![Figure 1. Design and synthesis of HSP90 CTD dimerization inhibitors. (A) Crystal structure of the HSP90 dimer from Saccharomyces cerevisiae (Protein Data Bank [PDB] accession number 2CG956), shown as a transparent surface with cartoon representation. One monomer is colored in white and one in red, with 3 domains (N terminal, middle, and C terminal) colored in different shades of red. (B) Dimeric CTD from human HSP90 (PDB accession number 3Q6M57). Both subunits are colored differently. Helices H4, H4′, and H5, H5′ form the CTD dimerization interface. Dashed lines show where the middle domains would be located. (C) Overlay of a hexameric α-aminoxy peptide with all-methyl side chains (blue sticks) onto Cβ atoms of hot spot amino acids I688, Y689, I692, and L69634 (gray sticks) on helix H5′ (sequence P681 to D699) shown in transparent cartoon representation, with backbone atoms shown as black lines. The right panel shows the structures rotated by 90° such that the helix C terminus is oriented toward the viewer. Cβ reference atoms of hot spot amino acids are depicted as magenta spheres and Cβ atoms of the α-aminoxy peptide as orange spheres. (D) Solid-phase synthesis of α-aminoxy hexapeptides 1 (AX) and 2. Reagents and conditions: a), (i) 20% piperidine in N,N-dimethylformamide (DMF), room temperature, 2 × 15 min; (ii) Phth-NOLeu-NOLeu-OH, BOP, HOBt, N-ethylmorpholine (NEM) in DMF, room temperature, 24 hours; b) 5% hydrazine hydrate in MeOH, 2 × 15 min; (ii) Phth-NOIle-NOIle-OH, BOP, HOBt, NEM in DMF, room temperature, 24 hours; c) (i) 5% hydrazine hydrate in MeOH, 2 × 15 min; (ii) Cbz-NOPhe-NOPhe-OH, BOP, HOBt, NEM in DMF, room temperature, 24 hours; (iii) trifluoroacetic acid/triethylsilane (98:2, v:v), room temperature, 1.5 hours; d) (i) 5% hydrazine hydrate in MeOH, 2 × 15 min; (ii) Phth-NOPhe-OH, BOP, HOBt, NEM in DMF, room temperature, 24 hours; e) 5% hydrazine hydrate in MeOH, 2 × 15 min; (ii) Cbz-NOTyr(t-Bu)-OH, BOP, HOBt, NEM in DMF, room temperature, 24 hours; (iii) trifluoroacetic acid/triethylsilane (98:2, v:v), room temperature, 1.5 hours. PEG AM resin, polyethylene glycol aminomethyl-polystyrene resin.](https://ash.silverchair-cdn.com/ash/content_public/journal/blood/132/3/10.1182_blood-2017-10-810986/4/blood810986f1.jpeg?Expires=1722446704&Signature=H~mMEdj1e8N3UR7qAl34PnMgQASBffcGGY900Ub3k82bPfZFEKU6Ip2UoDg7xbPIgZ2CHRWE3VK8-jIYw1UclYV9jnhnUPbX3fNlAwZmAQHJDlZim4zB7uAG3P8AiEcUX3NRPonOTJH0dUI5ldz6lzcxEaiz3LNQUnyXreY4e4TeayiGat0t8l3Y0GJtUGD5wNIoOCi9mmcTxq9KC05TA5dSE89UPTqwsQbIoaAXu1mAEN25L~8t26xQd-G8oUZ8ENxAF68Y9CjJWQ3-VJt84IsMHb8P8zI5h1yx89GgFrx11ijJ62A9qALlY0T4R0udKxzgVfh2L4sxcnM0PQAFXw__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Design and synthesis of HSP90 CTD dimerization inhibitors. (A) Crystal structure of the HSP90 dimer from Saccharomyces cerevisiae (Protein Data Bank [PDB] accession number 2CG956 ), shown as a transparent surface with cartoon representation. One monomer is colored in white and one in red, with 3 domains (N terminal, middle, and C terminal) colored in different shades of red. (B) Dimeric CTD from human HSP90 (PDB accession number 3Q6M57 ). Both subunits are colored differently. Helices H4, H4′, and H5, H5′ form the CTD dimerization interface. Dashed lines show where the middle domains would be located. (C) Overlay of a hexameric α-aminoxy peptide with all-methyl side chains (blue sticks) onto Cβ atoms of hot spot amino acids I688, Y689, I692, and L69634 (gray sticks) on helix H5′ (sequence P681 to D699) shown in transparent cartoon representation, with backbone atoms shown as black lines. The right panel shows the structures rotated by 90° such that the helix C terminus is oriented toward the viewer. Cβ reference atoms of hot spot amino acids are depicted as magenta spheres and Cβ atoms of the α-aminoxy peptide as orange spheres. (D) Solid-phase synthesis of α-aminoxy hexapeptides 1 (AX) and 2. Reagents and conditions: a), (i) 20% piperidine in N,N-dimethylformamide (DMF), room temperature, 2 × 15 min; (ii) Phth-NOLeu-NOLeu-OH, BOP, HOBt, N-ethylmorpholine (NEM) in DMF, room temperature, 24 hours; b) 5% hydrazine hydrate in MeOH, 2 × 15 min; (ii) Phth-NOIle-NOIle-OH, BOP, HOBt, NEM in DMF, room temperature, 24 hours; c) (i) 5% hydrazine hydrate in MeOH, 2 × 15 min; (ii) Cbz-NOPhe-NOPhe-OH, BOP, HOBt, NEM in DMF, room temperature, 24 hours; (iii) trifluoroacetic acid/triethylsilane (98:2, v:v), room temperature, 1.5 hours; d) (i) 5% hydrazine hydrate in MeOH, 2 × 15 min; (ii) Phth-NOPhe-OH, BOP, HOBt, NEM in DMF, room temperature, 24 hours; e) 5% hydrazine hydrate in MeOH, 2 × 15 min; (ii) Cbz-NOTyr(t-Bu)-OH, BOP, HOBt, NEM in DMF, room temperature, 24 hours; (iii) trifluoroacetic acid/triethylsilane (98:2, v:v), room temperature, 1.5 hours. PEG AM resin, polyethylene glycol aminomethyl-polystyrene resin.
