复旦大学：《药物设计学》课程教学资源（教学研究）靶向药物设计_Design, synthesis, and bioavailability evaluation of coumarin-based prodrug of meptazinol

Availableonlineatwww.sciencedirect.com Bioorganic BCIENCEODDIRECTO Medicinal Chemistry tters ELSEVIER Bioorganic Medicinal Chemistry Letters 15(2005)4953-4956 Design, synthesis, and bioavailability evaluation of coumarin-based prodrug of meptazinol Qiong Xie, Xiaolin Wang, Xinghai Wang, Zhiqiang Jiang and Zhuibai Q Department of Medicinal Chemistry, School of Pharmacy, Fudan Unitersity, 138 Yixueyuan Road, Shanghai 200032, PR China Received 5 May 2005: revised 18 July 2005: accepted 5 August 200 Available online 9 September 2005 Abstract-Based on the known coumarin-based prodrug system, a new meptazinol (2)-3-02-(propionyloxy) phenylJ-2 ability. The prodrug(3)showed a 4-fold increase in oral bioavailability over the parent drug meptazinol in al the ster(3) was designed and synthesized as prodrug to minimize the first-pass effect of meptazinol (1)and improve c 2005 Elsevier Ltd. All rights reserved Acting as a mixed agonist/antagonist opioid analgesic, the parent drug and coumarin 29-31 The maj Jor outstand meptazinol((+)-3-(3-ethyl-l-methyl-hexahydro-lH-aze- ing advantage of the prodrug system is that the hydroly- pin-3-yl) phenol, 1)has been marketed by Wyeth for sate coumarin has been found to be relatively nontoxic the treatment of moderate to severe pain since 1983 in many clinical and laboratory studies and included in the British Pharmacopoeia in 1998. Un- ce other typical opiates, meptazinol showed less resp: It was of considerable interest to apply the coumarin However, the clinical uses of meptazinol were still meptazinol (1) for protection against the enzyme metab- restricted by its low oral bioavailability(8.69%).Simi- olism. Among the several previously reported carboxyl lar to some drugs with phenol groups, meptazinol was ated phenyl propenoic acid as masked coumarin sily metabolized by enzymes in liver and caused seri- carriers, the he propionyloxy group-substituted phenyl ous first-pass effect. New clinical applications, pharma propenoic acid (2)was specifically chosen as our carrier cophores, and analgesic mechanism of meptazinol molecule simply because it could be prepared mostly ere reported recently7-10 both from Qiu's group and efficiently among all the known acetyl, iso-propiony other researchers and tert-butyryl coumarin carriers as described in the lit- erature3and the corresponding results of esterase kinet- As part of a continuing effort in our laboratory to devel- ics indicated that variations of the steric bulkiness of the op novel meptazinol prodrugs as potential therapeutic acyl group did not significantly affect the rate of the agents, Qiu and co-workers recently reported the syn- release of the parent drug. Therefore, we designed and thesis of three benzoyl esters(I-Ill) as meptazinol pro- synthesized meptazinol()-3-[2-(propionyloxy )phenyl] drugs. Among these three esters, analogue Ill showed 2-propenoic ester (3)as a potential prodrug to explore enhanced bioavailability presumably due to an en- this potential. Coumarin was converted into(2)-3-[2 hanced lipophilicity and metabolic stability. A couma (propionyloxy )phenyl]-2-propenoic acid(2)in six steps rin-based esterase-sensitive prodrug system and its using a modification of literature procedures3with the application for the preparation of prodrugs of amines total productivity of 20.4%(Fig. 1). The spectrum of recently. The design utilized an esterase-triggering intra- based on a J value of 12 uration of double bond which matched well molecular lactonization of cis-coumarinic acid to release with the data reported in Ref. 13. Keywords: Meptazinol: Coumarin-based prodrug: Synthesis; Coupling of meptazinol (1)with (2)-3-[2-(propiony y)phenyl]l-2-propenoic acid (2)was accomplished in responding author. Tel. +86 021 54237595: fax: +86 021 the presence of 1, 3-dicyclohexyl carbodiimide(DCc) 4237264;e-mail:zbqiu@shmu.edu.cn and 4-dimethylaminopyridine (DMAP)to give the 0960-894X/S- see front matter c 2005 Elsevier Ltd. All rights reserved. doi:10.1016jbmc200508.016

Design, synthesis, and bioavailability evaluation of coumarin-based prodrug of meptazinol Qiong Xie, Xiaolin Wang, Xinghai Wang, Zhiqiang Jiang and Zhuibai Qiu* Department of Medicinal Chemistry, School of Pharmacy, Fudan University, 138 Yixueyuan Road, Shanghai 200032, PR China Received 5 May 2005; revised 18 July 2005; accepted 5 August 2005 Available online 9 September 2005 Abstract—Based on the known coumarin-based prodrug system, a new meptazinol (Z)-3-[2-(propionyloxy) phenyl]-2-propenoic ester (3) was designed and synthesized as prodrug to minimize the first-pass effect of meptazinol (1) and improve the oral bioavail￾ability. The prodrug (3) showed a 4-fold increase in oral bioavailability over the parent drug meptazinol in rats.
