Spiroepoxide 1 was prepared the new tricyclic dehydrorubanone 7, con-20 g scale. Reduction with NaBH, in the from quinidine and converted into 8taining the 4-oxa-7-azatricyclo[4.3.1 .037 ' 1-presence of CeCI, provided rubanols amino alcohol 3 (86% over two steps). decan-Zone core structure. Similarly, 10a and 10b (1: 1.1). Homer-Wittig Dihydroxylation of enantiopure oxazatri-acetylated rubanone 9 was prepared on a reaction of 9 with diethyl cyanocylic olefin (E)-4 provided diastereomeric methylphosphonate was (2)-selective, diols 5a and 5b. Stereospecific conversion furnishing unsaturated nitrile (2)-13. of 1,2-~econdary,tertiary diol 5 b into te-Conversion into the a,b-unsaturated aldetracyclic spiroepoxide 6 was accomplished hyde (2)-14 and reduction afforded enanin high yield by a one-pot tosylation-cytiopure allylic alcohol (2)-12, which is a clization procedure. 1,2-Diol cleavage new isomer of the key quinidine metabowith NaIO, in 80% acetic acid afforded lite 15.
Epoxides are invaluable starting materials for organic synthesis, and enantiopure epoxides have found widespread use as chiral building blocks. In the preceding paper, we have shown that all four possible C(3)C( 10) diastereomeric spiroepoxides, derived from quinidine, are readily accessible."] The utility of crystalline spiroepoxide 111] is exemplified by stereospecific conversion into 8-amino alcohol 3 (Scheme 1). After the first stage, that is, the regio-and stereoselective nucleophilic opening of epoxide 1, the resulting azido alcohol 2 was 1 2 3 Scheme 1. Regio-and stereoselective nucleophilic opening of spiroepoxide 1. Highyield preparation of the twofold ,%amino alcohol 3 (the numbering of the quinidine skeleton follows cinchona alkaloid convention).