Synthesis of Erythrina and Related Alkaloids. XXVIII. Studies toward Total Synthesis of Non-aromatic Erythrina Alkaloids. (1). Synthesis and Isomerization of Unsaturated Bicyclic .DELTA.-Lactones.
作者:Yoshisuke TSUDA、Akiko ISHIURA、Saho TAKAMURA、Shinzo HOSOI、Kimiaki ISOBE、Kunihiko MOHRI
DOI:10.1248/cpb.39.2797
日期:——
As a model of the C/D ring system of erythroidines, bicyclic unsaturated δ-lactones were synthesized in a regio-selective manner, and their isomerization reaction in the presence of acid, base (DBU, 1, 8-diazabicyclo[5.4.0]undec-7-ene), and NaOH were studied. In the lactone form, the 6-ene (3) was the most unstable and isomerized to the 5-ene (1) then to the 1(6)-ene (2). The latter two lactones equilibrate to give ca. 3 : 2 mixture of 1 and 2 in the presence of DBU. On the contrary, in the opened form (NaOH), the lactone 1 was the most unstable and isomerized to 2 and 3. The 1(10)-ene (4) was inert under all of the conditions examined.
作为红细胞素C/D环系统的模型,合成了环状不饱和δ-内酯,并研究了它们在酸、碱(DBU,1, 8-二氮双环[5.4.0]十一烯)和氢氧化钠存在下的异构化反应。在内酯形式中,6-烯(3)是最不稳定的,并异构化为5-烯(1),然后再转变为1(6)-烯(2)。后两种内酯在DBU的存在下达到了大约3:2的1和2的平衡。相反,在打开状态下(氢氧化钠),内酯1是最不稳定的,异构化为2和3。1(10)-烯(4)在所有检查的条件下都表现惰性。