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Highly enantioselective synthesis, crystal structure, and circular dichroism spectroscopy of ( R )‐bambuterol hydrochloride
Author(s) -
Cao Gao,
Hu AiXi,
Zou KangSheng,
Xu Ling,
Chen JianLong,
Tan Wen
Publication year - 2008
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.20558
Subject(s) - chemistry , circular dichroism , hydrochloride , crystal structure , epoxide , bromide , ring (chemistry) , enantioselective synthesis , spectroscopy , stereochemistry , crystallography , organic chemistry , catalysis , physics , quantum mechanics
The present article describes the asymmetric synthesis of ( R )‐bambuterol hydrochloride based on 1‐(3,5‐dihydroxyphenyl)ethanone as starting material, which was esterified by dimethylcarbamic chloride, and brominated by copper (II) bromide. Then the carbonyl group was reduced efficiently using (−)‐B‐chlorodiisopinocamphenylborane [(−)‐DIP‐chloride™] as an asymmetrical reducing agent. Followed by epoxide ring closure with NaOH and ring expansion with tert ‐butylamine led to the desired product ( R )‐bambuterol with e.e. up to 99%. The optical properties and absolute configuration of ( R )‐bambuterol hydrochloride were further investigated using circular dichroism spectroscopy and X‐ray single crystal analysis. Chirality, 2008. © 2008 Wiley‐Liss, Inc.