. The term “C1–C12alkyl” includes within its definition the term “C1–C6alkyl”.

The term “C9–C20alkyl” refers to a straight or branched alkyl chain having from nine to twenty carbon atoms.

The term “C1–C12alkenyl” refers to a straight or branched chain hydrocarbon having from one to twelve carbon atoms, with at least one unsaturation. Typical alkenyl groups are groups such as vinyl, 1-propen-2-yl, 1-buten-4-yl, 2-buten-4-yl and 1-penten-5-yl.

The term “C9–C20alkenyl” refers to a straight or branched alkyl chain having from nine to twenty carbon atoms with at least one saturation.

The term “C9–C20alkoxy” refers to a straight or branched alkyl chain having from nine to twenty carbon atoms attached to an oxygen atom. Typical C9–C20alkoxy groups are, for example, decyloxy, and dodecyloxy.

The term “substituted alkyl” refers to alkyl groups which may be substituted with up to three substituent groups at any available point of attachment.

The term “cycloalkyl” refers to a species of alkyl containing from 3 to 15 carbon atoms without altering or resonating double bonds between carbon atoms.

The term “aryl” refers to, for example, a phenyl which is optionally substituted by one or more substituents such as halogen, alkyl, alkoxy or nitro.

The term “fused aryl” refers to a bicyclic or polycyclic ring system such as benzene ring having any two adjacent carbon atoms in common. Typical examples of fused aryl groups are naphthalene and anthracene.

The term “heteroatom” refers to N, O, S, and P.

The term “hydroxyprotecting group” refers to a substituent of an hydroxy group that is commonly employed to block or protect the hydroxy functionality while reactions are carried out on the other functional groups on the compound. Examples of such hydroxy protecting groups include tetrahydropyranyl, methoxymethyl, methylthiomethyl, t-butyl, t-amyl, trityl, benzyl, allyl, trimethylsillyl and (t-butyl)dimethylsilyl. The species of hydroxy protecting group is not critical so long as the derivatized hydroxy group is stable to the conditions of the subsequent reaction(s) and can be removed at the appropriate point without disrupting the remainder of the molecule. Preferred hydroxy protecting groups are benzyl and methyl. The term “protected hydroxy” refers to a hydroxy group bonded to one of the above hydroxy protecting groups.

Further examples of hydroxy protecting groups are described in T. W. Greene, “Protective Groups in Organic Synthesis” John Wiley and Sons, New York, N.Y. (2nd edition, 1991) Chapters 2 and 3.

One process for the preparation of cyclohexapeptide compounds of the general formula I above according to the present invention comprises:a) reacting a cyclohexapeptide compound of the general formula I above, wherein R1, R2, R4, R5, R6and R7are as defined above in the general formula I, R1and R3are both —OH, and R8and R9are —H (compound II), with an alcohol in the presence of an acid in an aprotic solvent at a temperature ranging from 0° C. to 60° to obtain the corresponding cyclohexapeptide derivative of the formula I wherein R1, R2, R4, R5, R6and R7are as defined in the general formula I, R1and R3are —OH or —OR, such that at least one of R1or R3is —OR, wherein R is C1–C12alkyl, C2–C12alkenyl, fused aryl, substituted aryl, a heterocyclyl containing 1–3 heteroatoms, mono or di-substituted aminoalkyl, or a hydroxy protecting group, and R8and R9are —H (compound III);b) reacting the compound III obtained in step (a) with an appropriate secondary amine in the presence of paraformaldehyde in an aprotic solvent at a temperature ranging from 60° C. to 150° C. to yield the desired compound of formula I, isolating and purifying the resulting compound of formula I from the reaction mixture in a known manner and if desired, converting the compound of formula I into its pharmaceutically acceptable salt in a known manner.

The final compounds of formula I can be purified by procedure well known in the art such as crystallization followed by filtration. Alternatively the solvent can be removed by extraction, evaporation and the intermediates can be purified if required by chromatography with solid support such as silica gel, alumina, RP-8 or RP-18.

The described process for the preparation of the cyclohexapeptide compound of general formula I is illustrated as follows:

The reaction of step (b) wherein the intermediate compounds III are reacted with a secondary amine in the presence of paraformaldehyde is known in the art as a Mannich Reaction.

