Oligosialyl-1,2-dialkyl-sn-glycerols and synthetic intermediates for their preparation

An oligosialyl-1,2-dialkyl-sn-glycerol represented by the following formula (I): ##STR1## wherein each R.sup.1 independently represents a group selected from the group consisting of a hydrogen atom and alkali metal atoms, each R.sup.2 independently represents an alkyl group having 14 to 18 carbon atoms, Ac represents an acetyl group, and n represents an integer of from 0 to 20, and synthetic intermediates for their preparation useful as an immuno-stimulating agent, an antitumor agent, and a diagnostic and therapeutic agent for cancers.

TECHNICAL FIELD 
The present invention relates to oligosialyl-1,2-dialkyl-sn-glycerols and 
synthetic intermediates for their preparation. More specifically, it 
relates to .alpha.2 .fwdarw.8 oligosialyl-1,2-dialkyl-sn-glycerols and 
synthetic intermediates for their preparation, and processes for preparing 
said compounds. 
BACKGROUND ART 
Various sugar chain structures containing a sialic acid have been found in 
gangliosides and glycoproteins. For example, some sialic acid-containing 
polysaccharides have been found in capsular components of certain 
pathogenic bacteria. The capsular polysaccharide isolated from Neisseria 
meningitidis Serotype C is composed of a single polymer consisting of 
N-acetylneuraminic acids connected with .alpha.2 .fwdarw. 9 bond. .sup.13 
C NMR spectroscopic study has revealed that the polymer (at 8- or 
9-position) has partially O-acetylated structures (A. K. Bhattachariee, H. 
J. Jennings, C. P. Kenny, A. Martin, I.C.P. Smith, J. Biol. Chem., 250, 
1926-1932, 1975). In addition, it has been reported that the capsular 
polysaccharide isolated from Escherichia coli Bos 12 is also a 
hetero-polymer having both .alpha.2 .fwdarw.9 and .alpha.2 .fwdarw. 8 
bonding structures and that the capsular polysaccharide isolated from 
Escherichia coli K1 is a homo-polymer having .alpha.2 .fwdarw.8 bonding 
structures (W. Egan, T. Y. Lui, D. Dorow, J. S. Cohem, J. D. Robine, E. C. 
Gotschlich, J. B. Robins, Biochemistry, 16, 3687-3692, 1977). Some of 
polysaccharides produced by bacteria have recently been found to have 
pharmacological activities such as immuno-stimulating activity and 
antitumor activity (E. C. Gotschlich, B. A. Franser, O. N. Shimura, J. B. 
Robbins, T. Y. Lui, J.Biol, Chem., 256, 8915-8921, 1981). They are 
substances of interest from their pharmacological activities. 
However, any process for chemical preparation of oligosialic acids as well 
as aforementioned sialic acid-containing polysaccharides has not been 
reported to date. 
Accordingly, an object of the present invention is to provide 
oligosialyl-1,2-dialkyl-sn-glycerols which are derivatives of oligosialic 
acids and synthetic intermediates for their preparation. In addition, the 
present invention provides a process for preparing said 
oligosialyl-1,2-dialkyl-sn-glycerols. 
DISCLOSURE OF THE INVENTION 
The inventors of the present invention succeeded in preparing 
oligosialyl-1,2-dialkyl-sn-glycerols by using an oligosialic acid as a 
starting material which was stereo-selectively prepared by the 
condensation between a sugar-donative sialic acid introduced by a 
facilitative group at the 3-position and a suitably protected 
sugar-accepting sialic acid. The present invention was achieved on the 
basis of these findings. The present invention thus relates to 
oligosialyl-1,2-dialkyl-sn-glycerols represented by formula (I); 
##STR2## 
synthetic intermediates for preparing said 
oligosialyl-1,2-dialkyl-sn-glycerol represented by formulas (II) and 
(III): 
##STR3## 
and a process for preparing said oligosialyl-1,2-dialkyl-sn-glycerol 
represented by formula (I) comprising the step of condensing a compound 
represented by formula (IV): 
##STR4## 
with a 1,2-dialkyl-sn-glycerol represented by formula (V): 
##STR5## 
to produce a synthetic intermediate represented by formula (II) for 
preparing said oligosialyl-1,2-dialkyl-sn-glycerol. 
##STR6## 
BEST MODE FOR CARRYING OUT THE INVENTION 
In formula (I), each R.sup.1 independently represents a radical selected 
from the group consisting of a hydrogen atom and alkali metal atoms. Among 
them, a hydrogen atom and a sodium atom are preferred. In formulas (I), 
(II), and (V), each R.sup.2 independently represents an alkyl group having 
14 to 18 carbon atoms. Among them, an alkyl group having 14 carbon atoms 
is prefered. Each R.sup.11 in formulas (II) and (IV) and each R.sup.2 1 in 
formula (III) independently represents a substituent selected from the 
group consisting of thiophenyl group and selenylphenyl group. Among them, 
thiophenyl group is preferred. Each .sup.1 2 in formulas (II) and (IV) and 
each R.sup.2 2 in formula (III) independently represents a carboxyl group 
which may optionally be protected. More specifically, examples of 
protective groups include methyl group, benzyl group, and allyl group. 
