Showing papers in "Tetrahedron Letters in 1993"

TL;DR: Chiral phosphinoaryl-and phosphinoalkyloxazolines, a new class of chelate ligands, were prepared via convenient routes as mentioned in this paper, and Palladium complexes of the new ligands have proved to be highly effective catalysts for allylic substitution reactions.

TL;DR: In this paper, a series of phosphorus-containing oxazoline ligands has been developed for asymmetric palladium catalysed allylic substitution of 1,3-diphenylprop-2-enyl-1-acetate 12 with the sodium salt of dimethylmalonate.

TL;DR: In this article, the reaction of vinyl boronic acids with the adducts of secondary amines and paraformaldehyde gives tertiary allylamines with the same geometry.

TL;DR: In the presence of tetrakis(triphenylphosphine)palladium, vinyl and aryl halides or triflates react very rapidly in piperidine or pyrrolidine with terminal alkynes to give conjugated enynes as mentioned in this paper.

TL;DR: In this article, head-to-tail cyclic peptides are made by an efficient three-dimensional orthogonal solid phase strategy (Fmoc/tBu/allyl), featuring side-chain anchoring to PAC or PAL supports, selective palladium (O)-catalyzed allyl removal, and resin-bound cyclization mediated by BOP/HOBt/DIEA.

TL;DR: Agelasphins having antitumor activity are the first examples of galactosylceramides containing an α-galactosym linkage.

TL;DR: The structure of a new ciguatoxin congener, CTX3C (1), isolated from cultures of a dinoflagellate Gambierdiscus toxicus was elucidated mainly o

TL;DR: In this paper, the mycelium of a strain of Penicillium sp. stuck on the marine alga Enteromorpha intestinalis was isolated from the mycosphere and its structures were elucidated by spectroscopic analyses.

TL;DR: Pimary hydroxyl groups in partially protected monosaccharide derivatives were selectively oxidised to carboxylic acids using sodium hypochlorite in the presence of catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyl oxy, free radical (TEMPO) as discussed by the authors.

TL;DR: The 1,1′-(azodicarbonyl)dipiperidine (ADDP)-tributylphosphine (TBP) system was developed as a new institute of the Mitsunobu reagent.

TL;DR: In this paper, the use of N,N′-di-(tert-butoxycarbonyl)thiourea 1 in the presence of mercuric chloride provides a very efficient method for the bis-Boc protected guanidine formation of the amino compounds which are highly deactivated either sterically or electronically.

TL;DR: Bis-urethane protected derivatives of 1-guanylpyrazole were prepared and found to readily react with relatively amines at room temperature to produce bis-protected guanidines in good yields.

TL;DR: Microginin, an angiotensin-converting enzyme inhibitory pentapeptide, was isolated from the freshwater blue-green alga Microcystis aeruginosa and its structure was elucidated to be 1 on the basis of 2D NMR data and chemical degradation.

TL;DR: Scandium trifluoromethanesulfonate (Sc(OTf)3) was used as a Lewis acid catalyst in the Diels-Alder reaction.

TL;DR: In this paper, the cross-coupling reaction between arylboronic acids, carbon monoxide (1 atm), and aryls iodides in the presence of palladium catalyst and base provided unsymmetrical biaryl ketones in high yields.

TL;DR: In this article, the second order molecular nonlinear optical properties of push-pull stillbenes can be substantially increased by replacing benzene with thiophene rings, and the properties of several dialkylamino-nitro substituted thiopene based stilbenes are presented.

TL;DR: The reaction of zirconacyclopentenes (1) with alkynes, nitriles, and aldehydes via cleavage of the CβCβ′ bond of 1 and displacement of ethylene by the donors to give the corresponding five-membered ZIRconacycles, providing a convenient means of selectively coupling alkynes with π-donor compounds.

TL;DR: In this article, three representative examples of duplex DNA, each eight base pairs in lenght, have been examined by ion-spray mass spectrometry and the ability to detect base-paired duplex ions in each case further indicates the use of this technique for monotoring noncovalent instructions in biological systems.

TL;DR: An easy and soft method of decomplexation of phosphine-borane complexes, by DABCO, allows its use in situ in asymmetric catalytic hydrogenation of double bonds with metal phosphine complexes as mentioned in this paper.

TL;DR: Altohyrtin A (1 ) has been isolated from the Okinawan marine sponge Hyrtios altum and the plane structure and parts of its relative configurations elucidated.

TL;DR: A facile preparation of polymer bound 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (P-EDC) from commercially available starting materials is described in this article.

TL;DR: In this article, large scale quantities of phosphodiester and phosphorothioate oligonucleotides are synthesized on an aminopolyethyleneglycol derivatized polystyrene (TentaGel) support.

TL;DR: The enantioselectivity in intramolecular C-H insertion reactions of α-diazo β-keto esters catalyzed by dirhodium(II) tetrakis[N-phthaloyl-(S)-phenylalaninate] was found to be substantially improved by evaluation of the alkoxy group of the ester moiety as mentioned in this paper.

TL;DR: In this article, the trisphosgene reaction in the presence of pyridine with a variety of diols including hindered tertiary and 1,3-cyclic Diols provided high yields of cyclic carbonates.

TL;DR: Taxotere, a highly promising anticancer drug, is synthesized through an efficient coupling of 7,10-diTroc-10-deacetylbaccatin III with enantiomerically pure (3R,4S)-1-tBOC-3-EEO- 4-phenylazetidin-2-one which is obtained via chiral ester enolate - imine cyclocondensation.

TL;DR: In this paper, a total synthesis of the potent non-opiate analgesic alkaloid epibatidine is described, in which the key step is a reductive palladium-catalysed Heck-type coupling.

TL;DR: In this paper, a stoichiometric formation of Cu(I)-amidines complexes allows to control the degree of substitution of resulting amidines, which is useful for the condensation of acetonitrile 1a and benzonitrile 2b with primary and secondary amines 2a-g into amidines 3a-j under mild conditions.

TL;DR: An oxazaborolidine derived from N-tosyl (αS,βR)-β-methyltryptophan (1) catalyzes the Diels-Alder reaction of 2-bromoacrolein and furan with 96:4 enantioselectivity, leading to an efficient synthesis of numerous chiral 7-oxabicyclo[2.2.1]heptene derivatives as mentioned in this paper.

TL;DR: Propranolol, a more potent optical isomer of the widely used β-blocker, was conveniently synthesized in a higly enantioselective manner by the lanthanum-(R )-(+)-binaphthol complex catalyzed asymmetric nitroaldol reaction as discussed by the authors.

TL;DR: In this paper, an enantioselective method for the synthesis of chiral cyanohydrins from aldehydes and trimethylsilyl cyanide is described.