1. Regulation of Nitrogen Fixation by Fe-S Protein II in Azotobacter vinelandii
2. Photoreduction of flavoproteins and other biological compounds catalyzed by deazaflavins. Appendix: photochemical formation of deazaflavin dimers
3. Synthesis of compounds 8 has been rationalized in terms of the initial addition of one molecule of DAD to 5, followed by cyclization with concomitant elimination of 6-methylamino-5-(1,2-bisethoxy-carbonylhydrazino)-3-(N-methylcarbamoylmethyl)uracil. This compound has however never been isolated [3]. In the synthesis of 8 we were able to isolate a compound, which analytical data suggest the structure 6-methylamino-5,5-bis (1,2-bisethoxycarbonylhydrazino)-3-(N-methylcarbamoylmethyl)uracil (Figure 1), white needles, mp 200-202°; nmr (90 MHz, DMSO-d6): δ 1.13 (t, 6H, 2 × ethyl CH3), 1.22 (t, 6H, 2 × ethyl CH3), 2.56 (d, 3H, CONCH3), 2.89 (br d, 3H, C(6)NCH3), 3.73-4.37 (m, 10H, N(3)CH2, 4 × ethyl CH2); ms: only signals from thermolysis products were observed. Anal. Calcd. for C20H32N8O11: C, 42.85; H, 5.75. Found: C, 43.01; H, 5.66. These findings suggest a cyclization mechanism, in which two molecules of DAD are involved instead of one, as postulated earlier.
4. Reaktionen mit Nitrosouracilderivaten, I. Eine neue Xanthin-Synthese