N-Benzylnicotinamide and N-benzyl-1,4-dihydronicotinamide: Useful models for NAD⁺ and NADH

3-Aminocarbonyl-1-benzylpyridinium bromide (N-benzylnicotinamide, BNA), C₁₃H₁₃N₂O⁺ Br, (I), and 1-benzyl-1,4-dihydropyridine-3-carboxamide (N-benzyl- 1,4-dihydronicotinamide, rBNA), C₁₃H₁₄N₂O, (II), are valuable model compounds used to study the enzymatic cofactors NAD(P)⁺ and NAD(P)H. BNAwas crystallized successfully and its structure determined for the first time, while a low-temperature high-resolution structure of rBNA was obtained. Together, these structures provide the most detailed view of the reactive portions of NAD(P)⁺ and NAD(P)H. The amide group in BNA is rotated 8.4 (4) out of the plane of the pyridine ring, while the two rings display a dihedral angle of 70.48 (17). In the rBNA structure, the dihydropyridine ring is essentially planar, indicating significant delocalization of the formal double bonds, and the amide group is coplanar with the ring [dihedral angle = 4.35 (9)]. This rBNA conformation may lower the transition-state energy of an ene reaction between a substrate double bond and the dihydropyridine ring. The transition state would involve one atom of the double bond binding to the carbon ortho to both the ring N atom and the amide substituent of the dihydropyridine ring, while the other end of the double bond accepts an H atom from the methylene group para to the N atom.