Diastereoselective Synthesis of α-Methyl and α-Hydroxy-β-Amino Acids via 4-Substituted-1,3-Oxazinan-6-ones

High anti Diastereoselectivity in a Tandem Oxyhomologation-Coupling Protocol for the Preparation of Amides and Peptides Incorporating α-Hydroxy β-Amino Acids

The one-pot MAC (Masked Acyl Cyanide) reaction is used to perform the tandem oxyhomologation reaction of N,N-dibenzyl-l-phenylalaninal and coupling with nitrogen nucleophiles to provide a wide selection of amide and peptide derivatives of (2S,3S)-allophenylnorstatin in generally good yields and with high anti selectivity, often with dr >98:2. The procedure works equally well with other selected N,N-dibenzyl α-amino aldehydes, and is used to achieve a very short synthesis of (2S,3S,S)-epibestatin.

Stereoselective Construction of the Methylcyclopentane Core of Peditithins B-H with Five Continuous Stereocenters

A stereoselective construction of the methylcyclopentane core (3) of jatrophane diterpenoids peditithins B-H was achieved in 14 steps from commercially available d-(+)-ribono-1,4-lactone (9). The linear 5-ene-heptanal derived from 9 was cyclized to the five-membered ring by an intramolecular carbonyl ene reaction, and five continuous stereocenters on 3 were stereoselectively introduced via a successive substrate-controlled manner, involving diastereoselective 1,4-addition, MoOPH-induced hydroxylation, and stereospecific epoxidation.

Reversal of Diastereoselectivity in a Masked Acyl Cyanide (MAC) Reaction: Synthesis of Protected erythro-β-Hydroxyaspartate Derivatives

Using Garner's aldehyde as a substrate, one-pot MAC hydroxyhomologation reactions proceeded in good yields and with anti selectivity for the first time (dr up to 9:1). The products were used to prepare a panel of protected derivatives of erythro-β-hydroxyaspartic acid and erythro-β-hydroxyasparagine as single enantiomers in a few steps.

The effect of N-methylation on transition state mimetic inhibitors of the Plasmodium protease, plasmepsin V

An N-methylation strategy has been applied to transition state mimetics that are potent inhibitors of plasmepsin V to improve their physical characteristics and their ability to reduce the viability of Plasmodium parasites in culture.

Cu(I)-catalyzed synthesis of dihydropyrimidin-4-ones toward the preparation of β- and β3-amino acid analogues

A copper(I)-catalyzed synthesis of substituted dihydropyrimidin-4-ones from propargyl amides via the formation of ketenimine intermediate has been successfully developed; the synthesis afforded good isolated yields (80-95%). The mild reaction conditions at room temperature allow the reaction to proceed to completion in a few hours without altering the stereochemistry. Further, by involving a variety of reactive nucleophiles, the obtained substituted dihydropyrimidin-4-ones were elegantly transformed into the corresponding β- and β(3)-amino acid analogues.

The Synthesis of a Chiral β-Amino Acid Derivative by the Grignard Reaction of an Aspartic Acid Equivalent

A novel synthetic route to chiral β-amino acid derivative has been developed by a Grignard reaction of 2,4,5-trifluo-rophenyl magnesium bromide with the Weinreb amide derivative of L-aspartic acid. The aspartic equivalent was synthesised from L-aspartic acid in four steps, and the Grignard reagent was prepared by Br–Mg-exchange reaction. The target compound was achieved after the Grignard reaction and a subsequent reduction. Tthe stereo structure of the chiral amine was well preserved from the L-aspartic acid.

Exploitation of the Arndt-Eistert Homologation of N-Methyl-±-Amino Acids for Concomitant Ester and N-Methyl Peptide Formation

Results from studies of the Arndt–Eistert homologation of N-methyl-α-amino acids with concomitant ester and amide formation is discussed. The applicability of the use of ultrasound was investigated in the Wolff rearrangement of diazoketones for the production of esters and amides. This methodology was then applied to a novel ‘N-methyl coupling’ that allows simultaneous β-amino acid formation. Conventional ‘PyBroP N-methyl couplings’ were also performed as a comparison to establish the validity of the method.

Solution-Phase Peptide Synthesis; Synthesis of 'North-Western' and 'South-Eastern' Fragments of the Antifungal Cyclodepsipeptide Petriellin A

The solution-phase synthesis of two highly modified peptides, a hexamer and a heptamer, that constitute the two halves of the antifungal cyclic depsipeptide, Petriellin A, is reported.