2005 Elsevier Ltd. All rights reserved. Acting as a mixed agonist/antagonist opioid analgesic, meptazinol ((±)-3-(3-ethyl-1-methyl-hexahydro-1H-aze￾pin-3-yl) phenol, 1) has been marketed by Wyeth for the treatment of moderate to severe pain since 19831 and included in the British Pharmacopoeia in 1998.2 Un￾like other typical opiates, meptazinol showed less respi￾ratory depression and lower addictive potential.3–5 However, the clinical uses of meptazinol were still restricted by its low oral bioavailability (8.69%).6 Simi￾lar to some drugs with phenol groups, meptazinol was easily metabolized by enzymes in liver and caused seri￾ous first-pass effect. New clinical applications, pharma￾cophores, and analgesic mechanism of meptazinol were reported recently7–10 both from Qiu
s group and other researchers. As part of a continuing effort in our laboratory to devel￾op novel meptazinol prodrugs as potential therapeutic agents, Qiu and co-workers recently reported the syn￾thesis of three benzoyl esters (I–III) as meptazinol pro￾drugs. Among these three esters, analogue III showed enhanced bioavailability presumably due to an en￾hanced lipophilicity and metabolic stability.11 A couma￾rin-based esterase-sensitive prodrug system and its application for the preparation of prodrugs of amines and cyclic prodrugs of peptides12–28 have been reported recently. The design utilized an esterase-triggering intra￾molecular lactonization of cis-coumarinic acid to release the parent drug and coumarin.29–31 The major outstand￾ing advantage of the prodrug system is that the hydroly￾sate coumarin has been found to be relatively nontoxic in many clinical and laboratory studies. It was of considerable interest to apply the coumarin￾based prodrug system for masking the phenol group of meptazinol (1) for protection against the enzyme metab￾olism. Among the several previously reported carboxyl￾ated phenyl propenoic acid as masked coumarin carriers, the propionyloxy group-substituted phenyl propenoic acid (2) was specifically chosen as our carrier molecule simply because it could be prepared mostly efficiently among all the known acetyl, iso-propionyl, and tert-butyryl coumarin carriers as described in the lit￾erature13 and the corresponding results of esterase kinet￾ics indicated that variations of the steric bulkiness of the acyl group did not significantly affect the rate of the release of the parent drug. Therefore, we designed and synthesized meptazinol (Z)-3-[2-(propionyloxy)phenyl]- 2-propenoic ester (3) as a potential prodrug to explore this potential. Coumarin was converted into (Z)-3-[2- (propionyloxy)phenyl]-2-propenoic acid (2) in six steps using a modification of literature procedures13 with the total productivity of 20.4% (Fig. 1). The spectrum of (2) has confirmed a Z-configuration of double bond based on a J value of 12.2 Hz,32 which matched well with the data reported in Ref. 13. Coupling of meptazinol (1) with (Z)-3-[2-(propionyl￾oxy)phenyl]-2-propenoic acid (2) was accomplished in the presence of 1,3-dicyclohexyl carbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) to give the 0960-894X/$ - see front matter
