1. Total synthesis of quadronoids through radical cyclization 2. total synthesis of (+) jujuyane through [5+3] cycloaddition reaction

Abstract

Development of new synthetic methodologies and their application to the total synthesis of natural products were studied. In the first part, core ring skeleton of Quadronoids was synthesized through tandem radical reaction sequence, which invloved the cyclopropyl methyl radical medicated rearrangement. This reaction was used as the key step in the total synthesis of Suberosenone and a formal total synthesis of Quadrone. Enediyne 137, prepared from β-keto ester 126, undergo tributyltin mediated radical reaction to form $[4.3.2.0 ^{1,5}]$ undecane 138. The resulting undecane 138 was converted to Suberosenone and Quadrone through manipulation of functional groups of A and C rings and stereoselective introduction of C-1 unit via 1,4-addition at C-9 position. A noteworthy aspect of this synthesis is one-pot construction of tricyclic ring system of Quadronoids. In the second part, new synthetic methodology for the construction of cyclooctanoids is developed. 3-oxidopyrylium ion, prepared from commercially available furfuryl alcohol, was used for this purpose. Thermal [5+3] cycloaddition reaction of 3-oxidopyrylium ion produced highly functionalized dimer 339, which contained eight-membered ring. This dimer was converted to ketone 355 via 6 steps. Kinetic resolution of ketone was accomplished through adductive formation with (+)-(S)-N,S-dimethyl-S-Phenylsulfoximine, separation and thermolysis of the adduct to regenerate resolved 355. In the advantage of conformational rigidity, (-)-355 was transformed to cyclooctane (-)-364 through stereocontrolled introduction of proper alkyl groups and opening of ether bridge. Stereoselective conversion of exo olefin to methyl group was accomplished by titanium mediated epoxide opening. Total synthesis of (+) Jujuyane was completed from cyclooctanoid (-) 379 via straightforward manners