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Showing papers in "Tetrahedron Letters in 1988"


Journal ArticleDOI
TL;DR: In this article, a synthesis of NCA's of α-amino acids using bis(trichloromethyl) carbonate has been reported; the triphosgene is used to supply phosgenes in situ in stoichiometric amounts; it is particularly effective for preparing NCA of amino acids with long, aliphatic side chains.

548 citations


Journal ArticleDOI
TL;DR: In this paper, a mild protection method for hydroxy functions with a MPM (4methoxybenzyl) group, various types of hydroxy compounds were treated with MPM trichloroacetimidate in the presence of an acid catalyst.

216 citations


Journal ArticleDOI
TL;DR: Absolute hardness, which is half the HOMO-LUMO gap in Hartree-Fock or Huckel theory, is shown to be an excellent measure of aromaticity, and a principle of maximum hardness is established.

197 citations


Journal ArticleDOI
TL;DR: The combination of Cp 2 MCl 2 -AgClO 4, (M=Zr, Hf) is effective for the activation of glycosyl fluorides, which enables the highly β-selective glycoside formation of D-mycinose by performing the reaction in benzene.

194 citations


Journal ArticleDOI
TL;DR: In this article, optically pure N-fluoro sultams (−)-3 and (+)-5 are shown to have enantioselective fluorinating reagents and unprecedented enantiomeric excesses up to 70% are observed when various prochiral metal enolates are fluorinated by using these new reagents.

184 citations


Journal ArticleDOI
TL;DR: It has been found that partially protected inositols are phosphorylated in near quantitative yields by use of N, N -diisopropyl dibenzyl phosphoramidite, 1- H -tetrazole and MCPBA in CH 2 Cl 2.

170 citations


Journal ArticleDOI
TL;DR: In this article, the synthesis of a new polymeric support for the preparation of fully protected peptide fragments by the Fmoc/t-butyl method is described, and data for coupling yields and racemization data are given.

168 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that mononium ions derived from aryl amines and aldehydes function as heterodienophiles in the presence of cyclopentadiene giving rise to novel tetrahydroquinolines.

164 citations


Journal ArticleDOI
TL;DR: Pd(II) catalyzed reaction of N-carbomethoxy-2-alkynylanilines with allyl chlorides produces 2-alkyl-3-allyl-N-Carbo-Methoxyindoles in the presence of oxirances as discussed by the authors.

163 citations


Journal ArticleDOI
TL;DR: T-butyl 2,2,2-trichloroacetimidate is an efficient reagent for the preparation of t- butyl ethers and esters in the presence of a catalytic amount of boron trifluoride etherate.

152 citations


Journal ArticleDOI
TL;DR: In this paper, Cp 2 HfCl 2 -AgClO 4 is particularly effective for this conversion, which leads to initial O-glycoside formation followed by rearrangement to C-congener.

Journal ArticleDOI
TL;DR: In this article, the acid-sensitive nucleoside 5′-O-triphosphates can be obtained in good yield directly from the unprotected nucleosides in the presence of a proton sponge.

Journal ArticleDOI
TL;DR: In this article, the reagent in methanol with monohydric phenols directly yields p -quinone ketals, also in good yields, and 4-alkyl-4-methoxycycloxycyclohexadienones.

Journal ArticleDOI
TL;DR: Readily available chiral tridentate ligand 8 catalyzes the highly Si-face selective addition of diethyl-, di-n-propylzinc and, more significantly, of divinylzinc to aromatic and aliphatic aldehydes whereas bidentates 11 and 12 exert a topologically reversed catalytic bias as mentioned in this paper.

Journal ArticleDOI
TL;DR: A pentacyclic aromatic alkaloid, ascididemin (1), with potent antineoplastic activity has been isolated from the Okinawan tunicate Didemnum sp..

Journal ArticleDOI
TL;DR: The first efficient chemical synthesis of (R)-carnitine has been accomplished on the basis of homogeneous enantioselective hydrogenation of ethyl 4-chloro-3-oxobutanoate as discussed by the authors.

Journal ArticleDOI
TL;DR: In this article, a representative selection of 1-alkynyldiisopropoxyboranes has been prepared in high yields from the reaction of 1 lithio-1-alkynes and triisophropoxy-boranes at −78°C, followed by treatment with hydrogen chloride.

Journal ArticleDOI
TL;DR: In this paper, the stereochemistry of the cembranolides isolated from the soft coral Sinularia mayi has been elucidated by means of 2D NMR spectroscopy and X-ray crystallography.

Journal ArticleDOI
TL;DR: A stereoselective synthesis of each of the four enantiomers of sphingosine from either L- or D-serine is reported, and the key steps involve the diastereoselectives addition of 1-lithiopentadecyne to aldehyde 4 and Mitsunobu inversion of propargyl alcohol 5.

Journal ArticleDOI
TL;DR: Optically active α-hydroxy ketones are obtained by oxidation of achiral ketones with molecular oxygen in two phase system using chiral phase transfer catalysts.

Journal ArticleDOI
TL;DR: In this paper, the asymmetric ene reaction of prochiral aldehydes with alkenes has been effected by chiral organoaluminum reagent providing optically active homoallylic alcohols in both enantiomeric forms with high enantiomic purity.

Journal ArticleDOI
TL;DR: In this article, a new activation system for glycosyi fluorides, Cp2 HfCl2-AgCIO4, enables highly efficient glycosidation of 1-fluoro-D-desosamine derivative.

Journal ArticleDOI
TL;DR: The isolation from Alexa leiopetala and identification by X-ray crystal structure analysis of (1R,2R,3R,4R,5S,6S)-2-hydroxymethyl-1-azabicyclo[3.3.0]octan-3,4,6-triol], a unique pyrrolizidine alkaloid, is described in this paper.

Journal ArticleDOI
TL;DR: In this article, the anomeric configuration of sialic acid and its derivatives was determined on the basis of the coupling pattern of C-1 in the gated proton-decoupled or selective proton decoupled 13C-NMR spectra.

Journal ArticleDOI
TL;DR: Good diastereoselectivity is reported in the cycloaddition reactions of Oppolzer's chiral sultam with nitrile oxides as mentioned in this paper, and a model is proposed which may apply to other non Lewis acid promoted reactions of this sULTam.

Journal ArticleDOI
TL;DR: In this paper, the chiral host compound derived from tartaric acid was found to be effective for optical resolution of bicyclic enones through complex formation between them, and was used to obtain a better optical resolution.

Journal ArticleDOI
TL;DR: A convenient, inexpensive method for the preparation of [(Ph 3 P)CuH] 6, a versatile reagent for the conjugate reduction of α,β-unsaturated carbonyl compounds, has been developed.

Journal ArticleDOI
TL;DR: Manganese-porphyrins and particularly Mn(TPP)(ClO4) were found to be much better catalysts for allylic N-tosylamination of alkenes by tosyliminoiodobenzene.

Journal ArticleDOI
TL;DR: Generation of the reformatsky reagent of difluoracetate from the iodide and the diffluoroketene silyl acetal and their aldol reaction are described in this article.

Journal ArticleDOI
TL;DR: Aldol reaction of methyl α-isocyanocarboxylates (CNCH(R)COOMe: R = H, Me, Et, i-Pr, Ph) with paraformaldehyde in the presence of 1 mol% of a chiral (aminoalkyl)ferrocenylphosphine-gold(I) complex gave optically active 4-alkyl-2-oxazoline-4-carboxylate as mentioned in this paper.