Synthesis of thiazole analogues of the immunosuppressive agent (1R,2S,3R)-2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)imidazole

Abstract

The synthesis of four of the diastereoisomers of 2-acetyl-5-(1,2,3,4-tetrahydroxybutyl)thiazole and two of the diastereoisomers of 2-acetyl-5-(1,2,3,4,5-pentahydroxypentyl)thiazole and 2-acetyl-4-(1,2,3,4,5-pentahydroxypentyl)thiazole are reported. These syntheses involve the condensation of 5- or 4-metallated 2-(1,1-dimethoxyethyl)thiazoles with 2,3-O-isopropylidene-D-erythrono-1,4-lactone or 5-O-(tert-butyldimethylsilyl)-2,3-O-isopropylidene-D-ribonolactone followed by reductive ring-opening of the resulting lactols. The stereochemistries and structures of some key compounds have been determined by single crystal X-ray structural analysis.