Stereospecific total syntheses of (±)-2-desoxystemodinone, (+)-2-desoxystemodinone, and (±)-stemodinol are described. Also described are the isolation of (+)-2-desoxystemodinone from S. maritima and its characterization. A strategy for the elaboration of the C/D ring systems of the stemodane diterpenoids, stemarin and aphidicolin, from a common 6-hydroxybicyclo[2.2.2]octan-2-one system is delineated and its efficacy is demonstrated by the synthesis of the stemodane diterpenoids and our previous synthesis of stemarin.

A stereospecific synthesis of (+)-aphidicol-15-ene is described. Pursuing a concept successfully applied to our total synthesis of stemarin and the stemodane diterpenoids, the C/D ring system was elaborated by functional group manipulation and rearrangement of a 6-hydroxybicyclo[2.2.2]octan-2-one system. RONALD B. KELLY, G. SANKAR LAL, GOPALA GOWDA et RABINDRA N. Rw. Can. J. Chem. 62, 1930Chem. 62, (1984. This concept was an efficient feature of total syntheses of stemarin (1)(1), and of 2-desoxystemodinone (2a) and stemodinol (2b)(2,3); we now wish to describe its application to a stereospecific synthesis of (+)-aphidicol-15-ene (5), a derivative of aphidicolin (3)(4).' This synthesis was undertaken as a model, relative to a projected total synthesis of aphidicolin.The keto alcohol 6, formerly encountered as an intermediate in our synthesis of (+)-2-desoxystemodinone (2a)(3), served also as an intermediate in the present synthesis. This intermediate, prepared from podocarpic acid (3), is the enantiomer represented by 6 and leads to the enantiomer 5 derived from aphidicolin (4).In preparation for the rearrangement of the bicyclic system of 6 to that of 5, it was necessary to reduce the secondary hydroxyl group to a methylene group and convert the keto

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2-Chloro-2-methyl-l-phenyl-l-propanone. Reaction of isobutyrophenone with lithium hexamethyldisilazane in THF (53%)-hexane (34%)-HMPA (13%) with Me2C(N02)Cl for 1 h at 25 °C gave 78% of the chloro ketone analyzed by the NMR singlet at 1.90 and identified by comparison of the NMR spectra and gas chromatography retention time with those of an authentic sample.Reaction of PhC(OLi)==CHCH3 with Me2C(N02)2 and Me2C(N02)S02PhMe-p. In addition to lc and 3c significant amounts of 5c (X = NCy and 5d (X = p-MePhSO^w ere formed. These products were identified by GC/MS and analyzed by NMR. For PhCOCH(Me)N02 analysis was based on the signal at 6.33 (q, J = 7 Hz, 1 H) in CDC13, while for PhCOCH(Me)-S02PhMe-p analysis was based on signals at 1.54 (d, J = 7 Hz, 3 H), 2.34 (s, 3 H), 5.27 (q, J = 7 Hz, 1 H) in CDC13 and the GC/mass spectrum, m/e 288 (M+), 155 (p-MePhS02), 139 (C6-H4S02), 133 (PhCOCHMe).

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