Titanium enolates of N-alkyldeneglycinates and derivatives react with aldehydes to give anti-isomers of β-hydroxy-α-amino esters and derivatives. Combination of the titanium enolates, generated by transmetalation of the corresponding lithium enolates with dichlorodiisopropoxytitanium, and bulky aliphatic aldehydes is most effective for the favored formation of anti-isomers.
Development of Highly Diastereo- and Enantioselective Direct Asymmetric Aldol Reaction of a Glycinate Schiff Base with Aldehydes Catalyzed by Chiral Quaternary Ammonium Salts
A highly efficient directasymmetricaldolreaction of a glycinate Schiff base with aldehydes has been achieved under mild organic/aqueous biphasic conditions with excellent stereochemical control, using chiral quaternary ammonium salt 1b as a phase-transfer catalyst. The initially developed reaction conditions, using 2 equiv of aqueous base (1% NaOH (aq)), exhibited inexplicably limited general applicability
Catalytic asymmetric synthesis of β-hydroxy-α-amino acid esters by direct aldol reaction of glycinate Schiff bases
作者:Naoki Yoshikawa、Masakatsu Shibasaki
DOI:10.1016/s0040-4020(02)00979-1
日期:2002.10
A catalyticasymmetricsynthesis of β-hydroxy-α-amino acid esters was developed using the directaldolreaction of glycinate Schiff bases with aldehydes. The reaction was catalyzed by heterobimetallic asymmetric complexes without preformation of enol silyl ethers from glycinate Schiff bases. anti-β-Hydroxy-α-amino acid esters were obtained as the major diastereomer in most cases, and moderate enantiomeric
Chirality Transfer from Guanidinium Ylides to 3-Alkenyl (or 3-Alkynyl) Aziridine-2-carboxylates and Application to the Syntheses of (2<i>R</i>,3<i>S</i>)-3-Hydroxyleucinate and <scp>d</scp>-<i>e</i><i>rythro</i>-Sphingosine
作者:Wannaporn Disadee、Tsutomu Ishikawa
DOI:10.1021/jo051495j
日期:2005.11.1
Reaction of chiral guanidinium ylides with alpha,beta-unsaturated aldehydes gives 3-(alpha,beta-unsaturated) aziridine-2-carboxylates in high diastereo- and enantioselectivities (up to 93% diastereomeric excess and 98% enantiomeric excess). 3-(l-Methylvinyl)- and 3-[(E)-pentadec-1-enyllaziridine-2-carboxylates were successfully employed to prepare (2R,3S)-3-hydroxyleucinate and D-erythro-sphingosine, respectively.
An enantioselective synthesis of (2S,3S)- and (2R,3S)-3-hydroxyleucine