South Parks Road, Oxford OX1 3QYStructural investigation of the products obtained by microbiological hydroxylation of substrates in the androstane, pregnane, and mstrane series has involved examining the l H n.m.r. spectra of 344 steroids, 243 of them being new compounds. Mild oxidation of the products gives polyketones in which the positions of the oxo-groups are characterised by the chemical and solvent shifts of the 18-H and 19-H signals. This information is supplemented by the chemical shifts of the products' 18-H and 19-H signals, and by the positions and form of their )CH-OH resonances : the latter are especially useful in establishing the configurations of the hydroxy-groups.FOR the past five years we have been studying the hydroxylation of mono-and di-oxygenated steroids with a range of micro-0rganisrns.l The intention was to vary the positions of the oxygen substituents around the steroid nucleus in a systematic manner: it was -gate, ibid., 1969, 463. hoped that the use of relatively simple substrates would facilitate interpret at ion of the microbiological behaviour. A considerable body of results has accrued from examining monoketones, keto-alcohols, and diketones derived from handrostane, 5a-pregnane, and 5a-cestrane ; a series of papers describing the work will be submitted shortly to this Journal. The preparation of substrates and related chemical studies are being recorded in a separate series2

Short and scalable total syntheses of lamellarin G trimethyl ether, lamellarin D trimethyl ether, lamellarin H, lamellarin η, dihydrolamellarin η, and lamellarin U have been realized in four to six linear steps with an overall yield of ≤22%. Highlights of the synthesis include single-step access to the central 1,2,4-trisubstituted pyrrole core in a highly regioselective manner via a one-pot [3+2] cycloaddition/ elimination/aromatization sequence-based domino process. Subsequent, palladium-mediated double C−H oxidative coupling in a single-pot operation provides access to the pentacyclic coumarin-fused pyrrolo-dihydroisoquinoline core present in lamellarins.

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A new one-pot, transition-metal, acid/base-free domino process is developed for the regioselective synthesis of 1,2,4-trisubstituted pyrroles. The process involves 1,3-dipolar cycloaddition of unsymmetrical azomethine ylide resulting from the thermal C−C bond cleavage of unactivated aziridines with β-bromo-β-nitrostyrene, followed by a cascade of elimination and aromatization reaction sequence to preferentially furnish 1,2,4-trisubstituted pyrroles instead of the expected 1,2,3-trisubstituted pyrroles, in good to excellent yields. Further, the application of the methodology for the formal synthesis of ningalin B is delineated.

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