Scheme 4. Synthesis of MQ237. Reagents, conditions and yields: (a) MsCl, Et₃N, CH₂Cl₂, 0 °C, 2 h, (98%); (b) LiBr, DMF, 130 °C, 90 min, (91%); (c) NaBH₄, EtOH, 23 °C, 1 h, (95%); (d) HCO₂H, 30% H₂O₂, 23 °C, 2 h, (81%); (e) TBSCl, imidazole, DMF, 23 °C, 16 h, (86%); (f) C₂(CN)₄, 3-butyn-1-ol, 23 °C, 72 h, (44%); (g) ClCH₂OMe, (i-Pr)₂NEt, CH₂Cl₂, 23 °C, 16 h, (78%); (h) TBAF, THF, 23 °C, 16 h, (71%); (i) 3-[4-(Iodomethyl)phenyl]-3-(trifluoromethyl)-3H-diazirine, Bu₄NI, NaH, THF, reflux 16 h, (52%); (j) 6 N HCl, THF, 23 °C, 2 h, (68%); (k) (1) SO₃–Me₃N, pyridine, 23 °C, 15 h; (2) 7 N NH₃ in MeOH, (MQ237, 30%).