Synthesis of Natural Products Containing Hydroxylated Pyrrolidines
This thesis contains two parts. The first part describes the synthesis of orthogonally protected L-2,3-cis-3,4-trans-DHP 1.44 in eleven steps starting from L-arabinose via double displacement of bis-mesylate 2,8. The second part describes the synthesis of the spiroacetal fragment of the alkaloid broussonetine H. (±)-2-(3-Bromopropyl)-1,7-dioxaspiro[5.5]undecane (3.38) was prepared in nine steps from 1,4- butanediol (1.49), propargyl bromide (3.33) and ?-valerolactone (1.51). Enantioenriched material, namely (2S)-2-(3-bromopropyl)-1,7-dioxaspiro[5.5]undecane (4.2) was synthesized in thirteen steps from (2S)-pentane-1,2,5-triol (4.14), trimethylsilylacetylene (4.22) and ?-valerolactone (1.51). The enantiomeric excess of the derived alcohol, (4S)-3-(1,7-dioxaspiro[5.5]undec-2-yl)propan-l-ol (4.28) was measured by its conversion into a Mosher ester derivative 4.28. This thesis also describes the progress towards the synthesis of the dihydroxypyrrolidine fragment 5.28 of broussonetine H from L-sorbose (1.48).