Synthesis, Spectroscopic and Crystal Structure Analysis of Two Dihydropyrimidines

Abstract

The preparation of two reduced pyrimidine derivatives, ethyl 3-acetyl-4-(4-methoxyphenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate and ethyl 4-(3,4-dimethoxyphenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate, is described, along with details of their crystal structure analysis.

Synthesis and Crystal Structure Analysis of Ethyl-4-(4-acetoxy-phenyl)-3-acetyl-6-methyl-2-thioxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylate

“…These features have been found mandatory for optimum calcium channel modulatory activity 13 . The central dihydropyrimidine ring is significantly puckered, assuming a conformation of twisted boat similar to those, reported earlier 14 . The plane calculation shows that the atoms C4 and N2 deviate from the mean plane N1/C2/C5/C6 constituting the ring by 0.3524(2)Å and -0.2168(2)Å respectively, indicating that the conformation of the ring is that of a twisted boat, with the atoms C4 and N2 being displaced by this overall planarity of the rest of the ring.…”

Synthesis and crystal structure analysis of two thiazolo[3,2-a]pyrimidine derivatives

“…The methoxy group on the aryl ring adopts anti-periplanar conformation with respect to C5-H5 bond. These features have been found mandatory for optimum calcium channel modulation activity from the recently proposed new binding-site model for this class of cardiovascular drugs [19]. In compound 2a, the central pyrimidine ring with a chiral C5 atom is significantly puckered and adopts a conformation which is best described as an intermediate between a boat and screw boat form similar to those reported earlier [20].…”

“…The plane calculation shows that the atoms C5 and N2 deviate from the mean plane C8/N1/C6/C7 constituting the ring by 0.359 Å and 0.071 Å respectively. The ring puckering parameters [19] for the pyrimidine ring are Q(2) = 0.248(3) Å, ϕ(2) = 110.3(8)° and θ = 65.5(6)° respectively. Symmetry code for 2a: i -x + 1, -y, -z + 1; ii -x + 1, -y, -z + 2; iii 1 -x, 1 -y, 1 -z. Symmetry code for 2b: i -x, -y + 2, -z; ii -x, -y + 1, -z -1; iii -x, -y, -z.…”

Ethyl (4-benzyloxyphenyl)-6-methyl-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carboxylate and a redetermination of ethyl (4RS)-4-(4-methoxyphenyl)-6-methyl-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carboxylate, as its 0.105-hydrate, both at 200 K: subtly different hydrogen-bonded ribbons

“…Compounds (III)-(VI) are all isostructural (Qin et al, 2006;Nayak et al, 2009Nayak et al, , 2010 and all form ribbons containing alternating R 2 2 (8) and R 4 4 (20) rings, just as in (II). Entirely similar ribbons are present also in the structures of compounds (VII) and (VIII) (Nayak et al, 2010), (XI) (Begum & Vasundhara, 2006), (XIII) (Begum & Vasundhara, 2009) and (XIV) (Li et al, 2007), although those in (XII) are weakly linked into sheets by C-HÁ Á ÁO hydrogen bonds in which one of the nitro-group O atoms acts as the acceptor. The supramolecular assembly in compounds (I)-(VIII), (XI), (XIII) and (XIV) thus involves, in every case, the linkage of inversion-related pairs of molecules by N-HÁ Á ÁS hydrogen bonds and the linkage of molecules related by translation by means of N-HÁ Á ÁO hydrogen bonds, to give ribbons containing alternating R 2 2 (8) and R 4 4 (20) rings.…”