The starting compounds II may be natural products such as mulundocandin, echinocandin B, aculeacin, pneumocandin Ao, pneumocandin Bo, pneumocandin Co and cilofungin.

In the process of the present invention, the alcohol used in step (a) may be an alkyl alcohol such as methanol or an aryl alcohol such as benzyl alcohol.

For step (a), suitable acids include strong organic acid such as trifluoroacetic acid, p-toluene sulphonic acid, camphor sulphonic acid or a lewis acid such as borontrifluoride etherate, titanium tetrachloride.

Suitable aprotic solvents used in steps (a) and (b) are selected from 1,4-dioxane, N,N-dimethylformamide(DMF), dimethylsulfoxide(DMSO), tetrahydrofuran(THF), toluene. The preferred one is 1,4-dioxane.

In step (b), the said secondary amines include compounds in which the nitrogen contains the same or different C1–C12alkyl, C2–C12alkenyl, aryl, substituted aryl, alkylaryl, substituted alkylaryl groups, and compounds in which the nitrogen atom of the secondary amine may be a part of a heterocyclic or substituted heterocyclic or fused heterocyclic. The heterocyclics may contain 1–3 of the same or different heteroatoms. Substituted heterocyclics may contain substituent(s) such as C1–C6alkyl, C1–C6alkenyl, aryl, amino, nitro and/or halogens.

The present invention provides a second process for the preparation of compounds of the general formula I comprising:a) reacting mulundocandin of the following formula IV,

with a nucleophile such as a thiol or a thioether in presence of an acid in an aprotic solvent at a temperature ranging from 0° C. to 60° to obtain the corresponding cyclohexapeptide derivatives of formula V;

wherein R1and R3are independently —OH or —SR such that at least one of R1or R3is —SR, wherein R is C1–C12alkyl, substituted alkyl of the type —(CH2)n—X, wherein n is 1–5 and X is Cl, Br, I, COOY, CN, NH2, or a heterocyclic and Y is a C1–C6linear or branched alkyl; C2–C12alkenyl; aryl; fused aryl; substituted aryl; heterocyclyl containing 1–3 heteroatoms; mono or di-substituted aminoalkyl; or a hydroxy protecting group;b) reacting the compounds of formula V as obtained in step (a) with an oxidising agent in an aqueous medium at a temperature ranging from 20° C. to 60° C. to obtain the corresponding sulfones of the formula VI, wherein in formula V above R1and R3are independently —OH or —S(O2)R, such that at least one of R1or R3is —SO2R, wherein R is a C1–C12alkyl, substituted alkyl of the type —(CH2)n—X, wherein n is 1–5 and X is Cl, Br, I, COOY, CN, NH2, a heterocyclic, Y is a C1–C6linear or branched alkyl chain; C2–C12alkenyl; aryl; fused aryl; substituted aryl; heteroaryl containing 1–3 heteroatoms; heterocyclyl containing 1–3 heteroatoms; mono or di-substituted aminoalkyl; or a hydroxy protecting group;c) reacting the sulfone (VI) obtained in step (b) with an appropriate nucleophile such as a carbon or nitrogen nucleophile in an appropriate solvent at a temperature ranging from 20° C. to 60° C. to obtain the desired compound of the formula I, isolating and purifying the resulting compound of the formula I from the reaction mixture in a known matter and, if desired, converting the compound of formula I into its pharmaceutically acceptable salt in a known manner

The final compound of formula I can be purified by procedure well known in the art such as crystallisation followed by filtration. Alternatively the solvent can be removed by extraction, evaporation and the intermediate can be purified if required by chromatography with solid support such as silica gel, alumina, RP-8 or RP-18.

The process for the preparation of the cyclohexapeptide compounds of general formula I is illustrated as follows:

The starting, compound, Mulundocandin, is a naturally occurring cyclic lipopeptide, which is isolated from the cultured broth of a strain ofAspergillus sydowi, a microorganism (Indian Patent No. 162032; The Journal of Antibiotics, Vol. XL No. 3, 275–277). Mulundocandin is useful as an antibiotic.

In the process of the present invention the said nucleophile used in step (a) may be a thioether such as methylthioglycolate or an aryl thiol such as thiophenol.

Step (a) is carried out in presence of an acid which may be a strong organic acid such as trifluoroacetic acid, p-toluene sulphonic acid, camphor sulphonic acid or a lewis acid such as boron trifluoride etherate, titanium tetrachloride.

