Urethane formation from condensed tannins and biodegradability of the urethane

(1)在DABCO（1，4-二氮杂双环[2，2，2]辛烷）或DBTDL（二月桂酸二正丁基锡）催化下，用等当量的苯基异氰酸酯（PI）处理简单单宁模型化合物。发现DABCO催化邻苯二酚型和间苯二酚型羟基形成氨基甲酸酯，而DBTDL催化醇羟基形成氨基甲酸酯。(2)在DABCO催化剂存在下，PI首先与儿茶素B环上的羟基反应，然后与儿茶素A环上的羟基反应，而儿茶素3位上的羟基完全不反应。相反，儿茶素与PI的反应性显着抑制在DBTDL催化剂的存在下，由于形成的二丁基锡-儿茶素络合物，沉淀，因此使儿茶素失活。(3)为了去除杉皮，在含水聚乙二醇400中用亚硫酸氢钠进行处理。在250℃处理下，内、外树皮均发生了大面积液化。至少有一部分缩合单宁被降解为单环芳香族化合物，如邻苯二酚和原儿茶酸。建立了一种新的羟基测定方法。

(1) Simple tannin model compounds were treated with an equivalent phenyl isocyanate (PI) in the presence of DABCO (1,4-diazabicyclo[2,2,2]octane) or DBTDL (di-n-butyltin dilaurate) as a catalyst. It was found that DABCO catalyzed urethane formation from catechol-and resorcinol-types of hydroxyl groups, while DBTDL catalyzed that from alcoholic hydroxyl groups.(2) PI reacted firstly with the hydroxyl groups in ring B and then with those in ring A of catechin, which was employed as a more relevant model, in the presence of DABCO catalyst, while hydroxyl groups in the position 3 of catechin did not react at all. On the contrary, reactivity of catechin with PI was dramatically suppressed in the presence of DBTDL catalyst, due to the formation of a dibutyltin-catechin complex, which precipitated and hence deactivated catechin.(3) In order to liquefy sugi bark, a treatment with sodium bisulfite in an aqueous polyethylene glycol 400 was conducted. Both inner and outer bark liquefied extensively by the treatment at 250℃. At least a part of condensed tannin was degraded to monocyclic aromatic compounds like catechol and protocaechuic acid. A new method of hydroxyl group determination was developed.