However, they are not limited to these groups and may be selected from 
those apparent to one of ordinary skill in the art. Among these groups, 
methyl group is preferred. Each R.sup.1 3 in formulas (II) and (IV) and 
each R.sup.2 3 in formula (III) independently represents a hydroxyl group 
which may optionally be protected. More specifically, examples of 
protective groups include benzyloxy group, acetyloxy group, and 
triphenylmethyloxy group. However, they are not limited to these groups 
and may be selected from those apparent to one of ordinary skill in the 
art. Among these groups, benzyloxy group is preferred. X in formula (IV) 
represents a halogen atom which may be a fluorine atom, a chlorine atom, a 
bromine atom, or an iodine atom. Among them, a chlorine atom is preferred. 
In formulas (I) to (IV), n represents an integer of from 0 to 20. Among 
them, 0 and 1 are preferred. 
For the condensation of the compound represented by formula (IV) with the 
dialkyl glycerol represented by formula (V), Hg(CN).sub.2 --HgBr.sub.2. 
AgOTf, Cp.sub.2 HfCl.sub.2 --AgOTf, Cp.sub.2 ZrCl.sub.2 --AgOTf or the 
like may be selected as a condensing agent. Among them, Hg(CN).sub.2 
--HgBr.sub.2 is preferred. The aforementioned condensation reaction may be 
carried out for 4 to 18 hours at from -20.degree. C. to room temperature 
under 760 mmHg (an ordinary pressure) in a solvent such as, for example, 
carbon tetrachloride, dichloromethane, 1,2-dichloroethane, or 
acetonitrile. According to a preferred embodiment in which Hg(CN).sub.2 
--HgBr.sub.2 is used as the condensing agent, the above-described 
condensation reaction may be carried out for 4 to 18 hours at from 
-20.degree. C. to room temperature under 760 mmHg in carbon tetrachloride 
as a solvent. 
An example of the process for preparing the synthetic intermediates and the 
oligosialyl-1,2-dialkyl-sn-glycerols of the present invention will be 
explained in schemes set out below. However, the scope of the present 
invention is not limited to the following reaction schemes. In the 
schemes, Bn represents a benzyl group, Me represents a methyl group, Ac 
represents an acetyl group, and Ph represents a phenyl group. 
##STR7## 
In the above-described schemes, reagents and reaction conditions preferably 
used are explained below, wherein A represents a catalyst, B represents a 
solvent, C represents a period of time, D represents a temperature, HMPT 
represents hexameth ylphosphoroustriamide, DMF represents 
dimethylformamide, AIBN represents azobisisobutyronitrile, THF represents 
tetrahydrofuran, NBS represents N-bromosuccinimide, and LDA represents 
lithium diisopropyl amine. 
1. 1.fwdarw.2 
(1) 
A: CCl.sub.4, HMPT 
B: THF 
C: 3.5 hours 
D: -10.degree. C. 
(2) 
A: SOCl.sub.2 , +DMF 
B: CH.sub.2 Cl.sub.2, Cl(CH.sub.2).sub.2 Cl, CH.sub.3 CN 
C: 30 minutes to overnight 
D: -20.degree. C. to 40.degree. C. 
2. 2+3.fwdarw.4, 5 
(1) 
A: HgBr.sub.2 +Hg(CN).sub.2 
B: CCl.sub.4 
C: 17 hours 
D: -10.degree. C. to room temperature 
(2) 
A: AgOTf, Ag.sub.2 CO.sub.3, AgCl.sub.4 
B: CH.sub.2 Cl.sub.2, Cl(CH.sub.2).sub.2 Cl, CH.sub.3 CN, CHCl.sub.3, 
toluene, benzene 
C: 2 hours to overnight 
D: -40.degree. C. to 60.degree. C. 
3. 4.fwdarw.6, 7 and 5.fwdarw.8, 9 
(1) 
A: AIBN, Ph.sub.3 SnH 
B: toluene 
C: 2 hours 
D: 80.degree. C. 
(2) 
A: AIBN, n-Bu.sub.3 SnH, Raney-Ni 
B: benzene 
C: 1 hour to overnight 
D: 80.degree. C. to 120.degree. C. 
4. 7.fwdarw.10 
(1) 
A: 10% Pd--C 
B: H.sub.2 O--CH.sub.3 OH 
C: overnight 
D: room temperature 
(2) 
A: 5% Pd--C, Pd(OH).sub.2, Pd-black 
B: CH.sub.3 OH, CH.sub.3 OH--AcOH, C.sub.2 H.sub.5 OH, C.sub.2 H.sub.5 
OH--CH.sub.3 COOC.sub.2 H.sub.5 
C: 2 hours to overnight 
D: room temperature to 60.degree. C. 