Suitable aprotic solvents used in steps (a) and (c) are selected from 1,4-dioxane, N, N-dimethylformamide(DMF), dimethylsulfoxide(DMSO), tetrahydrofuran(THF) and toluene. The preferred one is 1,4-dioxane.

In step (b), the suitable oxidising agent includes OXONE® (KHSO5.KHSO4.K2SO4:2:1:1; obtained from Aldrich Chemicals), hydrogen peroxide and metachloroperbenzoic acid. The preferrred one is OXONE®.

The said aqueous medium used in the oxidation step is usually a mixture of solvents consisting of water and a water soluble organic solvent such as acetonitrile, dimethylformamide, dimethylsulfoxide and tetrahydrofuran. About 1:1 v/v mixture of the solvents is preferred. The preferred water soluble organic solvent is acetonitrile.

In step (c), the said nucleophile includes a carbon nucleophile or a nitrogen nucleophile.

The carbon nucleophile may be a cyanide such as sodium cyanide, potassium cyanide and lithium cyanide.

The nitrogen nucleophile may be selected from an amine, azide, heterocyclyl, substituted heterocyclyl (containing 1–3 of the same or different heteroatoms), and aminoalkylamino compounds.

In the second process of the present invention the nucleophilic substitution may take place either at ornithine-5 position only or at both the ornithine-5 and homotyrosine-4 positions depending on the intermediates formed in step (a).

The preferred representatives of cyclohexapeptide compounds of formula I′ below are listed in the following Table I.

The compounds (6–47) listed in the Table 1 are prepared from Mulundocandin (Formula IV above, compound 1) as the starting material whereby in the general formula I R1is 12-methylmyristoyl; R1, R2, R3and R4each represent —OH, R5and R7each represents —CH3, R6represents —H and R8and R9are —H.

The preferred representatives of intermediate compounds III are compounds 2–5 as described in the experimental section of the specification.

The further preferred representative compounds given in Table II have the general formula I1above in which R8and R9are H and R1and R3are the groups shown in the Table.

The preferred representatives of intermediate compounds of general formula V and VI are compounds 49–53 as described in the experimental section of the specification.

The compound 55 as shown in Table II is obtained by reduction of compound 54 with a reducing agent such as CoCl2—NaBH4or by hydrogenation using raney nickel as a catalyst in presence of ammonia in alcoholic solvent.

The compounds of general formula I, if desired may be converted into their pharmaceutically acceptable salts.

Preferred pharmaceutically acceptable acid addition salts are those formed with mineral acid such as hydrochloric acid and those formed with organic acid such as acetic acid.

The compounds of present invention are soluble in lower alcohols and polar aprotic solvents such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and pyridine.

The compounds of present invention are useful for the control of both filamentous fungi and yeast. They are especially adaptable to be employed for the treatment of mycotic infections in mammals, especially those caused byCandidaspecies such asC. albicans, C.tropicalsandC.neoformaandAspergillusspecies such asA. fumigatus, A. flavusandA. niger. These type of infections are usually found in immunocompromised patients such as those suffering from AIDS.

The compounds of formula I of the present invention and pharmaceutically acceptable salts thereof may be administered orally, intramuscularly, intravenously or by other modes of administration. Pharmaceutical compositions which contain the compound according to the invention or a pharmaceutically acceptable salt or derivative thereof singly or in combinations can be prepared according to standard techniques by mixing the compound(s) with one or more pharmacologically acceptable excipients and/or auxiliaries such as fillers, emulsifiers, lubricants, masking flavours colorants or buffer substances, and converting the mixture into a suitable pharmaceutical form such as tablets, coated tablets, capsules or a suspension or solution suitable for enteral or parental administration. Further details of the production of suitable pharmaceuticals may be obtained from the literature which relates to the echinocandin type of antibiotics.

As cusomary, the galenic formulation and the method of administration as well as the dosage range which are suitable in a specific case depend on the species to be treated and on the state of the respective condition or disease, and can be optimized using methods known in the art. On an average, the daily dose of a compound of the formula I in a patient of about 75 kg weight is at least 0.001 mg to at most 10 mg, preferably at most 1.0 mg.

The compounds disclosed herein have basic amino-functionality at the ornithine/homotyrosine unit(s), imparting solubility of compounds through their salts.

