Showing papers in "Chemical Communications (london) in 1968"

Identification of steranes and triterpanes from a geological source by capillary gas liquid chromatography and mass spectrometry

Abstract: Steranes and triterpanes identification from Green River shale by capillary gas liquid chromatography and mass spectrometry

The chemistry and biosynthesis of loganin

Abstract: LOGAN I , a monoterpene glucoside first isolated from Strychnos nux vomica,l has been assigned the tentative formula (I) (without stereochemical details) on the basis of preliminary chemical characterization and biogenetic assumptions.2,3 Attention has been focussed on the structure of loganin because of an early postulate4 that a compound with similar features plays an important role in the biosynthesis of seco-iridoids; more recently, evidence has been found for a possible implication of loganin in the biosynthesis of indole alkaloids.5 We now present new results which strongly support the correctness of the original suggestion and define part of the stereochemistry of loganin. Ozonolysis of penta-acetyl-loganin (11), followed by treatment with silver oxide in alkaline solution, esterification with diazomethane and oxidation with chromic acid, gave, after g.1.c. purification, the oily keto-diester (111; M+ 214, [or]D +21"). This compound did not behave like a P-ketoester and gave upon Clemmensen reduction, in keeping with the assigned constitution, the knowns racemate of trans, trans-nepetic acid (IV), m.p. 110-112", PK*,,,~ 6.04 and ca. 9.64. The presence in loganin of a five-membered ring and its substitution pattern, but not its stereochemistry, are thus established. Reaction of (11) with bromine in tetrahydrofuran-water yielded a bromoliydrin (V), m.p. 149-ldl0, [XI, -38O, smoothly oxidized with chromic acid to the bromo-lactone (VI), m.p. 173", [a], -31". Brief treatment of (VI) with zinc in cold acetic acid produced a mixture of two compounds epiineric a t C-4 (VII), A: m.p.