Synthesis of methyl dihydrohardwickiate and its C-4 epimer.: Structural amendment of natural crolechinic acid

• Published in: Phytochemistry (Oxford) Vol. 53; no. 8; pp. 851 - 854
• Main Authors: Costa, Marta, Perles, Elaine C., Fujiwara, Fred Y., Imamura, Paulo M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01-04-2000; Elsevier
• Subjects: (+)-Methyl hardwickiate; Biological and medical sciences; Chemical constitution; Crolechinic acid; Diterpenes - chemical synthesis; Diterpenes - chemistry; Fundamental and applied biological sciences. Psychology; Magnesium - chemistry; Magnetic Resonance Spectroscopy; Plant physiology and development; Reduction; Stereochemistry; Stereoisomerism; South America; America; (+)-Methyl hardwickiate; Reduction; Crolechinic acid; Stereochemistry; Molecular structure; Epimer; Natural product; Medicinal plant; Folk medicine; Revision; Dicotyledones; Angiospermae; Carboxylate; Euphorbiaceae; Spermatophyta; Chemical synthesis; Comparative study
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/S0031-9422(99)00583-X

Reduction of the α,β-unsaturated ester moiety of (+)-methyl hardwickiate with magnesium in methanol afforded methyl (4a
S,6
S,8a
S,1
R,5
R)-5,6,8a-trimethyl-5-[2′-(3″-oxoyl)-ethyl-perhydro-1-naphthalenyl]-carboxaylate, while reduction with sodium in
n-propanol, followed by esterification with diazomethane, furnished its C-4 epimer. After comparison of the
1
H
- and
13
C
-NMR data of these compounds with those reported for crolechinic acid isolated from
Croton lechleri, a stereochemical revision for the natural product is suggested.