Abstract
New methods for the synthesis of homochiral C14 and C15-terpenoids desired as building blocks for phytilic side chain of natural α-tocopherol have been developed. A natural phytone resulted from the proposed effective method of chlorophyll ozonolysis was used in a synthesis of optically active terpenoids. Chiral chroman compound for vitamin E, namely, (S)-(-)-6benzyloxy-3,4-dihydro-2,5,7,8-tetramethylchroman-2-methanol was obtained by enantioselective transesterification of the corresponding racemic alcohol catalysed by Amano PS lipase from Burkholderia cepacia in ionic liquid [bmim]PF6.
Highlights
New methods for the synthesis of homochiral C14 and C15-terpenoids desired as building blocks for phytilic side chain of natural α-tocopherol have been developed
Synthesis of (3R,7R)-1-bromo-3,7,11-trimethyldodecane and (2R,6R)-2,6,10trimethylundecan-1-ol We proposed an original methods for the transformation of available homochiral (6R,10R)6,10,14-trimethylpentadecan-2-on 1, obtained by ozonolysis of chlorophyll, to (2R,6R)-2,6,10-trimethylundecan-1-ol 7 and (3R,7R)-1-bromo-3,7,11-trimethyldodecane ((3R,7R)-hexahydrofarnesyl bromide) 5 – synthones for the side chain of (2R,4'R,8'R)-αtocopherol (Scheme 2)
Phytone 1 is usually obtained by the ozonolysis of (2E,7R,11R)-phytol isolated from green plants by alkaline treatment of acetone extract of chlorophyll
Summary
New methods for the synthesis of homochiral C14 and C15-terpenoids desired as building blocks for phytilic side chain of natural α-tocopherol have been developed. Aldehyde 3 was obtained by the ozonolysis of mixture of enol acetates 2 in acetone in the presence of Ba(OH)[2] and was oxidized by the Jones reagent to acid 4. We have proposed an effective method for the synthesis of (S)-(-)-6-benzyloxy-3,4-dihydro2,5,7,8-tetramethyl-2H-1-benzopyran-2-methanol (S)-9 by kinetically selective acylation with vinyl acetate of the corresponding racemic alcohol in the presence of Amano PS lipase (from Burkholderia cepacia) in ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate [bmim]PF6) (Scheme 3).
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