THREE‐DIMENSIONAL ARCHITECTURE OF MONODISPERSE β‐BRANCHED LINEAR HOMO‐OLIGOPEPTIDES

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Abstract
The conformations in solution of a series of monodisperse L‐valine oligomers having the general formula BOC(L‐Val)nOMe* (n = 2–7) were investigated using polarimetry, UV absorption, and CD. We examined these oligopeptides in TFE, HFIP, HFA, and mixed fluoroalcoholic‐water media, and compared the results with those obtained in the analogous L‐isoleucine series, which in part have been previously reported. The β‐associated structure stands out clearly at the heptamer in the two β‐branched linear homo‐oligopeptide series in TFE. In HFIP and HFA, however, the oligomers exist essentially in an unordered conformation. Also, we demonstrated that addition of water to solutions of these oligopeptides in the fluoroalcohols forces the higher oligomers to assume β‐type associated structures. The aggregates could be disrupted by dilution or increasing temperature.