Synthesis of Biomimetic Thioesters for Studies of Ketoreductase Domains from the Biosynthesis of Cytotoxic Polyketides

Abstract

The synthesis of biomimetic thioesters for enzymatic studies of ketoreductase (KR) domains from polyketide synthases is described. A TBS-protected dihydroxyalkene fragment was synthesised by a sequence involving a Nagao acetate aldol reaction, a Mukaiyama propionate aldol reaction, and a methylene Wittig olefination. Fragment coupling to N-acetylcysteamine (SNAC) (E)-3-hydroxyhex-4-enethioates by an olefin cross-metathesis (OCM) and subsequent deprotection gave the potential KR product stereoisomers. An analogous OCM with a SNAC (E)-3-ketohex-4-enethioate did not give the desired KR precursor, but the reaction could successfully be replaced by a Horner–Wadsworth–Emmons olefination between a SNAC 3-ketothioester phosphonate and a TBS-protected dihydroxy aldehyde. After deprotection, an intramolecular cyclisation was observed that needs to be considered as a spontaneous side reactivity in the enzymatic assays.

Key words

biomimetic thioesters - biosynthesis - enzymic metathesis - Michael addition - natural products - olefination

Publikationsverlauf

Eingereicht: 19. September 2023

Angenommen nach Revision: 22. November 2023

Accepted Manuscript online:
22. November 2023

Artikel online veröffentlicht:
17. Januar 2024

• References and Notes

• 1a Sattely ES, Fischbach MA, Walsh CT. Nat. Prod. Rep. 2008; 25: 757
• 1b Friedrich S, Hahn F. Tetrahedron 2015; 71: 1473
• 2a Grininger M. Nat. Chem. Biol. 2023; 19: 401
• 2b Hertweck C. Angew. Chem. Int. Ed. 2009; 48: 4688
• 3 Franke J, Hertweck C. Cell Chem. Biol. 2016; 23: 1179
• 4a Weissman KJ. Beilstein J. Org. Chem. 2017; 13: 348
• 4b Drufva EE, Spengler NR, Hix EG, Bailey CB. ChemBioChem 2021; 22: 1122
• 5a Schröder M, Roß T, Hemmerling F, Hahn F. ACS Chem. Biol. 2022; 17: 1030
• 5b Wunderlich J, Roß T, Schröder M, Hahn F. Org. Lett. 2020; 22: 4955
• 5c Cacho RA, Thuss J, Xu W, Sanichar R, Gao Z, Nguyen A, Vederas JC, Tang Y. J. Am. Chem. Soc. 2015; 137: 15688
• 5d Siskos AP, Baerga-Ortiz A, Bali S, Stein V, Mamdani H, Spiteller D, Popovic B, Spencer JB, Staunton J, Weissman KJ, Leadlay PF. Chem. Biol. 2005; 12: 1145
• 5e Piasecki SK, Taylor CA, Detelich JF, Liu J, Zheng J, Komsoukaniants A, Siegel DR, Keatinge-Clay AT. Chem. Biol. 2011; 18: 1331
• 5f Häckh M, Lucas X, Marolt M, Leadlay PF, Müller M, Günther S, Lüdeke S. ChemBioChem 2019; 20: 1150
• 5g Häckh M, Müller M, Lüdeke S. Chem. Eur. J. 2013; 19: 8922
• 5h Bailey CB, Pasman ME, Keatinge-Clay AT. Chem. Commun. 2015; 52: 792
• 6a Kong R, Liu X, Su C, Ma C, Qiu R, Tang L. Chem. Biol. 2013; 20: 45
• 6b Palaniappan N, Alhamadsheh MM, Reynolds KA. J. Am. Chem. Soc. 2008; 130: 12236
• 7a Hemmerling F, Lebe KE, Wunderlich J, Hahn F. ChemBioChem 2018; 19: 1006
• 7b Aldrich CC, Beck BJ, Fecik RA, Sherman DH. J. Am. Chem. Soc. 2005; 127: 8441
• 8a Derra S, Schlotte L, Hahn F. Chem. 2023; 5: 1407
