Domino and one-pot syntheses of biologically active compounds using diphenylprolinol silyl ether

References

[1] Selected reviews on organocatalysis: (a) List B, eds. Asymmetric organocatalysis 1; lewis base and acid catalysts, Thieme, Stuttgart, 2012. (b) Dalko PI, editors. Comprehensive Enantioselective Organocatalysis: Catalysts, Reactions, and Applications. Weinheim: Wiley-VCH, 2013.Suche in Google Scholar

[2] (a) Wender PA, Croatt MP, Witulski B. New reactions and step economy: the total synthesis of (±)-salsolene oxide based on the type II transition metal-catalyzed intramolecular [4+4] cycloaddition. Tetrahedron 2006, 62, 7505–11. (b) Wender PA, Verma VA, Paxton TJ, Pillow TH. Function-oriented synthesis, step economy, and drug design. Acc Chem Res. 2008;41:40–9. (c) Wender PA. Toward the ideal synthesis and molecular function through synthesis-informed design. Nat Prod Rep. 2014;31:433–40.10.1016/j.tet.2006.02.085Suche in Google Scholar

[3] Gaich T, Baran PS. Aiming for the ideal synthesis. J Org Chem. 2010;75:4657–73.10.1021/jo1006812Suche in Google Scholar PubMed

[4] (a) Tietze LF. Domino reactions in organic synthesis. Chem Rev 1996, 96, 115–36. (b) Tietze LF, editors. Domino Reactions. Weinheim: Wiley-VCH, 2014.10.1002/9783527609925Suche in Google Scholar

[5] Enders D, Huttl MR, Grondal C, Raabe G. Control of four stereocentres in a triple cascade organocatalytic reaction. Nature. 2006;441:861–3.10.1038/nature04820Suche in Google Scholar PubMed

[6] Review; (a) Grondal C, Jeanty M, Enders D. Organocatalytic cascade reactions as a new tool in total synthesis. Nature Chem 2010, 2, 167–78. (b) Albrecht L, Jiang H, Jørgensen KA. A simple recipe for sophisticated cocktails: organocatalytic one-pot reactions–concept, nomenclature, and future perspectives. Angew Chem Int Ed. 2011;50:8492–82509. (c) Pellissier H. Recent Developments in asymmetric organocatalytic domino reactions. Adv Synth Catal. 2012;354:237–94. (d) Volla CM, Atodiresei I, Rueping M. Catalytic C–C. Bond-forming multi-component cascade or domino reactions: Pushing the boundaries of complexity in asymmetric organocatalysis. Chem Rev. 2014;114:2390–431. (e) Hong B-C, Raja A, Sheth VM. Asymmetric synthesis of natural products and medicinal drugs through one-pot-reaction strategies. Synthesis. 2015;47:3257–85.10.1038/nchem.539Suche in Google Scholar PubMed

[7] Ishikawa H, Suzuki T, Hayashi Y. High-yielding synthesis of the anti-influenza neuramidase inhibitor (-)-oseltamivir by three “one-pot” operations. Angew Chem Int Ed. 2009;48:1304–7.10.1002/anie.200804883Suche in Google Scholar PubMed

[8] Hayashi Y. Pot economy and one-pot synthesis. Chem Sci. 2016;7:866–80.10.1039/C5SC02913ASuche in Google Scholar PubMed PubMed Central

[9] Reviews, (a) Marques-Lopez E, Herrera RP, Christmann M. Asymmetric organocatalysis in total synthesis – a trial by fire. Nat Prod Rep 2010, 27, 1138–67. (b) Dibello E, Gamenara D, Seoane G. Organocatalysis in the Synthesis of Natural Products: Recent development in aldol and mannich reactions, and 1,4-conjugated additions. Current Organocatal. 2015;2:124–49. (c) Sun B-F. Total synthesis of natural and pharmaceutical products powered by organocatalytic reactions. Tetrahedron Lett. 2015;56:2133–40.10.1039/b924964hSuche in Google Scholar PubMed

[10] Hayashi Y, Gotoh H, Hayashi T, Shoji M. Diphenylprolinol silyl ethers as efficient organocatalysts for the asymmetric Michael reaction of aldehydes and nitroalkenes. Angew Chem Int Ed. 2005;44:4212–15.10.1002/anie.200500599Suche in Google Scholar PubMed

