Stereochemistry of 2,4-dimethyleicos-2-enoate from the pyruvylated glycolipid of Mycobacterium smegmatis.
The absolute stereochemistry of 2,4-dimethyleicos-2-enoic acid, isolated from the pyruvylated glycolipid of Mycobacterium smegmatis, has been determined. The two enantiomers of methyl 2,4-dimethyleicos-2-enoate were synthesised for the first time but could not be separated by gas chromatography on cyclodextrin phases. (E)-2-Methyloctadec-2-enoate, an intermediate in the synthesis, is a characteristic component of acyl trehalose glycolipids from Mycobacterium fortuitum. Ozonolysis of the fatty acid ester mixture, obtained from the pyruvylated glycolipid produced 2-methyloctadecanoate. It was identified as the (S)-enantiomer by comparison with (2R) and (2S)-2-methyloctadecanoic acid, intermediates in the synthesis of (4R)- and (4S)-2,4,-dimethyleicos-2-enoic acid, using enantioselective gas chromatography of the methyl esters with heptakis(2,6-di-O-methyl-3-O-pentyl)-beta-cyclodextrin as a chiral stationary phase. The natural acid was therefore determined to be 2E-(4S)-2,4-dimethyleicos-2-enoic acid.
Hartmann
S
S
Department of Chemistry, University of Newcastle upon Tyne, UK.
Besra
G S
GS
Fraser
J L
JL
König
W A
WA
Minnikin
D E
DE
Ridell
M
M
D005229:Fatty Acids, Monounsaturated / Q000737:chemistry*; D006017:Glycolipids / Q000737:chemistry*; D009161:Mycobacterium / Q000737:chemistry*
C091212:2,4-dimethyl-2-eicosenoic acid; D005229:Fatty Acids, Monounsaturated; D006017:Glycolipids