Diphosphatetraazacycloogtatetraenes. I. Syntheses and properties

A series of novel eight-membered heterocycles containing 1,3 and 1,5 phosphorus arrangements were synthesized. The 1,5-diphosphatetraazacyclooctatetraenes were obtained from the interaction of perfluoroalkyletheramidines and trichlorophosphoranes; the 1,3-isomers were prepared from perfluoroalkyletherimidoylamidines and imido-tetraphenyl-diphosphinic acid trichloride. The two series of cyclooctatetraenes exhibited infrared spectral absorptions characteristic for the given positional arrangement. However, electron impact fragmentation patterns of the two ring systems were closely comparable.     

Cyclic peptides of sarcosine. Syntheses and conformation.

A series of cyclic peptides of sarcosine with the general formula c-Sar-n, n=2-8, has been synthesized and conformational studies carried out both in solution and in the solid. The rings are conformationally very homogeneous and contain both cis and trans amide bonds. Their barriers to ring inversion are high; in the smaller rings this is attributed to steric hindrance, caused by the N-methyl-groups, whilst in the larger rings the folding of the chain in helical segments plays an important role.