A convenient new synthesis of homoserine lactone

Dinuclear zinc-catalyzed asymmetric [3 + 2] cyclization reaction for direct assembly of chiral α-amino-γ-butyrolactones bearing three stereocenters

A highly atom-economic and novel enantioselective [3 + 2] cyclization reaction for the construction of optical α-amino-γ-butyrolactones possessing three stereocenters.

Synthesis of α-Benzyloxyamino-γ-butyrolactones via a Polar Radical Crossover Cycloaddition Reaction

A direct catalytic synthesis of substituted α-benzyloxyamino-γ-butyrolactones is reported, starting from simple oxime acids and alkenes. The substituted O-benzyloxime acid starting materials are cyclized with oxidizable alkenes, via Polar Radical Crossover Cycloaddition (PRCC) reactions. The catalytic reaction is carried out using the Fukuzumi acridinium photooxidant and substoichiometric amounts of a redox-active cocatalyst. The utility of this method has been demonstrated through the use of 3 oxime acids and 19 oxidizable olefins.

Syntheses of optically active 2-amino-4-oxobutyric acid and N,O-protected derivatives

Strategies for the synthesis of optically active aspartaldehyde derivatives are reviewed. Most of them are using the chiral pool: allylglycine or naturally occurring homoserine, aspartic acid or methionine and side chain modifications. This will be developed in the first part. Some other original routes are also displayed in the second part. Different aspects of each strategy are discussed: the nature and number of steps, the problem of protecting groups, the price and availability of starting materials. Some synthetic applications of such interesting chiral synthons are shown in the last part.

An Olefination Entry for the Synthesis of Enantiopure alpha,omega-Diaminodicarboxylates and Azabicyclo[X.Y.0]alkane Amino Acids

A new approach for synthesizing alpha,omega-diaminodicarboxylates of various chain lengths has opened the way for making a series of azabicyclo[X.Y.0]alkane amino acids of different ring sizes. beta-Keto phosphonates 21-23 were synthesized in 71-90% yield by the addition of the lithium anion of dimethyl methyl phosphonate to the omega-methyl ester of alpha-tert-butyl N-(PhF)aspartate 3, glutamate 9, and aminoadipate 12 (PhF = 9-phenylfluoren-9-yl). alpha,omega-Diaminodicarboxylates 24-26 of nine to eleven carbon chain lengths were prepared in 78-87% yield from the Horner-Wadsworth-Emmons olefination of alpha-tert-butyl N-(PhF)aspartate beta-aldehyde (5) with aminodicarboxylate-derived beta-keto phosphonates 21-23. The power of this approach for making azabicyclo[X.Y.0]alkane amino acid was then illustrated by the first synthesis of enantiopure indolizidin-9-one amino acid 2 in nine steps and >25% overall yield from inexpensive aspartic acid as chiral educt. Hydrogenation of (2S,8S)-di-tert-butyl 4-oxo-2,8-bis[N-(PhF)amino]non-4-enedioate (24) in 9:1 EtOH:AcOH furnished a 9:1 diastereomeric mixture of 6-alkylpipecolate 28 that was subsequently transformed into azabicyclo[4.3.0]alkane amino acid 2 via lactam cyclization and protecting group manipulations. Because alpha,omega-diaminodicarboxylates 25 and 26 may be similarly converted to heterocycles of larger ring sizes and because alkylation of similar ketones can be used to attach side-chains at different points on the heterocycle, this olefination strategy greatly expands our methodology for synthesizing azabicyclo[X.Y.0]alkane amino acids for the exploration of conformation-activity relationships of various biologically active peptides.