Synthesis of 5-Hydroxy-4-methoxy-2-methylpyrylium Trifluoromethanesulfonate from Kojic Acid

Synthesis of Lasalocid-Based Bioconjugates and Evaluation of Their Anticancer Activity

“…Finally, to conjugate LAS with betulinic acid, the ionophore was transformed in the DBU-promoted reaction with 1,6-dibromohexane to the corresponding ester analog 5 (73%, Scheme ), fully compatible with the carboxyl group of betulinic acid. The NMR data of literature-known compounds 1 , 4 , and 5 were in good agreement with those found in the reference literature. − …”

“…All three precursors of 5-fluorouracil (compounds 1–3 ) were obtained on the basis of the one-pot base silylation/nucleoside coupling procedure published by Liu and co-workers, using BSA as the silylating agent and I 2 as the Lewis acid. On the other hand, compound 4 was formed in the reaction of kojic acid with thionyl chloride, as recently reported by Agyemang and Murelli, while 6-bromohexyl ester at the C1 position of LAS (compound 5 ) was resynthesized on the basis of the procedure published by us previously . The NMR data concerning literature-known products (compounds 1 , 4, and 5 ) were in good agreement with those found in the reference literature. − 1 H NMR, 13 C NMR, and 19 F NMR spectra of newly synthesized precursors 2 and 3 can be found in the Supporting Information (Figures S1–S6).…”

“…Second, as the native structure of kojic acid did not show sufficient reactivity with the C1 carboxyl of LAS, it was necessary to convert the hydroxyl group of this molecule to a more reactive primary chloride (compound 4, Scheme 1), which was quantitatively accomplished through the reaction of kojic acid with thionyl chloride. 32 Finally, to conjugate LAS with betulinic acid, the ionophore was transformed in the DBU-promoted reaction with 1,6dibromohexane to the corresponding ester analog 5 (73%, Scheme 2), 33 fully compatible with the carboxyl group of betulinic acid. The NMR data of literature-known compounds 1, 4, and 5 were in good agreement with those found in the reference literature.…”

“…The linkers introduced into the 5-fluorouracil molecule differed not only in their length (butyl, hexyl), but also chemical nature (aliphatic, ether). Second, as the native structure of kojic acid did not show sufficient reactivity with the C1 carboxyl of LAS , it was necessary to convert the hydroxyl group of this molecule to a more reactive primary chloride (compound 4 , Scheme ), which was quantitatively accomplished through the reaction of kojic acid with thionyl chloride …”