Towards the Synthesis and Biological Evaluation of

2nd-Generation Taxoid SB-T-1216

Adele Whaley

Professor Iwao Ojima

Mentors: Dr. Anushree Kamath and Jacob Vineberg

Department of Chemistry

State University of New York at Stony Brook

Stony Brook, New York, 11974-3400

Cancer

Cancer is a term used to describe diseases in whichabnormal cells divide uncontrollably and are able toinvade other tissues.

Cavenee, W. , White, R., Sci. Am., 1995, 72-79.

Figure 1: The accumulation of mutations within a cell results inthe loss of mechanisms that regulate cellular proliferation. Afterseveral rounds of division, this leads to a population of abnormalcells that disrupts tissue function.

Figure 2: The cell cycle.

Cancer Statistics

Cancer Treatment Methods

Surgery

Radiation Therapy

Immuno Therapy

Gene Therapy

Photodynamic Therapy

Chemotherapy

◦ Use of cytotoxic agents to induce apoptosis of cancerous cells.

◦ Traditional chemotherapeutic agents include the small molecular

members of the taxane family.

Taxol® and Taxotere®

FDA approval for ovarian cancer

(1992), metastatic breast cancer (1994),

non-small cell lung cancer (1999).

FDA approval for advanced breast

cancer (1996), non-small cell lung cancer

(1999), metastatic prostate cancer (2004).

Ojima, I., Miller, M. Chemistry and Chemical Biology of Taxane Anticancer Agents. The Chem. Rec. 2001, 1, 195-211.

Taxus brevifolia Taxus baccata

Paclitaxel and docetaxel are categorized as microtubule-stabilizing anticancer agents.

The cytotoxic activity of these drugs is attributed to their unique mechanism of

action- by binding to and inhibiting the depolymerization of microtubules, mitotic

arrest is induced between prophase and anaphase, leading to apoptosis of the

cancerous cells.

Paclitaxel and Docetaxel- Mechanism of Action

Figure 3: Microtubule formation and the mechanism of action of paclitaxel and docetaxel.

Figure 4: Mitotic arrest induced by paclitaxel and docetaxel between prophase and anaphase.

Ojima, I., Miller, M. Chemistry and Chemical Biology of Taxane Anticancer Agents. The Chem. Rec. 2001, 1, 195-211.

Georg, G. I., Boge, T. C., Cheruvallath, Z. S., Clowers, J. S., Harriman, G. C. B., Hepperle, M., Park, H. The medicinal chemistry of taxol. Taxol: Science and Applications, 1995, 317-375.

Issues with the Use of Paclitaxel and Docetaxel

Limited supply of naturally occurring paclitaxel◦ Paclitaxel is isolated from the bark of the Pacific Yew tree, Taxus

brevifolia, a non-renewable resource, through an extensive, low-yieldingprocess.

◦ In 1985, Potier et al. isolated 10-deacetylbaccatin III (10-DAB III) fromthe leaves of the European yew, Taxus baccata.

◦ The isolation of 10-DAB III pioneered the use of semi-syntheticmethods to secure a long term supply of paclitaxel, docetaxel, and theiranalogs.

◦ The Ojima-Holton β-lactam coupling method provides an effective andversatile route towards the synthesis of highly potent new generationtaxoids.

Ojima, I., Miller, M. Chemistry and Chemical Biology of Taxane Anticancer Agents. The Chem.

Rec., 2001, 1, 195-211

10-DAB III

Expression of MDR Phenotypes

◦ Cancerous cells that exhibit the multidrug resistant (MDR)

phenotype overexpress P-glycoprotein (Pgp), a transmembrane

pump that actively expels cytotoxic agents.

◦ Because paclitaxel and docetaxel are substrates of the Pgp pump,

their intracellular concentration remains at an innocuous level.

These agents are therefore ineffective against MDR cancers.

Ojima, I., Miller, M. Chemistry and Chemical Biology of Taxane Anticancer Agents. The Chem. Rec., 2001, 1, 195-211.

Higgins, CF., Linton, KJ. The ATP switch model for ABC transporters. Nat. Struct. Mol. Biol., 2004, 11(10), 918-26.

Figure 4: The Pgp pump is an effective ATP-binding cassette (ABC) transporter that actively effluxes various hydrophobic cytotoxic agents from cancerous cells.

The New Generation Taxoids

With the development of the β-Lactam Synthon Method (β-LSM), a series of new generation taxoids were prepared, whichexhibit at least 2 orders of magnitude greater activity against anumber of drug-resistant cell lines.

