6.7- Dimethyl-5,6,7,8-tetrahydropterin

New amino acid-tetrahydropterin conjugates were synthesized from A2-isobutyryl-6,7-dimethyl-5,6,7,8-tetrahydropterin (169) by either direct acylation (170) or via a succinate linker (171) followed by removal of protecting groups and ammonia treatment to deblock selectively the isobutyryl group (Scheme 26) <89MI 718-08). 

CloHi7N5O3, 5-Formyl-6,7-dimethyl-5,6,7,8-tetrahydropterine methano-late, 43B, 332... 

Abb. 5. Oxydationsverlauf des N(2 )-Dimethyl-tetrahydropterins (XLVI) zur paia-chinoiden Stufe (XLVIII) in einer Phosphatpufferlosung (0,1 M, pH 6,8). ------------- 5 min nach der Losung. 

Kaufman, der ein Zwischenprodukt bei der Oxydation von 6,7-Dimethyl-tetrahydropterin (Xe) mit Dichlorophenolindophenol in Trispuffer bei pH 6,8 erhielt (26). Da sich die Oxydation von XLVI nicht nach der Reaktion (9), die lcein Zwischenprodukt vorsieht, vollzieht, kann sie nur nach der Reaktion (8) verlaufen. Der allgemeine Mechanismus der Tetrahydropterin-Oxydation an der Luft ist also X -+ XL XXXVI. 

Scheme 2.4 Reaction of a dioxo-Mo(vi) complex with dimethyl-tetrahydropterin.

Figure 3. Difference spectrum of beef heart mitochondria. In the presence of A. Superoxide dismutase + 6,7-dimethyltetrahydropterin (stoichiometric amount) B. Superoxide dismutase + 6,7-dimethyl-tetrahydropterin (excess) C. Reoxidized mitochondria ...

Bovine superoxide dismutase and catalase were purchased from Sigma Chemical Co., glutathione peroxidase from Boehringer Mannheim and quinoxaline from Fluka AG. The synthesis of 6,7-dimethylperin and its 7,8-dihydro derivative has been described before. 6,7-Dimethyl-5,6,7,8-tetra-hydropterin was prepared by controlled potential electrolysis a 0.1 M phosphate buffer pH 7.0 at a glassy carbon or a mercury pool cathode. After complete electrolysis the tetrahydropterin was used in situ. 1,2,3,4-Tetrahydroquinoxaline was prepared by reducing quinoxaline in dry ether with lithium aluminium hydride or in ethanol with solid sodium. ... 

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