Synthesis of 5-(C15-25-alkyl/alkenyl)resorcinols via 8-(3,5-dihydroxyphenyl)octanal, the ozonolysis product of cardol, using Wittig amp; Grignard methodology

摘要

Methods are disclosed for the synthesis of nature-identical 5-alkylresorcinols (C), 5-alkenylresorcinols and 5-alkadienylresorcinols (D), each having a C15-25 side chain, from an aldehyde intermediate (B) derived by the ozonolysis of cardol. Cardol is an abundant alkylresorcinolic component which comprises compounds of formula D (R is optionally unsaturated C6-alkyl). It is present in the natural product Anacardium occidentale (the cashew tree) and is present in its industrial decarboxylation product, the semi-synthetic technical cashew nutshell liquid (CNSL). The methods include the use of: SL LI(i) Wittig (or its modifications) or LI(ii) the combination of a Grignard chain extension and dehydration of the 8-(3,5-dihydroxyphenyl)octan-1-ol intermediate to yield the alkenyl/alkadienyl resorcinols and LI(iii) subsequent reduction of the C=C bond(s) to yield 5-alkylresorcinol. /SL The nature-identical substances of this application occur notably in cereals (Graminae), wheat (Triticale species) and rye (Cereale secale). They are considered to confer health-promoting and some disease-preventive properties, and therefore may advantageously be used as a dietary supplement. The merits of the proposed route are the ready availability of the natural source for ozonolysis, the avoidance of protective group methodology and the requirement for availbale shorter chain reactants for the final synthetic steps.