Generic placeholder image

Current Organic Synthesis

Editor-in-Chief

ISSN (Print): 1570-1794
ISSN (Online): 1875-6271

Review Article

Comprehensive Account on the Synthesis of (-)-Balanol and its Analogues

Author(s): Sajjad Ahmad, Rabia Akhtar and Ameer Fawad Zahoor*

Volume 19, Issue 1, 2022

Published on: 09 August, 2021

Page: [56 - 85] Pages: 30

DOI: 10.2174/1570179418666210809131917

Price: $65

Abstract

Background: A variety of diseases have been associated with hyperactivation of protein kinase C (PKC) enzymes such as cancer, diabetes, asthma, cardiovascular and central nervous system disorders. There is a dire need to selectively inhibit these enzymes by synthesizing new potent inhibitors. Balanol, a fungal metabolite belonging to the PKC inhibitor family, is especially included in this aspect. Tremendous effort has been put towards the synthesis of balanol by different research groups.

Objectives: The aim of this review is to provide a detailed description of synthetic approaches adopted for the synthesis of key fragments of balanol (azepane and benzophenone). All the factors that resulted in excellent yield and high enantioselectivity have also been mentioned.

Conclusion: It has been shown throughout this review that the synthesis of hexahydroazepine and benzophenone cores of balanol was achieved by employing a variety of important key steps with commercially available starting precursors, which make this total synthesis more valuable. Moreover, this article provides ideas to the synthetic as well as pharmaceutical chemists for the synthesis of (-)-balanol and its analogues.

Keywords: Protein kinase C, balanol, chiral synthesis, benzophenone, azepine, phosphorylation.

