Moustafa F. Aly

Decarboxylative transamination. A new route to spirocyclic and bridgehead-nitrogen compounds. Relevance to α-amino acid decarboxylases

N-Substituted and α,α-disubstituted amino acids react with carbonyl compounds to generate 1,3-dipolar species under mild conditions mimicking α-amino acid decarboxylases; the 1,3-dipoles can be trapped both inter- and intra-molecularly to give bridgehead-nitrogen and spirocycli products in goood yield; pyridoxal is shown to react in an analogous fashion.

XY–ZH systems as potential 1,3-dipoles. Part 10. The decarboxylative route to azomethine ylides. Background and relevance to pyridoxal decarboxylases

The reaction of primary and α,α-disubstituted α-amino acids with pyridoxal in the presence of N-phenylmaleimide in various solvents at temperatures up to 120 °C gives rise to two series of cycloadducts. One series arises from azomethine ylides formed by decarboxylation of the intermediate pyridoxal imines whilst the other series arises via azomethine ylides derived by 1,2-prototropy in the same pyridoxal imines. The relevance of the decarboxylative route to azomethine ylides to the Strecker degradation and to pyridoxal-mediated decarboxylase enzymes is discussed.

Ready decarboxylation of imines of α-keto acids. Mechanism and application to thioamide synthesis

α-Keto a ids are readily decarboxylated via imine formation with primary and/or secondary amines even when imine–enamine isomerisation can occur; the process is thoyghy to involve an intermediate zwitteriion which can be trapped by sulphur to give thiamides in excellent yield.

New aspects of the formation of 2-substituted thiazolidine-4-carboxylic acids and their thiohydantoin derivatives

Aromatic aldehydes reacted readily with (R)-cysteine in boiling acidified methanol to give diastereomeric mixtures of the corresponding 2-(aryl substituted) thiazolidine-4-carboxylic acids. 4-Nitrobenzaldehyde under similar conditions afforded one isomer of 2-(4-nitrophenyl)thiazolidine-4-carboxylic acid, which epimerized in the NMR solvents into a diastereomeric mixture. 2-Nitrobenzaldehyde reacted with (R)-cysteine to afford 3,5-bis-(2-nitrophenyl)tetrahydro-1H-thiazolo[3,4-c]oxazol-1-one as the sole product, which collapsed in the NMR solvent into a diastereomeric mixture of the thiazolidine-4-carboxylic acids. The thiazolidine derivatives reacted smoothly with phenyl isothiocyanate to give single isomers of the corresponding thiohydantoins.