Synthesis of (+)/(−) pentenomycins via Me2AlCl induced cascade reaction

An efficient approach for the synthesis of (+) pentenomycin and (−) pentenomycin from d-ribose and d-mannose, respectively, is described using Tebbe olefination of lactones 9 and 7 followed by Me2AlCl induced disfavoured 5-(enol-endo)-exo-trig cyclization.