Total synthesis of (+-)-methyl vinhaticoate and (+)-methyl vouacapenate

Abstract

Total syntheses of the tetracyclic furanoid diterpenes methyl vinhaticoate (1) and methyl vouacapenate (2) are described. These syntheses of racemic 1 from the previously described intermediate 4 and of natural (+)-2 from podocarpic acid (3) required solution of two key problems. First, the secondary methyl group at CH had to be introduced with known stereochemistry so that the previously undefined configuration at that center could be determined to be a, as shown in 1 and 2. Second, a new method for elaboration of the furan moiety had to be developed. Treatment of 2-methoxymethylene ketones 28 and 47 with ethyl diazoacetate in the presence of copper sulfate was found to lead to furoic esters 29 and 48 which could readily be converted to the natural products.

19-(p-Bromophenyl)-12-methoxypodocarpa-8,11,13-trien-19-one, C24H27BrO2

“…Introduetlon. 11, provides a convenient source of chiral starting material for the synthesis of complex molecules (Spencer, Smith, Storm & Villarica, 1971;Bennett, Cambie, Franich & Fullerton, 1969). Attempts to functionalize podocarpic acid derivatives at the C(10) methyl group by photolysis of attached aryl ketone groups were unsuccessful, which was attributed to steric hindrance to n-electron delocalization between the aryl and carbonyl moieties (Smith, 1983).…”

Enantioselective Synthesis of the ABC Ring Motif of Norzoanthamine Based on Asymmetric Robinson Annulation Reactions

“…To circumvent this problem, we converted 15 to a β-keto aldehyde, that underwent a smooth Michael addition with MVK and triethylamine. 19 The Robinson cyclization proceeded cleanly with t BuOK to provide the tricyclic motif 16 in 75% yield over three steps. The final trans-anti-trans decalin 17 was synthesized after stereoselective reduction of 16 using lithium-ammonia conditions.…”

The chemistry of Brazilian leguminosae. LXI. (+)-Methyl Vouacapenate from Vouacapoua pallidior

“…In continuation of our work on the chemistry of Leguminosae (for Part LX see Dias et al, 1982), we wish to re port that the trunk wood of V.pallidior Ducke also contains a substantial quantity of the same compound. Methyl vouacapenate is also accesscible through total synthesis (Spencer et al, 1971). with the analogous published spectra (Spencer et al , 1971).…”

“…Methyl vouacapenate is also accesscible through total synthesis (Spencer et al, 1971). with the analogous published spectra (Spencer et al , 1971).…”