Graphical Abstract

[1]
Lampe, J.W.; Biggers, C.K.; Defauw, J.M.; Foglesong, R.J.; Hall, S.E.; Heerding, J.M.; Hollinshead, S.P.; Hu, H.; Hughes, P.F.; Jagdmann, G.E., Jr; Johnson, M.G.; Lai, Y-S.; Lowden, C.T.; Lynch, M.P.; Mendoza, J.S.; Murphy, M.M.; Wilson, J.W.; Ballas, L.M.; Carter, K.; Darges, J.W.; Davis, J.E.; Hubbard, F.R.; Stamper, M.L. Synthesis and protein kinase inhibitory activity of balanol analogues with modified benzophenone subunits. J. Med. Chem., 2002, 45(12), 2624-2643.
[http://dx.doi.org/10.1021/jm020018f] [PMID: 12036372]
[2]
Narayana, N.; Diller, T.C.; Koide, K.; Bunnage, M.E.; Nicolaou, K.C.; Brunton, L.L.; Xuong, N-H.; Ten Eyck, L.F.; Taylor, S.S. Crystal structure of the potent natural product inhibitor balanol in complex with the catalytic subunit of cAMP-dependent protein kinase. Biochemistry, 1999, 38(8), 2367-2376.
[http://dx.doi.org/10.1021/bi9820659] [PMID: 10029530]
[3]
Riber, D.; Hazell, R.; Skrydstrup, T. Studies on the SmI2-promoted pinacol-type cyclization: Synthesis of the hexahydroazepine ring of balanol. J. Org. Chem., 2000, 65(17), 5382-5390.
[http://dx.doi.org/10.1021/jo000538n] [PMID: 10993369]
[4]
Pande, V.; Ramos, M.J.; Gago, F. The Protein kinase inhibitor balanol: Structure-activity relationships and structure-based computational studies. Anticancer. Agents Med. Chem., 2008, 8(6), 638-645.
[http://dx.doi.org/10.2174/187152008785133056] [PMID: 18690827]
[5]
Denieul, M-P.; Laursen, B.; Hazell, R.; Skrydstrup, T. Synthesis of the benzophenone fragment of balanol via an intramolecular cyclization event. J. Org. Chem., 2000, 65(19), 6052-6060.
[http://dx.doi.org/10.1021/jo000750r] [PMID: 10987939]
[6]
Tammela, P.; Ekokoski, E.; García-Horsman, A.; Talman, V.; Finel, M.; Tuominen, R.; Vuorela, P. Screening of natural compounds and their derivatives as potential protein kinase C inhibitors. Drug Dev. Res., 2004, 63, 76-87.
[http://dx.doi.org/10.1002/ddr.10399]
[7]
Hudlický, T. Recent chemoenzymatic total syntheses of natural and unnatural products: Codeine, balanol, pancratistatin, and oseltamivir. Pure Appl. Chem., 2010, 82, 1785-1796.
[http://dx.doi.org/10.1351/PAC-CON-09-10-07]
[8]
Kulanthaivel, P.; Hallock, Y.F.; Boros, C.; Hamilton, S.M.; Janzen, W.P.; Ballas, L.M.; Loomis, C.R.; Jiang, J.B. Balanol: A novel and potent inhibitor of protein kinase C from fungus Verticillium balanoides. J. Am. Chem. Soc., 1993, 115, 6452-6453.
[http://dx.doi.org/10.1021/ja00067a087]
[9]
Koide, K.; Bunnage, M.E.; Gomez Paloma, L.; Kanter, J.R.; Taylor, S.S.; Brunton, L.L.; Nicolaou, K.C. Molecular design and biological activity of potent and selective protein kinase inhibitors related to balanol. Chem. Biol., 1995, 2(9), 601-608.
[http://dx.doi.org/10.1016/1074-5521(95)90124-8] [PMID: 9383464]
[10]
Gustafsson, A.B.; Brunton, L.L. Differential and selective inhibition of protein kinase A and protein kinase C in intact cells by balanol congeners. Mol. Pharmacol., 1999, 56(2), 377-382.
[http://dx.doi.org/10.1124/mol.56.2.377] [PMID: 10419557]
[11]
Gilmet, J.; Sullivan, B.; Hudlicky, T. Formal total synthesis of (-)- and (+)-balanol: Two complementary enantiodivergent routes from vinyloxiranes and vinylaziridines. Tetrahedron, 2009, 65, 212-220.
[http://dx.doi.org/10.1016/j.tet.2008.10.070]
[12]
Hardianto, A.; Yusuf, M.; Liu, F.; Ranganathan, S. Exploration of charge states of balanol analogues acting as ATP-competitive inhibitors in kinases. BMC Bioinformatics, 2017, 18(Suppl. 16), 572-583.
[http://dx.doi.org/10.1186/s12859-017-1955-7] [PMID: 29297286]
