131426-03-4Relevant articles and documents
Enantioselective synthesis of chromans for the preparation of enantiopure vitamin E and analogues
Tietze, Lutz F.,G?rlitzer, Jochen
, p. 877 - 885 (1997)
Coupling of the differently protected (hydroxymethyl)enynes 11 a-e and 12a-c with the iodoarene 7 in the presence of catalytic amounts of Pd(PPh3)4 afforded the arylenynes 5a-e and 6a-c which were transformed into the monoprotected chiral trihydroxy compounds 13 a-d and 14a,b by Sharpless bishydroxylation with >95% ee for 13 a-d, 91% ee for 14b, and 64% ee for 14a. A 5-step transformation of 13a led to the desired chroman derivative 3a which was cleaved to give the aldehyde 2 a known precursor for the enantioselective synthesis of vitamin E.
Highly stereoselective construction of the C2 stereocentre of α-tocopherol (Vitamin E) by asymmetric addition of Grignard reagents to ketones
Bieszczad, Bartosz,Gilheany, Declan G.
, p. 6483 - 6492 (2017/08/16)
Tertiary alcohol precursors of both C2 diastereoisomers of α-tocopherol were prepared in three ways by our recently reported asymmetric Grignard synthesis. The versatility of Grignard chemistry inherent in its three-way disconnection was exploited to allow the synthesis of three product grades: 77:23 dr (5 steps), 81:19 dr (5 steps) and 96:4 dr (7 steps, one gram scale) from readily available and abundant starting materials. The products were converted to their respective α-tocopherols in 3 steps, which allowed a definitive re-assignment of their absolute configurations.
