Showing papers in "Tetrahedron in 1990"

TL;DR: Sommer et al. as mentioned in this paper showed that a silyl group beta to the leaving group enormously enhances the rate of solvolysis, and that a gamma silyal group also has an enhancing effect, but that an alpha sily l group actually decreases reactivity in comparison with hydrocarbon models.

TL;DR: In this article, it was shown that β-acetoxy-nitro compounds react with α-isocyano-esters in the presence of an organic base to give pyrroles in good yield.

TL;DR: In this article, enol diisopinocampheylborinates, derived from achiral ethyl and methyl ketones by enolisation in the presence of tertiary amine bases (iPr2NEt or Et3N), undergo enantio-and diastereoselective aldol reactions with aldehydes.

TL;DR: In this article, the detailed template synthesis of a copper(I) catenate was described, and the corresponding free ligand, a catenand, was shown to be made of two interlocked 30 membered rings.

TL;DR: The complete synthesis of chlorophyll a starting from Knorr's pyrrole was described in detail in this article, with full experimental detail, in which the four pyrroles which are required for rings A, B, C and D were elaborated largely by known reactions, although with considerable improvements.

TL;DR: Tin(II) complexes prepared by treatment of SnCl2or Sn(SR)2 with appropriate amounts of RSH and Et3N appear to be the best reducing agents for azides (to amines) reported so far as mentioned in this paper.

TL;DR: Enzymic and synthetic approaches to the glycosidation of sialic acid by new methodologies are discussed, which aim to clarify their vital functions and identify the most difficult problem remaining.

TL;DR: In this article, a number of chiral secondary amines have been prepared and used as precursors to the corresponding chiral lithium amide bases, and the results with 4- tert -butylcyclohexanone are in disagreement with an earlier literature report, giving products of lower enantiomeric excess but higher optical rotation.

TL;DR: Topsentin C (7), dragmacidon A (8), and Dragmacidon B (9), three new brominated bis(indole) alkaloids, have been isolated from the Pacific Ocean sponge Hexadella sp collected off the coast of British Columbia as mentioned in this paper.

TL;DR: In this article, a series of palladium cyclizations of aryl iodides and vinyl bromides onto proximate alkenes or heteroaromatic rings (indole, pyrrole) lead to a wide variety of fused ring systems.

TL;DR: In this article, microwave irradiation using commercial domestic ovens is very efficient to activate potassium acetate on alumina in the absence of solvent (dry media) giving rise to remarkable rate enhancements in alkylation reactions with long chain halides.

TL;DR: The 4-O-Benzyl-23-Oisopropylidene-L-threose building block is a useful four-carbon building block for monosaccharide synthesis as discussed by the authors.

TL;DR: In this article, a reiterative two-carbon extension cycle consisting of four key transformations is used to synthesize polyhydroxylated natural products using a four-key extension cycle.

TL;DR: Two types of monocyclic azetidinones have been synthesized that do irreversibly inactivate HLE, and structure-activity relationships are in accord with the proposed mechanism.

TL;DR: In this article, three bromopyrrole alkaloids, ageliferin (1), bromoageliferins (2), and dibromo-agelifierin (3), have been isolated as potent actomyosin ATPase activators from the Okinawan marine sponge Agelas sp.

TL;DR: In this article, the preparation of chiral propargyl alcohols is described by LiNH2 or LDA induced double elimination, derived from chiral epoxychlorides derived from their corresponding epoxyalcohols.

TL;DR: In this article, the synthesis of optically pure thiazoline and thiazole containing amino acids of the constitution is described based on simple condensation reactions between cysteine esters and N-protected imino ethers derived from chiral amino acids.

TL;DR: In this article, Silylated cyanohydrins of benzaldehyde, 4-methoxybenzaldehyde, piperonal, 5-methylfurfural, butyraldehyde and crotonaldehyde were obtained in good yield and high enantiomeric excess (93%) after treatment with silyl chlorides and imidazole in DMF.

TL;DR: In this article, the kinetic isotope effects and product ratios can be taken as evidence for aggregate formation at the level of both the superbasic metalating reagent and the organometallic intermediates.

TL;DR: Stereocontrolled, second generation syntheses of the ABC and FG ring systems of brevetoxin B (1) are described in this paper, where two key intermediates 2 and 3 representing the ABC ring frameworks, were prepared from 2-deoxy-D-ribose via short and efficient sequences.