[13]
Hardianto, A.; Khanna, V.; Liu, F.; Ranganathan, S. Diverse dynamics features of novel protein kinase C (PKC) isozymes determine the selectivity of a fluorinated balanol analogue for PKCε. BMC Bioinformatics, 2019, 19(Suppl. 13), 342-352.
[http://dx.doi.org/10.1186/s12859-018-2373-1] [PMID: 30717648]
[14]
Hu, H.; Mendoza, J.S.; Lowden, C.T.; Ballas, L.M.; Janzen, W.P. Synthesis and protein kinase C inhibitory activities of balanol analogues with modification of 4-hydroxybenzamido moiety. Bioorg. Med. Chem., 1997, 5(9), 1873-1882.
[http://dx.doi.org/10.1016/S0968-0896(97)00125-9] [PMID: 9354244]
[15]
Akamine, P. Madhusudan; Brunton, L.L.; Ou, H.D.; Canaves, J.M.; Xuong, N.H.; Taylor, S.S. Balanol analogues probe specificity determinants and the conformational malleability of the cyclic 3′,5′-adenosine monophosphate-dependent protein kinase catalytic subunit. Biochemistry, 2004, 43(1), 85-96.
[http://dx.doi.org/10.1021/bi035042p] [PMID: 14705934]
[16]
Lai, Y-S.; Mendoza, J.S.; Jagdmann, G.E., Jr; Menaldino, D.S.; Biggers, C.K.; Heerding, J.M.; Wilson, J.W.; Hall, S.E.; Jiang, J.B.; Janzen, W.P.; Ballas, L.M. Synthesis and protein kinase C inhibitory activities of balanol analogs with replacement of the perhydroazepine moiety. J. Med. Chem., 1997, 40(2), 226-235.
[http://dx.doi.org/10.1021/jm960497g] [PMID: 9003521]
[17]
Heerding, J.M.; Lampe, J.W.; Darges, J.W.; Stamper, M.L. Protein kinase C inhibitory activities of balanol analogs bearing carboxylic acid replacements. Bioorg. Med. Chem. Lett., 1995, 5, 1839-1842.
[http://dx.doi.org/10.1016/0960-894X(95)00303-B]
[18]
Nitti, A.; Debattista, F.; Abbondanza, L.; Bianchi, G.; Po, R.; Pasini, D. Donor-acceptor conjugated copolymers incorporating tetrafluorobenzene as the π-electron deficient unit. J. Polym. Sci. A Polym. Chem., 2017, 55, 1601-1610.
[http://dx.doi.org/10.1002/pola.28532]
[19]
Nitti, A.; Bianchi, G.; Po, R.; Swager, T.M.; Pasini, D. Domino direct arylation and cross-Aldol for rapid construction of extended polycyclic π-scaffolds. J. Am. Chem. Soc., 2017, 139(26), 8788-8791.
[http://dx.doi.org/10.1021/jacs.7b03412] [PMID: 28621529]
[20]
Nitti, A.; Osw, P.; Calcagno, G.; Botta, C.; Etkind, S.I.; Bianchi, G.; Po, R.; Swager, T.M.; Pasini, D. One- pot regiodirected annulations for the rapid synthesis of π-extended oligomers. Org. Lett., 2020, 22(8), 3263-3267.
[http://dx.doi.org/10.1021/acs.orglett.0c01043] [PMID: 32255355]
[21]
Hu, H.; Hollinshead, S.P.; Hall, S.E.; Kalter, K.; Ballas, L.M. Synthesis and protein kinase C inhibitory activities of indane analogs of balanol. Bioorg. Med. Chem. Lett., 1996, 6, 973-978.
[http://dx.doi.org/10.1016/0960-894X(96)00151-5]
[22]
Defauw, J.M.; Murphy, M.M.; Jagdmann, G.E., Jr; Hu, H.; Lampe, J.W.; Hollinshead, S.P.; Mitchell, T.J.; Crane, H.M.; Heerding, J.M.; Mendoza, J.S.; Davis, J.E.; Darges, J.W.; Hubbard, F.R.; Hall, S.E. Synthesis and protein kinase C inhibitory activities of acyclic balanol analogs that are highly selective for protein kinase C over protein kinase A. J. Med. Chem., 1996, 39(26), 5215-5227.
[http://dx.doi.org/10.1021/jm960581w] [PMID: 8978850]
[23]
Srivastava, A.K.; Panda, G. Total synthesis of (-)-balanol, all stereoisomers, their N-tosyl analogues, and fully protected ophiocordin: An easy route to hexahydroazepine cores from garner aldehydes. Chemistry, 2008, 14(15), 4675-4688.
[http://dx.doi.org/10.1002/chem.200701991] [PMID: 18399526]
[24]
