ISSN:
0899-0042
Keywords:
diastereomeric amide
;
chiral synthon
;
oxazolidone
;
lithium hydroxide
;
cesium carbonate
;
ethylaluminum dichloride
;
Friedel-Crafts
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Two preparations of the enantiomers of 2 are described. The first makes use of the chromatographic separation of the diastereomeric amides 6a and 6b. Standard hydrolysis of these amides caused racemization, so a milder sequence was developed which utilized carbonyldiimidazole and 1 equivalent of 1 N LiOH. The second preparation involved classical resolution of 9 with (-)-cinchonidine. Subsequent transformations of this substrate involved ester formation, Friedel-Crafts acylation, and ester hydrolysis, all without racemization. The most notable of these reactions was the use of EtAlCl2 in the Friedel-Crafts step, which provided a mild acylation of 10. This second preparation affords a high yield, mild process for the potential preparation of kilogram quantities of (-)-(R)-2b.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/chir.530020108
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