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  • 1
    Electronic Resource
    Electronic Resource
    Studies on Amino Acids and Peptides, 13 Improved Synthesis of 5-Thioxo-L-proline and of Some N-Acyl and S-Alkyl Derivatives as Building Blocks in Peptide Synthesis (1989)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 819-823 
    Details
    ISSN: 0170-2041
    Keywords: L-Proline, S-alkyl-5-thioxo-, N-acyl-5-thioxo- ; Peptide building blocks ; 5-Thioxo-L-proline ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We herein report an improved synthetic pathway to 5-thioxo-L-proline (2) (using R,S nomenclature, the L form here possesses the S configuration). Compound 2 is synthesized from naturally occurring 5-oxo-L-proline (1) at room temperature with 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide (3) (Lawesson′s reagent, LR). The synthesis is an improved version of our previously published method. The optical purity of 2 has been proven by thin-layer chromatography based on chiral ligand exchange. The synthesis of N-acyl and S-alkyl derivatives of 5-thioxo-L-proline (Top-OH), 5-thioxo-L-proline methyl ester (Top-OCH3), and the pseudodipeptide Boc-L-Phe-Top-OCH3 is also described.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198919890231
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  • 2
    Electronic Resource
    Electronic Resource
    Studies on Amino Acids and Peptides, 9. 5-Thioxoproline and 5-Thioxoproline Esters - Synthesis and Crystal Structures (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 269-279 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Untersuchungen über Aminosäuren und Peptide, 9.  -  5-Thioxoprolin und 5-Thioxoprolinester.  -  Synthese und Kristallstrukturen5-Thioxoprolin (2a) wurde aus 5-Oxoprolin (1a) bei Raumtemperatur unter Verwendung von 2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetan-2,4-disulfid (3) in DME synthetisiert. Die milden Reaktionsbedingungen erforderten keinen Schutz der Carboxygruppe. 5-Thioxoprolinester werden entweder durch O → S-Austausch der entsprechenden 5-Oxoprolinester mit 3 oder durch Veresterung von 2a erhalten. Die Verbindungen 2a und 5-Thioxoprolin-methylester (2b) kristallisieren in der Raumgruppe P212121 mit Z = 8. Die Bindungsbstände und -winkel werden verglichen. Die kleinen Differenzen sind durch unterschiedliche Wasserstoffbrückenmuster zu erklären.
    Notes: 5-Thioxoproline (2a) is synthesized from 5-oxoproline (1a) at room temperature with 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide (3) in DME. The carboxy group requires no protection because of the mild reaction conditions. 5-Thioxoproline esters are synthesized either by thionation of the corresponding 5-oxoproline esters with 3 or by esterification of 2a. Compounds 2a and 5-thioxoproline methyl ester (2b) both crystallize in the space group P212121 with Z = 8. Bond lengths and angles in the compounds are compared, and the small differences explained by differences in hydrogen bond pattern.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619860206
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  • 3
    Electronic Resource
    Electronic Resource
    Studies on Amino Acids and Peptides, 11. Synthesis of Four MIF Analogues Containing an N-Terminal (S)-5-Thioxoprolyl Residue (1987)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 59-64 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Untersuchungen an Aminosäuren und Peptiden, 11. - Synthese von vier MIF-Analogen mit N-terminalem (S)-5-Thioxoprolyl-RestDie kürzlich synthetisierte Aminosäure (S)-5-Thioxoprolin ((S)-Top-OH) (1) wurde mit HCl · H-(S)-Leu-GlyNRR′ 6 mit Hilfe der Gemischtanhydrid-Methode gekuppelt. Die so erhaltenen Tripeptidamide (S)-Top-(S)-Leu-GlyNMR′ 7 sind neue Analoge des Hypothalamusfaktors MIF. Die Zwischenprodukte 6 wurden durch Aminolyse von Boc-(S)-Leu-GlyOEt mit dem entsprechenden Amin HNRR′ und anschließende Entfernung der Boc-Gruppe mit 4 M HCl/Dioxan gewonnen. Bei zwei Synthesen von 7 wurde das entsprechende N-carboxylierte Tripeptidamid 8 isoliert, d.h. Isobutylchlorformat hatte mit 1 reagiert. Verringerung der Isobutylchlorformat-Menge und der Aktivierungszeit vermindert das Ausmaß der 8-Bildung.
    Notes: The newly synthesized amino acid (S)-5-thioxoproline ((S)-Top-OH) (1) has been coupled with HCl · H-(S)-Leu-GlyNRR′ 6 by the mixed anhydride method. The resulting tripeptide amides (S)-Top-(S)-Leu-GlyNRR′ 7 are new analogues of the hypothalamic factor MIF. The intermediates 6 were synthesized by aminolysis of Boc-(S)-Leu-GlyOEt with the corresponding amine HNRR′ followed by removal of the Boc group by 4 M HCl/dioxane. In two syntheses of 7 the corresponding N-carboxylated tripeptide amide 8 was isolated, i.e. isobutyl chloroformate had reacted with 1. Decreasing the amount of isobutyl chloroformate used and the activation time decreases the amount of 8 formed.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198719870110
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