Heterocyclic compounds

The synthesis and characterization of a series of new 4(3H)-quinazolinones is being reported. The new 4(3H)-quinazolinones have either one or two chlorine atoms in the benzene ring and a thiazol-5-yl or 1,3,4-thiadiazol-5-yl substituent in position 3. The new compounds were synthesized in a two-step procedure described before for a different series of compounds. Substituted chloroanthranilic acids (or 3,5-dichloroanthranilic acid) and acetic anhydride yielded the intermediate 3,1-benzoxazin-4-ones which subsequently afforded the desired products by reaction with a substituted 2-aminothiazole or 2-amino-1,3,4-thiadiazole in the presence of dry pyridine. In addition to elemental analyses and melting points, the new compounds were characterized by their 1H and 13C nmr, ir, uv, and mass spectra. The new quinazoline derivatives are expected to be biologically active and will be tested for their potential anticancer and antiviral activity.

We report the development of a novel hetero-Diels-Alder reaction involving the use of allenyl carbonyls as heterodienes. We have described the synthesis of a variety of allenyl carbonyls via a base promoted and manganese mediated isomerization of alkynyl carbonyls for use in methodology studies. In our model studies, a variety of enamines were utilized effectively as dienophiles to form "hydrolyzed" Diels-Alder adducts while investigating optimal reaction conditions. Initial studies towards the synthesis of an allenyl ester tethered to an aldehyde for an eventual application in an intramolecular Diels-Alder reaction were performed. Possible mechanisms were proposed while computational studies were performed in attempt to rationalize product selectivity.

Briareum asbestinum, a soft coral, is a rich source of diterpenoid natural products. The secondary metabolites of B. asbestinum fall into four classes : asbestinins, briarellins, briareolate esters, and briaranes. Briareolate esters have been shown to possess biological activity and were previously only reported from Tobago. Our group recently isolated briareolate esters from a specimen collected off the coast of Boca Raton, Florida. To determine whether location has an impact on the chemistry produced by the organism, a method to discern between chemotypes was sought. Several techniques including thin layer chromatography (TLC), high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), and sclerite analysis were employed, with NMR being the most successful method. By utilizing both 1H and COSY NMR experiments, it is possible to differentiate between the chemotypes of B. asbestinum. Application of this method allowed analysis of chemical variability with respect to location.