The members of the TRPML subfamily of non-selective cation channels (TRPML1-3) are involved in the regulation of important lysosomal and endosomal functions, and mutations in TRPML1 are associated with the neurodegenerative lysosomal storage disorder mucolipidosis type IV. For in-depth investigation of functions and (patho)physiological roles of TRPMLs, membrane-permeable chemical tools are urgently needed. But hitherto only two TRPML inhibitors, ML-SI1 and ML-SI3, have been published, albeit without clear information about stereochemical details. In this investigation we developed total syntheses of both inhibitors. ML-SI1 was only obtained as a racemic mixture of inseparable diastereomers and showed activator-dependent inhibitory activity. The more promising tool is ML-SI3, hence ML-SI1 was not further investigated. For ML-SI3 we confirmed by stereoselective synthesis that the trans-isomer is significantly more active than the cis-isomer. Separation of the enantiomers of trans-ML-SI3 further revealed that the (-)-isomer is a potent inhibitor of TRPML1 and TRPML2 (IC₅₀ values 1.6 and 2.3 μM) and a weak inhibitor (IC₅₀ 12.5 μM) of TRPML3, whereas the (+)-enantiomer is an inhibitor on TRPML1 (IC₅₀ 5.9 μM), but an activator on TRPML 2 and 3. This renders the pure (-)-trans-ML-SI3 more suitable as a chemical tool for the investigation of TRPML1 and 2 than the racemate. The analysis of 12 analogues of ML-SI3 gave first insights into structure-activity relationships in this chemotype, and showed that a broad variety of modifications in both the N-arylpiperazine and the sulfonamide moiety is tolerated. An aromatic analogue of ML-SI3 showed an interesting alternative selectivity profile (strong inhibitor of TRPML1 and strong activator of TRPML2).

非选择性阳离子通道TRPML亚家族的成员（TRPML1-3）参与重要的溶酶体和内体功能的调节，并且TRPML1中的突变与IV型神经退行性溶酶体贮积病相关。为了深入研究TRPML的功能和（病理）生理作用，迫切需要膜可渗透的化学工具。但是迄今为止，尽管没有关于立体化学细节的明确信息，但仅公开了两种TRPML抑制剂ML-SI1和ML-SI3。在这项研究中，我们开发了两种抑制剂的总合成。ML-SI1仅以不可分离的非对映异构体的外消旋混合物形式获得，并显示出活化剂依赖性抑制活性。更有前途的工具是ML-SI3，因此没有进一步研究ML-SI1。反式异构体的活性明显高于顺式异构体。反式-ML-SI3对映体的分离进一步表明，（-）-异构体是TRPML1和TRPML2的有效抑制剂（IC ₅₀值为1.6和2.3μM ）和TRPML3的弱抑制剂（IC ₅₀值为12.5μM ），而（+）-对映异构体是TRPML1的抑制剂（IC ₅₀ 5.9μM ），但是是TRPML 2和3的活化剂。这使得纯（-）-反式-ML-SI3更适合作为化学工具研究TRPML1和2比外消旋体。对ML-SI3的12种类似物进行分析后，首次了解了该化学型中的结构-活性关系，并发现在这两种化学类型中存在多种修饰N-芳基哌嗪和磺酰胺部分是可耐受的。ML-SI3的芳族类似物显示出有趣的替代选择性（TRPML1的强抑制剂和TRPML2的强活化剂）。