ABSTRACrThe extremely chemically resistant component of the cell wall of spores, polens, and some microorganisms, sporopolenin, is generaly accepted to be derived from carotenoids or carotenoid esters. However, we report here that '3C NMR analyses of sporopoUenin from several sources shows that this widely held view is incorrect, with one possible exception. Sporopollenin is not a unique substance but rather a series of related biopolymers derived from largely saturated precursors such as fatty adds. The biopolymers contain widely varying amounts of oxygen in the form of ether, hydroxyl, carboxylic acid, ester, and ketone groups.The outer cell wall, or exine, of many spores, pollens, and certain microorganisms is made of sporopollenin. The
Lupeol (1), said to be the most abundant of the pentacyclic triterpenes,1 became of interest to us, notThe goal of the synthesis was the pentacyclic ketal ester 2 which embodies essentially all the asymmetry of (11) Although formally unnecessary, we also converted our (±)-2 to (±)-lupeol, but because of the small scale on which we carried out this transformation, the melting point (202-204°) of our material may be low.
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