2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmcl.2005.08.016 Keywords: Meptazinol; Coumarin-based prodrug; Synthesis; Bioavailability. * Corresponding author. Tel.: +86 021 54237595; fax: +86 021 54237264; e-mail: zbqiu@shmu.edu.cn Bioorganic & Medicinal Chemistry Letters 15 (2005) 4953–4956

4954 0. Xie et al. Bioorg. Med. Chem. Lett. 15(2005)4953-4956 HOH2C、 TBDMSOH BDMSOH2C LiAIHw/oC/15min TBDMS-CI/DMAP/OC/14h CH2 CH2CO)2O/DMAP/TEA CH3CH2COO 100% HOH.C H2O: THF: HOAc(1: 1: 3 )CH3 COQ MnO2 CH3CH2 COO Nac|O2H2O2/10℃ CHa CH2CO 89.5% Figure 1. Synthesis of the carrier molecule(2). TBDMS, tert-butyldimethyl silyl: DMAP, 4-dimethylaminopyridine. phenol ester(3) in 69% yield. 3 The synthetic route is As known to us, the prodrug can be hydrolyzed to mep outlined below(Fig. 2). The structures of the base and tazinol by the plasma esterase in vitro after the blood hydrochloride of this prodrug were determined by sample is collected, which can result in the concentration NMR. IR. and HR-ESL of meptazinol determined to be higher than the actual concentration. To prevent the above case occurring, As suggested by Franklin et al. 35 a good correlation was the esterase inhibitor Na S,Os was quantitatively added observed between meptazinol's analgesic potency and its to the plasma sample immediately after blood sample lasma concentration Thus in our hand oral bioavail was collected and centrifuged The HPLC system bility, which in turn indicated the bioactivity, of the was optimized on Frost. 37 prodrug and of the parent drug was measured in rats respectively Listed in Table 2 are the area under curve (AUC) lability (F%)of meptazin The bioavailability evaluation was designed as a three- intravenous(iv) versus intragastric (ig) administration way cross-over study. Six rats were divided into three as well as that of the meptazinol prodrug via ig groups randomly and evenly. During each period, there administration. The corresponding mean plasma is a 7 days'wash-out time. The routes of administration meptazinol concentration-time curves are shown in in each period for each rat were listed in Table I 3. (1)DCC/DMAP CHaCH2co0-C' Figure 2. Synthetic route of the meptazinol prodrug(3). Table 1. The routes of administration in each period for each rat Period II Period ll A, iv 29.7 umol/kg meptazinol; B, ig 92.8 umol/kg meptazinol; C, ig 92.8 umol/kg prodrug Table 2. AUC and absolute bioavailability of meptazinol and prodrug Meptazinol (iv) 9.7 umol/kg AUCo-lo(ng h/n 85.53 533.82

phenol ester (3) in 69% yield.33 The synthetic route is outlined below (Fig. 2). The structures of the base and hydrochloride of this prodrug were determined by NMR, IR, and HR-ESI.34 As suggested by Franklin et al.35 a good correlation was observed between meptazinol
