Abstract: Total syntheses of the two subunits corresponding to tunicamycins have been achieved. One of the key steps involves a cyclocondensation reaction of 7-carbon aldehydo nucleoside with activated diene 8 under catalysis with stannic chloride (see 7+ 8-9a, b). Stereospecific Fitzsimmons cycloadditions of dibenzyl azodicarboxylate to galactal 12 and glucal22 simplified construction of the amino pyranose systems.
