The asymmetric synthesis of α-amino and α-hydrazino acid derivatives via the stereoselective amination of chiral enolates with azodicarboxylate esters

Synthesis and Chemistry of α‐Hydrazino Acids

“…Only the a-carbon of 9 is attacked, with inversion of configuration to give the anti-a-hydrazino-b-hydroxy acid derivative 10, which is unstable and a very good intermediate in the synthesis of b-hydroxy dehydropiperazic acid [103]. [111] and the NÀN bond of 15 in order to prepare enantiopure a-amino acids.…”

“…Hydrogenolysis of N 1 ,N 2 -unsubstituted a-hydrazino acid derivatives readily occurs using Raney nickel [109,111,127,128,146]. This inexpensive reagent was used in a large-scale synthesis of AS-3201a potent aldose reductase inhibitor [146].…”

Chiral Building Blocks: Enantioselective Syntheses of Benzyloxymethyl Phenyl Propionic Acids

“…The aqueous layer was acidified with concentrated hydrochloric acid and the resulting white solid was collected by filtration, washing with water. The product was dried at the pump to give 3- (2- Representative procedure for the synthesis of acyloxazolidinones [7]: preparation of…”

A convenient method for the stereoselective preparation of 3-hydroxy-2-substituted propionaldehyde derivatives, C-terminal precursors for the synthesis of trans-alkene dipeptide isosteres

“…THPOCH2yCH 0 PNH/~SO2Ph R 2 Acyl oxazolidinones 6 [7,8] were obtained from the Evans chiral auxiliary 4 and acyl chlorides 5 under standard conditions (nBuLi, THE -78 °C). Then, titanium enolates derived from oxazolidinones 6 reacted with trimethyl orthoformate or triethyl orthoformate at 0 °C to give the crude products, which were washed with hexane to provide acetals 7 in >95% diastereoisomeric excess (de; determined by 'H NMR and GC analysis of S,R-7a, 7b).…”

“…To a solution of imide 6 [7,8] (1 mmole) in dry dichloromethane (3.3 ml) at 0 °C under N 2 was added dropwise a solution of TiC14 (1 M in CH2-C12, 1 ml, 1 mmole). After stirring for 10 min, diisopropylethylamine (DIEA) (0.129 g, 1 mrnole) was slowly added to the reaction mixture at 0 °C and subsequently trialkylorthoformate (1.2 mmole) was added to the resulting solution.…”