Flourination Of Triterpenoid Compounds Using Iron (III) Nitrate/Nabh4 And Selectfluor

Abstract

Fluorination is a typical strategy to greatly enhance a compound's chemical and biological characteristics. In this project, Dipterocarpol lactone II, a dammarane type triterpenoid, was attempted to be fluorinated using iron (III) nitrate/NaBH4 and selectfluor. Based on the property of the fluorinating agent, the alkene derivative IV acted as the reactant for the fluorination process. It was prepared with good efficiency via elimination reaction of the lactone alcohol III. The highly reactive radical intermediate resulted in many side reactions and by-products; hence, different conditions were adjusted to control the reaction and focus on the targeted products. Despite a number of spots emerging on the TLC plate of the fluorination process, two major new spots, including FA and FB, were observed, and presumed to be the reaction's main products. The two target products were successfully purified, yet the yield was quite low. The 1 H NMR spectra of two newly formed spots were obtained to initially verify the presence of fluorine in the dipterocarpol backbone. Since no peak was observed in the region of 5-4 ppm in the 1 H NMR spectrum of spot FB, the alkene IV was transformed into an alkane derivative in which the C2-C3 double bond of IV was altered to a single bond. For the isolated spot FA, it was presumed that there were two diastereomer products formed in the fluorination reaction of compound IV according to two proton signals appearing at 5.58 ppm and 4.91 ppm. In the presence of selectfluor and iron (III) nitrate/NaBH4, a fluorine atom was presumed to be successfully attached to the C-3 position of compound II. However, this was just an initial presumption based on the 1 H NMR spectrum, it is suggested to further characterize the achieved products to confirm assuredly the successful formation of a fluorinated derivative of Dipterocarpol lactone II.