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The reaction of primary amines with acetonylacetone is shown by H-1, C-13 and N-15 NMR spectroscopy to proceed to the N -substituted -2, 5-dimethylpyrroles via the intermediacy of N -substituted imines. Increased steric hindrance reduces rates of imine formation and decay.

The mechanism of the reactions of ammonia and benzaldehyde with three different beta-dicarbonyl compounds to form the corresponding dihyropyridines has been followed by NMR. In each case the pathway is shown to involve the reaction of benzaldehyde with one molecule of beta-dicarbonyl to give chalcone, and of the ammonia with a second molecule of beta-dicarbonyl to give an enamine. The rate determining stage is shown to be the Michael addition of the chalcone to the enamine.

We have synthesised dideoxyadenosine-5'-[alpha-32P]triphosphate [( alpha-32P] ddATP ) at a specific activity of 3000 Ci/mmol and directly compared it with cordycepin-5'-[alpha-32P]triphosphate [( alpha-32P] KTP ) as a means to 3'-end label DNA. The [alpha-32P] ddATP was found to be three to five times more efficient than [alpha-32P] KTP . Blunt and 3'-protruding ends were labelled more efficiently with [alpha-32P] ddATP using terminal transferase than were the 5'-ends with [gamma-32P]ATP using polynucleotide kinase by standard methods. This improvement in efficiency of labelling DNA and the simplicity of the method allows 3'-end labelling of DNA to become a realistic alternative to 5'-end labelling. We have also compared [alpha-32P] ddATP - and [alpha-32P] KTP -labelled DNA in Maxam and Gilbert sequencing procedures and find that both give equally good results.