A flexible total synthesis of the 2-nitropyrrole-derived marine natural product, (+)-heronapyrrole C, is reported. The approach is based on regioselective access to key building blocks containing the rare 4-substituted 2-nitropyrrole motif. Sharp less asymmetric epoxidation and dihydroxylation and a Shi epoxidation were used to introduce the five stereogenic centers of the bis-THF-diol side chain. The N-benzoyloxymethyl (Boz) protecting group was crucial for functionalization of the 2-nitropyrrole moiety and enabling final deprotection under mild conditions.
Synthesis of four stereoisomers of the higher dipteran juvenile hormone III bisepoxide
摘要:
The 6S,7S,10R-, 6S,7S,10S-, 6R,7R,10S- and 6R,7R,10R-stereoisomers of the juvenile hormone III bisepoxide from higher Dipteran insects have been synthesised in high stereoisomeric purity. The route involves Sharpless epoxidation of geraniol to enantiomeric epoxyalcohols, which are each elaborated via separable diastereomeric bromohydrins.
Total Synthesis of <i>ent</i>-Dioxepandehydrothyrsiferol via a Bromonium-Initiated Epoxide-Opening Cascade
作者:Jessica Tanuwidjaja、Sze-Sze Ng、Timothy F. Jamison
DOI:10.1021/ja9052366
日期:2009.9.2
In the first totalsynthesis of ent-dioxepandehydrothyrsiferol, the signature trans-anti-trans 7,7,6-fused tricyclic polyether framework was constructed in a single bromonium-initiated epoxide-openingcascade that incorporates both endo- and exo-selective epoxide openings, each directed by the substitution pattern of the epoxide (methyl groups). This study thus demonstrates the feasibility of a possible
Bis-tetrahydrofurans 1a and 1b, containing four chiral centers, are obtained with a 90 % isomeric purity from geranyl and neryl chlorides in four steps including two stereoselective cyclizations.
Total syntheses of the squalene-derived halogenated polyethers ent -dioxepandehydrothyrsiferol and armatol A via bromonium- and Lewis acid-initiated epoxide-opening cascades
作者:Brian S. Underwood、Jessica Tanuwidjaja、Sze-Sze Ng、Timothy F. Jamison
DOI:10.1016/j.tet.2013.04.041
日期:2013.6
Herein we describe in full our investigations leading to the first total syntheses of ent-dioxepandehydrothyrsiferol and armatol A. Discovery of a bromonium-initiated epoxide-opening cascade enabled novel tactics for constructing key fragments found in both natural products and have led us to revise the proposed biogeneses. Other common features found in the routes include convergent fragment coupling strategies to assemble the natural products' backbones and the use of epoxide-opening cascades for rapid constructions of the fused polyether subunits. Through de novo synthesis of armatol A, we elucidate the absolute and relative configuration of this natural product. (C) 2013 Elsevier Ltd. All rights reserved.