Structure of julimycin B-II: X-ray crystallographic analysis and absolute configuration of 6β-bromo-7β,7αβ-epoxy-4α,6α-dihydroxy-7α-methoxy-carbonyl-3β,4β-dimethyl-3αβ,7αβ-octahydrobenzo[c]furan-1-one

Abstract

The crystal structure 6β-bromo-7β,7αβ-epoxy-4α,6α-dihydroxy-7α-methoxycarbonyl-3β,4β-dimethyl-3αβ,7αβ-octahydrobenzo[c]furan-1-one, C₁₃H₁₇BrO₇, has been determined by three-dimensional X-ray analysis. The crystals are orthorhombic, with a= 17·17, b= 9·98, c= 8·13 Å, and Z= 4, in space group P2₁2₁2₁. The intensities were measured with a linear diffractometer by using Mo-K_α radiation. The structure was solved by the heavy-atom method and refined by least-squares to a final R of 0·077 for 480 independent reflexions. The absolute configuration was determined by the anomalous dispersion method. The bond distances, valency angles, and intermolecular separations are all as expected. The epoxide ring is inclined at ca. 77° to the approximately planar furan ring.