SYNTHESIS AND EVALUATION OF 3-MODIFIED 1D-MYO-INOSITOLS AS INHIBITORSAND SUBSTRATES OF PHOSPHATIDYLINOSITOL SYNTHASE AND INHIBITORS OF MYOINOSITOL UPTAKE BY CELLS

A number of 3-substituted 1D-myo-inositols were synthesized and evalua ted as substrates for phosphatidylinositol synthase and uptake by inta ct cells. 1D-3-Amino-, -3-chloro-, and -3-(acetylthio)-3-deoxy-myo-ino sitols were all synthesized by nucleophilic displacement of the 6-O-(t rifuoromethyl)sulfonyl group of yl-6-O-[(trifluoromethyl)-sulfonyl]-ch iro-inositol (which was prepared from L-quebrachitol), respectively, b y reaction with LiN3, followed by reduction of the azido function, and with LiCl and KSAc to give the O-protected compounds. O-Demethylation using BBr3 and concomitant acetal hydrolysis furnished the free-hydro xy 3-amino-and 3-chloro-3-deoxy-1D-myo-inositols. The 3-mercapto analo gue was obtained by removal of the acetal groups of the acetylthio ana logue, followed by acetylation and purification of the peracetate, and subsequent O-demethylation and deacetylation. The 3-deoxy derivative was synthesized from the 6-O-(imidazol-1-ylthiocarbonyl) compound via Barton-McCombie deoxygenation. The 3-azido derivative was directly syn thesized from 1L-1-O-tosyl-chiro-inositol via displacement with azide. The 3-keto analogue was prepared by Pt-catalyzed air oxidation of IL- chiro-inositol. The compounds were all evaluated as substrates for pho sphatidylinositol (PtdIns) synthase from mouse brain. The 3-NH2, 3-F, 3-deoxy, and 3-keto analogues all showed activity as substrates, as me asured by liberation of cytidine monophosphate. These compounds also s howed inhibition of the reaction of myo-[H-3]inositol with PtdIns synt hase. These results taken together indicate that these compounds are l ikely to be incorporated into phospholipids. As a further indication t hat these compounds might be useful as probes for the PtdIns pathway, it was demonstrated that the 3-NH2,3-F, and 3-deoxy compounds are take n up by intact fibroblast cells as evidenced by their competing with m yo-[H-3]inositol uptake.