Dinucleotide analog

Azacyclobutane dimers 28 were obtained (84H67, 84H1363) in high yields by irradiation of some pyrimidine 6-azapyrimidine dinucleotide analogs 27. They are unstable in aqueous solution and decomposed back to 27 (Scheme 8). 

Fig. 20. The diagram at the top is a schematic view of the active center as deduced from the X-ray data from the protein and several substrate related complexes. Bi, Ri, pi, R2, and B2 indicate the relative positions of the bases, riboses and phosphate of the dinucleotide analog UpcA. Position pi is occupied by S(V in the protein crystal. CMP, UMP, and analogs of these occupy Bi, Ri, and pi predominantly. 5 -AMP occupy Bj, Ra, and pi while 3 -AMP and 3 5 -A > p occupy Ba and R2 predominantly, and possibly to a lesser extent, Bi and Ri. B2 is the probable position of the second pyrimidine in dinucleotides such as CpU. The phosphate position in C > p cannot be observed owing to digestion but would be at pi if the base occupies the same position as in CMP. Four His 119 positions are indicated. I coincided with Pi but is a possible position in the absence of S(V or nucleotides. II is behind III and may be occupied by solvent. Ill is slightly stabilized by 3 -CMP. IV is the position occupied when B2 and It2 are occupied by adenosine phosphates. His 12 is behind pi and Ri. There is a solvent molecule, presumably water, behind p, as indicated by H20. Lys 41 enters from the upper right and is not in contact with pi but might contact pi. Asp 121 enters from...

Racemic 2-azabicyclo[2.2.1]hept-5-ene-3-one has great potential as a synthetic intermediate. The bicyclic lactam is a synthon for carbocyclic sugar amines, carbonucleo-sides, and carbocyclic dinucleotide analogs [239]. Chiral 2-azabicyclo[2.2.1]hept-5-ene-3-one 133 is key intermediate for the synthesis of (—)-carbovir 134, an antiviral agent effective against HIV. Nakano et al. [240] prepared chiral 133 by enantioselective trans-... 

Peng, Z.-H., Sharma, V., Singleton, S. F., and Gershon, P. D. (2002). Synthesis and application of a chain-terminating dinucleotide mRNA cap analog. Organic Letters 4, 161-164. 

Nicotinamide adenine dinucleotide (NAD+ in its oxidized form) and its close analog nicotinamide adenine dinucleotide phosphate (NADP+) are composed of two nucleotides joined through their phosphate groups by a phosphoanhydride bond (Fig. 13-15a). Because the nicotinamide ring resembles pyridine, these compounds are sometimes called pyridine nucleotides. The vitamin niacin is the source of the nicotinamide moiety in nicotinamide nucleotides. 

FIGURE 13-15 NAD and NADR (a) Nicotinamide adenine dinucleotide, NAD +, and its phosphorylated analog NADP+ undergo reduction to NADH and NADPH, accepting a hydride ion (two electrons and one proton) from an oxidizable substrate. The hydride ion is added to either the front (the A side) or the back (the B side) of the planar nicotinamide ring (seeTable 13-8). (b)The UV absorption spec-... 

The interpretation of density at pi is based on crystallographic titration of the sulfate in the protein crystal, the absence of a phosphate peak in difference maps for the mono- and dinucleotide, on arsenate and pyrophosphate binding, and by analogy with RNase-A where phosphate and arsenate peaks have been reported near His 119. 

The niacin vitamers in foods include nicotinic acid and nicotinamide (Fig. 4), which occur in limited quantities in the free form, and their coenzymes, nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) (93,96). The nicotinic acid analog of NAD as well as nicotinamide and nicotinic acid mononucleotides also occur in nature. In addition, niacin occurs as nicotinyl esters bound to polysaccharides, peptides, and glycopep-tides, which are known as niacytin and niacynogens, respectively. In general, the niacin vitamers in cereal grains and other seeds are principally the nicotinic acid forms, whereas those in meat and fish are primarily the nicotinamide forms (94,95). 

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