The crystal structures of two compounds. I. A base derived from veatchine. II. Alpha-triglycine
Organic chemists at the University of New Brunswick, while investigating the alkaloid veatchine derived from Garrya veatchii, had isolated a degradation product C16H15N which they believed to be a substituted phenanthridine. A sample was submitted to us for investigation by X-ray diffraction. Using...
| Summary: | Organic chemists at the University of New Brunswick, while investigating the alkaloid veatchine derived from Garrya veatchii, had isolated a degradation product C16H15N which they believed to be a substituted phenanthridine. A sample was submitted to us for investigation by X-ray diffraction. Using the phenanthrene-like nucleus as a "heavy atom" it was possible to determine the substituents. Difference syntheses indicated that the skeleton is not a phenanthridine but an aza-phenanthrene. The final structure obtained is l-methyl-7-ethyl-3-aza-phenanthrene. At one time the chemists were planning to synthesize each of nineteen isomers considered by them to be possible, but all of them in fact incorrect; the X-ray analysis directed them to the correct structure.
A desire to investigate the bond lengths and angles of a peptide group located between two other peptide groups prompted the investigations of alpha-triglycine. In the h01 projection all atoms are resolved. The molecule takes on the extended chain configuration, and is twisted only to an extent necessary to make fullest use of all possible hydrogen bonds. The present stage of refinement shows no particular conflict with those dimensions for polypeptide chains presented by Pauling and Cory.
Another approach to the phase problem through the intensity continuum is also described.
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