The following examples illustrate the invention but are not to be considered as limiting the scope of the invention.

In conjunction with the1H NMR spectra, the following abbreviations are used: “s” is singlet, “d” is doublet, “t” is triplet, “q” is quartet, “dd” is doublet of doublet, “br” is broad, “br.s” is broad singlet, “br.d” is broad doublet, “br.t” is broad triplet, “br.m” is broad multiplet, “J” indicates the coupling constant in Hertz (hz).1H NMR,13C NMR, IR, MS, HPLC, m.p. data refers to the free base of the subject compound, unless otherwise mentioned.

Melting points were recorded on a Kofler hot-plate apparatus and are uncorrected. IR spectra were obtained on a Perkin-Elmer 157 spectrophotometer using KBr pellets.1H NMR were recorded on a Brucker ACP-300 MHz instrument using CD3OD as solvent, unless otherwise mentioned. The chemical shifts are expressed in delta (δ) values (parts per million downfield from tetramethylsilane).13C NMR were recorded on a Brucker ACP-300 and the chemical shifts are expressed in ppm. Electron spray ionization mass spectra (ESI MS) were recorded on a VG QUATTRO II instrument. Perkin Elmer 235 HPLC were used for purification (Semipreparative column-Knauer Eurosphere 100, C-18 column, 250×16 mm, 10 μm, λ=220 & 270 nm) and for checking purity (Analytical column—YMC-Pack, AQ-313 S-5 120A ODS, C-18 column, 6×250 mm, 5 μm, λ=220 & 270 nm) of the compounds, according to the invention.

Procedure for the Preparation of Compounds 2 & 3:—

To a stirred solution of mulundocandin 1 (5.2 g, 5.15 mmol) in anhydrous 1,4-dioxane (150 ml), under nitrogen atmosphere was added anhydrous benzyl alcohol (10.45 g, 96.6 mmol), and a catalytic amount of p-toluenesulfonic acid (0.32 g, 1.66 mmol) and the resulting reaction mixture was stirred at ambient temperature for 1 hr. Reaction progress was monitored by TLC (20% MeOH/CHCl3). TLC analysis after 1 hr. showed no starting compound. The reaction was quenched at 5–10° C. by the addition of saturated aqueous NaHCO3and evaporated to smaller volume (25 ml). The above mixture was diluted with water (250 ml), extracted with n-butanol(3×150 ml) and washed with water (200 ml) followed by brine (200 ml). Combined organic extract was dried over anhydrous Na2SO4, filtered and concentrated in vacuum to give crude gummy product, which was then dissolved in a minimum amount of methanol(15 ml), adsorbed on silica gel (1:1 w/w), and was subjected to silica gel flash column chromatography. 0–15% MeOH/CHCl3was used as 5% step gradient elution. Evaporation of the appropriate fractions gave white compound 2 (3.8 g, 67.13%) and 3 (0.82 g, 13.37%).

Procedure for the Preparation of Compounds 4 & 5:—

To a stirred solution of mulundocandin 1 (2.2 g, 2.18 mmol) in anhydrous 1,4-dioxane (50 ml), under nitrogen atmosphere was added anhydrous methanol (6.0 ml, 147.9 mmol), and a catalytic amount of p-toluenesulfonic acid (0.12 g, 0.624 mmol) and the resulting reaction mixture was stirred at ambient temperature for 0.5 hr. Reaction progress was monitored by TLC (20% MeOH/CHCl3). The reaction workup and purification process are similar to that described for compounds 2 and 3. Evaporation of the appropriate fractions gave white compound 4 (1.55 g, 69.53%) and 5 (0.109 g, 4.82%).

In a 25 ml oven dried round-bottom flask were placed ornithine-5-benzylmulundocandin 2 (0.1 g, 0.091 mmol), piperidine (0.077 g, 0.91 mmol), paraformaldehyde (0.0546 g, 1.82 mmol), and anhydrous 1,4-dioxane (10 ml) and the ingredients were heated under reflux for 2 hr. Reaction progress was monitored by TLC (20% MeOH/CHCl3). TLC analysis after 2 hr. showed no starting compound. Reaction mixture was cooled to ambient temperature, the solvent was evaporated under vacuum to leave a crude residue, which was then diluted with water (100 ml) and extracted with n-butanol (3×50 ml). The n-butanol extract was washed with water (100 ml) followed by brine (100 ml). Combined organic extract was dried over anhydrous Na2SO4, filtered and concentrated in vacuum to give impure product, which was then dissolved in minimum amount of methanol (5 ml), adsorbed on silica gel (1:1 w/w), and was subjected to silica gel flash column chromatography. 0–25% MeOH/CHCl3was used as 5% step gradient elution. Evaporation of the appropriate fractions gave white compound 6 (0.03 g, 27.57%).

