Methyl L-sibirosaminide and N-acylkansosamine were synthesized via the same intermediate, methyl 4-amino-4,6-dideoxy-2,3-O-isopropylidene-3-C-methyl-cY+mannopyranoside ( 7), from L-rhamnose in 7 and 10 steps, respectively. Conversion of 7 into the title compounds was performed by N-methylation or N-(2methoxypropanoyl)ation followed by appropriate derivatization.
INTRODUCIION
Sibirosaminel (1) and N-acylkansosamine2 (2) form a unique class of branched-chain amino sugars. The former is a component sugar of an antibiotic, sibiromycin3, which has remarkable antitumor activity. Among the benzodiazepinone antitumor antibiotics, sibiromycin undergoes the most rapid reaction with DNA and forms the most stable adduct. It was at first proposed that the structure of methyl sibirosaminide is methyl 4,6-dideoxy-3-C-methyl-C(methylamino)-P_Daltropyranoside, this being based on chemical degradation, and lH-n.m.r.-spectral and optical data, by Mestensev and Kuljaeva4 in 1973. Since that proposal, various groups5 have reported the preparation of supposed sibirosamine derivatives which were, however, not comparable with those from the natural product. In 1982, Parker and Babine6 revised the configuration of sibirosamine to be L-manno, by synthesis of an N-tosylsibirosamine derivative which was directly compared with that from sibiromycin.
The other compound, N-acylkansosamine ( 2) is a component sugar of the antigenic trehalose-containing lipo-oligosaccharides of Mycobacterium kansasii and exists in the distal nonreducing terminus. For the structure of this novel branchedchain amino sugar, which is regarded as exclusive to M. kansasii and as its primary cell-wall immunodeterminant, Hunter er al.' proposed 4,6-dideoxy-4-(2-methoxypropanamido)-3-C-methyl-2-O-methyl-~-mannopyranose from 'H-and 13C-n.m.r.spectral and mass-spectrometric data. However, the decision as to the absolute 'To whom enquiries should be addressed.