Pasini, D.; Klopp, J.M.; Fréchet, J.M.J. Design, synthesis, and characterization of carbon-rich cyclopolymers for 193 nm microlithography. Chem. Mater., 2001, 13, 4136-4146.
[http://dx.doi.org/10.1021/cm0104304]
[25]
Klopp, J.M.; Pasini, D.; Byers, J.D.; Willson, C.G.; Fréchet, J.M.J. Microlithographic assessment of a novel family of transparent and etch-resistant chemically amplified 193-nm resists based on cyclopolymers. Chem. Mater., 2001, 13, 4147-4153.
[http://dx.doi.org/10.1021/cm010431w]
[26]
Jagdmann, G.E.; Defauw, J.J.M.; Lai, Y-S.; Crane, H.M.; Hall, S.E.; Buben, J.A.; Hu, H.; Gosnell, P.A. Novel PKC inhibitory analogs of balanol with replacement of the ester functionality. Bioorg. Med. Chem. Lett., 1995, 5, 2015-2020.
[http://dx.doi.org/10.1016/0960-894X(95)00344-S]
[27]
Hughes, P.F.; Smith, S.H.; Oslon, J.T. Two chiral syntheses of threo-3-hydroxylysine. J. Org. Chem., 1994, 59, 5799-5802.
[http://dx.doi.org/10.1021/jo00098a047]
[28]
Hu, H.; Jagdmann, G.E. Two efficient syntheses of (±)-anti-N-benzyl-3-amino-4- hydroxyhexahydroazepine. Tetrahedron Lett., 1995, 36, 3659-3662.
[http://dx.doi.org/10.1016/0040-4039(95)00623-K]
[29]
Tanner, D.; Almario, A.; Högberg, T. Total synthesis of balanol, part 1. Enantioselective synthesis of the hexahydroazepine ring via chiral epoxides and aziridines. Tetrahedron, 1995, 51, 6061-6070.
[http://dx.doi.org/10.1016/0040-4020(95)00264-9]
[30]
Tanner, D.; Tedenborg, L.; Almario, A.; Pettersson, I.; Csöregh, I.; Kelly, N.M.; Andersson, P.G.; Högberg, T. Total synthesis of balanol, part 2. Completion of the synthesis and investigation of the structure and reactivity of two key heterocyclic intermediates. Tetrahedron, 1997, 53, 4857-4868.
[http://dx.doi.org/10.1016/S0040-4020(97)00167-1]
[31]
Albertini, E.; Barco, A.; Benetti, S.; Risi, C.D.; Pollini, G.P.; Zanirato, V. Efficient synthesis of chiral N- tosyl-3,4-disubstituted hexahydroazepine from D-(-)-quinic acid. Synlett, 1996, 1996, 29-30.
[http://dx.doi.org/10.1055/s-1996-5304]
[32]
Albertini, E.; Barco, A.; Benetti, S.; Risi, C.D.; Pollini, G.P.; Zanirato, V. A unified asymmetric approach to substituted hexahydroazepine and 7-azabicyclo[2.2.1]heptane ring systems from D-(-)-quinic acid: Application to the formal syntheses of (-)-balanol and (-)-epibatidine. Tetrahedron, 1997, 53, 17177-17194.
[http://dx.doi.org/10.1016/S0040-4020(97)10139-9]
[33]
Naito, T.; Torieda, M.; Tajiri, K.; Ninomiya, I.; Kiguchi, T. A novel and chiral synthesis of both enantiomers of trans-3-amino-4-hydroxyhexahydroazepine, a key intermediate for the synthesis of balanol. Chem. Pharm. Bull. (Tokyo), 1996, 44, 624-626.
[http://dx.doi.org/10.1248/cpb.44.624]
[34]
Tuch, A.; Sanière, M.; Merrer, Y.L.; Depezay, J-C. Synthesis of (2S,3R)-3-amino-2-hydroxydecanoic acid and (3R,4R)-3-amino-4-hydroxyazepane from D-isoascorbic acid. Tetrahedron Asymmetry, 1996, 7, 2901-2909.
[http://dx.doi.org/10.1016/0957-4166(96)00381-3]
[35]
Wu, M.H.; Jacobsen, E.N. An efficient formal synthesis of balanol via the asymmetric epoxide ring opening reactions. Tetrahedron Lett., 1997, 38, 1693-1696.
[http://dx.doi.org/10.1016/S0040-4039(97)00192-5]
[36]
Coulon, E.; Andrade, M.C.C.D.; Ratovelomanana-Vidal, V.; Genêt, J-P. An efficient synthesis of (2S,3R)- 3-hydroxylysine via ruthenium catalyzed asymmetric hydrogenation. Tetrahedron Lett., 1998, 39, 6467-6470.
[http://dx.doi.org/10.1016/S0040-4039(98)01387-2]
[37]
Phansavath, P.; Paule, S.D.D.; Ratovelomanana-Vidal, V.; Genêt, J-P. An efficient formal synthesis of (-)-balanol by using ruthenium-catalyzed asymmetric hydrogenation. Eur. J. Org. Chem., 2000, 2000, 3903-3907.
