The use of electrogenerated acetonitrile anion allows the alkylation of N-Boc-4-aminopyridine in very high yields, under mild conditions and without by-products. The high reactivity of this base is due to its large tetraethylammonium counterion, which leaves the acetonitrile anion “naked.” The deprotection of the obtained compounds led to high yields in N-alkylated 4-aminopyridines. Nonsymmetrically dialkylated 4-aminopyridines were obtained by subsequent reaction of monoalkylated ones with t-BuOK and alkyl halides, while symmetrically dialkylated 4-aminopyridines were obtained by direct reaction of 4-aminopyridine with an excess of t-BuOK and alkyl halides. Some mono- and dialkyl-4-aminopyridines were selected to evaluate antifungal and antiprotozoal activity; the dialkylated 4-aminopyridines 3ac, 3ae and 3ff showed antifungal towards Cryptococcus neoformans; whereas 3cc, 3ee and 3ff showed antiprotozoal activity towards Leishmania infantum and Plasmodium falciparum. 1. Introduction N-Alkylated 4-aminopyridine is a common moiety in biologically active molecules. It is present, in fact, in compounds with different activities such as inhibitors of p38 MAP kinase [1], inhibitors of HIV-EP1 cellular transcription factor [2], inhibitors of coagulation Factor Xa [3], and -chemokine receptor CCR5 antagonists in anti-HIV therapy [4]; in particular we have focused our work on the development of new CYP51 inhibitors, active both on fungal strains [5] and Trypanosoma Cruzi [6]. Many literature data evidenced that the pyridine group can efficaciously replace the heme-iron chelating azole moiety present in classical azole CYP51 inhibitors and, therefore, the alkylation of 4-aminopyridine (4AP) represents an important goal in organic synthesis to develop novel classes of antifungal and antiparasitic drugs [7, 8]. Due to the wide presence of these products, the alkylation of 4-aminopyridine (4AP) is therefore an important goal in organic synthesis. Different approaches to obtain N-alkylated 4-aminopyridines have been reported in the literature. Some examples are the efficient condensation of 4AP with alcohols catalyzed by benzaldehyde [9] or copper [10, 11] or magnetite [12], the reaction of 4AP with an acyl chloride, and the following reduction of the amide with LiAlH4 [13]. The most straightforward method, however, is the direct alkylation of 4AP with alkyl halides, although it suffers from some drawbacks. The two different nitrogen atoms compete in the alkylation reaction and usually the more nucleophilic pyridine nitrogen atom reacts faster, leading to the
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