Aggregational behavior of N-butyloxycarbonyl-L-glutamic acid oligomeric benzyl esters (exact residue numbers 4, 6 and 8) in benzene. SAXS studies

N-Butyloxycarbonyl(BOC)-L-glutamic acid oligomeric benzyl esters with exact residue numbers (BOCN_pZ, N_p=4, 6 and 8) have been synthesized by a stepwise procedure in a liquid phase. The SAXS intensity spectra of the BOCN_pZ-benzene systems have been analyzed on the basis of the rod-like aggregate model, in which the #-sheet monomers are one-dimensionally stacked antiparallel to each other. The extracted parameters (the number-averaged aggregation number, the monomer-monomer bond energies corresponding to hydrogen bonding energies, and the number-averaged molecular weights) for these aggregates have been compared with those for the aggregates formed by N-acetyl-L-glutamic acid oligomeric benzyl esters (AN_pZ, N_p=4, 6 and 8) in benzene (PCCP, 2001, 3, 3140-3149). The results indicate that it is more difficult to form aggregates in the BOCN_pZ systems than in the AN_pZ systems. This difference is due to the bulky BOC group, which hinders the formation of aggregates.