2,3,5,6,7,8-Hexahydro-177-pyrido pyrimidine-1,3-dione

Treatment of ethyl 9-dimethylaminomethylene-3-formyl-6,7,8,9-tetrahy-dro-4/f-pyrido[],2-rz]pyrimidine-2-acetate with saturated NH3 ethanolic solution in a closed ampule at 100°C for 24 h, then with 5% HCl for 1 h at room temperature gave 6-formyl-2,3,6,7,8,9-hexahydro-ll//-dipyrido[l,2-u 5,6-c]pyrimidine-2,l 1-dione (01MI4). 

Photocyclization of A -(4-phenyl-4-pentenyl)monothiobarbiturate (327) afforded a mixture of l,2,3-trimethyl-9-phenyl-l,2,3,6,7,8-hexahydro-4//-pyrido[l,2-u]pyrimidine-2,4-dione and tricyclic nitrogen bridgehead compound 328 (96H(42)117). 

Acidimetric, spectrophotometric and HPLC assays were developed for determination of 2,3,5,6,7,8-hexahydro-l//-pyrido[l,2-c]pyrimidine-l,3-diones 135 (98M133). Its solubility properties were also characterized. Resolution of the enantiomers of 4-phenyl-2- 4-[4-(2-pyrimidinyl)piperazi-nyl]butyl perhydropyrido[l,2-c]pyrimidine-l,3-dione was achieved on hep-takis(2-N, V-dimethylcarbamoyl)- 6-cyclodextrines (01 JC(A)249). 

Semiempirical PM 3 MO calculations were performed on eight 4-aryl-2,3,5,6,7,8-hexahydro-l//-pyrido[l,2-c]pyrimidin-l,3-diones and on their dimers (00JPO213). In all of the calculated structures the aromatic ring is almost perpendicular to the plane of the pyrido[l,2-c]pyrimidin-l,3-dione fragment, which is in accordance with the X-ray data for 4-(4-methylphenyl) derivative. 

Characteristic H NMR data of (4a/ ,55)- and (4n5,5R)-2-substituted 5- [A-(/e/ /-butoxycarbonyl)-L-tryptophyl]amino perhydropyrido[l,2-c]pyri-midine-l,3-diones were tabulated (01JMC2219). C CPMASS NMR data of 4-(4-methoxyphenyl)perhydropyrido[l,2-c]pyrimidine were reported (00JST73). C NMR data were reported for eight 4-aryl-2,3,5,6,7,8-hexahydro-l//-pyrido[l,2-c]pyrimidin-l,3-diones in the solid state and in CDCI3 solution (00JPO213). The structure of 4-aryl-3,4-dihydro-2//-pyrido [l,2-c]pyrimidine-l,3-diones and their 2,3,5,6,7,8-hexahydro derivatives were characterized by H and C NMR data (99JHC389). Conformational analysis of 6-methyl-2,3,4,6,7,ll/)-hexahydro-l//-pyrimido[6,l-n]isoquino-lin-2-ones 138 and 139 were carried out by H and C NMR studies (97LA1165). 

Amino derivatives were prepared from 4-benzamido derivatives of 4,4 ,5,6,7,8-hexahydro-3H-pyrido[l,2-cJpyrimidin-3-ones (09S2802) and perhydropyrido[l,2-c]pyrimidine-l,3-diones (07SL1905) by heating in diluted H2S04 solution under reflux for 45 min. 

Treatment of 2-substituted 3-amino-4-cyano-2,4a,5,6,7,8-hexahydro-l/f-pyrido[l,2-c]pyrimidin-l-ones (130) with acyl chlorides afforded tricyclic 3,5-disubstituted 2,5,6,8,9,10,ll,lla-octahydro-l//-pyrido[l,2-c]pyrimido[5,4-e]pyrimidine-l,6-diones (131) (90MI3 93MI1, 93MI3). 

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