[11] Marigo M, Wabnitz TC, Fielenbach D, Jørgensen KA. Enantioselective organocatalyzed α sulfenylation of aldehydes. Angew Chem Int Ed. 2005;44:794–7.10.1002/anie.200462101Suche in Google Scholar PubMed

[12] For reviews, see: (a) Palomo C, Mielgo A. Diarylprolinol ethers: expanding the potential of enamine/iminium‐ion catalysis. Angew Chem Int Ed 2006, 45, 7876–80. (b) Mielgo A, Palomo C. α,α‐Diarylprolinol Ethers: New tools for functionalization of carbonyl compounds. Chem Asian J. 2008;3:922–48. (c) Xu LW, Li L, Shi ZH. Asymmetric synthesis with silicon-based bulky amino organocatalysts. Adv Synth Catal. 2010;352:243–79. (d) Jensen KL, Dickmeiss G, Jiang H, Albrecht L, Jørgensen KA. The diarylprolinol silyl ether system: A general organocatalyst. Acc Chem Res. 2012;45:248–64. (e) Gotoh H, Hayashi Y. in Sustainable catalysis, Dunn J, Hii KK, Krische M J, Williams M T. editor. Hoboken: Wiley, 2013:287–316. (f) Donslund BS, Johansen TK, Poulsen PH, Halskov KS, Jørgensen KA. The diarylprolinol silyl ethers: Ten years after. Angew Chem Int Ed. 2015;54:13860–74.10.1002/anie.200602943Suche in Google Scholar

[13] Hayashi Y, Okamura D, Yamazaki T, Ameda Y, Gotoh H, Tsuzuki S, et al. A theoretical and experimental study of the effects of silyl substituents in enantioselective reactions catalyzed by diphenylprolinol silyl ether. Chem Eur J. 2014;20:17077–88.10.1002/chem.201403514Suche in Google Scholar

[14] (a) Seebach D, Grošelj U, Badine D M, Schweizer W B, Beck A K. Isolation and x‐ray structures of reactive intermediates of organocatalysis with diphenylprolinol ethers and with imidazolidinones: a survey and comparison with computed structures and with 1‐acyl‐imidazolidinones: the 1,5‐repulsion and the geminal‐diaryl effect at work. Helv Chem Acta 2008, 91, 1999–2034. (b) Grošelj U, Seebach D, Badine DM, Schweizer WB, Beck AK, Krossing I, Klose P, Hayashi Y. Uchimaru T. Structures of the reactive intermediates in organocatalysis with diarylprolinol ethers. Helv Chem Acta. 2009;92:1225–59.10.1002/hlca.200890216Suche in Google Scholar

[15] Gotoh H, Uchimaru T, Hayashi Y. Two reaction mechanisms via iminium ion intermediates: the different reactivities of diphenylprolinol silyl ether and trifluoromethyl-substituted diarylprolinol silyl ether. Chem Eur J. 2015;21:12337–46.10.1002/chem.201500326Suche in Google Scholar

[16] 2-​[diphenyl[(trimethyl​silyl)​oxy]​methyl]​pyrrolidineSuche in Google Scholar

[17] Olpe HR, Demieville H, Baltzer V, Bencze WL, Koella WP, Wolf P, et al. The biological activity of d-baclofen (Lipresal^®). Eur J Pharmacol. 1978;52:133–6.10.1016/0014-2999(78)90032-8Suche in Google Scholar

[18] Gotoh H, Ishikawa H, Hayashi Y. Diphenylprolinol silyl ether as catalyst of an asymmetric, catalytic, and direct michael reaction of nitroalkanes with α,β-unsaturated aldehydes. Org Lett. 2007;9:5307–9.10.1021/ol702545zSuche in Google Scholar PubMed

[19] Zu L, Xie H, Li H, Wang J, Wang W. Highly enantioselective organocatalytic conjugate addition of nitromethane to α,β‐unsaturated aldehydes: three‐step synthesis of optically active baclofen. Add Synth Catal. 2007;349:2660–4.10.1002/adsc.200700353Suche in Google Scholar

[20] Hayashi Y, Sakamoto D, Okamura D. One-pot synthesis of (S)-baclofen via aldol condensation of acetaldehyde with diphenylprolinol silyl ether mediated asymmetric michael reaction as a key step. Org Lett. 2016;18:4–7.10.1021/acs.orglett.5b02839Suche in Google Scholar PubMed

