Correlations between steric/thermochemical parameters and O-/N-acylation reactions of cellulose

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• 作者：Kesavan Devarayan^a ; Taketoshi Hayashi^a ; Masakazu Hachisu^b ; Jun Araki^c ; Kousaku Ohkawa^a ; ^{kohkawa@shinshu-u.ac.jp}
• 关键词：Conjugated polymers ; Cellulose ; Molecular modeling ; Peptides ; Synthesis
• 刊名：Carbohydrate Polymers
• 出版年：2013
• 出版时间：15 April, 2013
• 年：2013
• 卷：94
• 期：1
• 页码：468-478
• 全文大小：1667 K

文摘

N^¦Á-t-Butyloxycarbonyl (Boc)-amino acids (X_aa = Gly, Ala, or ¦Â-Ala) were reacted with the cellulose hydroxyl groups (O-acylation) using N,N¡ä-carbonyl diimidazole. The degrees of substitution toward the total hydroxyl groups (DS % (/OH)s) were 38 % for O-(Boc-Gly)-Cellulose, 29 % for O-(Boc-Ala)-Cellulose and 53 % for O-(Boc-¦Â-Ala)-Cellulose. The one-by-one N-acylation between the O-(X_aa)-Celluloses and Boc-Ala-Gly using a water-soluble carbodiimide yielded the conjugates N-(Boc-Ala-Gly)-X_aa-Celluloses with DS % (/NH₂) values of 25 % (X_aa = Gly), 35 % (Ala), and 48 % (¦Â-Ala), respectively. The results were well correlated with ¦¤G and ¦¤E_strain profiles, which were predicted by semi-empirical thermochemical parameter calculation coupled with conformer search (R² > 0.90). N-Acylation of the O-(¦Â-Ala)-Cellulose using various length of oligo-peptides, Boc-(Ala-Gly)_n and Boc-(Gly-Ala)_n (where, n = 0.5, 1.0, 1.5, 2.0, 3.0), suggested that the DS % (/NH₂) was dependent on the structural features of the symmetric anhydrides as the N-acylating agents, including conformer populations and their transition energy.