Diels-Alderreactions of a heteroannularbicyclicdienone with acyclic dienes under Lewis acid catalysis at atmospheric and 7 Kbar pressure are presented. The pressure reactions are fast, high-yielding and highly diastereoselective en route to hydrophenanthrenones. As a consequence of some post-cycloaddition enolization. both cis and trans products are available.
Sunscreen compositions are described which contain certain substituted naphthalenylidenes which act as UV filters when incorporated in a carrier in amounts ranging from 0.1-50% by weight.
A concise totalsynthesis of the complex guanidinium toxin KB343 is reported traversing through an unusual sequence of chemoselective transformations and strategic skeletal reorganization. The absolute configuration is confirmed through an enantioselective route, and the structures of all key intermediates and the natural product itself are unassailably confirmed through X-ray crystallographic analysis