SYNTHESIS OF NATURALLY OCCURRING BENZOFURANS AND LIGNANS (ARIENSIN, PHYTOALEXINS, MORACINS, SAINFURAN)

Total syntheses of seven naturally occurring benzofurans and three naturally occurring lignans are presented in this dissertation along with an investigation of the structure of a Diels-Alder adduct obtained from two equivalents of methyl propiolate and 6-methoxy-2-isopropenylbenzofuran.; The syntheses of four 2-arylbenzofurans, the phytoalexins, moracins A and B, and the insect feeding deterrents, methylsainfuran and sainfuran, by employing an intramolecular Wittig reaction to forge the benzofuran heterocycle are described in Chapter 1.; Chapter 2 offers efficient syntheses of two 2-acetylbenzofurans, calebertin and caleprunin A, achieved by a one-step formation of the 2-acetylbenzofuran nucleus from the appropriately substituted salicylaldehyde and chloroacetone.; The synthesis of the 2-isopropenylbenzofuran, isoeuparin, from 3-iodo-2,4-dihydroxyacetophenone and cuprous isopropenylacetylide is presented in Chapter 3. Also this chapter describes an improved synthesis of 6-methoxy-2-isopropenylbenzofuran and the Diels-Alder adduct it forms with 2 equivalents of methyl propiolate. Two possible structures for this adduct and mechanisms for their formation are posed.; Use of diethylsuccinate dianion equivalent to construct the diarylbutane lignan skeleton for ((+OR-))-ariensin, an extract from the bark of the tree Bursera ariensis HBK, long known as a cicatrizing agent in folk medicine, is the subject of Chapter 4. This synthesis also afforded dihydrocubebin and heliobuphthalmin, also extractives of widely used folk remedies. Stereochemical control was achieved by use of the fact that both meso- and d,1- diarylsuccinic acids give only the trans-diarylsuccinic anhydride.