A series of novel benzimidazoles (BI) derived from the indole 2 was synthesized and evaluated as selective neuropeptide Y (NPY) Y1 receptor antagonists with the aim of developing antiobesity drugs. In our SAR approach, the (4-chlorophenoxy)methyl group at C-2 was kept constant and a series of BIs substituted with various piperidinylalkyl groups at N-1 was synthesized to identify the optimal spacing and orientation of the piperidine ring nitrogen relative to the benzimidazole. The 3-(3-piperidinyl)propyl in 33 was found to maximize affinity for the Y1 receptor. Because of the critical importance of Arg33 and Arg35 of NPY binding to the Y1 receptor, the incorporation of an additional aminoalkyl functionality to the structure of 33 was explored. Methyl substitution was used to probe where substitution on the aromatic ring was best tolerated. In this fashion, the C-4 was chosen for the substitution of the second aminoalkyl functionality. Synthesis of such compounds with a phenoxy tether using the 4-hydroxybenzimidazole 11 was pursued because of their relative ease of synthesis. Functionalization of the hydroxy group of 45 with a series of piperidinylalkyl groups provided the dibasic benzimidazoles 55-62. Among them, BI 56 demonstrated a Ki of 0.0017 microM, which was 400-fold more potent than 33. To evaluate if there was a stereoselective effect on affinity for these BIs, the four constituent stereoisomers (69-72) of the BI 60 were prepared using the S- and R-isomers of bromide 17. Antagonist activity of these BIs was confirmed by measuring the ability of selected compounds to reverse NPY-induced forskolin-stimulated cyclic AMP. The high selectivity of several BI antagonists for the Y1 versus Y2, Y4, and Y5 receptors was also shown.

中文翻译：

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一系列新型2-[（（4-氯苯氧基）甲基]苯并咪唑类化合物作为选择性神经肽Y Y1受体拮抗剂的合成与评价。

合成了一系列从吲哚2衍生出来的新型苯并咪唑（BI），并将其作为选择性神经肽Y（NPY）Y1受体拮抗剂进行评估，目的是开发抗肥胖药。在我们的SAR方法中，C-2处的（4-氯苯氧基）甲基保持恒定，并合成了一系列在N-1处被各种哌啶基烷基取代的BI，以鉴定哌啶环氮相对于N的最佳间距和方向苯并咪唑。发现33中的3-（3-哌啶基）丙基最大程度地增加了对Y1受体的亲和力。由于NPY的Arg33和Arg35与Y1受体结合的至关重要，因此探索了将额外的氨基烷基官能团结合到33的结构中的方法。甲基取代被用来探测芳香环上的取代最能被容忍的地方。以这种方式，选择C-4来取代第二个氨基烷基官能团。由于4-羟基苯并咪唑11的合成相对容易，因此进行了使用苯氧基系链的此类化合物的合成。用一系列哌啶基烷基将45的羟基官能化，得到二元苯并咪唑55-62。其中，BI 56的Ki值为0.0017 microM，是33的Ki的400倍。为了评估对这些BI的亲和力是否有立体选择作用，BI 60的四个组成立体异构体（69-72）为通过使用溴化物17的S和R异构体制备的这些BI的拮抗活性通过测量所选化合物逆转NPY诱导的福斯高林刺激的环AMP的能力来证实。