Metabolites of Microorganisms. 144th communication. The Crystal and Molecular Structure of 3‐Hydroxy‐4‐methylproline

A new amino acid isolated from the acid hydrolysate of the antibiotic Echinocandin B is shown by X‐ray analysis to be 2,3–trans‐3,4‐cis‐3‐hydroxy‐4‐methylproline. The crystals are orthorhombic, a = 5.633 Å, b = 8.760 Å, c = 14.314 Å, Z = 4, space group P212121. The structure was determined by direct methods and refined by least‐squares analysis to a final R value of 0.032 for 532 reflections. The molecule exists as a zwitterion forming one OH…O and two NH…O hydrogen bonds.