[21] (a) Hayashi Y, Itoh T, Aratake S, Ishikawa H. A diarylprolinol in an asymmetric, catalytic, and direct crossed-aldol reaction of acetaldehyde. Angew Chem Int Ed 2008, 47, 2082–4. (b) Hayashi Y, Samanta S, Itoh T, Ishikawa H. Asymmetric, Catalytic, and direct self-aldol reaction of acetaldehyde catalyzed by diarylprolinol. Org Lett. 2008;10:5581–3.10.1002/anie.200704870Suche in Google Scholar PubMed

[22] Okino T, Hoashi Y, Furukawa T, Xu X, Takemoto Y. Enantio- and diastereoselective michael reaction of 1,3-dicarbonyl compounds to nitroolefins catalyzed by a bifunctional thiourea. J Am Chem Soc. 2005;127:119–25.10.1021/ja044370pSuche in Google Scholar PubMed

[23] Baschieri A, Bernardi L, Ricci A, Suresh S, Adamo MFA. Catalytic asymmetric conjugate addition of nitroalkanes to 4‐nitro‐5‐styrylisoxazoles. Angew Chem Int Ed. 2009;48:9342–5.10.1002/anie.200905018Suche in Google Scholar PubMed

[24] Xu F, Zacuto M, Yoshikawa N, Desmond R, Hoerrner S, Itoh T, et al. Asymmetric synthesis of telcagepant, a CGRP receptor antagonist for the treatment of migraine. J Org Chem. 2010;75:7829–41.10.1021/jo101704bSuche in Google Scholar PubMed

[25] Paone DV, Shaw AW, Nguyen DN, Burgey CS, Deng JZ, Kane SA, et al. Potent, orally bioavailable calcitonin gene-related peptide receptor antagonists for the treatment of migraine:  discovery of N-[(3R,6S)-6-(2,3-Difluorophenyl)-2-oxo-1-(2,2,2-trifluoroethyl)azepan-3-yl]-4-(2-oxo-2,3-dihydro-1 H-imidazo[4,5-b]pyridin-1-yl)piperidine-1-carboxamide (MK-0974). J Med Chem. 2007;50:5564–7.10.1021/jm070668pSuche in Google Scholar PubMed

[26] Reviews, see (a) Farina V, Brown JD Tamiflu: the supply problem. Angew Chem Int Ed 2006, 45, 7330–4. (b) Shibasaki M, Kanai M. Synthetic strategies for oseltamivir phosphate. Eur J Org Chem. 2008;1839–50. (c) Magano J. Synthetic approaches to the neuraminidase inhibitors zanamivir (relenza) and oseltamivir phosphate (tamiflu) for the treatment of influenza. Chem Rev. 2009;109:4398–438. (d) Andraos J. Global green chemistry metrics analysis algorithm and spreadsheets: evaluation of the material efficiency performances of synthesis plans for oseltamivir phosphate (tamiflu) as a test case. Org Process Res Dev. 2009;13:161–85. (e) Magano J. Recent synthetic approaches to oseltamivir phosphate (Tamiflu™) for the treatment of influenza. Tetrahedron. 2011;67:7875–99. (f) Shibasaki M, Kanai M, Yamatsugu K. Recent development in synthetic strategies for oseltamivir phosphate. Isr J Chem. 2011;51:316–28. (g) Li N-G, Shi Z-H, Tang Y-P, Shi Q-P, Zhang W, Zhang P-X, Dong Z-X, Li W, Duan J-A. Recent progress on the total synthesis of (–)-oseltamivir phosphate (tamiflu) for the treatment of influenza disease. Curr Org Chem. 2014;18:2125–38.10.1002/anie.200602623Suche in Google Scholar PubMed

[27] Ishikawa H, Suzuki T, Orita H, Uchimaru T, Hayashi Y. High-yielding synthesis of the anti-influenza neuramidase inhibitor (-)-oseltamivir by two “one-pot” sequences. Chem Eur J. 2010;16:12616–26.10.1002/chem.201001108Suche in Google Scholar PubMed

[28] Mukaiyama T, Ishikawa H, Koshino H, Hayashi Y. One-pot synthesis of (-)-oseltamivir and mechanistic insights into the organocatalyzed michael reaction. Chem Eur J. 2013;19:17789–800.10.1002/chem.201302371Suche in Google Scholar PubMed

