Kristallstruktur und spektroskopische Untersuchungen von Dithiomalonsäurediamid H₂C(CS-NH₂)₂: Ein Beispiel für eine Helixstruktur / Crystal Structure and Spectroscopic Investigations of H₂C(CS-NH₂)₂: An Example for an Helix Structure

Abstract

<jats:title>Abstract</jats:title><jats:p> The crystal structure of dithiomalonediamide (H<jats:sub>2</jats:sub>C(CS-NH<jats:sub>2</jats:sub>)<jats:sub>2</jats:sub>) has been determined. The compound crystallizes in the orthorhombic space group P2nn, No. 34, with a = 4.354(3), b = 7.940(5) and c = 8.458(5) Å. The molecules are connected by S ··· H bridges to form helices along the crystallographic a axes.</jats:p>

Synthesis, X‐ray crystallographic structures of thio substituted N‐acetyl N′‐methylamide alanine and evaluation of sp2 sulfur parameters of the CFF91 force field

“…In the previous studies in this series (26,27), we derived sp 2 sulfur parameters for the CFF91 force field (28–30) and predicted that the thio substitution would restrict the conformational space available to the dipeptides as well as alter both the intramolecular and intermolecular hydrogen bonds. While the seven thio‐containing crystal structures for dithiomalonodiamide (31), thioacetamide (32), Boc‐Alat‐NHCH 3 (13) (Z)‐Glyt‐Gly‐OBzl (33), Boc‐Gly‐Alat‐Aib‐OMe (34), Boc‐Glyt‐Ala‐Aib‐OMe (34) and (Z)‐Glyt‐Glyt‐Gly‐OBzl (35) were used to evaluate the parameters and the accuracy of the calculated empirical conformational energy, they were nonideal candidates because all the molecules were end‐protected by bulky groups or contained the Aib residue, and therefore may have biased the conformation of an individual residue away from its global minimum in a dipeptide or peptide environment. Consequently, we therefore sought to synthesize, crystallize and obtain the three‐dimensional structures of Ac‐Alat‐NHMe and Act‐Ala‐NHMe (Alat = thio‐alanine and Act = thio‐acetyl) so as to allow a more precise evaluation of the validity of the newly derived thiopeptide parameters and their use for conformational calculations for thiopeptides.…”