Heptapeptide, cyclic, conformation

The spectral data of the patellamides was also reasssigned and the new assignments used for elucidation of the structures of three new metabolites, the octapeptide prepatellamide B formate (24) and the heptapeptides, prelissoclinamide 2 (25), and preulicyclamide (26) [58]. The molecular conformation of patellamide A (21) was determined by X-ray crystallography [59,60] and the solution conformations of patellamides B (22) and C (23) were determined by NMR spectroscopy and molecular dynamics [61]. The octapeptide preulithiacyclamide (27) is a potent inhibitor of Macrophage Scavenger Receptor and was isolated from L. patella from Palau along with other known cyclic peptides [62],... 

This concept for the cycle- and nnsatnration-free control of molecular shapes is likely to find multiple applications. For example, fonr stereoisomeric vicinal diflnorinated analogues of the natural cyclic heptapeptide unguisin A were found to adopt dramatically different secondary strnctnres as a function of stereoelectronic and steric interactions. The preferred conformations of PEG (polyethylene glycol) groups (popular solubilizing substitnents for many biomedical applications) are likely to be affected by the gauche effect as well. 

Yokokawa, F., Sameshima, H In, Y Minoura, K, Ishida, T, and Shioiri, T. (2002) Total synthesis and conformational studies of ceratospongamide, a bioactive cyclic heptapeptide from marine... 

---