[29] Hayashi Y, Ogasawara S. Time economical total synthesis of (-)-oseltamivir. Org Lett. 2016;18:3426–9.10.1021/acs.orglett.6b01595Suche in Google Scholar PubMed

[30] Ogasawara S, Hayashi Y. Multistep continuous-flow synthesis of (-)-oseltamivir. Synthesis. 2017;49:424–8.10.1055/s-2016-0036-1588899Suche in Google Scholar

[31] Zhu S, Yu S, Wang Y, Ma D. Organocatalytic michael addition of aldehydes to protected 2‐amino‐1‐nitroethenes: the practical syntheses of oseltamivir (tamiflu) and substituted 3‐aminopyrrolidines. Angew Chem Int Ed. 2010;49:4656–60.10.1002/anie.201001644Suche in Google Scholar PubMed

[32] (a) Rehak J, Hutka M, Latika A, Brath H, Almassy A, Hajzer V, et al. Thiol-free synthesis of oseltamivir and its analogues via organocatalytic michael additions of oxyacetaldehydes to 2-acylaminonitroalkenes. Synthesis 2012, 44, 2424–30. (b) Hajzer V, Latika A, Durmis J, Sebesta R. Enantioselective Michael addition of the 2‐(1‐ethylpropoxy)acetaldehyde to N‐[(1Z)‐2‐nitroethenyl]acetamide – optimization of the key step in the organocatalytic oseltamivir synthesis. Helv Chem Acta. 2012;95:2421–8.10.1055/s-0031-1290396Suche in Google Scholar

[33] Weng J, Li Y-B, Wang R-B, Lu G. Organocatalytic michael reaction of nitroenamine derivatives with aldehydes: short and efficient asymmetric synthesis of ( − )-oseltamivir. Chem Cat Chem. 2012;4:1007–12.Suche in Google Scholar

[34] Patora‐Komisarska K, Benohoud M, Ishikawa H, Seebach D, Hayashi Y. Organocatalyzed Michael addition of aldehydes to nitro alkenes – generally accepted mechanism revisited and revised. Helv Chem Acta. 2011;94:719–45.10.1002/hlca.201100122Suche in Google Scholar

[35] (a) Burés J, Armstrong A, Blackmond DG Mechanistic rationalization of organocatalyzed conjugate addition of linear aldehydes to nitro-olefins. J Am Che Soc 2011, 133, 8822–5. (b) Burés J, Armstrong A, Blackmond D G. Curtin–Hammett paradigm for stereocontrol in organocatalysis by diarylprolinol ether catalysts. J Am Che Soc. 2012;134:6741–50. (c) Bächle F, Duschmalé J, Ebner C, Pfaltz A, Wennemers H. Organocatalytic asymmetric conjugate addition of aldehydes to nitroolefins: identification of catalytic intermediates and the stereoselectivity‐determining step by ESI‐MS. Angew Chem Int Ed. 2013;52:12619–23. (d) Isenegger PG, Pfaltz A. Mass spectrometric back reaction screening of quasi-enantiomeric products as a mechanistic tool. Chem Rev. 2016;16:2534–43. (e) Földes T, Madarász Á, Révész Á, Dobi Z, Varga Sz, Hamza A, Nagy P R, Pihko P M, Pápai I. Stereocontrol in diphenylprolinol silyl ether catalyzed michael additions: steric shielding or curtin-hammett scenario? J Am Chem Soc. 2017;139:17052–63.10.1021/ja203660rSuche in Google Scholar PubMed

[36] (a) Schreiner PR Metal-free organocatalysis through explicit hydrogen bonding interactions. Chem Soc Rev 2003, 32, 289–96. (b) Zhang Z, Schreiner P R. Chem Soc Rev. 2009;38:1187–98.10.1039/b107298fSuche in Google Scholar PubMed

[37] (a) Yoshida J, Nagaki A, Yamada T Flash chemistry: fast chemical synthesis by using microreactors. Chem Eur J 2008, 14, 7450–9. (b) Webb D, Jamison T F. Continuous flow multi-step organic synthesis. Chem Sci. 2010;1, 675–80. (c) Wiles C, Watts P. Continuous flow reactors: a perspective. Green Chem. 2012;14:38–54. (d) Poechlauer P, Manley J, Broxterman R, Gregertsen B, Ridemark M. Continuous processing in the manufacture of active pharmaceutical ingredients and finished dosage forms: an industry perspective. Org Process Res Dev. 2012;16:1586–190. (e) Hartman R L, McMullen J P, Jensen K F. Deciding whether to go with the flow: evaluating the merits of flow reactors for synthesis. Angew Chem Int Ed. 2011;50:7502–19. (f) Newman S G, Jensen K F. The role of flow in green chemistry and engineering. Green Chem. 2013;15:1456–72. (g) Tsubogo T, Ishikawa T, Kobayashi S. Asymmetric carbon-carbon bond formation under continuous-flow conditions with chiral heterogeneous catalysts. Angew Chem Int Ed. 2013;52:6590–604.10.1002/chem.200800582Suche in Google Scholar PubMed

