Highly Efficient and Selective Procedures for the Synthesis of γ-Alkylidenebutenolides via Palladium-Catalyzed Ene-Yne Coupling and Palladium- or Silver Catalyzed Lactonization of (Z)-2-En-4-ynoic Acids. Synthesis of Rubrolides A, C, D, and E
New Concise and Efficient Synthesis of Rubrolides C and E via Intramolecular Wittig Reaction
作者:Nilesh P. Tale、Amol V. Shelke、Girdharilal B. Tiwari、Prerana B. Thorat、Nandkishor N. Karade
DOI:10.1002/hlca.201100351
日期:2012.5
A short total synthesis of rubrolides C and E has been achieved in four steps, using readily available 4‐methoxyacetophenone, 2‐bromoacetic acid, and the appropriate aromatic aldehyde, in 46 and 45% yield, respectively. Key reactions involved are α‐tosyloxylation of the aryl methyl ketone, intramolecularWittigreaction, Knoevenagel condensation, and demethylation.
The Pd(0)-catalyzed cross coupling between 4-bromo-2(5H)-furanones and arylboronic acids provides the corresponding 4-aryl-2(5H)-furanones in yields of 61-85%. By using this method in conjunction with furanolate chemistry, the marine antibiotics rubrolide C and E have been synthesized in highly efficient fashion (4 steps, overall yield = 61 and 56% respectively) from beta-tetronic acid. (C) 1998 Elsevier Science Ltd. All rights reserved.