Unusual sugars of the GPL-type antigen of Mycobacterium avium serovar 19. Stereoselective synthesis of methyl 6-deoxy-3-C-methyl-2,4-di-O-methyl-α-L-mannopyranoside and its C-4 epimer

K. Gyergyói; A. Tóth; I. Bajza; A. Lipták

doi:10.1055/s-1998-1608

Synlett 1998; 1998(2): 127-128
DOI: 10.1055/s-1998-1608

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Unusual sugars of the GPL-type antigen of Mycobacterium avium serovar 19. Stereoselective synthesis of methyl 6-deoxy-3-C-methyl-2,4-di-O-methyl-α-L-mannopyranoside and its C-4 epimer

K. Gyergyói^* , A. Tóth, I. Bajza, A. Lipták

^*Research Group for Carbohydrates of the Hungarian Academy of Sciences, H-4010 Debrecen, P.o.b. 55, Hungary

Abstract

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Completely reversed stereoselectivity of reduction of methyl 6-deoxy-2,3-O-isopropylidene-3-C-methyl-α-L-mannopyranoside (2) and its deisopropylidenated derivative (7) was observed. Compound 2 gave exclusively the L-talo-isomer (3) with NaBH₄ in MeOH, but the reduction of 7 with NaBH₄ in acetic acid resulted in the L-manno-derivative 8. It is assumed that in the first case the stereoselectivity is determined by the steric accessibility of the carbonyl group, while in the second case free OH-groups direct the selectivity of the reduction by complexation or ligand exchange.

glycopeptidolipid antigen - branched-chain sugars - stereoselective reduction

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