5- Carboxy-2-mercapto

Durch Decarboxylierung von 5-Carboxy-2-mercapto-l,3,4-oxadiazolen ist 2-Mercapto-1,3,4-oxadiazol praparativ zuganglich603. Die fur 5-substituierte 2-Mercapto-l,3,4-oxadiazole allgemein benutzte Methode (vgl. S. 541) laCt sich hier nicht anwenden denn man erhalt aus Formhydrazid und Schwefelkohlenstoff 2,5-Dithiono-2,3,4,5-tctrahydro-1,3,4-thiadiazol602 ... 

Ein Gemisch aus 3,5 g (0,0165 mol) 5-Carboxy-2-mercapto-l,3-benzothiazol. 8 ml Dimethylformamid und 35 ml Thionylchlorid wird auf 90° erhitzt. Die erhaltene klare Losung wird 4 h bei 92" geriihrt. Ober-schiissigcs Thionylchlorid wird i.Vak. abdestillicrt. Der Ruckstand kristallisiert beim Abkiihlen in Nadeln, die abfiltriert und aus 40 ml Ligroin umkristallisiert werden Ausbeute 2,6 g (68%) Schmp. 131°. 

Carboxy-2-mercapto- 979 2-Carboxy-6-methoxy- 880 5-(Carbuxy-methyl)-2-subst. 

This method has mainly been used to prepare thiazoles nonsubstituted in the 2-position and involves the replacement of a functional substituent (amino, halo, mercapto, hydroxy, or carboxy) by a hydrogen. In this way the often delicate cyclization of thioformamide can be avoided. 

With Sulfur Nucleophiles N-Carboxy-protected aziridine-2-carboxylates react with thiols to give P-mercapto-ot-amino acid derivatives. The reaction is usually catalyzed by BF3 and the yields range from fair to excellent [15, 16, 108-111]. With N-unprotected 3-substituted aziridine-2-carboxylates, the ring-opening with thiols usually takes place with anti stereoselectivity, especially in the case of the C-3 aliphatic substituted substrates. In cases in which C-3 is aromatic, however, the stereoselectivity has been found to be a function of the substitution pattern on the aromatic ring 3-p-methoxy ph eri yl-su bs li In led aziridines 143a (Scheme 3.51) and... 

Mercapto-3-phenyl- und 3-Phenyl-4-carboxy-cinnolin werden dagegen unter Ab-spaltung der Mercapto- bzw. Carboxy-Gruppe zu 3-Phenyl-l,4-dihydro-cinnolin reduziert. ... 

Brom-5-formyl-l-( 4-methoxy-henzyl)-imidazol l-Benzyl-4-brom-5-carboxy-...946 /-Benzyl-4-brom-5-mercapto-...946 4-Brom-5-methoxycarbonyl-]-methyl-...1047 1033 50% 67% 68% 50% ... 

There are many patents on the Beirut reaction thus 2-carbamoyl,57 2-amino-3-amidino-,58 2-methyl-3-carbamoyl-,59 2-amino-3-carbamoyl-,60 2-halomethyl-3-carboxy,61 2-mercapto-,62 and 2-trifluoromethyl63 quinoxaline 1,4-dioxides are just a few examples among the many quinoxaline derivatives prepared by this method. In a... 

Derivatives of compound 168, i.e., the 3-carboxy- and 3-mercapto-substituted compounds 171 [146] and 172 [148] were synthesized from oxindoles with the general formula 173. 

Converting enzyme (ACE) inhibitors 176) likewise prevent the formation of angiotensin II and are used in the treatment of renal and essential hypertension. Examples of orally active ACE-inhibitors are (2)-l-[(2S)-3-[N-(S)-mercapto-2-methylpro-panoyl]proline170) (captopril 77), l-[N-(S)-l-carboxy-3-phenylpropyl]-L-alanyl-L-proline-1 -ethyl ester177 (enalapril 78), and 2-[N-[(S)-l-ethoxycarbonyl-3-phenyl-propyl]-L-alanyl]-(lS,3S,5S)-2-azabicyclo[3.3.0]octane-3-carboxylic acid178) (Hoe 498 79). 

CN [OC-6-24-(25-fran.r)]-[/V-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-A/-(4-hydroxy-2-mercapto-l-methyl-l-butenyl)formamide]aqua[ 18-carboxy-20-(carboxymethyl)-8-ethenyl-13-elhyl-2,3-dihydro-3,7,12,17-tetra methyl-21//,23//-porphine-2-propanoato(5-)-/V21,/ /22, A 23, A/24]dihydrogencobaltate(2-)... 

Glutarsaure 2-Amino- -5-(1 -carboxy-2-mercapto-ethyl-amid) (Hydrochlorid) XV/1, 776... 

Imidazot 4-(3-Carboxy-propyl)-2-mercapto-1 -phenyl-tetrahydro-IV/Id, 252... 

Ultraviolet spectra of numerous pyrazines have been recorded, but in many cases without regard to the effects of ionization, and in various solvents. All pyrazines are basic and thus have both neutral (e.g., 5) and cationic (e.g., 6) forms. Pyrazines with a substituent containing an ionizable hydrogen, such as a carboxy, hydroxy, or mercapto group, may also exist in the anionic form (e.g., 7), the tautomeric neutral form (e.g., 2, R = H), a potentially zwitterionic form (8, R = H) or an isomeric cationic form (e.g., 9, R = H). Many published spectra are in fact of mixed ionic species to determine the spectrum of each ionic form it is necessary to measure its spectrum in a solution buffered at least two units above or below the pAa value (or values) of the substance. In nonaqueous solvents, the neutral (uncharged) species are favored. The ultraviolet spectra of pure species may then serve to characterize the pyrazine, may permit the correlation of spectra with structure, and may be used in quantitative determinations. 

Amino-4-mercapto-butansaure/Natronlauge) 2-(4-Carboxy-5,6-dihydro-4H-l,3-thiazin-2-yl)-6-... 

Die Reduktion von 4-Carboxy-4,5-dihydro- bzw. -2,3,4,5-tetrahydro-l,3-thiazolen mit Natrium/Ammoniak unter nicht absolut wasserfreien Bedingungen fiihrt zu 2-Alkyl-amino-3-mercapto-alkansauren6 7,... 

Hydroxy-6-carboxy- 315 4- Hydroxy-2-mercapto-6-trifluormethyl- 394 2-Hydroxy-1,4,5,6-tetrahydro- 314 4-Hydroxy-3,4,5,6-tetrahydro- 314... 

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