Aminoalcohols diastereomeric

W. Steuer, M. Schindler, G. Schill, and F. Erni, Supercritical fluid chromatography with ion-pairing modifiers separation of enantiomeric 1,2-aminoalcohols as diastereomeric ion pairs, J. Chromatogr., 447 287 (1988). 

This method can be applied to a series of different aldehydes, whereby enantioselectivities of up to 96% ee are obtained. It is noteworthy that - similiarly to the proline-catalyzed aldol reaction - the Mannich reaction can also be extended to an enantio- and diastereoselective process. For example, the uic-aminoalcohol 7 is formed with a diastereomeric ratio of 17 1 and an enantioselectivity of 65% ee (Scheme 5 reaction 2). 

Mitsunobu reactions have also been used for the cylization of 7-aminoalcohols toward azetidines. 7-Aminoalcohols 154, prepared from enantiopure ethynylaziridines, have been transformed into azetidines 155 upon treatment with dimethyl acetylenedicarboxylate and triphenylphosphine (Equation 35) <2001JOC1867>. N-Tosyl-substituted 7-aminoalcohols 156 yielded the corresponding 1-tosylazetidines 121 (Equation 36) with excellent diastereomeric (de = 99%) and enantiomeric excess (ee up to 99%) <2004EJ04471, 2005S3508>. 

Schiff bases of substituted benzaldehydes can be hydrodimerized at the mercury cathode in ethanol-ethyl acetate - water - Bu4N+Br in 25% to 66% yield to the diastereomeric 1,2-diamino compounds 407 Coelectrolysis of a Schiff base with a carbonyl compound forms aminoalcohols. 

Although this topic is covered by a large amount of literature, most of which has been exhaustively assembled in a review paper on the stereoselective synthesis of dia-stereomeric aminoalcohols,the stereochemical aspects of this type of reduction are frequently only partially outlined with a generic indication of the presence of dia,ster-eomers among the reaction products. However, in many cases, diastereomeric ratios as well as relative, or even absolute, configurations of the aminoaicohols produced are... 

Compound 24, the corresponding IV,]V -dioxide of 23, presents enhanced fluorescence when complexed with Sc(OTf)3. 24 forms a strong Sc[( )-24]2 complex whose fluorescence disappears upon addition of amino alcohols. Optically pure scandium complex formed with optically pure 24, Sc[(+)-24]2 generates diastereomeric complexes with a racemic aminoalcohol such as alaninol. The fluorescence signal could be switched off enantioselectively and it was exploited for sensing purpose. The enantiomers of 24 were obtained by chromatography on (R,R)-Whelk-01 (08JOC4267). 

Chiral 7V,A(-dibenzylated a-aminoaldehydes react w th 2-thienyllithium to form aminoalcohols (578) containing two chiral centers. The diastereomeric excess (de) ranges from 52 to 90%. A nonchelation controlled addition has been postulated <89H(28)707>. 

Although quinine and quinidine as well as cinchonidine and cinchonine are diastereoisomers, they are called often pseudoenantiomers because the cmcial for the catalytic or chiral discrimination 1,2-aminoalcohol functionality remains enantiomeric in these pairs (however, diastereomeric rather than enantiomeric character is sometimes observed in various applications [8]). 

The Henry reaction, or nitroaldo reaction, is one of the classic carbon-chain formation methods utilized in organic synthesis. It involves the condensation of nitroalkanes with aldehydes or ketones in the presence of bases (often catalytic amount) to afford the mixtures of diastereomeric 2-nitroalcohols, which in turn can be converted into other useful synthetic intermediates, such as 2-aminoalcohols, a-hydroxyketones, homologous ketones, and perhaps most importantly, nitroalkenes through various functional transformations. 

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