[http://dx.doi.org/10.1002/1099-0690(200012)2000:23<3903:AID-EJOC3903>3.0.CO;2-Q]
[38]
Cook, G.R.; Shanker, P.S.; Peterson, S.L. Asymmetric synthesis of the balanol heterocycle via a palladium-mediated epimerization and olefin metathesis. Org. Lett., 1999, 1(4), 615-617.
[http://dx.doi.org/10.1021/ol990705+] [PMID: 10823189]
[39]
Herdeis, C.; Mohareb, R.M.; Neder, R.B.; Schwabenländer, F.; Telser, J. Studies on the synthesis of chiral nonracemic 3,4-disubstituted azepanes, a formal synthesis of (+)- and (-)-balanol. Tetrahedron Asymmetry, 1999, 10, 4521-4537.
[http://dx.doi.org/10.1016/S0957-4166(99)00466-8]
[40]
Fürstner, A.; Thiel, O.R. Formal total synthesis of (-)-balanol: Concise approach to the hexahydroazepine segment based on RCM. J. Org. Chem., 2000, 65(6), 1738-1742.
[http://dx.doi.org/10.1021/jo991611g] [PMID: 10750493]
[41]
Masse, C.E.; Morgan, A.J.; Panek, J.S. An asymmetric aminohydroxylation approach to the azepine core of (-)-balanol. Org. Lett., 2000, 2(17), 2571-2573.
[http://dx.doi.org/10.1021/ol0061034] [PMID: 10990399]
[42]
Yadav, J.S.; Srinivas, C. An efficient approach for the synthesis of hexahydroazepine segment of balanol. Tetrahedron Lett., 2002, 43, 3837-3839.
[http://dx.doi.org/10.1016/S0040-4039(02)00681-0]
[43]
Yadav, J.S.; Srinivas, C. Ring expansion approach for the synthesis of the (3S,4S)- hexahydroazepine core of balanol and ophiocordin. Tetrahedron, 2003, 59, 10325-10329.
[http://dx.doi.org/10.1016/j.tet.2003.09.089]
[44]
Unthank, M.G.; Hussain, N.; Aggarwal, V.K. The use of vinyl sulfonium salts in the stereocontrolled asymmetric synthesis of epoxide- and aziridine-fused heterocycles: Application to the synthesis of (-)-balanol. Angew. Chem. Int. Ed., 2006, 45(42), 7066-7069.
[http://dx.doi.org/10.1002/anie.200602782] [PMID: 17009383]
[45]
Roy, S.P.; Chattopadhyay, S.K. Concise syntheses of stereoisomeric hexahydroazepine derivatives related to the protein kinase inhibitor balanol. Tetrahedron Lett., 2008, 49, 5498-5501.
[http://dx.doi.org/10.1016/j.tetlet.2008.07.031]
[46]
Sullivan, B.; Gilmet, J.; Leisch, H.; Hudlicky, T. Chiral version of the Burgess reagent and its reactions with oxiranes: Application to the formal enantiodivergent synthesis of balanol. J. Nat. Prod., 2008, 71(3), 346-350.
[http://dx.doi.org/10.1021/np0705357] [PMID: 18205317]
[47]
Sullivan, B.; Hudlicky, T. Chemoenzymatic formal synthesis of (-)-balanol. Provision of optical data for an often-reported intermediate. Tetrahedron Lett., 2008, 49, 5211-5213.
[http://dx.doi.org/10.1016/j.tetlet.2008.06.026]
[48]
Yaragorla, S.; Muthyala, R. Formal total synthesis of (-)-balanol: A potent PKC inhibitor. Tetrahedron Lett., 2010, 51, 467-470.
[http://dx.doi.org/10.1016/j.tetlet.2009.10.120]
[49]
Rohokale, R.; Dhavale, D. Chiron approach towards the synthesis of (2S,3R)-3- hydroxyornithine, (2S,3R)- 3-hydroxylysine and tetrahydroazepine core of (-)-balanol. Tetrahedron, 2016, 72, 4550-4555.
[http://dx.doi.org/10.1016/j.tet.2016.06.021]
[50]
Hollinshead, S.P.; Nichols, J.B.; Wilson, J.W. Two practical syntheses of sterically congested benzophenones. J. Org. Chem., 1994, 59, 6703-6709.
[http://dx.doi.org/10.1021/jo00101a032]
[51]
Denieul, M-P.; Skrydstrup, T. Application of an intramolecular Heck reaction for the construction of balanol aryl core structure. Tetrahedron Lett., 1999, 40, 4901-4904.
[http://dx.doi.org/10.1016/S0040-4039(99)00907-7]
[52]
Storm, J.P.; Andersson, C-M. An organoiron approach to the benzophenone appendage of the protein kinase C inhibitor balanol. Org. Lett., 1999, 1(9), 1451-1453.
