Bruce H. Toder

Andrographolide: an X-ray crystallographic analysis

The structure of andrographolide, isolated fromAndrographis paniculata Nees, has been established by means of a single crystal X-ray analysis. The crystals have the space groupP21, witha=6.550(1),b=8.005(2),c=17.991(7) Å,β=97.36(2)°, andZ=2. The structure was refined toR=7.3%. The molecular stereochemistry, bond distances, bond angles, and hydrogen bonding scheme have all been determined. The systematic name is 3-[2-[decahydro-6-hydroxy-5-(hydroxymethyl)-5,8a-dimethyl-2-methylene-1-naphthalenyl]ethylidine]dihydro-4-hydroxy-2(3H)-furanone.

Regiospecific Methylation of Cyclopentenone Derivatives

Abstract In connection with our continuing interest in cyclopentenone chemistry,1 we record here our observations concerning the regiospecific methylation of six simple cyclopentenones. Although several recent reports2 have demonstrated the feasibility of alkylating either the kinetically or thermodynamically derived dienolate of cyclohexenone systems, similar reports on the alkylation of cyclopentenone derivatives have remained obscure.3 This is presumably due, in the case of equilibrium alkylation, to the availability of alternative pathways (self-condensation) which compete efficiently with alkylation.

Crystal and molecular structure of (±)-cyclomethylenomycinA

The structure of (±)-cyclomethylenomycinA, a penultimate synthetic precursor of the antibiotic methylenomycinA, was determined by direct methods from MoKα diffractometer data. The crystals of (±)-cyclomethylen-omycinA are orthorhombic, space groupPbca, a=15.5724(1),b=11.4415(1),c=9.5454(1)Å, andZ=8. The structure was refined toR=0.077. The chemically determined structure was confirmed. Bond distances and angles are normal and there are no unusual C-H | | | O intermolecular contacts.