Figure 3.

Synthetic route to the quaternary ammonium hapten 1. Reagents and conditions: (a) potassium cyanide (KCN) and methanol; (b) trifluoromethanesulfonic anhydride, pyridine, and dichloromethane (DCM); (c) cesium acetate, 18-crown-6, and toluene, under reflux; (d) KCN and methanol; (e) tert-butyldimethylsilyl (TBDMS) triflate, 2,6-lutidine, and DCM, 0°C; (f) DCM, trifluoroacetic acid (TFA), and H₂O (1:1:0.2); (g) potassium permanganate (5% aqueous solution); (h) tert-butyl-6-aminohexanoate, triethylamine, and O-benzotriazol-1-yl-N, N,N′,N′-tetramethyluronium hexafluorophosphate; (i) tetrabutylammonium fluoride and tetrahydrofuran (THF); (j) H₂ [40 psi (280 kPa)], Pd/C, and methanol; (k) aqueous formaldehyde (37%), sodium cyanoborohydride (NaCNBH₃), and zinc (II) chloride; (l) lithium diisopropylamide (LDA), −78°C, 4-nitrophenylphosphorodichloridate, and THF; (m) methyliodide; and (n) TFA and DCM (1:1).