s analgesic potency and its plasma concentration. Thus in our hand, oral bioavail￾ability, which in turn indicated the bioactivity, of the prodrug and of the parent drug was measured in rats, respectively. The bioavailability evaluation was designed as a three￾way cross-over study. Six rats were divided into three groups randomly and evenly. During each period, there is a 7 days
wash-out time. The routes of administration in each period for each rat were listed in Table 1. As known to us, the prodrug can be hydrolyzed to mep￾tazinol by the plasma esterase in vitro after the blood sample is collected, which can result in the concentration of meptazinol determined to be higher than the actual concentration. To prevent the above case occurring, the esterase inhibitor Na2S2O5 was quantitatively added to the plasma sample immediately after blood sample was collected and centrifuged.36 The HPLC system was optimized on Frost.37 Listed in Table 2 are the area under curve (AUC) and absolute bioavailability (F%) of meptazinol via intravenous (iv) versus intragastric (ig) administration as well as that of the meptazinol prodrug via ig administration. The corresponding mean plasma meptazinol concentration–time curves are shown in Figure 3. CH3CH2COO HOOC OH N CH3 (1)DCC/DMAP (2)HCl-ether CH3CH2COO C O N CH3 O HCl 1 2 3 + Figure 2. Synthetic route of the meptazinol prodrug (3). Table 1. The routes of administration in each period for each rat No 1 2 3 4 5 6 Period I A A B B C C Period II B B C C A A Period III C C A A B B A, iv 29.7 lmol/kg meptazinol; B, ig 92.8 lmol/kg meptazinol; C, ig 92.8 lmol/kg prodrug. Table 2. AUC and absolute bioavailability of meptazinol and prodrug (n = 6) Meptazinol (iv) Meptazinol (ig) Prodrug (ig) 29.7 lmol/kg 92.8 lmol/kg 92.8 lmol/kg Mean SD Mean SD Mean SD AUC0!10 (ng h/ml) 1985.53 533.82 712.63 118.69 2631.78 1385.30 F%a 12.12 3.57 51.75 32.99 a F% = (AUC0!10 (ig)/92.8)/(AUC0!10 (iv)/29.7). Figure 1. Synthesis of the carrier molecule (2). TBDMS, tert-butyldimethyl silyl; DMAP, 4-dimethylaminopyridine. 4954 Q. Xie et al. / Bioorg. Med. Chem. Lett. 15 (2005) 4953–4956

0. Xie et al Bioorg. Med. Chem. Lett. 15(2005)4953-4956 12. Wang, B; Zhang, H; Wang, W. Bioorg. Med. Chem. Lett. 1996,6,945 B. Zhang, H; Zhang, A; Wang, w. Bioorg. Med. 1998,6,417 Is Bioorg. Med. Chem. Lett. 1996, 6, 2827".; Smith, T D ng. H: Shan, Camenisch, G. P; Wang Wang, B; Borchardt, R. T Pharm. Res. 1998.15.1174 16. Wang, B, Wang, W: Camenisch, G. P-; Elmo, J; Zhang, Tine H. Borchardt, R. T. Chem. Pharm. Bull.(Tokyo) 1999, Meptazinol (iv)-Meptazinol (ig)-Prodrug(ig) 17. Gudmundsson, O. Pauletti, G. M.; Wang, w: Shan, D Figure 3. Mean plasma meptazinol concentration curves after iv Zhang, H. Wang, B; Borchardt, R. T. Pharm. Res. 1999, and ig administration of meptazinol and ig ad tion of prodrug K: Wang, W: Zhang, H; Shanm, D 1999.53,370 The absolute bioavailability of meptazinol prodrug (3 19. Gudmundsson. O. Jois S. D. S: Vander Velde. D. G via ig administration was 51. 75%+ 32.99%(n=6). this Siahaan, T.J.; Wang, B. Borchardt, R. T.J. Pept. Res. indicated a more than 4-fold increase over the value ob- 1999,53,383. tained for meptazinol, 12.12%+3.57%. Based on the 20. Liao, Y; Wang, B. Bioorg. Med. Chem. Letf. 1999, 9, 1795 AUCo-10 and F% between the two groups suggested 21. Wang, W:Camenisch, G D. C: Zhang. H ng, B. J. Controlled Release 2000. 