Phospholipids chiral at phosphorus. Part 3. Preparation and spectral properties of chiral thiophospholipids

Abstract

The thiophospholipid 1,2-dipalmitoyl-sn-glycero-3-thiophosphocholine (DPPsC) was shown to be a mixture of 2 diastereomers by 31P NMR. The isomer that resonates at the lower field in CDCl3 (56.12 ppm) was designated as isomer A and the other (resonates at 56.07 ppm) as isomer B. Phospholipase A2 from 4 different sources (bee venom, Naja naja venom, Crotalus adamanteus venom and porcine pancreas) hydrolyzed the isomer B of DPPsC specifically, whereas phospholipase C from 2 different sources (Bacillus cereus and Clostridium perfringens) hydrolyzes isomer A specifically. So that the 2 diastereomers could be separated, DPPsC(A + B) was first digested with phospholipase A2 to give 1-palmitoyl-sn-glycero-3-thiophosphocholine (MPPsC) (which is designated as isomer B of MPPsC) and the unreacted DPPsC(A). Reacylation of MPPsC(B) gave pure DPPsC(B). The properties of DPPsC(A) and DPPsC(B) were investigated by 31P, 13C, 1H and 14N NMR. 1H and 13C NMR showed that both isomers in methanol solution have conformational properties similar to those of the natural phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. Isomers A and B showed small but significant differences in the chemical shifts of the C in the chiral C center and the P in the chiral P center.