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.
Isomerization of α-Pinene Oxide with Chromic Acid Adsorbed on Silica Gel or Alumina
We are studying the isomerization of a-pinene oxide ( 1 )1'~3) and we have investigated the reaction of the title. It was found that a-campholenaldehyde (4) and carvone (7) can be produced at a high selectivity using chromic acid adsorbed on silica gel (H2Cr04/Si02) and that on alumina (H2Cr04/A1203 ), respectivety. Many studies have reported 6) that silica gel and alumina are used for the isomerization of ( 1 ). There are, however, few reports that ( 4 ) and ( 7 ) are synthesized at a high selectivity. Although the catalyst, H2Cr04/Si02"'g', used for this study is understood an effective catalyst for the oxidation of alcohols, there is no instance that the catalyst has been applied to the isomerization of (1).
Reactivity of methyl labdanolate with lead tetraacetate
The reactivity of the methyl labdanolate, 3 with Pb(OAc)4 and/or Pb(OAc)4/I2 was studied. The long distance functionalization at C-12 led to compounds 8b and9b, whose oxidation with RuO4 produced 16 at a 100% yield. Compounds 14 and 15 were obtained from 16 (3:1). These compounds were also obtained from the O3 oxidation of 8b and/or 9b at a lower yield, in addition to compound 16 that was obtained at a 57% yield in the same reaction. Also, when 3 was treated with Pb(OAc)4, β -fragmentation products 7c and 7d were obtained; and when the same reaction was carried out with Pb(OAc)4/I2 the α-iodoketones 20b and 20c were also obtained.