J. A. Galvez

Stereoselective synthesis of α-hydroxy-β-amino acids using D-glyceraldehyde as the homochiral source

Abstract A systematic study of the diastereoselective addition of methyl organometallic compounds to the benzyl imine derived from conveniently protected D -glyceraldehyde in order to develop a new approach to enantiomerically pure α-hydroxy-β-amino acids is reported. Methylmagnesium bromide addition afforded the corresponding adduct, which can be further elaborated to give (2 S ,3 R )-3- amino -2- hydroxybutanoic acid, with complete diastereoselectivity.

Reversal of the stereochemical course of the addition of phenylmagnesium bromide to N-benzylimines derived from R-glyceraldehyde depending on the O-protecting group and its application to the synthesis of both enantiomers of phenylglycine

Abstract The N -Benzyl imines derived from 2,3-di- O -benzyl- D -glyceraldehyde and 2,3-di- O -isopropylidene- D -glyceraldehyde reacted with phenylmagnesium bromide to afford fully protected aminodiols with total diastereoselectivity. The stereochemical course of the addition reaction depends on the nature of the O -protecting group. These compounds can be easily transformed to enantiomerically pure ( R ) and ( S ) α -phenylglycine.

A new approach to the stereoselective synthesis of conveniently protected α-allyl substituted amino acids; chiral key compounds in the synthesis of constrained peptide isostere constituents

Abstract Enantiomerically pure α-allyl-N-Boc-aminoamides were prepared by Curtius rearrangement of α,α-dialkyl chiral 2-cyanoesters obtained by the diastereoselective allylation of chiral 2-cyanoesters according to a modification of our previously described procedure.

Diastereoselective Strecker reaction of D-glyceraldehyde derivatives. A novel route to (2S,3S)- and (2R,3S)-2-amino-3,4-dihydroxybutyric acid

Abstract Efficient and stereoselective synthetic routes to enantiomerically pure (2R,3S)- and (2R,3S)-2-amino-3,4-dihydroxybutyric acid have been developed using the stereoselective Strecker type reaction of carbonyl compounds derived from appropriately protected D-glyceraldehyde. The stereoselectivity of the cyanide addition was shown to be dependent on the presence of metal complexing agents, which is essential in the case of (2R)-2,3-di-O-benzyl-D-glyceraldehyde. In addition, theoretical calculations to rationalize the stereochemical course of the reaction have been performed.

Chiral 2-cyano esters as synthetic intermediates in the synthesis of R and S α-methylvaline

Abstract A divergent stereoselective synthesis of R and S α-methylvaline from (2RS) (1S,2R,4R)-10-dicyclohexylsulfamoylisobornyl 2-cyano-3-methylbutanoate has been developed.

Stereoselective amination of chiral enolates: Synthesis of enantiomerically pure α,β-diamino acids, chiral key compounds in the synthesis of conformationally constrained peptido- and non-peptidomimetics

Abstract This work describes an efficient synthesis of enantiomerically pure (R)-2-aminomethylalanine, (R)-2-aminomethylnorvaline, (R)-2-aminomethylvaline, (R)-2-aminomethylleucine and (R)-2-aminomethylphenylalanine by electrophilic amination of chiral 2-cyanoesters with O-(diphenylphosphinyl)hydroxylamine followed by appropiate reduction and hydrolysis.

The synthesis of enantiomerically pure (2R)-α-methylisoserine

Abstract The title compound was prepared by diastereoselective methylation of chiral (1 S ,2 R ,4 R )-10-dicyclohexylsulfamoylisobornyl acetoxycyanoacetate and subsequent nitrile hydrogenation.

On the synthesis of (S)-α-methylaspartic acid by diastereoselective alkylation of a chiral 2-cyanopropanoate

Abstract A novel and efficient procedure for the synthesis of optically pure α-methylaspartic acid, based on the diastereoselective alkylation of (1 S ,2 R ,4 R )-10-(dicyclohexylsulfamoyl)isobornyl 2-cyanopropanoate with α-halocarbonyl compounds, is described.

A New Conformationally Restricted Aspartic Acid Analogue with a Bicyclo[2.2.2]octane Skeleton

The bicyclo[2.2.2]octane cage in (2R,3S-3-benzamido-3- methoxycarbonylbicyclo[2.2.2]octane-2-carboxylic acid, C 18 H 21 NO 5 , has approximate D3 symmetry and the three six-membered rings of this fragment all deviate slightly from ideal boat conformations. The values determined for the torsion angles about the N-Cα (φ) and Cα-CO (φ) bonds correspond to a semi-extended conformation for the amino acid residue. The crystal structure is stabilized by two intermolecular hydrogen bonds (O-H...O and N-H...O) involving the carboxylic acid, the benzamido and the methyl ester groups.

(1R,2R,3S,4S,5S,6S)-exo-2-Cyano-exo-3-[(S)-1,2-dibenzyloxyethyl]-exo-5-iodobicyclo[2.2.1]heptane-endo-2,6-carbolactone

In the title compound (C 25 H 24 INO 4 ), an enantiomerically pure iodolactone, the absolute configurations at the chiral C1, C2, C3, C4, C5 and C6 centres have been unambiguously assigned as 1R, 2R, 3S, 4S, 5S and 6S, respectively. In the bicyclo[2.2.1]]heptane (norbornane) unit, the six-membered ring presents a boat conformation, and is fused with a five-membered lactone ring which adopts an envelope conformation.