Configuration and conformation of (3S,3aR,4R,7S,7aS)-4-methyl-7-(2-propyl)-2-oxo-2,3,3a,4,5,6,7,7a-octahydro-3-benzofurancarboxylic acid

The crystal structure determination of the title compound,
C13H2004, together with the knowledge of the
configuration of the starting menthyl reagent, define both
its absolute configuration and that of the menthyl ester
from which it is obtained by hydrolysis. The structure
of the title compound in the crystal is compared with
that obtained for the isolated molecule by molecularmechanics
energy minimization. The largest discrepancies
are observed for the carboxyl group which, in the
crystal, is involved in hydrogen bonding with the same
group of an adjacent molecule packed about a twofold
axis of theP21212 space group. The conformation of
the molecule is discussed.