General Procedure for the Preparation of Compounds 7–46:—

To a stirred solution of compound 2, 3 or 4 (1 eq.) in anhydrous 1,4-dioxane (10–40 ml) was slowly added secondary amine (10 eq.) and paraformaldehyde (20 eq.) and the ingredients were heated under reflux(100–120° C.) for 2–31 hr. Reaction progress was monitored by TLC (20% MeOH/CHCl3). The reaction workup and purification process are similar to the described for compound 6. Stoichiometric ratios of starting compound, secondary amine, paraformaldehyde and anhydrous 1,4-dioxane are given in Table-III. Yield, m.p., reaction time, molecular formula and molecular weight of the compounds (7–46) are given in Table-III.

To a stirred solution of ornithine-5-benzylmulundocandin 2 (0.2 g, 0.182 mmol) in anhydrous N,N-dimethylformamide (10 ml) was added imidazole (0.122 g, 1.8 mmol), paraformaldehyde (0.108 g, 3.6 mmol) and heated under reflux for 15 hr. Reaction progress was monitored by TLC (20% MeOH/CHCl3). The reaction work-up and purification procedure was similar to that of compound 6. Yield of the white solid 47 (0.03 g, 13.42%).

To a stirred solution of mulundocandin 1 (4.8 g, 5.15 mmol) in anhydrous 1,4-dioxane (150 ml), under nitrogen atmosphere was added anhydrous methylthioglycolate (11.87 g, 111.83 mmol) and a catalytic amount of p-toluenesulfonic acid (0.338 g, 1.758 mmol) and the reaction mixture was stirred at ambient temperature for 1.5 hr. Reaction progress was monitored by TLC (20% MeOH/CHCl3). TLC analysis after 1.5 hr. showed no starting compound. The reaction was quenched at 5–10° C. by the addition of saturated aqueous NaHCO3and evaporated to smaller volume (25 ml). The above mixture was diluted with water (250 ml), extracted with n-BuOH (3×150 ml), washed with water (200 ml) followed by brine (200 ml). Combined organic extract was dried over anhydrous Na2SO4, filtered and was concentrated in vacuum to give gummy product, which was then dissolved in a minimum amount of methanol (MeOH) (15 ml), adsorbed on silica gel (1:1 w/w), and was subjected to silica gel flash column chromatography. 0–15% MeOH/CHCl3was used as 5% step gradient elution. Evaporation of the appropriate fractions gave white compound 49 (3.171 g, 60.75%) and 49 (0.885 g, 15.69%).

Procedure for the Preparation of Compounds 51 & 52:—

To a stirred solution of mulundocandin 1 (2.3 g, 2.28 mmol) in anhydrous 1,4-dioxane (100 ml), under nitrogen atmosphere was added anhydrous thiophenol (4.29 g, 38.95 mmol) and a catalytic amount of p-toluenesulfonic acid (0.23 g, 1.196 mmol) and the reaction mixture was stirred at ambient temperature for 3 hr. Reaction progress was monitored by TLC (20% MeOH/CHCl3). The reaction workup and purification process were similar to that described for compounds 49 and 50. Yield of the white solid 51 (1.241 g, 49.44%) and 52 (0.478 g, 17.57%).

To a stirred solution of thioether 48 (0.515 g, 0.47 mmol) in 70 ml of 1:1 acetonitrile/water at ambient temperature was added OXONE® (0.577 g, 0.94 mmol). After a period of 1 hr. TLC analysis (20% MeOH/CHCl3) showed conversion to a more polar product to be complete. The reaction mixture was evaporated under reduced pressure to smaller volume (25 ml). White sold precipitated out was filtered off, washed with water (25 ml) dried under high vacuum to yield nearly 90% pure sulfone 52 (0.45 g, 84.90%). This was used without purification for further reactions.(OXONE=KHSO5, KHSO4, K2SO4; 2:1:1).

