ChemInform Abstract: A Friedel-Crafts Cyclization Approach Toward Cephalotaxine.
Abstract
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ChemInform Abstract
N-Protection of the azepinone (I) with the anhydride (II) followed by reaction with methyllithium (IV) yields the ring-opened carbinol (V) which is cyclized with 4-toluenesulfonic acid to produce the spiro compound (VI). Ozonolysis of (VI) forms the amino ketone (VII) which is deprotected and then coupled with the sulfonates (VIII) to give the N-alkylation products (IX). Only the derivative (IXa) is cyclized in polyphosphoric acid, producing the cephalotaxine skeleton (Xa).