[38] Hessel V. Novel process windows – gate to maximizing process intensification via flow chemistry. Chem Eng Technol. 2009;32:1655–81.10.1002/ceat.200900474Suche in Google Scholar

[39] Pei Z, Li X, von Geldern TW, Madar DJ, Longenecker K, Yong H, et al. Discovery of ((4R,5S)-5-Amino-4-(2,4,5- trifluorophenyl)cyclohex-1-enyl)-(3- (trifluoromethyl)-5,6-dihydro- [1,2,4]triazolo[4,3-a]pyrazin-7(8 H)-yl)methanone (ABT-341), a highly potent, selective, orally efficacious, and safe dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes. J Med Chem. 2006;49:6439–42.10.1021/jm060955dSuche in Google Scholar PubMed

[40] Hayashi Y, Itoh T, Ohkubo M, Ishikawa H. Asymmetric michael reaction of acetaldehyde catalyzed by diphenylprolinol silyl ether. Angew Chem Int Ed. 2008;47:4722–4.10.1002/anie.200801130Suche in Google Scholar PubMed

[41] Ishikawa H, Honma M, Hayashi Y. One‐pot high‐yielding synthesis of the DPP4‐selective Inhibitor ABT‐341 by a four‐component coupling mediated by a diphenylprolinol silyl ether. Angew Chem Int Ed. 2011;50:2824–7.10.1002/anie.201006204Suche in Google Scholar PubMed

[42] Funk CD. Prostaglandins and leukotrienes: advances in eicosanoid biology. Science. 2001;294:1871–5.10.1126/science.294.5548.1871Suche in Google Scholar PubMed

[43] Das D, Chandrasekhar S, Yadav JS, Gree R. Recent developments in the synthesis of prostaglandins and analogues. Chem Rev. 2007;107:3286–337.10.1021/cr068365aSuche in Google Scholar PubMed

[44] (a) Corey EJ, Weinshenker NM, Schaaf TK, Huber W Stereo-controlled synthesis of dl-prostaglandins F_2α and E2. J Am Chem Soc 1969, 91, 5675–7. (b) Corey E J, Cheng X M. The Logic of chemical synthesis, New York: Wiley, 1995.10.1021/ja01048a062Suche in Google Scholar

[45] Coulthard G, Erb W, Aggarwal VK. Stereocontrolled organocatalytic synthesis of prostaglandin PGF_2α in seven steps. Nature. 2012;489:278–81.10.1038/nature11411Suche in Google Scholar

[46] Pelss A, Gandhamsetty N, Smith JR, Mailhol D, Silvi M, Watson A, et al. Re‐optimization of the organocatalyzed double aldol domino process to a key enal intermediate and its application to the total synthesis of Δ¹²‐prostaglandin J₃. Chem Eur J. 2018;24:9542–5.10.1002/chem.201802498Suche in Google Scholar

[47] Hayashi Y, Umemiya S. Pot economy in the synthesis of prostaglandin a₁ and e₁ methyl esters. Angew Chem Int Ed. 2013;52:3450–2.10.1002/anie.201209380Suche in Google Scholar

[48] Umemiya S, Nishino K, Sato I, Hayashi Y. Nef reaction with molecular oxygen in the absence of metal additives, and mechanistic insights. Chem Eur J. 2014;20:15753–9.10.1002/chem.201403475Suche in Google Scholar

[49] Biellmann J-F. Enantiomeric steroids: synthesis, physical, and biological properties. Chem Rev. 2003;103:2019–34.10.1021/cr020071bSuche in Google Scholar

