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1.
A convergent synthesis of the key synthetic intermediate of hemibrevetoxin B was achieved via the intramolecular allylation of an α-chloroacetoxy ether and subsequent ring-closing metathesis. 相似文献
2.
Concise construction of the trans-fused 7/7/6/6 tetracyclic ether part of hemibrevetoxin B (1) was achieved by a convergent strategy based on coupling reaction of an acyl anion equivalent, reductive cyclization of an α,ε-dihydroxyketone, and introduction of a methyl group at the central ring junction by the Nicolaou method. The resultant tetracyclic ether was transformed into the known intermediate, which was already converted to 1 by the Yamamoto group, thereby completing the formal total synthesis of 1. 相似文献
3.
Synthesis of the ABCDE ring fragment of ciguatoxins has been achieved in a highly stereocontrolled and convergent manner via the B-alkyl Suzuki-Miyaura coupling-based approach. 相似文献
4.
Masayuki Inoue 《Tetrahedron letters》2004,45(10):2053-2056
We report a new reaction for the direct construction of O,S-acetals, key intermediates in the assembly of fused polycyclic ethers. α-Fluorosulfides and secondary alcohols were coupled by the action of Yb(OTf)3 to generate O,S-acetals in high yield. The neutral and selective nature of the reaction should be useful for synthesizing natural and artificial polyethers with multisensitive functionalities. 相似文献
5.
《Journal of carbohydrate chemistry》2013,32(6-7):403-416
Abstract Glucuronic acid‐containing di‐ and trisaccharide thioglycoside building blocks, ethyl (benzyl 2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranosyluronate)‐(1 → 2)‐3‐O‐allyl‐4,6‐di‐O‐benzyl‐1‐thio‐α‐D‐mannopyranoside, ethyl (benzyl 2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranosyluronate)‐(1 → 2)‐6‐O‐acetyl‐3‐O‐allyl‐4‐O‐benzyl‐1‐thio‐α‐D‐mannopyranoside and ethyl (2,3,4‐tri‐O‐benzyl‐β‐D‐xylopyranosyl)‐(1 → 4)‐[(benzyl 2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranosyluronate)‐(1 → 2)]‐3‐O‐allyl‐6‐O‐benzyl‐1‐thio‐α‐D‐mannopyranoside, corresponding to repetitive structures in the capsular polysaccharide (CPS) of Cryptococcus neoformans, have been synthesized. The blocks contain an orthogonal allyl group in the 3‐position of the mannose residue to allow formation of the (1 → 3)‐linked mannan backbone of the CPS and benzyl ethers as persistent protecting groups to facilitate access to acetylated target structures. The glucuronic acid moiety was introduced using an acetylated trichloroacetimidate donor and the xylose residue employing the benzoylated bromo sugar to ensure β‐selectivity in the couplings. Exchange to benzyl protecting groups was then performed at the di‐ or trisaccharide level. Assembly of suitable blocks employing DMTST as promoter in diethyl ether then afforded, in high yield and with stereoselectivity, a protected pentasaccharide corresponding to a C. neoformans serotype D CPS structure. 相似文献
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8.
A.R. Nazemi 《Communications in Nonlinear Science & Numerical Simulation》2012,17(4):1696-1705
This paper proposes a feedback neural network model for solving convex nonlinear programming (CNLP) problems. Under the condition that the objective function is convex and all constraint functions are strictly convex or that the objective function is strictly convex and the constraint function is convex, the proposed neural network is proved to be stable in the sense of Lyapunov and globally convergent to an exact optimal solution of the original problem. The validity and transient behavior of the neural network are demonstrated by using some examples. 相似文献
9.
Layne T. Watson 《Mathematical Programming》1980,19(1):92-101
The Chow—Yorke algorithm is a nonsimplicial homotopy type method for computing Brouwer fixed points that is globally convergent. It is efficient and accurate for fixed point problems. L.T. Watson, T.Y. Li, and C.Y. Wang have adapted the method for zero finding problems, the nonlinear complementarity problem, and nonlinear two-point boundary value problems. Here theoretical justification is given for applying the method to some mathematical programming problems, and computational results are presented.This work was partially supported by NSF Grant MCS 7821337. 相似文献
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