Cholecystokinin (CCK) is a 33 amino acid peptide which acts as a digestive hormone in peripheral tissues and functions as a neurotransmitter, widely distributed throughout the brain and central nervous system. Two types of CCK receptors exist, those primanly located in peripheral tissues, CCK, receptors, and those primarily located in the brain and central nervous system, CCK2 receptors. Tetronothiodin 1 is a recently discovered potent CCK2 receptor antagonist Isolated from the culture Streptomyces sp NR0489 It consists of an oxaspirobicyclic unit and a functionalized tetrahydrothiophene moiety, linked by a macrocyclic framework. This thesis details the first studies towards the synthesis of the substituted tetrahydrothiophene moiety of tetronothiodm Four different approaches were attempted; a route in which the key step proceeded via a nitro-aldol reaction, a dicarboxylic acid cyclisation route, cyclisations of substituted butadlenes, and finally 1,3-dlpolar cycloaddition reactions of novel thiocarbonyl yhdes and dipolarophiles.