A-amino- -hydroxy

Carbohydrate-derived titanium cnolates also provide yvn-x-amino-/l-hydroxy esters of high diastcrcomeric and enantiomeric purity. For this purpose, the lithium enolate derived from ethyl (2,2,5,5-tetramcthyl-2,5-disilapyrrolidin-l-yl)acetate is first transmctalated with chloro(cy-clopentadienyl)bis(1,2 5,6-di-0-isopropylidene-a-D-glucofuranos-3-0-yl)titanium and subsequently reacted with aldehydes.. vj-n-a-Amino-/ -hydroxy esters are almost exclusively obtained via a predominant /te-side attack (synjanti 92 8 to 96 4 87-98% ee for the xvn-adducts)623-b. 

By ozonolysis and subsequent in situ acylation in the presence of base, the enantiopure 1,2-oxazine 177 (R = Bn) was converted to the highly functionalized a-amino-/ -hydroxy ester 181 along with a minor product 5-hydroxylated oxazine 182 <2005EJ0998>. Similarly, D-erythrose-derived syn- and 7 // -compounds 183 afforded the expected diastereomeric syn- and /f-oxazine esters 184 and 5-hydroxylated oxazine 185 <2005EJ0998>. The arbinose-derived anti-configured 1,2-oxazine 186 was subjected to an ozonolysis/elimination sequence which provided the desired functionalized a-amino ester 187 in 75% yield. 

Mit Carbonyl-Verbindungen fiihren vergleichbare Reaktionen zu a-Amino-/ -hydroxy-carbonsauren. 

This reaction type has also been used for the diastereoselective reduction of a variety of structurally related o -amino-/3-keto esters (equations 9 and 10). Treatment of rac-73 with a substoichiometric amount of chiral mediator 72, using formic acid and triethylamine as the hydrogen source, gave the enantiomerically pure a-amino-/ -hydroxy ester (R,S)-syn-74 in 100% yield with 95 5 dr and 99% ee (equation 9), via the diastereoselective reduction of (S)-73. The unreacted R)-73 efficiently racemizes through tautomerization under these reaction conditions. 

Serine, CH2(OH)—CH(NH2)—COOH, a-Amino -Hydroxy Propionic Acid... 

A mild and efficient method for the aminolysis of oxiranes in aprotic solvents using metal ion salts of Li+, Na+, Mg2+, Ca2+, and Zn2+ as Lewis acid has been reported <90TL4661). The reaction rates depend, in addition to the nature of the amine and epoxide, also on the type of the metal ion of the catalyst salt. The stereoselectivity observed in these reactions is complete inversion of configuration. Epoxy carboxylic acids are cleanly ring-opened by primary amines at C-2 to provide a-amino-/ -hydroxy acids <92TL2497>. 

Abbreviations AON, anterior olfactory nucleus mAChR, muscarinic cholinergic receptor nAChR, nicotinic cholinergic receptor alpha and beta adrenergic receptors NMDA, N-methyl-D-Aspartate receptor AMPA, a-amino-hydroxy-5-methyl-4-isoxazolepropionic acid receptor GABAa/b, gamma aminobutyric acidreceptor. 

Threonine a-amino, -hydroxy-valerate Cohen and Patte, 1963... 

The memory of chirality concept has been employed in a strategy for the synthesis of chiral a,/ -diamino- and a-amino-/ -hydroxy ester derivatives via asymmetric imino-aldol and aldol reactions, starting from protected aminoesters. The route can 0 be extended to the enantioselective synthesis of aziridines. 

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