Two new improved approaches to the synthesis of coumarin-based prodrugs
摘要:
Our laboratory has recently reported the development of a coumarin-based, esterase-sensitive prodrug system for the preparation of prodrugs of amines, peptides, and peptidomimetics. Biological evaluations including animal studies have demonstrated me clinical potential of this prodrug system. However, the original synthetic method used required a long sequence of reactions with a relatively low overall yield. In this report, we describe two new approaches to the synthesis of these coumarin-based prodrugs. The first approach is a photochemical approach taking advantage of the photoisomerization of cinnamic acid and its derivatives. The second approach is through the catalytic hydrogenation of a triple bond for the generation of me cis double bond in the coumarinic acid moiety. Both approaches allow for the synthesis of these prodrugs in fewer steps with much improved overall yield. (C) 1999 Elsevier Science Ltd. All rights reserved.
(Ethoxycarbonyliodomethyl)triphenylphosphonium Iodide: A Convenient Reagent for the Direct Synthesis of β-Substituted Propiolic Acids<i>via</i>the Corresponding Esters
作者:Jaques Chenault、Jean-François E. Dupin
DOI:10.1055/s-1987-27983
日期:——
Reaction between (ethoxycarbonyliodomethyl)triphenylphosphonium iodide, potassium carbonate, and various aromatic or aliphatic aldehydes in a liquid solid two phases system gives ß-substituted propiolic esters. The corresponding acids are obtained in good yield by hydrolysis.
β-Deprotonation by lithium di-isopropylamide. Vinyl carbanions from oxygen heterocycles in the synthesis of carboxylic acids in the benzofuran, flavone, and coumarin series and in the regiospecific acylation of 2,6-dimethylchromone
作者:Ana M. B. S. R. C. S. Costa、Francis M. Dean、Michael A. Jones、Dennis A. Smith、Rajender S. Varma
DOI:10.1039/c39800001224
日期:——
Lithiumdi-isopropylamide at –70 °C can remove the α-proton frombenzofuran in the absence of activating groups and the β-proton if such groups are present; in flavone and 4-methoxycoumarin β-deprotonation occurs readily and the carbanions are easily carboxylated giving acids not previously accessible, while in 2,6-dimethylchromoneβ-deprotonation is kinetically favoured allowing 3-acylation to be
A cationic rhodium(I)/(R)-H8-BINAP or (R)-Segphos complex catalyzes an intramolecular [2 + 2 + 2] cycloaddition of unsymmetrical dienynes, leading to fused tri- and tetracyclic cyclohexenes bearing two tertiary or quaternary carbon centers in high yields with high enantio- and diastereoselectivity.