Pyrimidines hexahydro

Furo[2,3-amino-synthesis, 4, 986 Furo[3,4-d]pyrimidinedione synthesis, 4, 987 Furopyrimidines, 4, 986 Furo[2,3-d]pyrimidines synthesis, 4, 986 Furo[3,2-d]pyrimidines synthesis, 4, 987 Furo[3,2- 6]pyrone synthesis, 4, 994 Furo[3,2-c]pyrone synthesis, 4, 993 Furo[3,2-6]pyrrole, hexahydro-biological activity, 6, 1024 1 H-Furo[3,4-6]pyrrole-2,3-dione, 4,6a-diphenyl-6-(phenylimino)-6,6a-dihydro-synthesis, 6, 1004 Furopyrroles... 

Gas-phase basity and proton affinity values for 3,4,6,7,8,9-hexahydro-2/f-pyrido[l,2-n]pyrimidine were determined and they were compared to other super bases, including its lower and higher piperidine ring homologs (94JP0725, 01JPO25). 

The relative stereostructure of 9-acetyl-7-hydroxy-l,2-dimethyl-7-meth-oxycarbonyl-4-phenyl-6-oxo-l, 4,7,8-tetrahydro-6/7-pyrido[l, 2-u]pyri-midine-3-carboxylate 122 was justified by an X-ray diffraction analysis (97JOC3109). The stereochemistry and solid state structure of racemic trans-6,9-//-l, 6-dimethyl-9 z-ethoxy-9-hydroxy-4-oxo-l,6,7,8,9,9 z-hexahydro-4//-pyrido[l,2- z]pyrimidine-3-carboxylate (123), adopting a cw-fused conformation, were determined by X-ray investigations (97H(45)2175). 

Perhydropyrido[l,2-a]pyrimidin-2-one was A -alkylated with 1,4-dibro-mobutane to yield a 1-(4-bromobutyl) derivative (94MIP6). 6-Methyl-4-oxo-4/f-],6,7,8,9,9a-hexahydro-4//-pyrido[],2-a]pyrimidine-3-carboxylate 138 was alkylated with alkyl chlorides 139 to give 1-substituted derivatives 140 (97MIP2). 

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). 

Reaction of perhydropyrido[l, 2-n]pyrimidine with BrCN in the presence of MgO in a 1 1 mixture of CHCI3 and MeOH at 40 °C resulted in the formation of the ten-membered 6-methoxy-3,4,7,8, 9,10-hexahydro-l,5-diazecine-l,5-(2//,6//)-dicarbonitrile. Similar reaction of perhydropyrido[l, 2-n]pyrimidin-2-one led to the nine-membered 6-methoxy-4-oxo-2,3,4,5,6,7,8,9-octahydro-l//-l,5-diazonine-l-carbonitrile (99AJC1131). 

Treatment of perhydropyrimidide 325 with NaOt-Bu gave 1,2,3,4,6,7-hexahydro-8//-pyrido[l, 2-a]pyrimidin-8-one 326 (00MI25). 

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). 

Reaction of 5-cyano-6-methoxy-l,2,3,4-tetrahydropyridin-2-ones 387 with 1,3-propanediamine in boiling A/, A -dimethylacetamide gave 9-cyano-l,2,3,4,7,8-hexahydro-6//-pyrido-[l,2-n]pyrimidin-6-ones 388 either via route a or via route b (95H(41)2173). 

A diastereomeric mixture of l-alkyl-7-(]-alkylperhydropyrido[l,2-u]-pyrimidin-6-yl)-],2,3,4,8,9-hexahydro-9u-pyrido[],2-u]pyrimidines 412 was obtained in the reaction of glutaraldehyde and A-alkyl-1,3-propanediamines in the presence of a drop of AcOH at 0 °C, then at ambient temperature for 13 h (96H(43)2487). 

Among other bicyclic amidine catalysts, 3,4,6,7,8,9-hexahydro-2//-pyrido[l,2-n]pyrimidine was also applied in the preparation of /3-alkoxy nitriles from Q ,/3-unsaturated nitriles and alcohols (99GEP 19803515). The azido group could be smoothly converted into a trifluoroacetylamido group by treatment with (Cp3CO)2 in the presence of Ph3P and 2,3-dihydro-2//-pyrido[l,2-n]pyrimidin-2-one under Ar in THE (99HCA2380). 

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). 

Reaction of 4-cyano-3-imino-2,3,5,6,7,8-hexahydro-l//-pyrido[l,2-c]pyr-imidin-l-one 169 with 2-chloroethyl isocyanate at ambient temperature and under reflux gave N-acylated 170 and tetracyclic derivative 171, respectively (95MI1). Similar reaction of 3-amino-4-cyano-2,4a5,6,7,8-hexahydro-l// pyrido[l,2-c]pyrimidin-1-ones 172 afforded tricyclic compounds 173. 

Bei der Photoreduktion von Uridin wird als Nebenprodukt durch Photohydratation 6-Hydroxy-2,4-dioxo-I-(fi-D-ribofuranosyl)-hexahydro-pyrimidin gebildet. Die Photoreduktion von Thymidin mit Natriumboranat ver-lauft langsamer und kann nicht vom zweiten, Licht-unabhangigen Schritt abgegrenzt werden2. 

Athyl-5-phenyl-barbitursaure liefert durch Reduktion mit einem kleinen OberschuB an Natriumboranat/Bortrifluorid 2,4-Dioxo-5-dthyl-5-phenyl-hexahydro-pyrimidin. Zum Gelingen der Reaktion muB der reduzierte Ansatz mit alkalischem Wasserstoffper-oxid oxidiert werden (s.S. 58, 81). Die Reduktion gelingtmeist nur bei 5-Phenyl-barbitur-sauren3. 

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