Reactions of diterpenoids on solid supports II. Behavior of di- and tricyclic diterpenoids on alumina containing oxidants
The behavior of epimanool (1), epimanool oil, larixol (2), cis-abienol (3) and methyl dehydroabietate (4) on alumina impregnated with oxidants (H2CrO4 and KMnO4) has been studied. This has led to the methyl ketone (5) and norambrenolide (8) - precursors of the perfume substances 14,15,17-trinorlabdane-8,13-dione (6), 8α-hydroxy-14,15-bisnorlabd-II-en-13-one (7), and methyl 7-oxodehydroabietate (14). α-Levantenolide (11) has been synthesized in one stage from cis-abienol (3)for the first time.
Tobacco chemistry. 27. The structures of four stereoisomeric 8, 12x1-epoxylabd-14-en-13xl-ols isolated from Greek Nicotiana tabacum L.
The structures of four stereoisomeric 8,12x1-expoxylabd-14-en-13x1-ols** obtained from Greek tobacco were determinedby spectroscopic means and by conversion to 12-norambreinolide. Plausible routes for the formation of the new labdanols and related tobacco constituents from a common precursor, abienol, are discussed.
Comments on “the kinetics of methanation on nickel catalysts”
A new model of intermediate wassuggested as a mechanism of methanation, the main point being that the deposited carbon on the surface of the catalyst is the active intermediate which forms from dissociation of adsorbed CO. Another mechanism for formation of the carbon intermediate was proposed by other authors. The modification suggested was to change the step of carbon formation from 2CO + ( ) ..lambda.. 2(CO) ..-->.. (C) + (CO/sub 2/) to (CO) + 2(H) ..-->.. (C) + H/sub 2/O. It was also proposed that this latter step was the slow step. The authors of this letter question the identification of the limiting step. They suggestthat one of the hydrogenation steps might be a reasonable limiting step. Rate equations are presented to illustrate their suggestion.