Investigations of amination reactions on an antimalarial 1,2,4-triazolo[4,3-a]pyrazine scaffold

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Smith, Henry ST
Giuliani, Ben
Wijesekera, Kanchana
Lum, Kah Yean
Duffy, Sandra
Lock, Aaron
White, Jonathan M
Avery, Vicky M
Davis, Rohan A
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2025
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Abstract

1,2,4-Triazolo[4,3-a]pyrazines have previously been explored by the Open Source Malaria project as potent in vitro and in vivo antimalarial drug leads. With a view to generating a library of unique antimalarial 1,2,4-triazolo[4,3-a]pyrazines and exploring regiochemical preference for nucleophilic amines, we utilised the known synthetic 5-chloro-3-(4-chlorophenyl)-[1,2,4]triazolo[4,3-a]pyrazine (1) as a scaffold for aminations with 14 commercially available primary amines. Reacting scaffold 1 with excess primary amine at room temperature for 16 h generated the desired amine analogues in respectable yields (18–87%) and high purity (≥95%) following chromatography workup. The structures of the 14 previously undescribed amine analogues 2–15 were fully characterised following 1D/2D NMR, UV, and HRMS data analyses. X-ray crystallographic analysis of crystals obtained from the aminated products 2, 7, 10, and 15 are also reported here. The new library of amine-substituted triazolopyrazines was screened against the Plasmodium falciparum 3D7 strain. The tertiary alkylamine products 10–14 displayed antimalarial activity with IC50 values ranging from 9.90 to 23.30 µM against P. falciparum 3D7, with compounds 10–12 demonstrating no toxicity at 80 µM against the human embryonic kidney cell line HEK293.

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Beilstein Journal of Organic Chemistry

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21

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© 2025 Smith et al.; licensee Beilstein-Institut. This is an open access article licensed under the terms of the Beilstein-Institut Open Access License Agreement (https://www.beilstein-journals.org/bjoc/terms), which is identical to the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0). The reuse of material under this license requires that the author(s), source and license are credited. Third-party material in this article could be subject to other licenses (typically indicated in the credit line), and in this case, users are required to obtain permission from the license holder to reuse the material.

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Organic chemistry

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Smith, HST; Giuliani, B; Wijesekera, K; Lum, KY; Duffy, S; Lock, A; White, JM; Avery, VM; Davis, RA, Investigations of amination reactions on an antimalarial 1,2,4-triazolo[4,3-a]pyrazine scaffold, Beilstein Journal of Organic Chemistry, 21, pp. 1126-1134

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