Showing papers in "Tetrahedron Letters in 1990"

TL;DR: NIS together with a catalytic amount of trifluoromethanesulfonic acid proved to be very convenient for the rapid, high-yielding and stereoselective (1,2-trans) glycosidation of esterified thioglycosides with glycosyl acceptors.

TL;DR: PyBOP as discussed by the authors, an analog of BOP where dimethylamino groups are replaced with pyrrolidino, is the only analog exhibiting equivalent properties in peptide bond formation.

TL;DR: Manganese complex of the optically active salen ligand [ N,N '-bis[(S )-3-(1-phenylpropyl)salicylidene]-(1 R,2 R )-1,2-diphenylethylenediaminato] was found to be an effective catalyst for the enantioselective epoxidation of olefins as discussed by the authors.

TL;DR: In this paper, N-Iodosuccinimide/trifluoromethanesulfonic acid, which had been shown to promote the solvolysis of disarmed n-pentenyl glycosides, was found to induce the same reactivity with disarmed thioglycosides as substrates.

TL;DR: Bisoxazolines (1, 7) prepared from diethyl malonate and chiral amino alcohols were converted into their Cu(II) complexes which, upon activation, exhibit high enantioselectivity of up to 99 %ee for catalytic cyclopropanation of olefins as discussed by the authors.

TL;DR: In this article, the stereochemistry of many alternating (1,3,5...) polyol chains can be determined by preparation and 13C NMR analysis of two frame-shifted polyacetonide derivatives.

TL;DR: Rychnovsky's recent correlation of the stereochemistry-dependent 13 C NMR chemical shifts of 4,6-disubstituted 1,3-diol acetonides with diol stereochemistry may be extended to more highly substituted dioxolanes bearing substituents in the 5-position as discussed by the authors.

TL;DR: Tertiary amine oxides have been utilized to effect cobalt-mediated intramolecular cyclizations of enynes (Pauson-Khand reactions) at room temperature as discussed by the authors.

TL;DR: In this article, a specific glycosidation of partially-benzoylated thioglycosides with perbenzylated donors was demonstrated in the presence of the promotor iodonium dicollidine perchlorate.

TL;DR: In this article, the reduction of a variety of achiral ketones with catecholborane as stoichiometric reductant and 0.1 equiv of oxazaborolidine 2 as catalyst in toluene at −78°C proceeds in > 95% yield and with enantioselectivities in the range 30:1 to 9: 1, depending on substrate.

TL;DR: In this paper, the oxazaphopholidine borano complex was described and the preparation of (+) and (−)-PAMP 7a, DIPAMP 9a or β-BNPE 9b from the same complex was discussed.

TL;DR: In this article, neutral and basic amino acid residues at the N-terminus of α-hydroxy-β-amino dimethyl phosphonate were incorporated in a tripeptidic framework suitable for the aspartyl protease renin.

TL;DR: Preliminary studies indicate that the new analog induces the differentiation of human leukemia HL-60 cells, with little or no calcemic activity.

TL;DR: In this paper, the major phytoalexin of oat leaves is not the 4-H-3,1-benzoxazin-4 one previously reported, but the corresponding amide.

TL;DR: Sodium triacetoxyborohydride is a reagent of choice in the reductive amination of aldehydes and saturated aliphatic ketones with primary and secondary amines as mentioned in this paper.

TL;DR: Isoazolidines are reductively cleaved to 1,3-amino alcohols by reacting with Mo(CO)6 and water as mentioned in this paper. Reaction conditions are simple, mild and selective giving good yields of highly functionalized products with complete retention of configuration of the stereocenters.

TL;DR: In this article, Nα-Fmoc protected amino acid derivatives with hydroxyl-functions provided by polystyrene and cellulose derived support materials are achieved in high yields with 2,4,6-masitylenesulfonyl-3-nitro-1,2,4-triazelide (MSNT) in the presence of 1-methyltmidazole (MeIm).

TL;DR: In this article, a method for aminolysis of 1,2-epoxides by means of metal salts is described, which is a simple, efficient, inexpensive, anti stereoselective, and highly regi-lective method.

TL;DR: In this article, a convenient method has been developed for direct conversion of nitriles to amidines in high yields, which can also be applied to the preparation of guanidines from N-alkyl cyanamides.

TL;DR: In this article, the 3,6-bis[trifluoromethyl] -et-[methoxycarbonyl]-1,2,4,5-tetrazines were reactivated with dienophiles.

TL;DR: A new convenient strategy for functionalization of the 2-position of cyclodextrins involving deprotonation ofcyclodextrin by sodium hydride followed by a nucleophilic attack of the resultant cyclodeXTrin oxyanion on the desired electrophile gives a high yield of the cyclodeixxtrin derivative.

TL;DR: In this paper, a power-variable electrophilic trifluoromethylating agent was developed for the first time, which was shown to be a good electrophlic reagent.

TL;DR: Thiols and selenols are smoothly oxidised in high yield to disulphides and diselenides by sodium perborate at room temperature using Na6(CO3SO4)(SO4)SO4 as oxidant.

TL;DR: In this paper, X-ray diffraction analyses of sulfinamide 8 and sultam (R)-2 are presented, and the results show that sultams are highly diastereoselective.

TL;DR: Preparation of the spiro beta-lactam 7 and its evaluation as a poliovirus and human rhinovirus 3C-proteinase inhibitor is described.

TL;DR: In this paper, the design and synthesis of new fluorogenic substrate probes for HIV protease based on resonance energy transfer arc was described, and these substrates permit sensitive, continuous measurement of protease activity.

TL;DR: In this article, the presence of biphenylenediol 8 accelerates the rate of some Diels-Alder reactions, and a complex involving two hydrogen bonds is proposed.

TL;DR: Macrolactonization of 3,5- O -(3,4-dimethoxybenzylidene)-9,11-O -(2,4,6-trimethylbenzo-idene)(9 S )-9-dihydroerythronolide A seco-acid (4 ) was reexamined under various conditions and found to proceed rapidly only by treatment of 4 with Yamaguchi's reagent, 2.4, 6-trichlorobenzoyl chloride, in the presence

TL;DR: In this article, two new cytotoxic phenols, hericenone A (1 ) and B (4 ) were isolated from the mushroom Hericium erinaceum.

TL;DR: In this article, the highest enantioselectivities were achieved in catalytic asymmetric dihydroxylations using potassium hexacyanoferrate(III) [potassium ferricyanide, K3Fe(CN)6] as the reoxidant.