65. 245 22. Liao, Y; Hendrata, S: Bae, S. Y, Wang, B. Chem. propionyloxy)phenyl]-2-propenoic meptazinol ester Pharm. Bull. (Tokyo)2000, 48, 1138 hydrochloride (3),was ned and synthesized to 23. Ouyang, H der Velde. D. G: Borchardt. R. T minimize the first-pass meptazinol and en Siahaan, T.J. J. Pept. Res. 2002, 59, 183. hance the oral bioavailability. Biological evaluation 24. Tang, F; Borchardt, R T Pharm. Res. 2002, 19,787 data indicated that there was a 4-fold increase in oral 25. Ouyang, H. Tang, F; Siahaan, T. J:Borchardt, R.T. bioavailability of this prodrug compared to the parent drug meptazinol. This coumarin-based prodrug showed 26. Yang,J. Z; Chen, W: Borchardt,. T.J. Pharmacol Exp.Ther.2002,303,840 a superior oral bioavailability to the earlier reported 27. Chen, W; Yang, J.Z.:Andersen, R:Nielsen,L.H meptazinol benzoyl esters. These results highligh Borchardt, R. T.J. Pharmacol. Exp. Ther. 2002, 303, 849 the potential of using coumarin-based esterase-sensitive 28. Zych, L A Yang, W; Liao, Y; Griffin, K.R Wang, B system as a prodrug template for other drug molecules Bioorg. Chem. 2004. 32, 109 besides meptazinol 29. Shan, D: Nicolaou, M. G: Borchardt, R. T: Wang, B. J. Pharm.Sci.1997,86,765 30. Gudmundsson, O. S: Vander Velde, D. G: Jois, S.D. Acknowledgment Bak, A. Siahaan, T.J.; Borchardt, R. T.J. Pept. Res This project was supported by National Natural Science 31. Borchardt. R. T.J. Controlled Release 1999. 62. 231 Foundation of China(No. 30271539, 2003-2005) 32.Sp data of the carrier molecule H NMR DCl13)57.46(d,IH,7.36(t,IH),7.22(t,lH),7.08 J=121H),2.8(q,2H,J=76Hz),1.25(t,3H References and notes J=7.6Hz) 33. Synthesis of()-3-[2-(propionyloxy)phenyl]-2-propenoic 1. Med Actual/ Drugs Today, 1983, 19, 415 meptazinol ester hydrochloride (3). A solution of 2 2. Great britain medicines Commission. british pharmaco- (0.73 g, 3.32 mmol) in dry CH2Cl(15 ml) was added poria, London: Bernan Assoc. 1998, 859 DCC(0.75 g, 3.64 mmol)atOC. After stirring for 10 min, 3. Stephens, R. J; Waterfall, J. F ; Franklin, R. A.Gen. this was followed by the addition of 1(0. 70 g, 3.00 mm Pharmacol. 1978.9. 73 in dry CH2Cl2(40 ml) and DMAP(0.07g, 0.57 mmol) 4. Hoskin, P. J; Hanks, G. W. Drugs 1991, 41, 326 After stirring at0C for 2 h and at room temperature fo 5. Holmes, B; Ward, A. Drugs 1985, 30, 285 h. the solution was cooled below -20 oC for 30 min and 6. Norbury, H. M. Franklin, R. A; Graham, D. F. Eur J filtered. The filtrate was acidified to pH 7.0 using 2.5%o Clin. Pharmacol. 1983. 25.77 acetic acid, then extracted with CH,C1,(5 ml). The 7. Tzschentke, T. M.: Bruckmann. W: Friderichs, E. Ne combined organic layer was dried over MgsOa and rosci. Lett. 2002. 329. 25 evaporated to give a brown oil (1.54 g). The oil was 8. Zhang, H: Zhang, Y. Q: Qiu, Z. B: Zhao, Z. Q hromatographed on a silica gel column to afford the Neurosci. Lett. 2004. 