Cross Interaction Between Auxiliaries: The Chirality of Amino Alcohols by NMR
作者:Victoria Leiro、José Manuel Seco、Emilio Quiñoá、Ricardo Riguera
DOI:10.1021/ol8008528
日期:2008.7.3
The absolute configuration of sec/prim- and prim/sec-1,2-amino alcohols is determined by comparison of the (1)H NMR chemical shifts of the auxiliary OMe or C alpha H groups at the corresponding bis-(R) and bis-(S)-MPA derivatives. This is the first NMR method that allows the assignment of absolute configuration without resorting to the shifts of hydrogens at the substrate and is based on the cross anisotropic interactions between auxiliaries.
Kinetic Resolution of the Racemic 1-(Aryloxazol-2-yl)carbinols with Achiral Carboxylic Acids by Asymmetric Esterification: A New Method for the Preparation of Chiral 1,2-Amino Alcohols
作者:Isamu Shiina、Kenya Nakata、Keisuke Ono
DOI:10.3987/com-10-s(e)120
日期:——
An efficient kinetic resolution of racemic 1-(aryloxazol-2-yl)carbinols with achiral carboxylic acids using pivalic anhydride in the presence of (R)-benzotetramisole ((R)-BTM) is reported. It was determined that the naphth[1,2-d]oxazole moiety at the C-1 position in the alcohols is a suitable structure to attain a high selectivity. An application to produce optically pure 1,2-amino alcohols was developed by the kinetic resolution of the racemic 1-(aryloxazol-2-yl)carbinols followed by a two-step cleavage of the aryloxazole part to form the corresponding amino group. Transition states that provide the desired (R)-esters from (R)-1-(benzoxazol-2-yl)ethan-1-ol or the undesired (S)-esters from (S)-1-(benzoxazol-2-yl)ethan-1-ol are disclosed by DFT calculations. Another transition state that affords the desired (R)-ester from (R)-1-(naphth[1,2-d]oxazol-2-yl)ethan-1-ol included in the racemic mixture is also estimated, and the structural features of these transition states are discussed.