Showing papers in "Tetrahedron in 1994"

TL;DR: The use of chiral oxazolines as ligands in asymmetric catalysis has been extensively studied in the literature as mentioned in this paper, with a large number of important publications detailing oxazoline-related chemistry, suggesting that research in this area, as in synthetic organic chemistry in general, has yet to mature.

TL;DR: In this article, a meso-substituted dipyrromethane with an aldehyde was shown to be compatible with aliphatic or aromatic aldehydes.

TL;DR: New glycosphingolipids, named agelasphins, have been isolated by antitumor and immunostimulatory bioassay-guided purification from an extract of a marine sponge, Agelas mauritianus.

TL;DR: In this paper, a modular building block strategy for the covalent assembly of porphyrin-containing model systems is presented, where the major design constraints are to achieve directed coupling of free base and/or metalloporphrin building blocks in dilute solution under non-acidic non-metalating conditions.

TL;DR: The chiral epoxidation of olefins with per&d8 and monooxygenases with cytochromes P-450 shows good chiral recognition ability, and the chiral reagents used in this synthesis show low levels of chiral specificity.

TL;DR: In this article, a series of Pd allyl complexes are shown to be highly reactive catalysts for the reaction between (E,E)-1,3-diphenyl-2-propenyl acetate and dimethyl malonate ion; the enantiomer excess varies between 67% and 98% depending on how the reaction is conducted.

TL;DR: In this paper, the steric properties of the ester group have a profound influence on enantioselectivity in the epoxidation reaction, with bulkier esters affording highest ee's.

TL;DR: In this article, the use of Schiff base substrates in amino acid synthesis is briefly reviewed, and a new active catalyst species is proposed for asymmetric PTC alkylation of active methylene compounds.

TL;DR: On the basis of the newly proposed hypothesis on the mechanism of asymmetric induction, highly efficient (salen)manganese(III) complex was constructed as a catalyst for asymmetric epoxidation.

TL;DR: Variolin B (1), a new type of pyridopyrrolopyrimidine alkaloid with antitumour and antiviral properties, has been isolated from the Antarctic sponge Kirkpatrickia varialosa, and its structure determined by X-ray crystallography.

TL;DR: The TADDOLate method of adding dialkyl zinc reagents to aldehydes enantioselectively is compared with other Lewis acid or amino alcohol mediated methods.

TL;DR: In this article, aryl and alkyl triisopropoxy titanium reagents (free of Li, Mg, or Zn salts) are prepared from the corresponding Li or Grignard reagents and ClTi(OiPr)3, with careful removal of salts (centrifugation of LiCl or of dioxane·MgX2, and addition of 12crown-4).

TL;DR: In this paper, a cyano group was introduced on the binaphthyl skeleton by nickel-catalyzed cyanation of 2-diphenylphosphinyl-2-trifluoromethanesulfonyloxy 1,1′-binaphTHyl.

TL;DR: A series of chiral enantiomerically pure mercaptoaryl-oxazolines has been synthesized as discussed by the authors, and copper(I) thiolate complexes derived from these ligands proved to be efficient catalysts for the 1,4-addition of Grignard reagents to cyclic enones.

TL;DR: A short synthesis of carbazoloquinone cyanamides based on a palladium-promoted oxidative coupling was described in this article, where the key step was described as a short synthesis.

TL;DR: In this article, an asymmetric reductive reductive amination procedure for the conversion of ketones to chiral hydrazines and amines was described. But the reduction products, N-acylhydrazines, were converted to hydrazine or amine through hydrolysis or treatment with samarium(II) iodide, respectively.

TL;DR: The history of ciguatera research at the University of Hawaii during the past 35 years revolves around the search for a molecular structure and strays upon some unexpected paths, far removed from the original goal as mentioned in this paper.

TL;DR: The palladium-catalyzed reaction of 2-alkynylbenzamides gave 3-alkylidenisoindole derivatives as discussed by the authors, which is the same as 3-carboxylates.

TL;DR: Two pyridopyrrolopyrimidine alkaloids, variolin A (2) and N(3′)-methyl tetrahydrovariolin B (3), have been isolated from the Antarctic sponge Kirkpatrickia varialosa, and their structures determined by X-ray crystallography and interpretation of spectral data respectively as discussed by the authors.

TL;DR: The deprotonation of (R)- or (S)-1-phenylethyl N,N-diisopropyl carbamate with s-butyllithium/TMEDA in unpolar solvents (e.g. ether or hexane) at −78°C produces configurationally stable ion pairs which are substituted stereospecifically by different electrophiles as mentioned in this paper.

TL;DR: In this article, a variety of Hantzsch esters have been oxidized with potassium permanganate, and the structure of the final products dramatically depends on the nature of the 4-substituent and on the experimental conditions.

TL;DR: A pentacyclic compound was synthesized as an important intermediate of antitumor antibiotic dynemicins as discussed by the authors, using the Heck reaction using catalytic Pd reagent, and an unusual spiro ring compound was found to be produced via intramolecular conjugate addition.

TL;DR: In this article, the synthesis of pyrano-and furano-sugar lactams from the corresponding corresponding corresponding lactones, in a five-step sequence, is described.

TL;DR: In this article, the condensation reactions of acetophenone, cyclohexanone, isophorone, phenylacetonitrile, p-nitrophenylacetitrile and indene with benzaldehyde were studied in water in heterogeneous phase in the presence and absence of anionic and cationic surfactants such as SLS, CTACl, (CTA)2SO4 and CTAOH.