1,721,158 research outputs found
Permanganate oxidation of ergosterol
No full textThe oxidation of ergosterol in methylcyclohexane with aqueous permanganate affords 3β,5α,6α-trihydroxyergosta-7,22-diene, 7α,8α-epoxy-5α-ergost-22-ene-3β,5,6α-triol (major component), 3β,5α,6α,7α-tetrahydroxyergosta-8(14),22-diene, and 3β,5α,6α,7α-tetrahydroxyergosta-8(9),22-diene. The product obtained by M. Fieser et al. and identified as 3β,5α,6α-trihydroxyergosta-7,14,22-triene has been demonstrated to be constituted mainly of 3β,5α,6α-trihydroxyergosta-7,9(11),22-triene and 3β,5α,6α-trihydroxyergosta-7,22-diene, with 3β,5α,6α-trihydroxyergosta-7,14,22-triene as a minor component. The trienic compounds were formed during the isolation procedure used by the author
Sterol synthesis: Chemical synthesis of 3β-hydroxy-5α-cholest-7-ene-9α-carbonitrile
No full text3beta-Hydroxy-5alfa-cholest-7-ene-9alfa-carbonitrile was obtained via hydrocyanation of 3beta-acetoxy-5alfa-cholest-8-en-7-one by diethylaluminum cyanide. The resulting 9alfa-cyano-7-ketone was reduced with sodium borohydride to 7alfa-hydroxy-compound. These compounds were characterized by infrared, nuclear magnetic resonance, and mass spectral measurement
Stereospecific synthesis of the marine sterol stellasterol, (22E,24S)-5α-ergosta-7,22-dien-3β-ol
No full textSynthesis of lichesterol [ergosta-5,8(9),22-trien-3β-ol]
No full textErgosta-5,8(9),22-trien-3β-ol has been synthesized and its identity with lichesterol has been confirmed. Ergosteryl acetate was transformed into 7α-[NN′-bis(ethoxycarbonyl)hydrazino]ergosta-5,8(9), 22-trien-3β-yl acetate which was converted into lichesterol by reduction with lithium in ethylamine
A simple modular synthesis of pyridinoline a collagen cross-link of biochemical interest
No full textA simple convergent synthesis of the collagen cross-link pyridinoline starting from glycine is reported
A practical and simple synthesis of (2S,5R)- and (2S,5S)-5-hydroxylysine and of a related alpha-amino acid required for the synthesis of the collagen cross-link pyridinoline
No full textA four step synthesis of (2S,5R)- and (2S,5S)-5-hydroxylysine using Williams' glycine template methodology for controlling the stereogenicity at the alpha-position is reported. This route offers the possibility for the synthesis of all possible isomers of 5-hydroxylysine and of an important alpha-amino acidic iodohydrin required for the construction of the hydroxylated side chain of the collagen cross-link pyridinoline
Mild regeneration of the carboxylic group of amino acid alkyl esters by aqueous methanolic sodium hydrogen carbonate via 5-oxazolidinones
No full textA simple racemization-free procedure allows the regeneration of the carboxylic acid group of amino acid alkyl esters by way of an intermediate 5-oxazolidinone which is hydrolyzed by treatment with sodium hydrogen carbonate in aqueous methano
Retro-1,4-cycloaddition of adducts derived from stereoidal 5,7-dienes and 4-phenyl-1,2,4-triazoline-3,5-dione
No full text1,4-Cycloadducts of various steroidal 5,7-dienes and 4-phenyl-1,2,4- triazoline-3,5-dione gave the corresponding steroidal 5,7-dienes in high yields when heated with organic bases at reflux for 15 min
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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