A solution of ornithine-5-sulfone 52 (0.5 g, 0.443 mmol) and sodium cyanide (0.1 g, 2.04 mmol) in anhydrous N,N-dimethylformamide (10 ml), under nitrogen atmosphere was stirred at ambient temperature for 1 hr. Reaction progress was monitored by TLC (20% MeOH/CHCl3). The reaction mixture was diluted with water (150 ml), extracted with n-BuOH (3×100 ml), washed with water (150 ml) followed by brine (150 ml). Combined organic extract was dried over anhydrous Na2SO4, filtered and was concentrated in vacuum to give a crude product. This was then dissolved in a minimum amount of MeOH (5 ml), adsorbed on silica gel (1:1 w/w), and was subjected to silica gel flash column chromatography. 0–20% MeOH/CHCl3was used as 5% step gradient elution. Evaporation of the appropriate fractions gave ornithine-5-cyanocompound 54 (0.16 g, 35.55%). Yield is calculated from nearly 90% pure starting compound.

To a saturated solution of ammonia in anhydrous methanol (10 ml) was added 53 (0.1 g, 0.098 mmol) and a catalytic amount of Raney Nickel (0.03 g). The reaction vessel (hydrogenation bottle, 250 ml) was evacuated by aspirator and thoroughly purged with hydrogen (three times). The resulting heterogeneous mixture was stirred under hydrogen atmosphere at 45 lb/in2pressure for 4 hr. TLC analysis (20% methanol/CHCl3) showed complete conversion to a more polar product. The catalyst was filtered off through celite and the filtrate was concentrated under vacuum to give a crude product, which was subjected to reverse-phase (5 g, C-18) flash column chromatography eluting with 50–90% acetonitrile/water as 10% step gradient. Lyophilization of the appropriate fractions provided 55 (0.053 g, 52.79%).

To a stirred solution of ornithine-5-sulfone 52 (0.1 g, 0.089 mmol) in anhydrous 1,4-dioxane (10 ml), under nitrogen atmosphere was added 4-(2-aminoethyl) morpholine (0.495 g, 3.8 mmol) and the reaction mixture was stirred at 25–60° C. for 1 hr. Reaction progress was monitored by TLC (20% MeOH/CHCl3). The reaction work-up was similar to that described for compound 54. Crude product was purified by using reverse-phase (4 g, C-18) flash column chromatography eluting with 50–90% acetonitrile/water as 10% step gradient. Lyophilization of the appropriate fractions provided 56 (0.07 g, 70.5%) Yield is calculated from nearly 90% pure starting compound.

To a stirred solution of ornithine-5-sulfone 53 (0.1 g, 0.089 mmol) in anhydrous 1,4-dioxane (10 ml), under nitrogen atmosphere was added imidazole (0.024 g, 0.356 mmol) and the reaction mixture was stirred at 25–60° C. for 1 hr. Reaction progress was monitored by TLC (20% MeOH/CHCl3). After one hour the reaction mixture was diluted with water (100 ml), extracted with n-BuOH (3×50 ml), washed with water (100 ml) followed by brine (100 ml). Combined organic extract was dried over anhydrous Na2SO4and was concentrated in vacuum to give a crude product. The crude product was purified by using reverse-phase (5 g, C-18) flash column chromatography eluting with 50–90% acetonitrile/water as 10% step gradient. Lyophilization of the appropriate fractions provided 57 (0.06 g, 64.03%) Yield is calculated from nearly 90% pure starting compound.

Note Starting compound (ornithine-5 and homo-tyrosine-4-disulfone mulundocandin) for the preparation of compounds 57, 58 and 59, was prepared from thioether 49 using the process outlined for preparation of compound 52.

Using the process outlined for the preparation of 53, a solution of ornithine-5 & homo-tyrosine-4-disulfone mulundocandin (0.5 g, 0.4 mmol) and anhydrous sodium cyanide (0.2 g, 4.08 mmol) in anhydrous N,N-dimethylformamide (10 ml), under nitrogen atmosphere was stirred at ambient temperature for 1 hr to yield dicyanomulundocandin 58 (0.19 g, 46.22%).

ESI MS (ES+): for C60H101N11O16