Phanindra Chandra Dutta

Synthetic studies on terpenoids. Part XVI. Synthesis of 3β,17-diacetoxyphyllocladen-15-one

A stereoselective synthesis of 3β,17-diacetoxyphyllocladen-15-one (XIX) from ethyl 5,5-ethylenedioxy-2-oxo-cyclohexanecarboxylate proceeding in ten stages via methyl 13,13-ethylenedioxy-3-oxopodocarpa-5,9(11)-diene-8β-carboxylate (V) and methyl 3β-hydroxy-13-oxopodocarpane-8β-carboxylate (XII) is described. The ester (XII) has been correlated with a known degradation product from phyllocladene. Some by-products from the hydrogenation of the diene (V) are discussed.

Synthetic studies on terpenoids. Part XV. Syntheses of 8β-methyl-podocarpanes

Stereospecific syntheses of 3-acetoxy-8β,13α-dimethylpodocarpan-12-one (IX), the corresponding Δ13-ketone (XI), and 3-acetoxy-8β-methylpodocarpa-5,9(11),13-trien-12-one (XII) are described.

Synthetic studies on terpenoids. Part XVIII. Stereocontrolled synthesis of (±)-1,2,3,4,4a,9,10,10aα-octahydro-1α-methylphenanthrene-1β,4aβ-dicarboxylic acid and the 7-methoxy-analogue: a potential intermediate for diterpenoid syntheses

A stereocontrolled synthetic route to (±)-1,2,3,4,4a,9,10,10aα-octahydro-1α-methylphenanthrene-1β,4aβ-di-carboxylic acid (Ia) and the 7-methoxy-analogue (Ib) is described. The present approach differs basically from earlier ones and proceeds through polyhydrobenzindenone intermediates. 2,3,4,5-Tetrahydro-3-methylbenz[e] inden-1-one (Va) and the corresponding 7-methoxy-compound (Vb) were transformed through several steps into cis-9b-acetonyl-3a,4,5,9b-tetrahydro-3-methylbenz[e]inden-1-one (XIIIa) and its methoxy-derivative (XIIIb). These unsaturated diketones underwent intramolecular Michael condensation, affording tetracyclic bridged ketones (XIVa and b), which were converted into the acids (Ia and b). In the methoxy-series, disproportionation of a polyhydrobenzindenone derivative was noted.