PHOTOLYSIS OF α-DIAZOCYCLOPENTANONES. RING CONTRACTION TO FUNCTIONALISED CYCLOBUTANES AND SYNTHESIS OF JUNIONONE, GRANDISOL AND PLANOCOCCYL ACETATE

Article abstract of DOI:10.1016/S0040-4020(01)88398-8

Photolysis of diazoketone 19 in methanol furnished the cyclobutane carboxylate 20.Photolysis in aqueous sodium bicarbonate-THF afforded the acid 21 in better yield.Reduction of the ester followed by oxidation and a subsequent Wittig reaction furnished (+/-) junionone (3).Photolysis of the diazoketone 24 resulted in a 1:1 mixture of cyclobutane carboxylates 25.Treatment of the corresponding carboxylic acids with hydriodic acid furnished the bicyclic lactone 27, a known precursor of grandisol (1).The diazoketone 28, on photolysis yielded a mixture of cyclobutane carboxylates 29 and 30.Conversion of the trans acid 31 to a methyl ketone followed by oxidative functionalisation of the phenyl group gave the keto ester 36 which was isomerised under acid catalysis to 37, which in optically active form had been a precursor to (-) grandisol.Photolysis of diazoketone 38 afforded the cyclobutane carboxylates 39 and 40 in 2:1 proportion.The corresponding mixture of acids on treatment with methyl lithium and subsequent acetylation furnished the keto acetates 43 and 44, resulting in a formal synthesis of planococcyl acetate (4).