developed in our laboratory was used to produce a versatile and convergent synthesis of an advanced tetracyclic intermediate for the construction of ouabagenin and closely related analogs.Key words: organic chemistry, synthesis, cycloaddition, polycyclization, Michael reaction, DielsAlder reaction, steroids, oubain, ouabagenin, natural products.
A new synthesis of(-)-rishitin (1) is reported, starting with chiral pool molecules. The crucial step is a stereoselective vinyl radical cyclization, which gives a 10:1 ratio of 21 to 22. (C) 1997 Elsevier Science Ltd.