and formylated at C-5 to give 18. A hetero-Diels-Alder reaction with Danishefsky's diene and 18 was effected with the aid of sonication and ZnCl2, yielding a model, 20, for a putative C-glycoside intermediate in the biosynthesis of sarubicin A, 1. However, when 18 and the triethylsiloxydiene derived from 3-penten-2-one were treated under the same conditions no reaction occurred, while p-dimethylaminobenzaldehyde
合成了3,6-二羟基
蒽酰胺5和其5-丙基衍
生物15。发现前者非常不稳定,而后者则稳定并且可以可逆地氧化为类似的醌。3,6-二甲氧基
蒽酰胺被保护为
丙酮乙缩醛,并在C-5甲酰化,得到18。借助超声处理和ZnCl 2与Danishefsky's diene和18进行的杂Diels-Alder反应,产生了20的模型,用于建立沙比霉素A 1的
生物合成中的C-糖苷中间体。但是,当18在相同条件下处理与
3-戊烯-2-酮衍生的三乙基甲
硅烷氧基二烯没有反应发生,而对-二甲基
氨基
苯甲醛仅产生醛醇产物23。