IODONIUM ION-MEDIATED MANNOSYLATIONS OF MYOINOSITOL - SYNTHESIS OF A MYCOBACTERIA PHOSPHOLIPID FRAGMENT

Iodonium ion-mediated glycosylation of 1-O-allyl-3,4,5-tri-O-benzyl-6-O-para-methoxybenzyl-D/L-myo-inositol by ethyl 2-O-benzoyl-3,4,6-tri-O-benzyl-l-thio-alpha-D-mannopyranoside gave, after removal of the para-methoxybenzyl group and column chromatography, an alpha/beta-mixture of the individual diastereoisomeric disaccharides. Subsequent stereospecific glycosylation of the alpha(1-2) linked mannopyranosyl-D-myo-inositol enantiomorph by the same ethyl 1 -thiomannopyranoside donor afforded, after debenzoylation, benzylation and subsequent deallylation the partially benzylated 2,6-dimannopyranosyl-D-myo-inositol derivative, the HO-1 position of which was phosphorylated, via the H-phosphonate method, with 1,2-dipalmitoyl-sn-glycerol. Oxidation of the intermediate phosphonate diester, and subsequent hydrogenolysis of the O-benzyl groups, furnished the target compound 1-O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)-2,6-di-O-alpha-D-mannopyranosyl-D-myo-inositol.