APPROACH TOWARDS AN EPC-SYNTHESIS OF NODUSMICIN .4. CONSTRUCTION OF THE HIGHLY HINDERED TRISUBSTITUTED DOUBLE-BOND OF NODUSMICIN

The highly substituted subunit 6 of our convergent synthesis of nodusm icin was prepared utilizing Evans' oxazolidinone protocol. Compound 6 was then adjoined to the decalin subunit 7 using Martin's olefination method. To improve on the formation of the hindered trisubstituted dou ble bond, the following model reactions were devised: reductive coupli ng of ester and keto functionality of tricycle 16 led to the alpha-hyd roxyketone, which was converted to the cyclic sulfate 19 via the diol. Sodium naphthalide then converted 19 to the olefins 20. (C) 1997 Else vier Science Ltd.