SIMPLE SYNTHESIS OF 5-SUBSTITUTED RESORCINOLS - A REVISITED FAMILY OFINTERESTING BIOACTIVE MOLECULES

The reaction of 3,5-dimethoxybenzyl trimethylsilyl ether (3) with diff erent aldehydes (n-PrCHO, n-C11H23CHO, MeCHO, PhCHO) in the presence o f lithium powder and a catalytic amount of naphthalene (4 mol %) gave, after hydrolysis, the expected alcohols 4 in moderate yields. The deh ydroxylation of these compounds through the corresponding mesylates 5 or directly from benzylic derivatives by catalytic hydrogenation, affo rded compounds 6, which are finally demethylated to yield 5-alkyl-3,5- dihydroxyresorcinols, such as olivetol (7a), grevillol (7b), 1,3-dihyd roxy-5-propylbenzene (7c), or dihydropinosilvine (7d). Dehydration of alcohol derivatives 4 followed by demethylation led to hydroxylated st ilbene-type structures, such as pinosilvine (9d), resveratrol (9e), or piceatannol (9f), which in some cases can be hydrogenated to give sat urated molecules such as combretastanin B-4 tetramethyl ether (6f) or chrysotobibenzyl (6g). Finally, when the naphthalene-catalyzed lithiat ion of compound 3 was performed in the presence of other electrophiles [Me(3)SiCl, t-BuCHO, CH3(CH2)(4)CHO, 4-Me(3)SiOC(6)H(4)CHO, (CH2)(5)C O, PhN=C=O, PhN=CHPh], the expected reaction products 12 were isolated , after hydrolysis.