Stereocontrolled generation of the (2R) chroman core of vitamin E: total synthesis of (2R,4'RS,8'RS)-alpha-tocopherol.
(2R,4'RS,8'RS)-alpha-tocopherol (1) was prepared using, as the two key steps, a novel diastereoselective TiCl(4)-promoted (S)-sulfoxide-directed allylation of ketal 2 with allyl trimethyl silane 3 to efficiently generate the challenging (2R) stereocenter of the chroman moiety and a cross-metathesis reaction with olefin 4 to efficiently join the lipophilic alkyl chain present in the final target.
Departamento de Química Orgánica (C-I), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
Gloria
G
Hernández-Torres
Antonio
A
Urbano
M Carmen
MC
Carreño
Françoise
F
Colobert
D000475:Alkenes / Q000737:chemistry; D002384:Catalysis; D002839:Chromans / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism; D024502:alpha-Tocopherol / Q000138:chemical synthesis* / Q000737:chemistry
D000475:Alkenes; D002839:Chromans; D024502:alpha-Tocopherol