[14C]CI-980 (14b) was synthesized in eight steps starting from [U-14C]benzene (5), which was converted to bromo[14C]benzene (6) in the presence of tetrabutylammonium bromide as catalyst. Reaction of 6 with the anion of N-ethoxycarbonyl-N′-methoxy-N′-methyl-L-alaninamide (4a) gave the chiral (S)-ketone 8 with ee exceeding 96%. Sodium borohydride reduction of 8, followed by sequential condensation with ethyl 6-amino-4-chloro-5-nitro-2-pyridine carbamate (11), chromium trioxide oxidation, and catalytic hydrogenation over Raney nickel gave the free base form of [14C]CI-980 (14a), which was extremely unstable and readily aromatized to 15. The free base 14a was, however, isolated under specially developed conditions and converted to the crystalline isethionate salt 14b in pure form.
[14C]CI-980(14b)是以[U-14C]苯(5)为起点,在
四丁基溴化铵作为催化剂的存在下,分八个步骤合成的,然后将[U-14C]苯(5)转化为
溴[14C]苯(6)。6 与 N-乙氧羰基-N′-甲氧基-N′-甲基-L-丙
氨酰胺(4a)的阴离子反应,得到手性(S)-酮 8,ee 超过 96%。
硼氢化钠还原 8,然后依次与 6-
氨基-4-
氯-5-硝基-2-
吡啶氨基甲酸乙酯(11)缩合、
三氧化铬氧化和在雷尼
镍上催化加氢,得到游离碱形式的 [14C]CI-980 (14a),它极不稳定,很容易芳香化为 15。不过,游离碱 14a 在专门开发的条件下被分离出来,并以纯净的形式转化为晶体状的异
硫酸盐 14b。