A range of guanidine-based pyridines, and related compounds, have been prepared (19 examples). These compounds were evaluated in relation to their competitive inhibition of bovine pancreatic trypsin. Results demonstrate that compounds in which the guanidinyl substituent can form an intramolecular hydrogen bond (IMHB) with the pyridinyl nitrogen atom (6a–p) are better trypsin inhibitors than their counterparts (10–13) that are unable to form an IMHB. Among the compounds 6a–p, examples containing a 5-halo substituent were, generally, found to be better trypsin inhibitors. This trend was inversely related to electronegativity, thus, 1-(5-iodopyridin-2-yl)guanidinium ion 6e (${\mathrm{K}}_{\mathrm{i}}$ = 0.0151 mM) was the optimum inhibitor in the 5-halo series. Amongst the isomeric methyl substituted compounds, 1-(3-methylpyridin-2-yl)guanidinium ion 6h demonstrated optimum levels of trypsin inhibition (${\mathrm{K}}_{\mathrm{i}}$ = 0.0140 mM). In order to rationalise the measured enzyme inhibition, selected compounds were docked with bovine and human trypsin with a view to understanding active site occupancy and taken together with the ${\mathrm{K}}_{\mathrm{i}}$ values the order of inhibitory ability suggests that the 5-halo 2-guanidinyl pyridine inhibitors form a halogen bond with the catalytically active serine hydroxy group.

已经制备了多种基于胍的吡啶和相关化合物（19个实例）。评估这些化合物对牛胰胰蛋白酶的竞争抑制作用。结果表明，化合物，其中取代基胍基可与所述吡啶基的氮原子（分子内氢键（IMHB）6A-P ）是更好的胰蛋白酶抑制剂比它们的对应物（10 - 13），它们不能形成一个IMHB。在化合物6a-p中，通常发现含有5个卤素取代基的实例是更好的胰蛋白酶抑制剂。这种趋势与电负性成反比，因此，1-（5-碘吡啶-2--2-基）胍离子6e（${\mathrm{ķ}}_{\mathrm{一世}}$ = 0.0151 mM）是5卤系列的最佳抑制剂。在异构的甲基取代的化合物中，1-（3-甲基吡啶-2-基）胍鎓离子6h表现出最佳的胰蛋白酶抑制水平（${\mathrm{ķ}}_{\mathrm{一世}}$ = 0.0140 mM）。为了合理化所测得的酶抑制作用，将选定的化合物与牛和人胰蛋白酶对接，以了解其活性位点的占有率，并与${\mathrm{ķ}}_{\mathrm{一世}}$ 值的抑制能力顺序表明5-卤代2-胍基吡啶抑制剂与催化活性丝氨酸羟基形成卤素键。