✍ Scribed by A. B. Mauger; W. J. Rzeszotarski; R. A. Ford
No coin nor oath required. For personal study only.
The PMR spectra of several cyclic and acyclic dipeptide derivatives representing portions of the actinomycin structure have been studied. In the spectra of the acyclic compounds temperature‐dependent duplicity resulted from the equilibration of conformers possessing cis and trans peptide bonds. The lanthanide shift reagent Eu(FOD)~3~ was utilized to distinguish N‐methyl groups in the two conformations and observations were made on the steric dependence of the observed shifts. The origin of the wide variation in chemical shift of N‐methylvalyl α‐protons is discussed in relation to the conformation of actinomycin.
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## Abstract __cis__(4‐H,11b‐H)‐4‐Aryl‐1,6,7,11b‐tetrahydro‐2__H__,4__H__‐[1,3]oxazino [4,3‐__a__]isoquinoline and the related thiazino compound preferentially adopt in solution the O (or S) inside __cis__‐conformation in contrast to __cis__(1‐H,4a‐H)‐1‐arylperhydropyrido[1,2‐__c__][1,3]oxazine whic