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.