Synthesis of Ethyl 4-[N,N-bis(p-toluenesulfonyl)]aminobenzoate
In the present work, experimental conditions for the synthesis of Ethyl 4-[N,N-bis(p-toluenesulfonyl)]amino-benzoate have been disclosed.
The first step involves the synthesis of 1-(p-toluenesulfonyl) imidazole: An anhydrous THF solution (10 mL) of imidazole (3.6 g, 52.9 mmol) was stirred under nitrogen, followed by the dropwise addition of a THF (8mL) solution of p-toluenesulfonyl chloride (5 g, 26.2 mmol) over 10 min.
On the other hand, C-3-tosylated catechin 10 and C-3 tosylated epicatechin 11 were synthesized in three steps: (i) synthesis of 1-(p-toluenesulfonyl)imidazole, (ii) preparation of a sulfonating agent, and (iii) tosylation (Scheme 2).
PEG 4000 (20 g, 5 mmol) was dissolved in 100 mL C[H.sub.2][Cl.sub.2], and p-toluenesulfonyl chloride (TsCl) (3.81 g, 20 mmol) and 28 mL triethylamine were added to the above solution under continuous stirring.
Abbreviation sPCL-b-PEG-GA: Star-shaped poly(e-caprolactone)-Poly(ethylene glycol) block copolymer modified by glycyrrhetinic acid TsCl: p-Toluenesulfonyl chloride EDC: 1-(3-Dimethylaminopropyl)-3- ethylcarbodiimide DMAP: 4-Dimethylaminopyridine NHS: N-Hydroxysuccinimide GA: Glycyrrhetinic acid N[H.sub.2]-PEG-GA: Amine-terminated polyethylene glycol modified by glycyrrhetinic acid sTO-PEG-OTs: Bistosylation polyethylene glycol sPCL-OH: Star-shaped polycaprolactone terminated with hydroxyl group sPCL-COOH: Star-shaped polycaprolactone terminated with carboxyl group PTOL: Pentaerythritol CL: Caprolactone PEG: Polyethylene glycol.
As soon as the milky solution cooled to room temperature, 7.83 g (35.25 mmol) of powdered 1-(p-toluenesulfonyl
) imidazole was added and stirred for 2 hours.
Fabrication of HPC-mefenamic acid conjugates was achieved by using p-toluenesulfonyl
chloride as carboxylic acid (a functional group in drug) activator at 80C for 24 h under nitrogen atmosphere.
Polyethylene glycol 400 for synthesis (HO[(C[H.sub.2]C[H.sub.2]O).sub.n]H) (average molecular mass 380-420 g/mol, [T.sub.g] = -5[degrees]C) and p-toluenesulfonyl
chloride (99wt%) were purchased from Merck.
chloride, poly(ethylene glycol) monomethyl ether having molecular weight of 550g/mol (MPEG-550), triethylamine, and thiourea (purchased from Aldrich Chemicals Co.) were used without purification.
The HPC-Ibuprofen conjugates as macromolecular prodrugs were therefore synthesized employing homogenous and one pot reaction methodology using p-toluenesulfonyl