Do Khac Manh Do Khac Manh Duc

An unusual acid-catalysed rearrangement of 8-methylenebicyclo[4.2.0]octan-2-ones; X-ray crystal structure of 4-isopropyl-1,5-dimethylbicyclo[3.2.1]oct-3-ene-6,7-dione

The reactions of the 8-methylenebicyclo[4.2.0]octan-2-ones (5) and (6) with toluene-p-sulphonic acid in boiling benzene lead to (9) and (11), respectively, by an unusual rearrangement; the structure of (9) was established by the X-ray diffraction analysis of the derived diketone (10).

δ8(9)-Sandaracopimaradiene

Abstract Recently a new method for α-alkylation of carbonyl compounds, by way of cyclopropanation of their enol ethers and acid-catalyzed hydrolysis of the resultant cyclopropyl ethers, was introduced and applied to a stereospecific angular methylation1 and to the general construction of acyl, quaternary carbon sites.2 The following transformation of ketol, a degradation product of manool,3 into δ8(9)-sandaracopimaradiene (4b),4,5 represents another example of the power of the new synthetic method. In view of a former synthesis of manool3 and the recent interconversion of 4b with isopimaradiene (2a) and sandaracopimaradiene (2b)5 the experiments discussed below complete the total synthesis of the two natural, diterpenic hydrocarbons.6

Synthesis of α-linked 3′-deoxy-cyclitol and -aminocyclitol glycosides

Unsaturated and saturated α-linked cyclitol and aminocyclitol glycosides have been prepared by a boron trifluoride–ether catalysed addition reaction of (3) and (4) to the appropriately functionalised cyclitol derivatives (2), followed by regiospecific hydrogenation from the β face; the structure and conformation of all products have been proved by 1H and 13C n.m.r. spectroscopy and chemical ionisation mass spectrometry.

A short synthesis of (+)-isophyllocladene and (+)-phyllocladene

Rearrangement of the ketone (4) obtained by photochemical cycloaddition of allene to Δ8(14)-podocarpen-13-one (5) leads to (+)-Δ15-isophyllocladen-14-one (3), which can be converted into (+)-isophyllocladene (2) or (+)-phyllocladene (1).

Synthesis of (+)-14-hibanone

Acetolysis of the tetracyclic epimeric alcohols, precursors of the biogenetic intermediate postulated by Edwards, which were prepared from Δ8(14)-podocarpen-13-one via a photochemical adduct with dichloroethylene, leads to (+)-14α-hibyl acetate, ultimately converted into (+)-14α-hibaone.