Org. Chem., 35,549 (1970), and ref 31. (39) Wlthout results of the LIAIH4 reductions of 17 and 16, formation of a ketal which must be either Wamqn-cis or bms-antkis from m enedione which must be either trans-siyn-cis or trans-antl-trans would not sufflce to deflne the configwatlon of the -a s trans-syn-cls, because lt is possible to suggest mechanisms by which a trans-anti-trans enedione might have led to a trans-anticis ketal durlng Synthesis of either 20 or 22 from 6g.(40) A mixture of 2.675 g of MI and 2.30 mL of concentrated H2S04 diluted to 10.0 mL with water: cf. C. DJerassi, R. R. Engie, and A. Bowers, J. Org. chem., 21, 1547 (1956).(41) It is probable that material lose during this purification resulted largely from the unsuspected volatility of the product.Diterpenoid Total Synthesis, an A -, B -C Approach.Synthesis of 4a-carbomethoxy-4~,1O-dimethyl-trans-7-decalone (4),2 4~-carbethoxy-l0-cyano-4a-methyltrans-7-decalone (15), and several derivatives of 4j3,10-iminobismethyl-4a-methyl-trans-7-decalone (6a) is described. Compounds 4 and 15 are of interest as intermediates for synthesis of the abietic-pimaric and the podocarpic families of diterpenoid resin acids, respectively, and 6 is a similar intermediate for diterpenoid alkaloid synthesis. Alkylation of diethyl methylmalonate with 6-bromovaleronitrile affords cyano diester 7 which is cyclized to 2carbethoxy-2-methyl-6-cyanocyclohexanone (8) by KOt -Bu. Ethoxide-catalyzed reaction of 8 with methyl vinyl ketone gives a 4555 mixture of octalones 13 and 14 which can be hydrogenated either selectively to produce a mixture of the 4@-carbethoxydecalone 15 and 4a-carbethoxyoctalone 14 or exhaustively to afford a mixture of the two trans decalones 15 and 16. Several chemical procedures for separating 15 from 14 or from 16 are described. Decalone 4 is produced from 16 either by ketalization, LiAlH4 reduction to imino alcohol 23, Huang-Minlon reduction, ketal hydrolysis, Jones oxidation, and esterification, or by LiAlH4 reduction to the imino diol (which exists as amino ether tautomer 24), Huang-Minlon reduction, Jones oxidation, and esterification. Concentrated HzS04 converts 15 to the 4&lO-dicarboximido decalone 21 which by LiAlH4 reduction, diacetylation, methanolysis of the O-acetate, and Jones oxidation gives the N-acetyl derivative of 6a. Alternatively the N-mesyl derivative of 6a is obtained by ketalization of 21, LiAlH4 reduction, mesylation, and ketal hydrolysis, and by omitting the mesylation step 6a itself is available. Reduction of the ketal of 21 by sodium bis(2-methoxyethoxy)aluminohydride selectively removes oxygen from the C-4 substituent, giving lactam 32 which is hydrolyzed to keto lactam 33. 1 2 3 P ; Qo \ *osb'*o ', '\ C02Me MeOpC 4 5 6 a , R = H b, R = Ac c, R = M scarbomethoxy-2,6-dimethylcyclohexanone followed by reduction. However, that Michael reaction is unsatisfactory> as is often the case when the appropriate a hydrogen of a ketonic addend is not activated by a second electron-withdrawing group. Furthermore, even if that reaction were ...
