Synthesis of the four stereoisomers of 1-azabicyclo[2.2.2]oct-3-yl-α-hydroxy-α-(4-phenylboronic acid)-α-phenylacetate (QNB-boronic acid), including a preparative HPLC method to separate diastereoisomeric mixtures with high optical purity
作者:P. Nanjappan、K. Ramalingam、D.J. Nowotnik
DOI:10.1016/s0957-4166(00)82085-6
日期:1992.10
The four stereoisomers of 1-azabicyclo[2.2.2]oct-3-yl-alpha-hydroxy-alpha-(4-phenylboronic acid)-alpha-phenylacetate (QNB boronic acids, 1a-1d) were synthesized initially via 1-azabicyclo[2.2.2]oct-3-yl-alpha hydroxy-alpha-(4-iodophenyl)-alpha-phenylacetate (iodo-QNBs, 6a-6d) using an adaptation of a published procedure. The number of steps involved were reduced substantially using a distinctly different approach. This involved the synthesis of diastereoisomers of QNB-boronic acid, followed by separation and isolation of enantiomers by preparative reversed-phase HPLC. An improved method of synthesis of alpha-hydroxy-alpha-(4-aminophenyl)-alpha-phenyl-acetic acid (3a and 3b) from alpha-hydroxy-alpha-(4-nitrophenyl)-alpha-phenylacetic acid (2a and 2b) is also described.