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

The synthesis of four of the diastereoisomers of 2-acetyl-5-(1,2,3,4-tetrah ydroxybutyl)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-ery throno-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 determ ined by single crystal X-ray structural analysis.