Absolute Stereochemistry of 1,2-Diols from Lipids of Thermomicrobia.

1,2-Diol based phospholipids are a well-known feature of bacteria from the class Thermomicrobia. Since these bacteria contain only lipids with an alkyldiol-1-phosphate backbone instead of sn-glycero-3-phosphate, it is important to elucidate the stereochemistry of the 1,2-diols. We have studied the absolute stereochemistry of long-chain 1,2-diols isolated from Thermorudis pharmacophila (formerly known as Thermomicrobia sp. WKT50.2) by nuclear magnetic resonance (NMR) using α-methoxyphenylacetic acid (MPA). Low-temperature (-60 °C) NMR of bis-(R)-MPA ester showed (R) stereochemistry of the 1,2-diols. This is the first report concerning the stereochemistry of natural 1,2-diols, which replace the glyceride moiety in phospholipids. The (R) stereochemistry of the diols is expected as it is the same configuration as for the common bacterial lipid backbone-sn-glycero-3-phosphate. This is the first application of low-temperature NMR of a single MPA derivative for assignment of stereochemistry of natural 1,2-diols. The results were confirmed by the comparison of NMR data with bis-(R)-MPA ester of (R) and rac-1,2-octanediol.