356 prodrug base as a yellow oil (0.90 g, 68.9%). To a solution 9. Wang, P. F; Zhang, Y.Q.; Qiu, Z.B.; Zhao, Z.Q. Acta of the base(0.02 g)in dry ether (4 ml) was added HCI Phvsiol. Sin. 2004. 56. 295 ether (0.3 ml) to modulate ph to 4. The solution was 10. Li, W, Hao, J. L, Tang, Y. Chen, Y; Qiu, Z. B. Acta ten ure to afore Pharmacol. Sin. 2005. 26. 334 drochloride 3 as a yellow solid(0.02 g, 92.3%) 11. Lu, M. Y, Zhang, C. J Hao, J. L, Qiu, Z. B. Bioorg 34. Spectral data of the prodrug base and its hydrochloride Med. Chem. Lett. 2005. 15. 2607 (3): Spectral data of the prodrug base: H NMR(CDCl3)

The absolute bioavailability of meptazinol prodrug (3) via ig administration was 51.75% ± 32.99% (n = 6). This indicated a more than 4-fold increase over the value ob￾tained for meptazinol, 12.12% ± 3.57%. Based on the two sides t-test (P < 0.01), differences in the values of AUC0!10 and F% between the two groups suggested great statistical significance. propionyloxy)phenyl]-2-propenoic meptazinol ester hydrochloride (3), was designed and synthesized to minimize the first-pass effect of meptazinol and en￾hance the oral bioavailability. Biological evaluation data indicated that there was a 4-fold increase in oral bioavailability of this prodrug compared to the parent drug meptazinol. This coumarin-based prodrug showed a superior oral bioavailability to the earlier reported meptazinol benzoyl esters.11 These results highlight the potential of using coumarin-based esterase-sensitive system as a prodrug template for other drug molecules besides meptazinol. Acknowledgment This project was supported by National Natural Science Foundation of China (No. 30271539, 2003–2005). References and notes 1. Med Actual/Drugs Today, 1983, 19, 415. 2. Great Britain Medicines Commission. British Pharmaco￾poeia, London: Bernan Assoc. 1998, 859. 3. Stephens, R. J.; Waterfall, J. F.; Franklin, R. A. Gen. Pharmacol. 1978, 9, 73. 4. Hoskin, P. J.; Hanks, G. W. Drugs 1991, 41, 326. 5. Holmes, B.; Ward, A. Drugs 1985, 30, 285. 6. Norbury, H. M.; Franklin, R. A.; Graham, D. F. Eur. J. Clin. Pharmacol. 1983, 25, 77. 7. Tzschentke, T. M.; Bruckmann, W.; Friderichs, E. Neu￾rosci. Lett. 2002, 329, 25. 8. Zhang, H.; Zhang, Y. Q.; Qiu, Z. B.; Zhao, Z. Q. Neurosci. Lett. 2004, 356, 9. 9. Wang, P. F.; Zhang, Y. Q.; Qiu, Z. B.; Zhao, Z. Q. Acta Physiol. Sin. 2004, 56, 295. 10. Li, W.; Hao, J. L.; Tang, Y.; Chen, Y.; Qiu, Z. B. Acta Pharmacol. Sin. 2005, 26, 334. 11. Lu, M. Y.; Zhang, C. J.; Hao, J. L.; Qiu, Z. B. Bioorg. Med. Chem. Lett. 2005, 15, 2607. 12. Wang, B.; Zhang, H.; Wang, W. Bioorg. Med. Chem. Lett. 1996, 6, 945. 13. Wang, B.; Zhang, H.; Zhang, A.; Wang, W. Bioorg. Med. Chem. 1998, 6, 417. 14. Wang, B.; Wang, W.; Zhang, H.; Shan, D.; Smith, T. D. Bioorg. Med. Chem. Lett. 1996, 6, 2823. 15. Camenisch, G. P.; Wang, W.; Wang, B.; Borchardt, R. T. Pharm. Res. 1998, 15, 1174. 16. Wang, B.; Wang, W.; Camenisch, G. P.; Elmo, J.; Zhang, H.; Borchardt, R. T. Chem. Pharm. Bull. (Tokyo) 1999, 47, 90. 