[50] (a) Kametani T, Nemoto H Recent advances in the total synthesis of steroids via intramolecular cycloaddition reactions. Tetrahedron 1981, 37, 3–16. (b) Chapelon A S, Moralëda D, Rodriguez R, Ollivier C, Santelli M. Enantioselective synthesis of steroids. Tetrahedron. 2007;63:11511–616. (c) Gupta P, Panda G. Asymmetric assembly of steroidal tetracyclic skeletons. Eur J Org Chem. 2014;8004–19.10.1016/S0040-4020(01)97707-5Suche in Google Scholar

[51] See the references cited therein Koshino S, Kwon E, Hayashi Y. Total synthesis of estradiol methyl ether and its five-pot synthesis with an organocatalyst. Eur J Org Chem. 2018;5629–38.10.1002/ejoc.201800910Suche in Google Scholar

[52] Funk RL, Vollhardt KPC. The cobalt way to dl-estrone, a highly regiospecific functionalization of 2,3-bis(trimethylsilyl)estratrien-17-one. J Am Chem Soc. 1979;101:215–17.10.1021/ja00495a035Suche in Google Scholar

[53] Ananchenko SN, Torgov IV. New syntheses of estrone, d,1-8-iso-oestrone and d,1-19-nortestosterone. Tetrahedron Lett. 1963;4:1553–8.10.1016/S0040-4039(01)90870-6Suche in Google Scholar

[54] Yeung Y‐Y, Chein R‐J, Corey EJ. Conversion of torgov’s synthesis of estrone into a highly enantioselective and efficient process. J Am Chem So. 2007;129:10346–7.10.1021/ja0742434Suche in Google Scholar

[55] (a) Hajos ZG, Parrish DR German Patent DE 2102623. July 29, 1971. (b) Hajos Z G, Parrish D R. Asymmetric synthesis of bicyclic intermediates of natural product chemistry. J Org Chem. 1974;39:1615–21.Suche in Google Scholar

[56] (a) Eder U, Sauer G, Wiechert R German Patent DE 2014757, Oct 7, 1971 (b) Eder U, Sauer G, Wiechert R. New Type of asymmetric cyclization to optically active steroid CD partial structures. Angew Chem Int Ed Engl. 1971;10:496–7.Suche in Google Scholar

[57] Bradshaw B, Bonjoch J. The wieland–miescher ketone: a journey from organocatalysis to natural product synthesis. Synlett. 2012;23:337–56.10.1055/s-0031-1290107Suche in Google Scholar

[58] Jhuo D‐H, Hong B‐C, Chang C‐W, Lee G‐H. One-pot organocatalytic enantioselective domino double-michael reaction and pictet-spengler–lactamization reaction. a facile entry to the “inside yohimbane” system with five contiguous stereogenic centers. Org Lett. 2014;16:2724–7.10.1021/ol501011tSuche in Google Scholar

[59] Halskov KS, Donslund BS, Barfüsser S, Jørgensen KA. Organocatalytic asymmetric formation of steroids. Angew Chem Int Ed. 2014;53:4137–41.10.1002/anie.201400203Suche in Google Scholar

[60] Prévost S, Dupré N, Leutzsch M, Wang Q, Wakchaure V, List B. Catalytic asymmetric Torgov cyclization: a concise total synthesis of (+)-estrone. Angew Chem Int Ed. 2014;53:8770–3.10.1002/anie.201404909Suche in Google Scholar

[61] Hayashi Y, Koshino S, Ojima K, Kwon E. Pot economy in the total synthesis of estradiol methyl ether by using an organocatalyst. Angew Chem Int Ed. 2017;56:11812–15.10.1002/anie.201706046Suche in Google Scholar

[62] Mukaiyama T, Ogata K, Sato I, Hayashi Y. Asymmetric organocatalyzed michael addition of nitromethane to a 2-oxoindoline-3-ylidene acetaldehyde and the three one-pot sequential synthesis of (-)-horsfiline and (-)-coerulescine. Chem Eur J. 2014;20:13583.10.1002/chem.201403932Suche in Google Scholar

[63] Jossang A, Jossang P, Hadi HA, Sévenet T, Bodo B. Horsfiline, an oxindole alkaloid from horsfieldia superba. J Org Chem. 1991;56:6527–30.10.1021/jo00023a016Suche in Google Scholar

[64] Anderton N, Cockrum PA, Colegate SM, Edgar JA, Flower K, Vit I, et al. Oxindoles from Phalaris Coerulescens. Phytochemistry. 1998;48:437–9.10.1016/S0031-9422(97)00946-1Suche in Google Scholar