The nucleophilic attack of amines at C(17) or C(17)/C(20) positions of geldanamycin’s (GDM) benzoquinone, via initial 1,4-Michael conjugate addition mechanism, yield new analogs with closed or open ansa-bridges (1-31), respectively. X-ray structures of analogs 22 and 24 reveals an unexpected arrangement of the ansa-bridge in solid (conformer B), that is located between those of conformers A, prevailing in solution (trans-lactam), and C, crucial at binding to Hsp90 (cis-lactam). The structure of a new-type conformer B allows to better understand the molecular recognition mechanism between the GDM analogs and the target Hsp90. Combined analysis of: anticancer test results (SKBR-3, SKOV-3, PC-3, U-87, A-549) and those performed in normal cells (HDF), K_D values and docking modes at Hsp90 as well as clogP parameters, reveals that the rigid C(17)-arm (piperidyl, cyclohexyl) with a H-bond acceptor as carbonyl group together with a lipophilicity clogP∼3 favor high potency of analogs, even up to IC₅₀ ∼0.08 μM, at improved selectivity (SI_HDF>30), when compared to GDM. The most active 25 show higher anticancer potency than 17-AAG (in SKOV-3 and A-549) as well as reblastatin (in SKBR-3 and SKOV-3). Opening of the ansa-bridge within GDM analogs, at the best case, decreases activity (IC₅₀∼2 μM) and toxicity in HDF cells (SI_HDF∼2-3), relative to GDM.

胺的在C（17）或C（17）/ C的亲核攻击（20）格尔德霉素的（位置GDM）苯醌，经由初始1,4-迈克尔共轭加成机制，收率新类似物具有封闭或者打开的柄-bridges（1 - 31），分别。类似物的X射线结构22和24揭示了意想不到的排列柄-bridge在固体（构象异构体B）中，位于这些构象异构体A，在通行溶液（之间的反式β-内酰胺），和C，在关键结合Hsp90（顺式-内酰胺）。新型构象异构体B的结构可以更好地理解GDM类似物与目标Hsp90之间的分子识别机制。组合分析：抗癌测试结果（SKBR-3，SKOV-3，PC-3，U-87，A-549）和在正常细胞（HDF）中进行的测试，在Hsp90和c处的K _D值和对接模式logP参数表明，具有H键受体作为羰基的C（17）刚性臂（哌啶基，环己基）和亲脂性clogP〜3有助于类似物的高效能，甚至在₅₀到IC ₅₀〜0.08μM与GDM相比，提高了选择性（SI _HDF > 30）。活性最高的25种抗癌药比17-AAG（在SKOV-3和A-549中）以及relastatin（在SKBR-3和SKOV-3中）。所述的开口柄内-bridge GDM类似物，在最好的情况下，降低的活性（IC ₅₀在HDF细胞（SI〜2μM）和毒性_HDF ~2-3），相对于GDM。