Showing papers in "Tetrahedron in 1992"

TL;DR: In this article, a series of predefined, short peptide sequences are assembled by manual or automated spotting of small aliquots of solutions containing the activated amino acid derivatives onto marked positions on the sheets.

TL;DR: In this paper, a chiral ester enolate-imine condensation giving 3-hydroxy-4-aryl-β-lactams with excellent enantiomeric purity is successfully applied to the asymmetric synthesis of the enantiomersically pure taxol C-13 side chain, N-benzoyl-(2R,3S)-3-phenyl-isoserine and its analogs.

TL;DR: In this article, a series of new polyisoprenylated benzophenone derivatives named guttiferones A-E (1, 2, 3, 4, 5) were found to inhibit the cytophatic effects of in vitro HIV infection.

TL;DR: In this article, a simple, "one-pot" procedure for the conversion of vicinal diols into epoxides via halohydrin ester intermediates has been developed.

TL;DR: In this article, a 2-symmetric 5-aza-semicorrins are readily prepared in enantiomerically pure form starting from pyroglutamic acid.

TL;DR: In this paper, the chiral Lewis acid catalysts used in the present study are the titanium complex, prepared in-situ from disulfonamide and Ti(O-i-Pr) 4.

TL;DR: In this paper, a unified aromaticity scale is presented based upon the family of aromaticity indices previously introduced for differing ring systems, and the resonance energies of a range of heterocycles have been calculated, on a common basis, from experimental heats of formation and correlated with the aforementioned indices.

TL;DR: In this paper, the synthesis of peroxytetradecanoic acid from hydrogen peroxide and free carboxylic acid has been investigated using a two phase system of toluene and water.

TL;DR: In this paper, the diastereoselective anti-aldol reactions of the β-keto imide 3a, the related ethyl ketone 20b, and its diasterer 22b have been studied.

TL;DR: Several pyrazolo[3,4-d ]pyrimidine analogues of the potent antitumor agent N -{4]-2-(2-amino-4(3 H )-oxo-7 H -pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl}-L-glutamic acid (LY231514, 5) have been prepared.

TL;DR: Using the Schlenk trick (precipitation of MgX2 from ethereal solutions by the addition of 1,4-dioxane) mixtures of a Grignard reagent RMgX (X = Cl, Br, I) and 0.5 equiv.

TL;DR: The role played by the macrocyclic ligand in modifying the reactivity of monoalkylammonium carbamates towards R′X has been rationalized and the influence of parameters such as solvent, temperature and CO2 pressure on the yield and selectivity of the process leading to organic carbamate has been also settled as discussed by the authors.

TL;DR: Optically active ferrocenylbisphosphine ligands containing 2-(dialkylamino)ethylamino group on the ferrocensylmethyl position have been prepared and used for the gold(I)-catalyzed asymmetric aldol reaction of isocyanoacetate with aldehydes as mentioned in this paper.

TL;DR: The I2/NaBH4-I2 system is also useful for the reduction of carboxylic esters and acids to the corresponding alcohols in 60-90% yields.

TL;DR: Diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylates can be readily oxidized under neutral conditions using pyridinium chlorochromate adsorbed on a solid support as mentioned in this paper.