[http://dx.doi.org/10.1021/ol9910060] [PMID: 10825993]
[53]
Storm, J.P.; Andersson, C-M. Iron-mediated synthetic routes to unsymmetrically substituted, sterically congested benzophenones. J. Org. Chem., 2000, 65(17), 5264-5274.
[http://dx.doi.org/10.1021/jo000421z] [PMID: 10993355]
[54]
Laursen, B.; Denieul, M-P.; Skrydstrup, T. Formal total synthesis of the PKC inhibitor, balanol: Preparation of the fully protected benzophenone fragment. Tetrahedron, 2002, 58, 2231-2238.
[http://dx.doi.org/10.1016/S0040-4020(02)00096-0]
[55]
Patil, M.L.; Deshpande, V.H.; Ramlingam, S.; Borate, H.B. Synthetic studies towards the benzophenone precursor for balanol. Tetrahedron, 2004, 60, 1869-1873.
[http://dx.doi.org/10.1016/j.tet.2003.12.029]
[56]
Nicolaou, K.C.; Bunnage, M.E.; Koide, K. Total synthesis of balanol. J. Am. Chem. Soc., 1994, 116, 8402-8403.
[http://dx.doi.org/10.1021/ja00097a072]
[57]
Nicolaou, K.C.; Koide, K.; Bunnage, M.E. Total synthesis of balanol and designed analogues. Chemistry, 1995, 1, 454-466.
[http://dx.doi.org/10.1002/chem.19950010711]
[58]
Lampe, J.W.; Hughes, P.F.; Biggers, C.K.; Smith, S.H.; Hu, H. Total synthesis of (-)-balanol. J. Org. Chem., 1994, 59, 5147-5148.
[http://dx.doi.org/10.1021/jo00097a014] [PMID: 11667382]
[59]
Lampe, J.W.; Hughes, P.F.; Biggers, C.K.; Smith, S.H.; Hu, H. Total synthesis of (-)- and (+)-balanol. J. Org. Chem., 1996, 61(14), 4572-4581.
[http://dx.doi.org/10.1021/jo952280k] [PMID: 11667382]
[60]
Adams, C.P.; Fairway, S.M.; Hardy, C.J.; Hibbs, D.E.; Hursthouse, M.B.; Morley, A.D.; Sharp, B.W.; Vicker, N.; Warner, I. Total synthesis of balanol: A potent protein kinase C inhibitor of fungal origin. J. Chem. Soc. Perkin Trans., 1995, 1, 2355-2362.
[http://dx.doi.org/10.1039/p19950002355]
[61]
Miyabe, H.; Torieda, M.; Kiguchi, T.; Naito, T. Total synthesis of (-)-balanol. Synlett, 1997, 1997, 580-582.
[http://dx.doi.org/10.1055/s-1997-3236]
[62]
Miyabe, H.; Torieda, M.; Inoue, K.; Tajiri, K.; Kiguchi, T.; Naito, T. Total synthesis of (-)-balanol. J. Org. Chem., 1998, 63, 4397-4407.
[http://dx.doi.org/10.1021/jo980208r]
[63]
Saha, T.; Maitra, R.; Chattopadhyay, S.K. A unified approach to the important protein kinase inhibitor balanol and a proposed analogue. Beilstein J. Org. Chem., 2013, 9, 2910-2915.
[http://dx.doi.org/10.3762/bjoc.9.327] [PMID: 24454570]
[64]
Lai, Y-S.; Mendoza, J.S.; Hubbard, F.; Kalter, K. Synthesis and PKC inhibitory activities of balanol analogs with a cyclopentane substructure. Bioorg. Med. Chem. Lett., 1995, 5, 2155-2160.
[http://dx.doi.org/10.1016/0960-894X(95)00367-3]
[65]
Lai, Y-S.; Stamper, M. Heteroatom effect in the PKC inhibitory activities of perhydroazepine analogs of balanol. Bioorg. Med. Chem. Lett., 1995, 5, 2147-2150.
[http://dx.doi.org/10.1016/0960-894X(95)00364-Y]
[66]
Lai, Y-S.; Menaldino, D.S.; Nichols, J.B.; Jagdmann, G.E.; Mylott, F.; Gillespie, J.; Hall, S.E. Ring size effect in the PKC inhibitory activities of perhydroazepine analogs of balanol. Bioorg. Med. Chem. Lett., 1995, 5, 2151-2154.
[http://dx.doi.org/10.1016/0960-894X(95)00365-Z]
[67]
Mendoza, J.S.; Jagdmann, G.E.; Gosnell, P.A. Synthesis and biological evaluation of conformationally constrained bicyclic and tricyclic balanol analogues as inhibitors of protein kinase C. Bioorg. Med. Chem. Lett., 1995, 5, 2211-2216.
[http://dx.doi.org/10.1016/0960-894X(95)00382-4]

Rights & Permissions Print Cite
© 2024 Bentham Science Publishers | Privacy Policy