Oxidative transformations of cembrane diterpenoids III. Epoxycembrenes
Summary1. It has been established that the epoxidation of cembrene with perbenzoic and peracetic acids takes place stereospecifically at each of the trisubstituted double bonds with the formation of 4S,5R-, 7S,8S-, and 11S,12S-monoepoxycembrenes, the structures and absolute configurations of which have been established by spectral methods.2. Epoxidation of cembrene at the C11–C12 double bonds under the conditions used takes place preferentially as compared with epoxidation at the C7–C8 double bond.
Organic reactions in a solid matrixI , , Alumina-induced oxirane rearrangements
Abstract A fairly generation transformation of methyldialkyl-substituted 1,2-epoxides to the corresponding vinylidene, allylic secondary alcohols, on contact with active Al2O3, is described. A systematic study of some of the reaction variables of this transformation has also been carried out. The epoxides thus studied include those derived from the following olefins: 1-methylcyclopentene, 1-methylcyclohexene, 1-methylcycloheptene, α-pinene and Δ3-carene.
Synthesis of 2,4-dideoxy-.beta.-D-erythro-hexopyranosyl nucleosides
The synthesis of 1-(2,4-dideoxy-β-D-erythro-hexopyranosyl)thymine (12) 1 was accomplished using two different synthetic routes. It was obtained starting either from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose or from tri-O-acetyl-D-glucal. The other modified nucleosides, with either a cytosine, guanine, or adenine moiety, were synthesized using the second reaction scheme. Deoxygenation reactions were accomplished with the (2,4-dichlorophenoxy)thiocarbonyl derivatives generated in situ