The final biosynthetic step towards plantazolicin (PZN) comprises N(α),N(α)-arginyl methyltransferase (PznL) mediated N-terminal bismethylation. We show that PznL processes truncated desmethyl-plantazolicin analogues, but only those with an N-terminal guanidine side chain derived from arginine. PznL specificity, which is narrow, depends on the side chain of the N-terminal amino acid linked to an azole, and not so much on the number of azoles.

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Three imidazolium silanethiolates relevant to the active site of cysteine proteases have been synthesized and investigated by X-ray diffraction, IR spectroscopy and computational methods. As indicated by crystallographic and FT-IR data in the solid state, the transfer of proton from thiol to imidazole takes place and a thiolato-imidazolium ion pair is formed. The FT-IR spectra of crystalline imidazolium silanethiolates exhibit intense continua characteristic for systems containing highly polarizable protons. DFT and ab initio HF calculations confirm the transfer of proton and prove the cooperativity of hydrogen bonds in the studied systems.

Katarzyna Baranowska and Natalia Piwowarska S1. Comment The crystal structure of the title compound shows an asymmetric unit consisting of one pentachlorobenzenethiolate anion and one 2,2,6,6-tetramethylpiperidinium cation. The ammonium thiolate forms a dimer [C 6 Cl 5 S (-) H 2 N (+) C 5 H 6 Me 4 ] 2 (Fig.