Die Synthese von 6-und 7-Amino-, -Methylamino-und -Dimethylaminc-1,3-dimethyllumazinen (2-4 und 12-14) wird beschrieben, wobei der nucleophile Austausch bei den 7-Halogen-1,3-dimethyllumazinen 10, 11 recht glatt verlauft. Fur die Darstellung der 6-Amino-Derivate erwies sich dagegen die Amidierung des 6-Hydroxy-l,3-dirnethyllumazins (I) mit Diamidophosphorsaure-phenylestern als vorteilhafter. Das 6-Amino-I ,3-dimethyllumazin (2) gewinnt man besser aus 6-Chlor-l,3-dimethyllumazin (7) iiber das 6-Hydrazino-Derivat 5 und nachfolgende Reduktion. Durch pK,-Wert-Bestimmung und Aufnahme der Spektren der Kationen sowie der neutralen Verbindungen la& sich zeigen, daL3 die Protonierung in beiden Reihen an N-5 erfolgt. Die physikalischen Eigenschaften werden diskutiert.Pteridines, LXXIII). -Synthesis and Properties of 6-and 7-Amino-l,3-dimethyllumazines The synthesis of 6-and 7-amino-, -methylamino-, and -dirnethylamino-l,3-dirnethyllumazines (2 -4 and 12 -14) is described. The nucleophilic displacement reaction proceeds easily with the 7-halo-I ,3-dimethyllumazines 10, 11 whereas the amidation of 6-hydroxy-I ,3-dimethyllumazine (1) with phenyl diamidophosphates is recommended for the formation of &amino derivatives. 6-Amino-l,3-dirnethyllumazine (2) is synthesized best from 6-chloro-l,3-dimethyllumazine (7) via the 6-hydrazino derivative 5 and subsequent reduction. From pK, value determinations and UV absorption spectra of the cationic and neutral forms can be seen that protonation takes place in both series at N-5. The physical properties of the newly synthcsized compounds are discussed.Anknupfend an Untersuchungen uber G2) und 7-Hydroxylumazine3) interessierten uns die entsprechenden 6-und 7-Amino-l,3-dimethyllumazine und einige ihrer physikalisch-chemischen Eigenschaften. In der Literatur ist lediglich das 7-Amino-I ,3-dimethyllumazin (12) genannt, das Blicke und God14) durch Cyanmethylierung des 5,6-Diamino-l,3-dimethyluracils zum 6-Amino-5-cyanmethylamino-1,3-dimethyluracil, dessen Cyclisierung zum 7-Amino-5,6-dihydro-1,3-dimethyllumazin (21) und anschliefiende Oxidation dargestellt haben. Da wir nach einem allgemeineren Syntheseweg -auch fur 6-und 7-substituierte Amino-l,3-dimethyllumazine -suchten, erschien die Darstellung aus 6-bzw. 7-Halogen-I ,3-dimethyllumazinen (7, 8, 10, 11) mit nachfolgender nucleophiler Substitutionsreaktion am erfolgreichsten.
Lurnazine sind der radikalischen nucleophilen Substitution zuglnglich und liefern bei fehlenden Substituenten am Pyrazinteil der Molekule in regioselektiver Reaktion mit Acylradikalen die entsprechenden 7-Acyllumazine (12 -21). Alkylsubstituenten in 7-Stellung dirigieren den eintretenden Acylrest in die 6-Position (23-27). Donatorsubstituenten, wie die Amino-, Hydroxy-, Alkoxy-bzw. Methylthio-Gruppe, in 6-(28-32) und 7-Position (48-52, 55) begiinstigen die radikalische Acylierung (34 -35) in der Nachbarstellting und verlaufen teilweise mit recht guten Ausbeuten. Die neuartigen Verbindungen werden durch pK,-Werte, UV-und NMR-Spektren charakterisiert . Pteridines, LXXIV I). -Acylations of Lumazines by Radical Nucleophilic SubstitutionLumazines are prone to radical nucleophilic substitutions and form with acyl radicals at the unsubstituted pyrazine moiety in a regioselective reaction 7-acyllumazines (12-21). Alkyl substituents in 7-position direct the entering acyl residue into the 6-position (23 -27). Donorsubstituents such as amino, hydroxy, alkoxy, and methylthio groups, respectively, in 6-(28-32) or 7-position (48-52, 55) support the radical substitution at the adjacent C-atom to give the products (34 -45) generally in reasonable yields. The newly synthesized compounds have been characterized by pK, determinations, UV, and NMR spectra.
A new synthesis of deoxysepiapterin (2), one of the two yellow eye pigments of the Drosophila mutant sepia, is described. The synthetic approach makes use of a homolytic nucleophilic acylation of 7-(alky1thio)pteridine derivatives (1 1, 13,15, 18, 20) leading to the corresponding 6-acyl derivatives (21-27). Desulfurizations have been achieved for the first time in the pteridine series using Runey-Co, Runey-Cu, or Cu-A1 alloy in alkaline medium. Besides cleavage of the C(7)-S bond, further reductions of the C=O group at C(6) and the C(7)=N(8) bond are detected as side reactions leading to 6-(1 -hydroxyalkyl) (34, 35,42, 43) and 6-acyl-7,S-dihydro derivatives (2, 36, 37), respectively. The newly synthesized compounds have been characterized by elemental analysis, pK determination, UV and 'H-NMR spectra.
From the solutions of some double cyanides MNi(CN)4 (M = Cu2+, Cd2+, Zn2+) in ammonia clathrates can be obtained with benzene which are of the type of HOFMANN's compound {Ni(CN)2NH3C6H6}. The conditions of formation of these new clathrates have been studied and their structure is discussed. The dry salt [Cd(NH3)6] [Ni(CN)4] has been degraded to CdNi(CN)4, the reaction having been followed by means of tensiometric measurements; thereby the triammonate has been found to be the only intermediate.
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