Reaction of stereoisomeric 8-bromo-9-(2,3-O-isopropylidene-2,3,4-trihydroxybutyl)adenines (8) with concentrated aqueous ammonia, sodium hydride, potassium tert-butoxide, or 1,8-diazabicyclo[5,4,0]undec-7-ene afforded 4e-O,8-anhydro-9-(2,3-O-isopropylidene-2,3,4-trihydroxybutyl)adenines 9 (derivatives of 1,3-oxazepino[2,3-e]adenine). The CD spectra of optically active stereoisomers of 9 have been studied and it was found that for threo isomers 9a and 9b their character corresponds to 5'-O,8-cycloadenosine. The compounds 9 were also prepared by oxidative cyclization of 9-(2,3-O-isopropylidene-2,3,4-trihydroxybutyl)adenines (7) with lead(IV) acetate in benzene. Reaction of 9-(4-hydroxybutyl)adenine (14) with lead(IV) acetate smoothly afforded the seven-membered ring derivative, 4'-O,8-anhydro-9-(4-hydroxybutyl)adenine (15); no anhydro products with five-, six-, and eight-membered ring were found. 2',3'-O-Isopropylideneinosine (16) reacted with lead(IV) acetate to give 5'-O,8-cyclo-2',3'-O-isopropylideneinosine (17) whereas 9-(4-hydroxybutyl)hypoxanthine (18) afforded no cyclic products.
立体异构体8-
溴-9-(2,3-
O-
异丙基-2,3,4-
三羟基丁基)
腺嘌呤(
8)与浓
氨水、
氢化
钠、
叔丁醇钾或
1,8-二氮杂双环[5,4,0]十一
烯反应,得到4e-
O,8-去
水-9-(2,3-
O-
异丙基-2,3,4-
三羟基丁基)
腺嘌呤9(1,3-
噁唑并[2,3-
e]
腺嘌呤的衍
生物)。对
9的光学活性立体异构体的CD光谱进行了研究,发现对于
threo异构体
9a和
9b,它们的特征对应于5'-
O,8-环
腺苷。化合物
9也可以通过9-(2,3-
O-
异丙基-2,3,4-
三羟基丁基)
腺嘌呤(
7)与
醋酸铅(IV)在
苯中
氧化环化制备而成。
9-(4-羟基丁基)腺嘌呤(
14)与
醋酸铅(IV)反应顺利地得到七元环衍
生物4'-
O,8-去
水-
9-(4-羟基丁基)腺嘌呤(
15);没有发现五元、六元和八元环的去
水产物。2',3'-
O-
异丙基核苷(
16)与
醋酸铅(IV)反应,得到5'-
O,8-环-2',3'-
O-
异丙基核苷(
17),而9-(
4-羟基丁基)
次黄嘌呤(
18)没有产生环状产物。