Naslov
Diastereoselective Aldol Reaction of 7-Bromo-5- pyrido-1,4-benzodiazepin-2-one; Relative and Absolute Configuration of All Stereoisomers

Autori
Majerić-Elenkov, Maja ; Žiher, Dinko ; Višnjevac, Aleksandar ; Hameršak, Zdenko ; Kojic-Prodic, Biserka ; Šunjic, Vitomir

Izvornik
Croatica chemica acta (0011-1643) 74 (2001), 3; 707-724

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
1 ; 4-benzodiazepines ; Enantioseparation ; Hplc chiral chromatography ; Relative and absolute configuration

Sažetak
Aldol reaction of C(3) carbanion of 7-bromo-5-pyrido- 1, 4-benzodiazepin-2-one (1) with representative aliphatic and aromatic aldehydes and ketones afforded racemic mixtures syn/anti-7-bromo-3-(1˘-hydroxy-1˘- phenylmethyl)-1-methyl-5-(2'-pyridyl)-2, 3-dihydro-1H- 1, 4-benzodiazepin-2-one (2/3), syn/anti-7-bromo-3- (1˘-hydroxy-1˘-phenylmethyl)-1-methyl-5-(2'- pyridyl)-2, 3-dihydro-1H-1, 4-benzodiazepin-2-one (4/5) and syn/anti-7-bromo-3-(1˘-hydroxy-2˘-methylethyl)-1- methyl-5-(2'-pyridyl)-2, 3-dihydro-1H-1, 4- benzodiazepin-2-one (6/7) with 60-85% diastereoselectivity. For prevailing diastereomeric racemates (ą)-2 and (ą)-4 syn relative configuration is deduced, whereas prevailing diastereomer (ą)-7 has anti configuration. Configurational assignment is based on 1H-NMR data and X-ray structure analysis, and the origin of inversion of diastereoselectivity is discussed. Racemic mixtures are separated on chiral HPLC column, and on the bases of the CD spectra (3R) absolute configuration is determined for (+)-enantiomers, and (3S) configuration for (-)- enantiomers. Consequently, (3R, 1˘S) configuration is assigned to syn-(+)-enantiomers and (3R, 1˘R)- configuration to anti-(+)-enantiomers. In an attempt to use enantiomerically pure compounds 2-7 as catalysts in asymmetric alkylation of benzaldehyde by diethyl zinc, these ligands proved chemically and configurationally unstable.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA