Constitution and absolute configuration of meta,meta-bridged, strained biphenyls from Myrica nagi; X-ray analysis of 16-bromomyricanol

Abstract

Chemical and spectroscopic studies lead to the [7,0]metacyclophane structures (2) and (3) for myricanol and myricanone, phenolic extractives from Myrica nagi. X-Ray analysis of the meta-bridged biphenyl, 16-bromomyricanol (nitromethane solvate), by the heavy-atom method, confirmed these assignments, and gave the absolute configuration of myricanol. The compound crystallises in the monoclinic space group P2₁ with Z= 2 in a unit cell of dimensions a= 6·02, ± 0·01, b= 17·34 ± 0·02, c= 11·22 ± 0·02 Å, and β= 98·4°± 0·2°; the structure was refined to R 0·057 for 1075 independent reflections. C.d. measurements suggest that myricanol prefers the same conformation in solution as in the crystalline state. The biphenyl nucleus in 16-bromomyricanol is deformed by meta,meta-bridging. Similar strain in myricanone (3) is relieved by rearrangement with Lewis acids to the ortho,meta-bridged ketone (13). The natural phenols may be biogenetically related to diarylheptanoids.