Evolution of a short route to strychnine by using the samarium-diiodide-induced cascade cyclization as a key step
This comprehensive report accounts the development of a highly diastereoselective samarium diiodide-induced cascade reaction of substituted indolyl ketones. The complexity-generating transformation with SmI2 allows the diastereoselective generation of three stereogenic centers including one quaternary center in one step. The obtained tetra- or pentacyclic dihydroindole derivatives are structural motifs of many monoterpene indole alkaloids, and their subsequent transformations gave way to one of the shortest approaches towards strychnine (14 % overall yield in ten steps, or 10 % overall yield in eight steps). During the course of this report we discuss the influence of substituents on the cyclization step, plausible mechanistic scenarios for the SmI2-induced cascade reaction, diastereoselective reductive amination, and regioselective dehydratization protocols towards the pentacyclic core structure of strychnos alkaloids.
A short formal total synthesis of strychnine with a samarium diiodide induced cascade reaction as the key step
Brevity is the soul of wit! The power of SmI2-induced cyclizations has been demonstrated by the shortest formal total synthesis of (±)-strychnine to date, which features a new cascade reaction. Only one protective-group transformation is required. The ketyl-aryl coupling/acylation cascade also efficiently proceeds with other indole derivatives with excellent diastereoselectivities.
Conformationally constrained analogues of diacylglycerol. 12. Ultrapotent protein kinase C ligands based on a chiral 4,4-disubstituted heptono-1,4- lactone template
Conformationally constrained analogues of diacylglycerol (DAG) built on a 5-[(acyloxy)methyl [-5-(hydroxymethyl)tetrahydro-2-furanone template (1, Chart 1) were shown previously to bind tightly to protein kinase Cα (PK- Cα) in a stereospecific manner. The
INTRAMOLECULAR CATALYSIS IN THE ENOLISATION REACTIONS OF 4-OXOHEPTANEDIOIC ACID AND ITS MONOETHYL ESTER
Measurements have been made on the rates of iodination of 4-oxoheptanedioic acid (4-ketopimelic acid) and its monoethyl ester in dilute hydrochloric and self-buffered aqueous solutions at 25 deg C.The rates are independent of the halogen concentration and represent the rates of enolisation of the substrates.In pure water, large acceleration relative to acetone were observed and attributed to intramolecular acid catalysis.In self-buffered solutions the only important mechanism for both substrates is intramolecular base catalysis.For the dicarboxylic acid in its mono-dissociated form no evidence of bifunctional catalysis was found.It was confirmed that for the enolisation reactions of carbonyl compounds very special reaction conditions and/or structure effects are required in order to detect bifunctional catalysis.This is apparently the case even when bifunctional catalysis should in principle be promoted by intramolecular assistance by two carboxyl groups as in the case of 4-oxoheptanedioic acid.
Cox, Brian G.,Maria, Paolo De
p. 369 - 373
(2007/10/02)
Novel Synthesis of (R)-(+)-γ-Butyrolactone-γ-3-propionates by Fermenting Baker's Yeast and Enantiomeric Purity Determination Using NMR Technique
Optically pure (R)-(+)-γ-butyrolactone-γ-3-propionates 1 were prepared by reducing the precourser, 3-ketoheptane-1,5-dicarboxylic acid monoesters, with fermenting baker's yeast.The optical purity (more than 98percent) was determined by means of HPLC analysis and NMR determination.
Moriuchi, Fumio,Muroi, Hisae,Aibe, Hiroshi
p. 1141 - 1144
(2007/10/02)
More Articles about upstream products of 1506-55-4