Alcohols a-amino

TV-aluminum imines are another example of masked inline derivatives of ammonia. They are easily synthesized by partial reduction of nitriles with diisobutylaluminum hydride (D1BAL-H)6. Addition of lithium organic reagents to /V-aluminum iniines 7 derived from O-protected cyanohydrins 6 provides a-amino alcohols 8a and 8b in moderate yields and low to good diastereo-selectivities n 12. 

Because of their interest in physiologically active selenophenes, Magde-sieva and co-workers147 I4S have prepared some a-amino alcohols (115). Ketones (114) were nitrosated and the oximes thus obtained were reduced with lithium aluminium hydride. 

Racker et al. have developed an interesting new combinatorial method for the synthesis of [l,4]oxazepin-7-ones (eg 139, R = Ph) from aldehydes and a-amino alcohols with the Baylis-Hillman reaction being a key step . 

This a-amino alcohol is obtained by dibutylation of (lS,2R)-norephedrine. 

The mechanism for the oxidative photofragmentation of a,/ -amino alcohols is consistent with a preference for anti geometry in the cleavage step (Ci, X. Kellett, M. A. Whitten, D. G., J. Am. Chem. Soc., 1991, 113, 3893). Provide a rationalization based on the frontier orbitals of the system. 

Cyclic chiral a-amino ketones are reduced by BH3, NaBH , or LiAlH predominately to chiral /ran.r-a-amino alcohols (80 90% yield). 

The 1,3-proton shift reaction has also been applied to the synthesis of a-(perfluoroalkyl)-a-amino acids, specifically 3.3,3-trifluoroalanine.2 -26 Attempts to prepare the A-benzylimine of ethyl 3,3.3-trifluoro-2-oxopropanoate by direct condensation with benzylamine were very difficult due to the exceptionally high stability of the intermediate a-amino alcohol, which fails to dehydrate. By contrast, 1-phenylethanamine reacted with ethyl 3,3,3-trifluoro-2-oxo-propanoate to form ketimine 33 in 83 % yield.26 The 1,3-proton shift reaction of 33 is much faster than those of ketimines derived from perfluoroalkyl ketones or perfluoroaldehydes (see Table 5). Complete conversion in triethylamine required 6 hours at room temperature and afforded the isomeric Shiff base 34 in 92 % yield. Mild hydrolysis of Shifif base 34 gives a-amino ester 35, which in turn hydrolyzes to 3,3,3-trjfluoroalanine hydrochloride (36). 

Unsymmetrical secondary and tertiary amines. Unsymmetrical amines are obtained in 50-95% yield by reaction of an alcohol and amine in the presence of this ruthenium catalyst. The intramolecular version of this reaction provides an efficient synthesis of cyclic amines either from oc,a>-amino alcohols and an alcohol or from a,tu-diols and an amine. The cyclization is useful for preparation of tetrahydroiso-quinolines.3... 

Chiral diol (9) and an a-amino alcohol mediated reduction of prochiral ketones with LAH gives alcohols in almost quantitative yields and up to 98% ee. 305 ... 

Analytical Properties Separation of primary a-amino alcohols, for example, p-hydroxyphenethylamines and... 

Asymmetric cyclopropanation. Three laboratories have reported that copper complexes of chiral bis(oxazolines) are effective catalysts for asymmetric cyclopropanation of alkenes with diazoacetates. Bis(oxazolines) such as 1 are readily available by condensation of a-amino alcohols with diethyl malonate followed by cyclization, effected with dichlorodimethyltin or thionyl chloride. Cyclopropanation of styrene with ethyl diazoacetate catalyzed by copper complexes of type 1 indicates... 

Highly efficient catalytic asymmetric cyclopropanation can be effected with copper catalysts complexed with ligands of type 2.3 These bis(oxazolines) are prepared by reaction of dimethylmalonyl dichloride with an a-amino alcohol. As in the case of ligands of type 1, particularly high stereoselectivity obtains when R is /-butyl. Cyclopropanation of styrene with ethyl diazoacetate catalyzed by copper complexed with... 

Asymmetric transfer hydrogenation.1 Bis(oxazolines) lacking a methylene bridge such as 3 are prepared by reaction of dimethyl oxalate with a-amino alcohols,... 

Oxidation has been reported to occur with a number of compounds which contain nitrogen but possess no a-amino-alcohol structure.11 13 14 Thus, cystine, methionine, and tryptophan are oxidized, though without... 

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