◦ Enantiopure β-lactam can be prepared via the Staudinger [2+2] ketene-imine cycloaddition, followed by enzymatic resolution, and the chiral esterenolate-imine cyclocondensation.

◦ The new generation taxoids are subsequently obtained in the coupling ofthis enantiopure β-lactam to a modified baccatan, followed bydeprotection.

The 2nd-generation taxoid SB-T-1216 shows excellent activity ina variety of cancer cell lines.

Ojima, I., et. al. Syntheses and Structure-Activity Relationships of the Second-Generation Antitumor Taxoids: Exceptional

Activity against Drug-Resistant Cancer Cells. J. Med. Chem. 1996, 39, 3889-3896.

Ojima, I., Das, M. Recent Advances in the Chemistry and Biology of New Generation Taxoids. J. Nat. Prod. 2009, 72, 554–565.

SB-T-1216

Staudinger [2+2] Ketene-Imine Cycloaddition

Followed by Enzymatic Resolution

Brieva, R., Crich, J.Z., Sih, C., Chemoenzymatic Synthesis of the C-13 Side Chain of Taxol: Optically Active-3-Hydroxy-4-Phenyl β-lactam Derivatives. J. Org. Chem.,

1993, 58, 1069-1075.

Lopez, R., Sordo, T.L, Sordo, J.A., Gonzalez, J. Torquoelectronic Effect in the Control of the Stereoselectivity of Ketene-Imine Cycloaddition Reactions. J. Org. Chem.,

1993, 58(25), 7036-7037.

Palomo, C., Jesus, M., Inaki, A., Oiarbide, G.M. Assymetric Synthesis of β-lactams by Staudinger Ketene-Imine Cycloaddition Reactions. J. Org. Chem., 19939 1999(12),

3223-3235.

Figure 5: Mechanism of the Staudinger reaction towards cis β-lactam synthesis

Chiral Ester Enolate-Imine Cyclocondensation

King, B., Sharpless, B. An efficient synthesis of enantiomerically pure trans-2-phenylcyclohexanol. Tetrahedron Lett. 1994, 35, 5611-5612.

Sharpless, B., Kold, H., VanNieuwenhze, M. Catalytic Asymmetric Dihydroxylation. Chem. Rev. 1994, 94, 2483-2547.

Figure 7: Catalytic cycle of Sharpless

asymmetric dihydroxylation.

Figure 6: Sharpless’ phthalazine class of chiral ligands.

Figure 8: Selective nickel insertion followed by reductive elimination.

Ojima, I., Habus, I., Zhao, M., Zucco, M., Park, Y., Sun, C., Brigaud, T. New and Efficient Approaches to the Semisynthesis of

Taxol and its C-13 Chain Analogs by Means of the β-Lactam Synthon Method. Tetrahedron. 1992, 4, 6985-7012.

Figure 9: Asymmetric enolate-imine cyclocondensation.

Figure 10: E-enolate formation and Z-enolate formation with their respective transition states.

Figure 11: Mechanism of chiral ester enolate-imine cyclocondensation.

Synthesis of SB-T-1216

C-10 Modification: C-7 protection followed by C-10 acylation

C-13 Modification: Ojima-Holton coupling

Ojima, I., Slater, J., Michaud, E., Kuduk, S., Bounaud, P., Vrignaud, P., Bissery, M., Veith, J., Pera, P., Bernacki, R. Syntheses and

Structure-Activity Relationships of the Second-Generation Antitumor Taxoids: Exceptional Activity against Drug-Resistant

Cancer Cells. J. Med. Chem. 1996, 39, 3889-3896.

Conclusions and Ongoing Research

The β-LSM is an effective route towards the synthesis ofnew generation taxoids, which exhibit greater efficacyagainst drug-resistant cell lines than their parent taxoids.

Enantiopure β-lactam can be prepared via the Staudinger[2+2] ketene-imine cycloaddition, followed by enzymaticresolution, and the chiral ester enolate-iminecyclocondensation.

SB-T-1216 is subsequently obtained in the coupling of thisenantiopure β-lactam to a modified baccatan, followed bydeprotection.

This material will be used for further ongoing researchefforts towards understanding the detailed mechanism ofaction of this next generation taxoid.

Acknowledgments

Advisor: Professor Iwao Ojima

Mentors: Dr. Anushree Kamath and Jacob Vineberg

Notable Group Members: Edison S. Zuniga and Joshua Seitz

This research was supported by a grant from the National

Cancer Institute (CA 103314 to I.O.)

Thank You