• 8b Guth FM, Lindner F, Rydzek S, Peil A, Friedrich S, Hauer B, Hahn F. ACS Chem. Biol. 2023;
• 8c Gilbert IH, Ginty M, O’Neill JA, Simpson TJ, Staunton J, Willis CL. Bioorg. Med. Chem. Lett. 1995; 5: 1587
• 8d Taft F, Brünjes M, Knobloch T, Floss HG, Kirschning A. J. Am. Chem. Soc. 2009; 131: 3812
• 8e Berkhan G, Merten C, Holec C, Hahn F. Angew. Chem. Int. Ed. 2016; 55: 13589
• 8f Hollmann T, Berkhan G, Wagner L, Sung KH, Kolb S, Geise H, Hahn F. ACS Catal. 2020; 10: 4973
• 8g Hahn F, Kandziora N, Friedrich S, Leadlay PF. Beilstein J. Org. Chem. 2014; 10: 634
• 8h Wagner L, Stang J, Derra S, Hollmann T, Hahn F. Org. Biomol. Chem. 2022; 20: 9645
• 9 Cheng-Sánchez I, Sarabia F. Synthesis 2018; 50: 3749
• 10 Sundaram S, Kim HJ, Bauer R, Thongkongkaew T, Heine D, Hertweck C. Angew. Chem. Int. Ed. 2018; 57: 11223
• 11 (2R,3R,5S)-3,5-Bis{[tert-butyl(dimethyl)silyl]oxy}-1-[(3aR,6S)-8,8-dimethyl-2,2-dioxido-tetrahydro-3H-3a,6-methanobenzo[c]isothiazol-1(4H)-yl]-2-methyldodecan-1-one (18) A stirred solution of propionylated Oppolzer sultame 16 (2.78 g, 10.3 mmol, 1.2 equiv) in CH₂Cl₂ (14.2 mL, 0.7 m) was cooled to 0 °C, and DIPEA (2.68 mL, 15.4 mmol, 1.8 equiv) and TMSOTf (3.24 mL, 17.9 mmol, 2.1 equiv) were added dropwise. The resulting solution was allowed to warm to r.t. and stirred overnight. In a separate flask, a solution of aldehyde 15 (2.45 g, 8.54 mmol, 1.0 equiv) in CH₂Cl₂ (14.2 mL, 0.6 m) was cooled to –78 °C. After dropwise addition of a 1 M solution of TiCl₄ in CH₂Cl₂ (8.54 mL, 8.54 mmol), the solution was stirred for 15 min at –78 °C. Subsequently, the auxiliary-containing solution was added very slowly, while keeping the temperature below –75 °C. After stirring the mixture at –78 °C for 1 h, the reaction was quenched by the addition of sat. aq NH₄Cl. The phases were separated and the aqueous one was extracted with CH₂Cl₂ (×3). The combined organic phases were washed with brine, dried (MgSO₄), and filtered. The crude aldol product was dissolved in CH₂Cl₂ (42.7 mL, 0.2 M), and the solution was cooled to –78 °C. After dropwise addition of 2,6-lutidine (1.50 mL, 12.8 mmol, 1.5 equiv) and TBSOTf (2.77 mL, 12.8 mmol, 1.5 equiv), the solution was allowed to warm to r.t. and stirred for 3 h. The reaction was quenched by the addition of sat. aq NH₄Cl. The resulting phases were separated, and the aqueous one was extracted with CH₂Cl₂ (×3). The combined organic phases were washed with brine, dried (MgSO₄), and filtered. Purification by flash chromatography [silica gel, cyclohexane–EtOAc (15:1)] gave a light-brown oil; yield: 4.86 g (7.23 mmol, 85% over two steps); R_f = 0.19 (cyclohexane–EtOAc, 15:1); [α]_D ²⁰ +24.3 (c = 1.0, CH₂Cl₂).