17. Gudmundsson, O.; Pauletti, G. M.; Wang, W.; Shan, D.; Zhang, H.; Wang, B.; Borchardt, R. T. Pharm. Res. 1999, 16, 7. 18. Wang, B.; Nimkar, K.; Wang, W.; Zhang, H.; Shanm, D.; Gudmundsson, O.; Gangwar, S.; Siahaan, T.; Borchardt, R. T. J. Pept. Res. 1999, 53, 370. 19. Gudmundsson, O.; Jois, S. D. S.; Vander Velde, D. G.; Siahaan, T. J.; Wang, B.; Borchardt, R. T. J. Pept. Res. 1999, 53, 383. 20. Liao, Y.; Wang, B. Bioorg. Med. Chem. Lett. 1999, 9, 1795. 21. Wang, W.; Camenisch, G.; Sane, D. C.; Zhang, H.; Hugger, E.; Wheeler, G. L.; Borchardt, R. T.; Wang, B. J. Controlled Release 2000, 65, 245. 22. Liao, Y.; Hendrata, S.; Bae, S. Y.; Wang, B. Chem. Pharm. Bull. (Tokyo) 2000, 48, 1138. 23. Ouyang, H.; Vander Velde, D. G.; Borchardt, R. T.; Siahaan, T. J. J. Pept. Res. 2002, 59, 183. 24. Tang, F.; Borchardt, R. T. Pharm. Res. 2002, 19, 787. 25. Ouyang, H.; Tang, F.; Siahaan, T. J.; Borchardt, R. T. Pharm. Res. 2002, 19, 794. 26. Yang, J. Z.; Chen, W.; Borchardt, R. T. J. Pharmacol. Exp. Ther. 2002, 303, 840. 27. Chen, W.; Yang, J. Z.; Andersen, R.; Nielsen, L. H.; Borchardt, R. T. J. Pharmacol. Exp. Ther. 2002, 303, 849. 28. Zych, L. A.; Yang, W.; Liao, Y.; Griffin, K. R.; Wang, B. Bioorg. Chem. 2004, 32, 109. 29. Shan, D.; Nicolaou, M. G.; Borchardt, R. T.; Wang, B. J. Pharm. Sci. 1997, 86, 765. 30. Gudmundsson, O. S.; Vander Velde, D. G.; Jois, S. D.; Bak, A.; Siahaan, T. J.; Borchardt, R. T. J. Pept. Res. 1999, 53, 403. 31. Borchardt, R. T. J. Controlled Release 1999, 62, 231. 32. Spectral data of the carrier molecule (2): 1 H NMR (CDCl3) d 7.46 (d, 1H), 7.36 (t, 1H), 7.22 (t, 1H), 7.08 (d, 1H), 7.00 (d, 1H, J = 12.2 Hz), 6.05 (d, 1H, J = 12.2 Hz), 2.58 (q, 2H, J = 7.6 Hz), 1.25 (t, 3H, J = 7.6 Hz). 33. Synthesis of (Z)-3-[2-(propionyloxy)phenyl]-2-propenoic meptazinol ester hydrochloride (3). A solution of 2 (0.73 g, 3.32 mmol) in dry CH2Cl2 (15 ml) was added DCC (0.75 g, 3.64 mmol) at 0 C. After stirring for 10 min, this was followed by the addition of 1 (0.70 g, 3.00 mmol) in dry CH2Cl2 (40 ml) and DMAP (0.07 g, 0.57 mmol). After stirring at 0 C for 2 h and at room temperature for 4 h, the solution was cooled below
20 C for 30 min and filtered. The filtrate was acidified to pH 7.0 using 2.5% acetic acid, then extracted with CH2Cl2 (5 ml). The combined organic layer was dried over MgSO4 and evaporated to give a brown oil (1.54 g). The oil was chromatographed on a silica gel column to afford the prodrug base as a yellow oil (0.90 g, 68.9%). To a solution of the base (0.02 g) in dry ether (4 ml) was added HCl– ether (0.3 ml) to modulate pH to 4. The solution was concentrated and dried at room temperature to afford hydrochloride 3 as a yellow solid (0.02 g, 92.3%). 34. Spectral data of the prodrug base and its hydrochloride (3): Spectral data of the prodrug base: 1 H NMR (CDCl3) Figure 3. Mean plasma meptazinol concentration–time curves after iv and ig administration of meptazinol and ig administration of prodrug in rats. Q. Xie et al. / Bioorg. Med. Chem. Lett. 15 (2005) 4953–4956 4955

