Synthetic Studies Towards Alkaloid 205B, Yaoshanenolide B And(-)-salprzelactone

The dissertation focuses on(?)synthetic studies on alkaloid 205B(?)synthetic studies on Yaoshanenolide B(?)studies on the First Asymmetric Total Synthesis of(-)-salprzelactone.Alkaloid 205 B,one of the compounds isolated from skin extracts of the Panamanian frog Dendrobates pumilio,possesses an unusual and unique 8b-azaacenaphthylene ring system.We respectively by ene-alkyne cyclization reaction;RCM reaction form a nine-member ring;RCM reaction step by step form a six-member ring and a five-member ring;and intramolecular aza-Prins cyclization reaction on the synthesis of 205 B.Finally,we have accomplished the total synthesis of 1-118 from 1-74 in seven steps with a 22% overall yield.1-118 was the diastereoisomer of 205 B,which might also possess some unveiled interesting activities.Yaoshanenolide B possess a tricyclic spirolactone,which was isolated from the bark of Machilus yaoshansis by Shi and co-workers.Yaoshanenolide B has been found to exhibit nonselective cytotoxic activity against some human cancer cell lines.Based on the biosynthetic scenario,we commenced by reacting diene 2-37 with racemic dienophile 2-24 in intermolecular Diels-Alder reaction to form the tricyclic spirolactone 2-23.The tricyclic spirolactone 2-23 was then treated with Dodecanal in the tandem Micheal-Aldol reaction condition failed to deliver the desired product 2-30.(-)-salprzelactone,a seco-norabietane diterpenoid with a new carbon skeleton,was isolated by Wu and co-workers from the roots of Salvia przewalskii in 2013.(-)-salprzelactone showed stronger antibacterial activity.The naphthamide 3-22 and 3-26 could be generated from aldehyde 3-21 and the known enatiomerically pure compound 3-33 by a stereoselective aldol reaction.Treatment of 3-22 with acid provided(-)-salprzelactone(3-1).Treatment of 3-26 with acid provided 14-epi-(-)-salprzelactone(3-27),a diastereoisomer of(-)-salprzelactone(3-1).