A Carbohydrate-Based Total Syntheses of (+)-Pyrenolide D and (-)-4-epi-Pyrenolide D

Efficient total syntheses of (+)-pyrenolide D (5) and (-)-4-epi-pyrenolide D (6) have been achieved from a known 5-deoxy-D-xylose derivative 9 in ten steps with 19% overall yield either exclusively as 5 or as pure 5 and 6 in a 3:2 ratio. Key steps involved are one-pot epoxidation-cyclization by Corey-Chaykvosky reagent, reductive Barton-McCombie deoxygenation, and per-acid mediated oxidative spiroketalization.