Crystal and molecular structure of bromohelenalin (C15H17O4Br)

Abstract

Bromohelenalin C₁₅H₁₇O₄Br crystallises in the orthorhombic space group P2₁2₁2₁ with Z= 4 in a unit-cell of dimensions, a= 8·873 ± 0·004, b= 12·272 ± 0·003, and c= 13·187 ± 0·003 Å. Intensities were measured on a diffractometer and the structure refined to a final R of 5·8% for 1125 observed reflections. The conformation of the seven-membered ring is a deformed chair, with 1- and 5-junctions trans and the lactone junction is cis. The carbon skeleton is biogenetically abnormal, a methyl group having migrated from position 4 to 5. The bond distances and angles are normal. The standard deviations are 0·01–0·02 Å for the interatomic distances and 0·6–0·9° for the bond angles.