4956 0. Xie et al/ Bioorg. Med. Chem. Lett. 15(2005)4953-4956 67.60dd,H,J1=7.33Hz,J2=1.37Hz),7.34(dt,lH, NHCH2×2),282(m,3H,NCH3),2.59(q,2H, J1=7.53Hz,J2=1.37Hz),7.27m,H),7.22dt,iH, J=742Hz,COCH2CH3),283-1.40(m,8H,CH2×4 J1=7.52Hz,J2=1.02Hz),7.l4(m,IH),7.l0(dd,1H, 1.13(t,丑H,J=742Hz,COCH2CH3),0.49(m,3H J1=8.20Hz,J2=1.02Hz),7.07(d,1H,J=12.3Hz,cis- CH2CH3).C NMR(DMSO-d6):8171.2(C=O), 162.8 CH×1),6.946.90(m,2H),6.22(d,IH,J=12.3Hz, C=O,149.6,147.3,144.8,143.3,138.4,129.5,128.9, cis-=CH×1),2.90(m,1H,NCH2),2.72-2.65(m,2H, 127.4,124.9,123.7&123.3,121.9,120.8,119.7,1193, NCH2),2.60(q,2H,J=7.52Hz,COCH2CH3),2.54 60&628,59.3&57.7,47.1&46.3,44.2&43.8,36.0& 248(m,IH,NCH2),2.44(s,3H,NCH3),213-1.52(m, 35.3,33.5&33.0,26.9,26.4&24.8,20.7,9.1,8.3.HR 8H,CH2×4),1.28(t,3H,J=7.52Hz,COCH2CH3) ESI M+l] caled for C27H34NO4 436.24823, found 060(t, 3H, J=7.52 Hz, CH2CH3) Spectral data of the 436.24848.FTIR:3404(YN+H),2937,1758(c=0 drug hydrochloride (3): H NMR (DMSO-d6): 8 1606( Phenyl),1458,113l(Ycoc,950,761,702 l0.l8(brs,≈1/2H H, D,O exchange),8.63(br s, 35. Franklin. R. A: Pierce. D. M.: Goode. P. G.J. Pharr 1/2H, N-H, D,O exchange), 7.60(t, IH, J=7.42 Hz, Pharmacol!1976,28,852 Ar-H),7.45-7.38(m, 2H, Ar-H x2),7.31-7.00(m, 6H, 36. Hu, X.Y. Liu, F. Luo, Y. Yaowu Fenxi Zazhi(chinese) ArH×5,ci=CH×1),6.32(dd,H,J1=4.3Hz, 1997,l7,124 J2=12.1Hz;cis-=CH×1),3.94-3.09(m,4H,37. Frost,T. Analyst1981,l06,999

d 7.60 (dd, 1H, J1 = 7.53 Hz, J2 = 1.37 Hz), 7.34 (dt, 1H, J1 = 7.53 Hz, J2 = 1.37 Hz), 7.27 (m, 1H), 7.22 (dt, 1H, J1 = 7.52 Hz, J2 = 1.02 Hz), 7.14 (m, 1H), 7.10 (dd, 1H, J1 = 8.20 Hz, J2 = 1.02 Hz), 7.07 (d, 1H, J = 12.3 Hz, cis- = CH · 1), 6.94–6.90 (m, 2H), 6.22 (d, 1H, J = 12.3 Hz, cis- = CH · 1), 2.90 (m, 1H, NCH2), 2.72–2.65 (m, 2H, NCH2), 2.60 (q, 2H, J = 7.52 Hz, COCH2CH3), 2.54– 2.48 (m, 1H, NCH2), 2.44 (s, 3H, N-CH3), 2.13–1.52 (m, 8H, CH2 · 4), 1.28 (t, 3H, J = 7.52 Hz, COCH2CH3), 0.60 (t, 3H, J = 7.52 Hz, CH2CH3). Spectral data of the prodrug hydrochloride (3): 1 H NMR (DMSO-d6): d 10.18 (br s, 1/2 H, N+–H, D2O exchange), 8.63 (br s, 1/2 H, N+ –H, D2O exchange), 7.60 (t, 1H, J = 7.42 Hz, Ar-H), 7.45–7.38 (m, 2H, Ar-H · 2), 7.31–7.00 (m, 6H, Ar-H · 5, cis- = CH · 1), 6.32 (dd, H, J1 = 4.3 Hz, J2 = 12.1 Hz; cis- = CH · 1), 3.94–3.09 (m, 4H, NHCH2 · 2), 2.82 (m, 3H, N-CH3), 2.59 (q, 2H, J = 7.42 Hz, COCH2CH3), 2.83–1.40 (m, 8H, CH2 · 4), 1.13 (t, 3H, J = 7.42 Hz, COCH2CH3), 0.49 (m, 3H, CH2CH3). 13C NMR (DMSO-d6): d 171.2 (C@O), 162.8 (C@O), 149.6, 147.3, 144.8, 143.3, 138.4, 129.5, 128.9, 127.4, 124.9, 123.7 & 123.3, 121.9, 120.8, 119.7, 119.3, 66.0 & 62.8, 59.3 & 57.7, 47.1 & 46.3, 44.2 & 43.8, 36.0 & 35.3, 33.5 & 33.0, 26.9, 26.4 & 24.8, 20.7, 9.1, 8.3. HR￾ESI [M+1]+ calcd for C27H34NO4 436.24823, found 436.24848. FT-IR: 3404 (cN+H), 2937, 1758 (cC@O), 1606 (cphenyl), 1458, 1131 (cC–O–C), 950, 761,702. 35. Franklin, R. A.; Pierce, D. M.; Goode, P. G. J. Pharm. Pharmacol. 1976, 28, 852. 36. Hu, X. Y.; Liu, F.; Luo, Y. Yaowu Fenxi Zazhi (Chinese) 1997, 17, 124. 37. Frost, T. Analyst 1981, 106, 999. 4956 Q. Xie et al. / Bioorg. Med. Chem. Lett. 15 (2005) 4953–4956