A total synthesis of (+)- and (-)-dihydrokavain with a sonochemical blaise reaction as the key step

Starting from 2,3-O-isopropylidene-D-glyceraldehyde (2) as chiral material, the naturally occurring (S)-(+)-dihydrokavain (1a) was synthesized by a procedure that involves a sonochemical Blaise reaction as the key step. The absolute configuration of (S)-(+)-dihydrokavain (1a) is demonstrated for the first time by total synthesis from a chiral source. Its opposite enantiomer, (R)-(-)-dihydrokavain (1b), was also synthesized after inversion of the chiral center in a Mitsunobu reaction. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).