The invention describes novel malonates and a process for using said malonates for the preparation of chiral epoxides of formula
having a cyclanic (1R) configuration, the group in position 2 having a transconfiguration and the epoxy group having a cis-configuration with respect to the substituent in position 1 and wherein R is an alkyl group from C1 to C4, linear or branched, and R1 is an alkyl or an alkenyl group from C2 to C8, linear or branched. The above process comprises the rearrangement of malonate (VII) to malonate (VI) and the decarboxylation reaction of
into an ester of formula
followed by the stereoselective epoxidation of the thus-obtained compound.
Epoxides, process for their preparation and their use for the
申请人:Firmenich SA
公开号:US05962706A1
公开(公告)日:1999-10-05
Epoxides of formula ##STR1## having a cyclanic (1R) configuration, the group in position 2 being in a trans configuration and the epoxy group being in a cis configuration with respect to that in position 1 of the ring, and in which R represents a lower alkyl group and R.sup.1 represents a saturated or unsaturated, linear or branched hydrocarbon group having from 1 to 8 carbon atoms, are useful molecules for the preparation of very prized perfuming ingredients. A process for the preparation of the opoxides (I) is also described.
A New Variant of the Claisen Rearrangement from Malonate-Derived Allylic Trimethylsilyl Ketene Acetals: Efficient, Highly Enantio- and Diastereoselective Syntheses of (+)-Methyl Dihydroepijasmonate and (+)-Methyl Epijasmonate
Complete chirality transfer occurs in the smooth Claisenrearrangement of the trimethylsilyl (TMS) ketene acetals, which were prepared from allylic malonates (R)-1 (R=pentyl, 2-(Z)-pentenyl). These are in turn accessible by enantioselective reduction/esterification or by enzymatic kinetic resolution. The cis configuration in (+)-3 was achieved by highly syn-selective epoxidation of (+)-2, followed