Synthetic efforts toward the synthesis of octalactins
摘要:
Octalactin B was synthesized from the commercially available methyl-3-butenoate and isobutyraldehyde, using enantioselective allyl- and crotyltitanations to control the stereogenic centers at C3, C4, C7, C8, and C13. Moreover, the two other key-step reactions are a cross-metathesis reaction and a lactonization, using the effective anhydride MNBA, to build up the eight-membered ring lactone. (C) 2008 Elsevier Ltd. All rights reserved.
Octalactin A, an antitumor agent containing an eight-membered lactone moiety, has been stereoselectively prepared by means of enantioselective aldol reactions of selected silyl enolates with achiral aldehydes, promoted by a chiral Sn(II) complex. The medium-sized lactone part was effectively constructed by way of a new and rapid mixed-anhydride lactonization using 2-methyl-6-nitrobenzoic anhydride
A method for the synthesis of octalactin B is established via a new and quite effective mixed-anhydride lactonization for the synthesis of an eight-membered ring moiety using 2-methyl-6-nitrobenzoic anhydride with DMAP. Both an optically active linear precursor of the lactone and a sidechain of octalactins are prepared by the enantioselective aldol reaction of ketene silyl acetals with aldehydes.
synthesized in a direct, and efficient manner. Lactone 1 was made using a substrate controlled lactonization reaction using the carbodiimide EDCI and two crotylborane additions were used to access the precursor hydroxyacid. The importance of proper substitution in the hydroxyacid tether is noted for successful medium-ring lactonization. Synthesis of the sidechain vinyl iodide 2 employed an asymmetric allenylboronate
β-Hydroxy Esters as Malonic Semialdehyde Proelectrophiles in Enantioselective Butadiene-Mediated Crotylation: Total Synthesis of Octalactins A and B
作者:Jessica Wu、Michael J. Krische
DOI:10.1021/acs.orglett.4c01644
日期:2024.6.7
Tractable and commercially available esters (and amides) of β-hydroxypropionic acid serve as malonic semialdehyde proelectrophiles in enantioselective ruthenium-catalyzed hydrogen autotransfer crotylations mediated by butadiene. Through iterative asymmetric butadiene-mediated crotylations of ethyl 3-hydroxypropanoate, total syntheses of the polyketide natural products octalactin A and B were achieved
易处理和市售的 β-羟基丙酸酯(和酰胺)在丁二烯介导的对映选择性钌催化氢自转移邻电中用作丙二醛亲电试剂。通过迭代不对称丁二烯介导的 3-羟基丙酸乙酯 crotylatation,聚酮天然产物八乳酸酯 A 和 B 的完全合成以比以前可能的步骤更少。