¹H NMR (500 MHz, CDCl₃): δ = 4.15 (dt, J = 8.7, 3.3 Hz, 1 H, 3-H), 3.87 (dd, J = 7.5, 5.0 Hz, 1 H, 20-H), 3.78–3.74 (m, 1 H, 5-H), 3.49 (d, J = 13.8 Hz, 1 H, 14-H), 3.43 (d, J = 13.8 Hz, 1 H, 14-H), 3.38 (dq, J = 6.7, 4.0 Hz, 1 H, 2-H), 2.06–1.83 (m, 5 H, 16-H, 17-H, 18-H, 19-H), 1.59–1.53 (m, 2 H, 4-H), 1.49–1.42 (m, 2 H, 6-H), 1.40–1.33 (m, 2 H, 16-H, 17-H), 1.31–1.26 (m, 10 H, 7-H, 8-H, 9-H, 10-H, 11-H), 1.17 (s, 3 H, 22-H), 1.14 (d, J = 6.7 Hz, 3 H, 13-H), 0.96 (s, 3 H, 22-H), 0.89–0.86 (m, 12 H, 12-H, 25-H), 0.84 (s, 9 H, 25-H), 0.14 (s, 3 H, 23-H), 0.11 (s, 3 H, 23-H), 0.03 (s, 3 H, 23-H), 0.02 (s, 3 H, 23-H). ¹³C NMR (125 MHz, CDCl₃): δ = 173.8 (t, C-1), 69.9 (t, C-5), 69.6 (t, C-3), 65.5 (t, C-20), 53.4 (s, C-14), 48.1 (q, C-21), 47.9 (q, C-15), 46.9 (t, C-2), 44.8 (t, C-18), 39.9 (s, C-4), 38.9 (s, C-19), 38.8 (s, C-6), 33.0 (s, C-16), 32.0 (s, C-9), 29.9 (s, C-8), 29.5 (s, C-10), 26.7 (s, C-17), 26.2 (p, C-25), 26.1 (p, C-25), 25.1 (s, C-7), 22.8 (s, C-11), 21.5 (p, C-22), 20.0 (p, C-22), 18.3 (q, C-24), 14.3 (p, C-12), 9.8 (p, C-13), –3.71 (p, C-23), –3.75 (p, C-23), –4.0 (p, C-23), –4.8 (p, C-23). HRMS (ESI⁺): m/z [M + H]⁺ calcd for C₃₅H₇₀NO₅SSi₂: 672.4508; found: 672.4503
• 12 Ge H.-M, Huang T, Rudolf JD, Lohman JR, Huang S.-X, Guo X, Shen B. Org. Lett. 2014; 16: 3958
• 13 S-[2-(Acetylamino)ethyl] (3S,4E,6S,7R,9S)-7,9-Bis{[tert-butyl(dimethyl)silyl]oxy}-3-hydroxy-6-methylhexadec-4-enethioate (23) Grubbs–Hoveyda II catalyst S1 (8.1 mg, 13.0 μmol, 5 mol%) was added to a stirred solution of secondary alcohol (S)-12 (180 mg, 777 μmol, 3.0 equiv) and terminal alkene 11 (118 mg, 259 μmol, 1.0 equiv) in CH₂Cl₂ (5.2 mL, 0.05 m), and the mixture was refluxed for 6 h. The solvent was then removed in vacuo and the residue was purified by flash chromatography [silica gel, cyclohexane–EtOAc (1:1)] to give a brownish oil; yield: 164 mg (254 μmol, 98%); R_f = 0.22 (cyclohexane–EtOAc, 1:1); [α]_D ²⁰ –9.3 (c = 1.0, CH₂Cl₂). ¹H NMR (500 MHz, CDCl₃): δ = 5.80 (br, 1 H, NH), 5.70 (ddd, J = 15.5, 7.2, 0.6 Hz, 1 H, 5-H), 5.49 (ddd, J = 15.5, 6.6, 0.8 Hz, 1 H, 4-H), 4.59–4.56 (m, 1 H, 3-H), 3.73–3.67 (m, 2 H, 7-H, 9-H), 3.48–3.44 (m, 2 H, 18-H), 3.10–3.01 (m, 2 H, 17-H), 2.82–2.74 (m, 2 H, 2-H), 2.33–2.28 (m, 1 H, 6-H), 1.97 (s, 3 H, 20-H), 1.45–1.39 (m, 4 H, 8-H, 10-H), 1.31–1.26 (m, 10 H, 11-H, 12-H, 13-H, 14-H, 15-H), 0.97 (d, J = 6.9 Hz, 3 H, 21-H), 0.89–0.87 (m, 21 H, 16-H, 24-H), 0.06–0.04 (m, 12 H, 22-H). ¹³C NMR (125 MHz, CDCl₃): δ = 198.8 (q, C-1), 170.5 (q, C-19), 134.7 (t, C-5), 130.9 (t, C-4), 73.5 (t, C-7), 70.5 (t, C-9), 69.9 (t, C-3), 51.2 (s, C-2), 42.2 (t, C-6), 41.6 (s, C-8), 39.5 (s, C-18), 38.1 (s, C-10), 32.0 (s, C-14), 29.9 (s, C-12), 29.5 (s, C-13), 29.0 (s, C-17), 26.1 (p, C-24), 26.0 (p, C-24), 25.1 (s, C-11), 23.4 (p, C-20), 22.8 (s, C-15), 18.3 (q, C-23), 15.2 (p, C-21), 14.3 (p, C-16), –3.6 (p, C-22), –3.9 (p, C-22), –4.0 (p, C-22), –4.1 (p, C-22). HRMS (ESI⁺): m/z [M + Na]⁺ calcd for C₃₃H₆₇NNaO₅SSi₂: 668.4171; found: 668.4151
• 14 Ollevier T, Li Z. Adv. Synth. Catal. 2009; 351: 3251
• 15a Nising CF, Bräse S. Chem. Soc. Rev. 2012; 41: 988
• 15b Nasir NM, Ermanis K, Clarke PA. Org. Biomol. Chem. 2014; 12: 3323