?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fd-scholarship-dev.library.pitt.edu%2F9433%2F&rft.title=Total+Synthesis+of+(%2B)-Dactylolide.+Studies+on+the+Cascade+Cyclization+Reactions+of+Epoxides%2FPolyepoxides+Initiated+by+Single+Electron+Transfer&rft.creator=Wan%2C+Shuangyi&rft.description=The+total+synthesis+of+the+marine+macrolactone+(%2B)-dactylolide+was+achieved+in+a+highly+convergent+and+efficient+way+(Scheme+I).+The+route+involves+the+coupling+of+two+functionalized+fragments+of+the+molecule%2C+an+%C2%A6%C3%81%2C%C2%A6%C3%82-unsaturated+aldehyde+and+a+1%2C3-syn-diol%2C+to+form+a+cyclic+%C2%A6%C3%81%2C%C2%A6%C3%82-unsaturated+cyclic+acetal.+Both+enantiopure+fragments+arise+from+asymmetric+vinylogous+Mukaiyama+aldol+reactions.+The+key+transformations+in+this+synthesis+include+a+sequential+Peterson+olefination%2FPrins+cyclization+reaction+to+construct+the+2%2C6-cis-disubstituted-4-methylenetetrahydropyran+core+efficiently+and+stereoselectively%2C+a+Mislow-Evans+selenoxide-selenate+%5B2%2C3%5D+sigmatropic+rearrangement+to+transpose+allylic+alcohol+transposition+and+an+intramolecular+Horner-Emmons+macrocyclization.A+systematic+study+on+the+cascade+cyclizations+of+epoxides%2Fpolyepoxides+initiated+by+single+electron+transfer+has+been+carried+out+(Scheme+II).+Four+monoepoxides+and+six+diepoxides+were+tested.+The+results+showed+that+the+bicyclo%5B3.1.0%5D+epoxonium+ion+intermediates+formed+in+the+cyclization+favor+5-exo-cyclization+in+the+nonpolar+solvent+(1%2C2-dichloroethane)+while+in+the+polar+solvent+(CH3CN)%2C+they+prefer+6-endo-selectivity.+However%2C+the+bicyclo%5B4.1.0%5D+epoxonium+ion+intermediates+usually+give+7-endo+regiochemical+selectivity+in+the+presence+of+substitution-induced+bias.+However%2C+without+the+substituent+effect%2C+6-exo+and+7-endo-cyclizations+are+two+competitive+pathways.&rft.date=2008-01-17&rft.type=University+of+Pittsburgh+ETD&rft.type=PeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fd-scholarship-dev.library.pitt.edu%2F9433%2F1%2Fwans_etd2007.pdf&rft.identifier=++Wan%2C+Shuangyi++(2008)+Total+Synthesis+of+(%2B)-Dactylolide.+Studies+on+the+Cascade+Cyclization+Reactions+of+Epoxides%2FPolyepoxides+Initiated+by+Single+Electron+Transfer.++Master's+Thesis%2C+University+of+Pittsburgh.++++(Unpublished)++