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Enantioselective Synthesis of the Chromane Moiety of Vitamin E
Author(s) -
Tietze Lutz F.,
Görlitzer Jochen,
Schuffenhauer Ansgar,
Hübner Matthias
Publication year - 1999
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199905)1999:5<1075::aid-ejoc1075>3.0.co;2-i
Subject(s) - chemistry , enantioselective synthesis , moiety , enantiopure drug , alkene , ketone , alkyne , aldehyde , stereoselectivity , stereochemistry , alcohol , organic chemistry , medicinal chemistry , catalysis
Several new approaches for the enantioselective synthesis of the chromane moiety of vitamin E are described. Sonogashira coupling of 3a with the alkyne 4 and subsequent elimination gave 6 , which was bis(hydroxylated) in 93% yield and with 85% ee . Recrystallization gave enantiopure 7a , which was hydrogenated and transformed into the vitamin E precursor 11 . The bis(hydroxylation) of 18 and 21 to give 9 and 22 , respectively, was less than satisfactory, proceeding with ee values of 28% and 18%. In contrast, stereoselective allylation of ketone 15 followed by removal of the protecting group or ozonolysis of the allyl moiety furnished the allyl alcohol 26 and the aldehyde 27 , respectively, in almost enantiopure form, which again could be used as precursors for vitamin E. Partial hydrogenation of 5a gave the alkene 32a and that of 28 the alkene 30b , both of which show interesting atropisomerism.