消旋11-去甲胡桐素A的合成方法改进及其药理学评价

本文发展一个实用改进方法以合成具有抗人免疫缺陷病毒(HIV-1)的天然产物的类似物11-去甲胡桐素A［(±)-1］，方法改进包括以间苯三酚为起始原料与正丁酰乙酸乙酯在饱和氯化氢甲醇存在下，经过Pechmann反应生成5，7-双羟基-4-正丙基香豆素(3)，再与巴豆酸用多聚磷酸作溶剂及催化剂进行酰化，同时分子内环合得到收率为70%关键中间体苯并二氢吡喃酮(4)，并与缩醛1，1-二乙氧基-3-甲基-2-丁烯用微波辅助催化得到苯并吡喃(6)， 最后用Luche还原以CeCl₃·7H₂O作催化剂， 在低温下经NaBH₄选择性还原化合物(6)得到目标产物即消旋11-去甲胡桐素A (±)-1。上述4步反应总收率32%， 比原方法提高1倍。体外研究表明(±)-1对HIV-1(野株)及耐药株均有明显抑制逆转录酶和P24抗原的活性， (±)-1在细胞培养内分别与作用机制不同的3种治疗艾滋病药物(AZT、 T-20、 Indinavir)都有明显的协同作用。小鼠急性毒性， (±)-1的LD₅₀灌胃给药为735.65 mg·kg^-1， 腹腔给药为525.10 mg·kg^-1。小鼠灌胃给与(±)-1血浆峰浓度(C_max)与药时曲线面积AUC_0-∞分别为0.54 μg·mL^-1及1.08 (μg·mL^-1)·h。为了初步观察(±)-1的体内药效，采用血清药理学方法，小鼠腹腔注射1次(±)-1或临床有效对照药奈韦拉平，30 min和60 min后血清有相似的抑制HIV-1逆转录酶活性。实验结果提示去甲11-胡桐素A值得进一步研究。

Improved synthesis and pharmacological evaluation of racemic 11-demethylcalanolide A

An improved and practical synthesis of racemic 11-demethylcalanolide A [(+/-)-1] was developed. This improved process involved Pechmann reaction on phloroglucinol with ethyl butyrylacetate to give 5,7,-dihydroxy4-n-propylcoumarin (3). Poly phosphoric acid (PPA) catalyzed acylation of compound (3) with crotonic acid, then intramolecular cyclization was achieved simultaneously in one step to afford the key intermediate chromanone (4). A microwave assisted synthetic method preparing chromene (6) using chromenynation of chromanone (4) with 1, 1-diethoxy-methyl-2-butene was conducted. Luche reduction of chromene (6) using NaBH4 with CeCl3 x 7H2O preferably gave (+/-)-1. The overall yield of this four step synthesis of (+/-)-1 was around 32% increasing one fold more than that of the previous method. An in vitro investigation showed that (+/-)-1 exhibited inhibitory activities against both wild-type and drug-resistant HIV-1 in HIV-1 RT and cell culture assay, and significant synergistic effects in combination with AZT, T-20, and indinavir. Its LD50 of acute toxicity in mice by intragastric administration and by intraperitoneal injection were 735.65 mg kg(-1) and 525.10 mg x kg(-1), respectively. The Cmax and AUC(0-infinity) were 0.54 microg x mL(-1) and 1.08 (microg x mL(-1) x h, respectively. The dynamics study of the inhibition of mice sera on HIV-1 RT showed that mice treated with 100 mg x kg(-1 (+/-)-1 once intraperitoneally were similar to that of 5 mg x kg(-1) of known clinical effective anti-HIV-1 drug neverapine. The results suggested that further investigation of the anti-HIV candidate (+/-)-1 was warranted.