Stereoselective Michael addition of 6-amino-1,3-dimethyl-2,4-pyrimidinedione to the exocyclic methylene of three sesquiterpene lactones.1H and13C NMR evidence of a new C-C bond and lactam formation

1H,13C 2D NMR and X-ray studies of the products of the reaction between dibenzylidencyclohexanone and 6-amino-1,3-dimethyl uracil

The reaction of the 6-amino-1,3-dimethyl uracil with the dibenzylidencyclohexanone (1), provided three adducts whose structures result from nucleophilic attack yielding the monoadduct 3 and two isomeric bisadducts (4 and 5) in moderate yields (50-60%). The structures obtained in this study were elucidated with 2D high resolution NMR experiments, variable temperature NMR and X-ray crystallographic studies. In compound 3, the tricyclic skeleton is essentially planar and the cyclohexane ring addopts an envelope conformation. The structures 4 and 5 correspond to two isomeric spiro compounds.

2D 1H and 13C NMR evidences of the [2 + 2] autodimerization of 2-benzyl-5-benzylidene cyclopentanone yielding two different diphenyl, dispiro cyclobutane derivatives

The ene-ene [2 + 2] cycloaddition of 2-benzyl-5-benzylidenecyclopentanone proceeds smoothly and spontaneously in benzene-d6 or deuteriochloroform solution to give two different diphenyl dispiro [4.1.4.1] dodecan-4,11-diones. Detailed 1H and 13C 2DNMR spectroscopy (COSY, HMQC, HMBC) were performed in order to prove the existence in solution of two cyclobutane derivatives, one a previously described photodimer obtained by the UV irradiation of crystals of 2-benzyl-5-benzylidenecyclopentanone.

2D 1H and 13C NMR evidence for stereoselective formation of a new bond C-N, C-S or C-C in the reaction of ivalin acetate with substituted pyrimidines

Several pyrimidine derivatives of ivalin acetate were synthesized as potential anti HIV agents. High stereoselective Michael addition to ivaline acetate was observed and a new C-C, C-N or C-S bond was formed. 2D NMR 1H and 13C as well as X-ray crystallographic studies were performed on the compounds herein described to establish the structure and stereochemistry.