B. V. Unkovskii

Nucleophilic substitution at the C(4) atom in series of functionally 4-substituted hexahydropyrimidine-2-thiones. Synthesis of 4-alkylthiohexahydropyrimidine-2-thiones

Nucleophilic substitution at the C(4) atom in 4-hydroxy(alkoxy)hexahydropyrimidine-2-thiones under the influence of alkanethiols in acidic, neutral, and basic media, as a result of which 4-alkylthiohexahydropyrimidine-2-thiones are formed, was studied. Hydrolysis and alcoholysis of the latter lead to the corresponding 4-hydroxy- or 4-alkoxyhexahydropyrimidine-2-thiones. The three-dimensional structures of the 4-alkylthiopyrimidines obtained were established by PMR spectroscopy, and it was shown that the stereoisomers with an axially oriented alkylthio group are thermodynamically more stable.

Reactivity and stereochemical structure of 4-hydroxy- and 4-alkoxyhexahydropyrimidine-2-thiones

Substituted 4-hydroxyhexahydropyrimidine-2-thiones were obtained by the reaction of β-isothiocyanatoaldehydes with ammonia or methylamine. When heated with alcohols in the presence of p-toluenesulfonic acids, the synthesized compounds gave the corresponding 4-alkoxyhexahydropyrimidine-2-thiones, which were converted into other 4-alkoxy derivatives by the action of the respective alcohols and were hydrolyzed to the initial 4-hydroxyhexahydropyrimidine-2-thiones by the action of an aqueous solution of oxalic acid or potassium hydroxide. The reaction of the 4-hydroxyhexahydropyrimidine-2-thiones with methyl iodide led to the formation of 2-methylthio-4-hydroxy-3,4,5,6-tetrahydropyrimidine hydriodides. It was shown by PMR spectroscopy that the stereoisomers in which the hydroxyl (or alkoxyl) group has the axial orientation are thermodynamically more stable.

N-Glycosides. 4. Synthesis of 3-glycosyl-4-hydroxyhexahydropyrimidine-2-thiones on the basis of glycosyl isothiocyanates

The reaction of peracetylgluco(galacto)pyranosyl isothiocyanates with β-aminopropionaldehyde diethylacetal gave the corresponding glycosylthioureas, which, after removal of the protective groups, are converted spontaneously to 3-gluco(galacto)pyranosyl-4-hydroxyhexahydropyrimidine-2-thiones.

Structure of salts of substituted 2-alkylthiotetrahydropyrimidines

The structure and ring-chain tautomerism of 2-alkylthio-3,4,6,6-tetramethyl-4-hydroxy-3,4,5,6-tetrahydropyrimidine hydrohalides (Alk = CH3, C2H5, n-C3H7, n-C4H9, iso-C4H9, CH2C6H5 Hal = Cl, Br, I) were analyzed by means of UV, IR, and PMR spectroscopy. It is shown that the cations of the salts in the crystalline state and in solutions exist primarily in the cyclic form.

N-glycosides. 7. Synthesis of 4,5′-anhydro-3-(2′,2′-O-isopropylidene-Β-D-ribofuranosyl)-4-hydroxyhexahydropyrimidine-2-thiones

Reaction of 2,3-O-isopropylideneribofuranosylamine p-toluene-sulfonate with Β-isothiocyantoaldehydes in the presence of bases leads to the formation of 4,5′-anhydro-3-(2′,3′-O-isopropylidene-Β-D-ribofuranosyl)-4-hydroxyhexahydropyrimidine-2-thiones, whose steric structure was established by PMR spectroscopy.

Reactivities of heterocyclic amides and thioamides

Abstract2-Alkylmercapto-4-hydroxy-3,4,5,6-tetrahydro- and 2-alkylmercapto-3,6-dihydropyrimidines were synthesized by the reaction of substituted 4-hydroxyhexahydro- and 1,2,3,6-tetrahydropyrimidine-2-thiones with alkyl halides. It is shown that the nucleophilic center in the alkylation is the sulfur atom. The capacity of the synthesized compounds for prototropic ring-chain tautomerism was established.