(3) 
A: 0.025 N.multidot.NaOH 
B: THF-CH.sub.3 OH 
C: 2 hours 
D: room temperature 
(4) 
A: no particular catalyst 
B: CH.sub.3 OH 
C: 2 hours to overnight 
D: room temperature to 60.degree. C. 
5. 10.fwdarw.11 
(1) 
A: 0.2 N NaOH 
B: THF - CH.sub.3 OH 
C: 3 hours 
D: room temperature 
(2) 
A: 0.2 to 1 N NaOH 
B: CH.sub.3 OH 
C: 2 hours to overnight 
D: room temperature to 60.degree. C. 
6. 2+A .fwdarw.12 
(1) 
A: HgBr.sub.2 +Hg(CN).sub.2 
B: CCl.sub.4 
C: 4 days 
D: -10.degree. C. to room temperature 
(2) 
A: AgoTf, Ag.sub.2 CO.sub.3, AgClO.sub.4, CH.sub.2 Cl.sub.2, 
Cl(CH.sub.2).sub.2 Cl, CH.sub.3 CN, CHCl.sub.3 
B: toluene, benzene 
C: 6 hours to 4 days 
D: -40.degree. C. to 60.degree. C. 
7. 12.fwdarw.13 
(1) 
A: NBS 
B: CH.sub.3 CN--H.sub.2 O 
C: 2.5 hours 
D: room temperature 
(2) 
A: no particular catalyst 
B: no particular solvent 
C: 0.5 hour to overnight 
D: room temperature to 70.degree. C. 
(3) 
A: t-BuOK 
B: t-BuOH-THF 
C: 2 hours 
D: -10.degree. C. 
(4) 
A: NaH, LDA 
B: t-BuOH-DMF 
C: 0.5 hour to overnight 
D: -40.degree. C. to room temperature 
8. 13.fwdarw.14 
(1) 
A: CCl.sub.4, HMPT 
B: THF 
C: 22 hours 
D: -10.degree. C. to room temperature 
(2) 
A: SOCl.sub.2 +DMF 
B: CH.sub.2 Cl.sub.2, Cl(CH.sub.2).sub.2 Cl, CH.sub.3 CN 
C: 3 hours to overnight 
D: -20.degree. C. to 40.degree. C. 
9. 14+3.fwdarw.15+16 
(1) 
A: HgBr.sub.2 +Hg(CN).sub.2 
B: CCl.sub.4 
C: 22 hours 
D: -10.degree. C. to room temperature 
(2) 
A: AgOTf, Ag.sub.2 CO.sub.3, AgClO.sub.4 
B: CH.sub.2 Cl.sub.2, Cl(CH.sub.2).sub.2 Cl, CH.sub.3 CN, CHCl.sub.3, 
toluene, benzene 
C: 30 minutes to overnight 
D: -40.degree. C. to 60.degree. C. 
10. 16.fwdarw.17 
(1) 
A: AIBN, Ph.sub.3 SnH 
B: benzene 
C: 1 hour 
D: 80.degree. C. 
(2) 
A: AIBN, n-BuSnH, Raney Ni 
B: toluene 
C: 1 hour to overnight 
D: 80.degree. C. to 120.degree. C. 
11. 17.fwdarw.18 
(1) 
A: 10% Pd-C 
B: CH.sub.3 OH 
C: overnight 
D: room temperature 
(2) 
A: 5% Pd--C, Pd(OH).sub.2, Pd-black 
B: H.sub.2 O--CH.sub.3 OH, H.sub.2 O--C.sub.2 H.sub.5 OH, C.sub.2 H.sub.5 
OH 
C: 2 hours to overnight 
D: room temperature to 60.degree. C. 
(3) 
A: 0.2 N NaOH 
B: THF-CH.sub.3 OH 
C: overnight 
D: room temperature 
(4) 
A: 0.2N to 1N NaOH 
B: CH.sub.3 OH 
C: 2 hours to overnight 
D: room temperature to 60.degree. C. 
A preferred embodiment of the present invention will be explained by way of 
examples set out below. However, the scope of the present invention is not 
limited to these examples (numbers of the compounds in the examples 
correspond to the numbers of the compounds in the schemes set out above). 
In the examples, compounds 1 and 2 are described by Ito et al. ( Y. Ito, M. 
Numata, M. Sugimoto, and T. Ogawa, J. Am. Chem. Soc., 1989, 111, pp. 
8508-8510); compound 3 is described by Baer et al. (E. Baer and N. Z. 
Stanacev, J. Biol. Chem., 240, 1965, pp. 44-48), by Kates (M. Kates, T. H. 
Chem, and N. Z. Stamacev, Biochemistry, 2, 1963, pp. 394-397), and by 
Ogawa et al. (T. Ogawa and K. Beqqu, Agric. Biol. Chem., 46, 1982, pp. 
255-262); and compound A is described by Ito et al. (Y. Ito, M. Numata, M. 
Sugimoto, and T. Ogawa, J. Am. Chem. Soc., 1989, 111, pp. 8508-8510). In 
these experiments, the aforementioned compounds were prepared according to 
processes described in the above-described documents.