Microwave-assisted regioselective synthesis of natural 6-prenylpolyhydroxyisoflavones and their hydrates with hypervalent iodine reagents

Microwave-assisted oxidative rearrangement of 3'-iodotetraalkoxychalcones with hypervalent iodine such as [hydroxy(tosyloxy)iodo]benzene or [bis(trifluoroacetoxy)iodo] benzene, followed by microwave-mediated hydrolysis and in situ cyclization of the resultant acetals gave 6-iodotrialkoxyisoflavones. Pd(0)-catalyzed coupling reaction of the 6-iodoisoflavones with 2-methyl-3-butyn-2-of under microwave irradiation gave 6-alkynylisoflavones, whose hydrogenation gave the respective hydrates of wighteone, lupisoflavone and derrubone. Wighteone (1a), lupisoflavone (1b) and derrubone (1c) were obtained by dehydration of their respective hydrates under microwave irradiation. (c) 2006 Elsevier Ltd. All rights reserved.