Enantiodifferentiation in Taste Perception of the phyllodulcins

Abstract

Abstract Both enantiomers of phyllodulcin 1 have been prepared. Ester 2 was synthesized in a Wittig reaction from O -benzyl isovanillin. The corresponding stilbene carboxylic acid 3 could be cyclized with CF 3 CO 2 H to produce the 3′-benzyl ether 4 of (±)-phyllodulcin. Acylation with (1 R ,4 S )-camphanoyl chloride gave first 5 and after hydrogenolysis of the benzyl ether group in 5 the diastereomeric esters 6 . The diastereomerically pure 8-(1 R ,4 S )-camphanoate (+) −6 of ( R )-phyllodulcin could be isolated by repeated recrystallization. With (1 S ,4 R )-camphanoyl chloride the enantiomeric 8-(1 S ,4 R )-camphanoate (−) −6 of ( S )-phyllodulcin could be prepared via ent- 5 from a mixture of the diastereomeric esters ent- 6 . Ethanolysis of (+) −6 gave ( R )-phyllodulcin [(+) −1 ] with 99% ee. The enantiomeric (S)-(−) −1 with 98% ee could be obtained from (−) −6 . While (+) −1 , the enantiomer occuring in fermented leaves of amacha, has an intense sweet taste, the enantiomer (−) −1 is completely tasteless.