Pigments of fungi. Part 70. Total synthesis of (R)-semixanthomegnin and the X-ray crystal structure of (±)-7-chloro-10-methoxy-3-methyl-3, 4-dihydro-1 H-naphtho[2, 3-c]pyran-1, 6, 9-trione

Abstract

The synthesis of (R)-semixanthomegnin was reported. It was prepared from (R)-propylene oxide in seven steps. A single-crystal x-ray structure analysis of (±)-7-chloro-10-methoxy-3-methyl-3, 4-dihydro-1H-naphtho[2, 3-c ]pyran-1, 6, 9-trione confirmed the regiochemistry of the cycloaddition reaction between 2, 5-dichloro-1, 4-benzoquinone and the highly oxygenated, chiral butadiene derivative.