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[structure: see text]. An efficient three-step synthesis of chiral 3H-quinazoline-4-one derivatives from commercial materials is disclosed. The Mumm reaction of imidoyl chloride with alpha-amino acids followed by reductive cyclization affords enantiomerically pure (ee >93%) quinazoline-4-ones in good overall yield. A comparison with existing approaches indicates that this method is superior for hindered substrates.

The flash vacuum pyrolysis (900-940°C) of a series of N-Rsubstituted carbazole-l,2-dicarboxylic anhydrides (R = methyl, phenyl, o-tolyl, benzyl, and ethyl) leads to 1,2-didehydrocarbazoles which undergo ring expansion, cyclisation, and other reactions but which appear not to undergo ring contraction to exocyclic carbenes. Thus the N-methyl compound 4 gives phenanthridine in 27% yield, the N-phenyl compound 5 undergoes C-2'-C-1 cyclisation to indolo[3,2,1-jk]carbazole 27, and the N-o-tolyl compound 6 gives both C-6'-C-l cycli-sation and 2'-CH3-C-1 cyclisation. The N-benzyl compound 7 mainly suffers loss of the benzyl group, but a minor product, benzo[a]carbazole 33, is probably formed by an intramolecular cycloaddition. The N-ethyl compound 8 forms mainly carbazole and phenanthridine and in addition the minor C-2' -C-1 cyclisationproducts pyrrolo[3,2,1-jk]carbazole 44 andits 4 5 dihydro derivative 45. The formation of phenanthridine from the N-methyl anhydride 4 has been investigated by labelling of 4 with ' :' C at C-9a.

A synthesis of N-acetyl-4-deoxyneuraminic acid (11) from N-acetylneuraminic acid (1) via the corresponding unsaturated derivative (4) is described. This synthesis of the important N-acetylneuraminic acid aldolase (EC 4.1.3.3) inhibitor overcomes several difficulties associated with two previously published syntheses.