Synthesis of Carba-strigol analogues

Abstract

This thesis describes the synthesis of novel strigol analogues in which the enol-ether oxygen in th analogues has been replaced by a methylene group. These compounds are called carba-strig analogues. The GR 5 carba-strigol analogue { 3-Methyl-5[(-3-ethanylidene-4,5-dihydro-: oxo-2(3H)furanone)-1')-2(SH)furanone} was prepared by a Wittig reaction of th a-triphenylphosphorane of y-butyrolactone and 5-[(1-oxoethyl)-2'-]-3-methyl-2(SH)furanone. The othe three carba-strigol analogues, E-3-Methyl-5{[-3-ethanylidene)-1')-3,3a,6,6a-tetrahydro-2H-cyclc penta[b]furan-2-one}-2(SH)furanone, E-3-Methyl-5{[(-3-ethanylidene)-1']-3,3a,4,8b-tetrahydrc -4H-indeno[1,2-b]-furan-2-one }-2(3H)furanone and E-3-Methyl-5{ [(-3-ethanylidene)-1')-3,3,3a,4,6a -tetrahydro-4H-cyclopenta[b)furan-2-one }-2(3H)furalnone were prepared by coupling the respectiv parent lactones to 5-[(1-oxoethyl)-2-)-3-methyl-2(SH)furanone using LDA an (methoxythiocarbonyl)disulphide. An alternative approach to the synthesis of E-3-Methyl-5 { [-3-ethanyl idene)-1']-3,3a,6,6a-tetrahydro-2H-cyclopenta[b)furan-2-one}-2(SH)furanone, and E-3-Methyl -5{[(-3-ethanylidene)-1')-3,3a,4,8b-tetrahydro-4H-indeno[1,2-b]-furan-2-one}-2(3H)furanone using the Wittig-Homer method is also described. The facile synthesis of 5-[(1-oxoethyl)-2-] and 5-brom substituted 3-methyl-2(SH)furanones as well as model compounds for the carba-strigol analogues of GF 7, GR 28 and GR 24 {E-3-Benzylidene-3,3a,6,6a-tetrahydro-6H-cyclopenta[b)-furan-2-one, E-3 Benzylidene-3,3a,4,6a-tetrahydro-4H-cyclopenta[b)-furan-2-one and E-3-Undecylidene-3,3a,4,8b~ -tetrahydro-4H-indeno[1,2-b]-furan-2-one}, is also reported.