Protosappanins E-1 and E-2, stereoisomeric dibenzoxocins combined with brazilin from sappan lignum.
作者:Masahiro NAGAI、Seiji NAGUMO
DOI:10.1248/cpb.38.1490
日期:——
An inseparable mixture of two new dibenz[b, d]oxocins combined with brazilin, named protosappanins E-1 (1) and E-2 (2), was obtained from the heartwood (Sappan Lignum) of Caesalpinia sappan L. (Leguminosae). They were separated from each other as isomeric hexamethyl ethers C38H38O<11>, [α]23D -80.8°(3) and [α]24D -9.6°(4). The mixture of 1 and 2 afforded brazilin and protosappanin B on reductive cleavage with sodium borohydride in alkaline methanol. On acid treatment, one of the hexamethyl ethers (3) yielded the other hexamethyl ether (4), l-11b-hydroxybrazilin trimethyl ether (13), and the dimethylacetal (11) of the trimethyl ether of protosappanin C. Compounds 1 and 2 were concluded to consist of protosappanin C combined with 11b-hydroxybrazilin through an acetal linkage and to be stereoisomeric in respect of the acetal carbon. The stereochemistries at the acetal carbons of 3 and 4 were determined by means of nuclear magnetic resonance (nuclear Overhauser effect) experiments.
从苏木(Sappan Lignum)的心材(Sappan Lignum)中分离出两种新的二苯并[b, d]氧杂蒽与巴西林的不可分离混合物,分别命名为原苏木素E-1(1)和E-2(2)。它们彼此分离为异构体六甲基醚C38H38O<11>、[α]23D -80.8°(3)和[α]24D -9.6°(4)。在碱性甲醇中,1和2的混合物与硼氢化钠发生还原裂解,生成巴西林和原苏木素B。在酸性处理中,其中一种六甲基醚(3)生成另一种六甲基醚(4)、l-11b-羟基巴西林三甲基醚(13)和原苏木素C的三甲基醚的二甲基缩醛(11)。化合物1和2被证实由原苏木素C与11b-羟基巴西林通过缩醛键结合而成,并且在缩醛碳方面是立体异构体。通过核磁共振(核奥弗豪泽效应)实验确定了3和4的缩醛碳的立体化学性质。