New Methodologies for Oligosaccharide Synthesis
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1 New Methodologies for ligosaccharide Synthesis Man-Kit Lau Department of Chemistry Michigan State University March 10, 2004
2 utline 1. Introduction 2. Solid Phase Approach: Automated ligosaccharide Synthesizer 3. Solution Phase Approach: ptimer ne-pot ligosaccharide Synthesis 4. Summary
3 utline 1. Introduction 2. Solid Phase Approach: Automated ligosaccharide Synthesizer 3. Solution Phase Approach: ptimer ne-pot ligosaccharide Synthesis 4. Summary
4 What are ligosaccharides? H H H H H H H H H CH 2 H H H H H H D-Glucose H H H HW? H H H H H Maltotriose H H H Lehninger, A. L.; Nelson, D. L.; Cox, M. M. Principles of Biochemistry, Worth Publishers, Inc., 1993.
5 Traditional View of ligosaccharides Plant Animal Energy Storage Starch Glycogen Structural Scaffold Cellulose Chitin Starch Cellulose Lehninger, A. L.; Nelson, D. L.; Cox, M. M. Principles of Biochemistry, Worth Publishers, Inc., 1993.
6 Cell Surface Glycoproteins cell surface glycoproteins act as protein ligands for cell-cell recognition Bertozzi, C. R.; Kiessling, L. L. Science 2001, 291, Sears, P.; Wong, C.-H. Angew. Chem. Int. Ed. 1999, 38, 2300.
7 Synthetic Chemistry is Key to Studying Glycobiology Biopolymer DNA Primary Synthetic Methods 1. Automated nucleic acid synthesis 2. Polymerase chain reaction (PCR) Protein 1. Automated peptide synthesis 2. verexpression system 3. Even unnatural proteins can be made now ligosaccharide 1. Isolation from natural sources 2. Enzymatic synthesis 3. Chemical synthesis Protein and DNA Synthesis: Template Driven Glycoprotein Synthesis: Post-Translational Attachment Koeller, K. M.; Wong, C.-H. Chem. Rev. 2000, 100, 4465.
8 Glycoprotein Biosynthesis Structural homogeneity is difficult to achieve. Bertozzi, C. R.; Kiessling, L. L. Science 2001, 291, 2357.
9 Possible Routes to Homogeneous ligosaccharides ligosaccharides Natural Sources Enzymatic Synthesis Chemical Synthesis Ultimate Goal: General and Efficient Synthesis of ligosaccharides Koeller, K. M.; Wong, C.-H. Chem. Rev. 2000, 100, Plante,. J.; Palmacci, E. R.; Seeberger, P. H. Science 2001, 291, Sears, P.; Wong, C.-H. Science 2001, 291, 2344.
10 ligosaccharides Synthesis: A Big Challenge There are no universal reaction conditions for oligosaccharides synthesis - Hans Paulsen Paulsen, H. Angew. Chem. Int. Ed. Engl. 1982, 21, 155.
11 Structural Complexity of DNA and Peptides Monomeric Building Blocks ligomeric Biomolecules Nucleotide nucleotide (H) 2 P base DNA (linear) H amino acid Amino Acid R NH 2 CH Polypeptide (linear) Linhorst, T. K. Essentials of Carbohydrate Chemistry and Biochemistry, Wiley-VCH: Weinheim, 2003.
12 Structural Complexity of ligosaccharides Monomeric Building Blocks ligomeric Biomolecules pyranoside H H H H H H H H H H H H H H H a H b Linear and branched! Linhorst, T. K. Essentials of Carbohydrate Chemistry and Biochemistry, Wiley-VCH: Weinheim, 2003.
13 Possible Isomers Among Biopolymers ligomer ligonucleotides ligopeptides ligosaccharides Dimer Trimer Tetramer ,560 Pentamer ,144,640 Linhorst, T. K. Essentials of Carbohydrate Chemistry and Biochemistry, Wiley-VCH: Weinheim, 2003.
14 Selective Protection and Deprotection Steps 1 o hydroxyl anomeric hydroxyl H H H H H H H H H H H H H H CH 2 H aldehyde 3 x 2 o hydroxyl H H H H 2 N H glucosamine 1 o amine
15 Selective Protection and Deprotection Steps H H H CH 3 H methyl-d-glucopyranoside 1. ClCH 2 C()Cl DMF, -50 o C, 55% 2. BzCl, pyridine, 90% Bz Bz MCA CH 3 Bz Bz H thiourea CH 2 Cl 2 Bz Bz CH 3 Ac = Bz = MCA = monochloroacetyl = Cl Linhorst, T. K. Essentials of Carbohydrate Chemistry and Biochemistry, Wiley-VCH: Weinheim, 2003.
16 Glycosidic Bond Formation R R R R glycosyl donor L activator (Lewis Acid) R R R R R R R R oxonium ion glycosyl acceptor R' H R R R R R' L = R = Br SR, NH CCl 3 etc.,,, etc.
17 Classical Approaches Towards ligosaccharide Synthesis 1. Chemical Synthesis: eg. Glycosyl halide coupling. Ac Ac Ac Ac Ac Br RH, Ag 2 C 3, CH 2 Cl 2 -AgBr Ac Ac Ac R -AgBr Ac anchimeric assistance Ac Ac Ac Ac Ac R H Linhorst, T. K. Essentials of Carbohydrate Chemistry and Biochemistry, Wiley-VCH: Weinheim, 2003.
18 Classical Approaches Towards ligosaccharide Synthesis 2. Enzymatic Synthesis: eg. Synthesis of the core trisaccharide of N-linked glycoprotein. H H H H H H pnp b-mannosidase from H H H Helix pomatia (edible snails) H H + H H H H NHAc H NHAc H H NHAc H NHAc 20% yield pnp: para-nitrophenyl Scigelova, M.; Singh, S.; Crout, D. H. G. J. Chem. Soc., Perkin Trans , 7, 777. Koeller, K. M.; Wong, C.-H. Chem. Rev. 2000, 100, 4465.
19 utline 1. Introduction 2. Solid Phase Approach: Automated ligosaccharide Synthesizer 3. Solution Phase Approach: ptimer ne-pot ligosaccharide Synthesis 4. Summary
20 Solid Phase: Automated ligosaccharide Synthesizer The first automated oligosaccharide synthesizer based on Applied Biosystems Inc. Model 433A Peptide synthesizer Plante,. J.; Palmacci, E. R.; Seeberger, P. H. Science, 2001, 291, 1523.
21 Solid Phase Synthesis of ligosaccharides P 1 P 4 P 4 P4 1 Deprotection 1 Coupling 1 P 3 P 1 H P 1 P 2 P 2 P 2 P 5 P 8 2 P 7 P 6 Deprotection... P 1 P 4 1 P 2 P 5 2 P 6 P 9 P 8 3 P 12 P 10 P 11 Coupling P 1 P 4 1 P 2 P 5 P 8 2 H P 6 = H 2 C HC n P = protecting group Fréchet, J. M. J.; Schuerch, C. J. Am. Chem. Soc. 1971, 93, 492.
22 First Solid Phase Synthesis of Disaccharide Bn Bn H Bn Bn Bn R Bn Br Bn Bn R Bn Bn Bn Bn 75% yield H 2 C H = R = HC Bn = n N 2 Fréchet, J. M. J.; Schuerch, C. J. Am. Chem. Soc. 1971, 93, 492.
23 Solid Phase Synthesis of ligosaccharides Using Glycal Assembly P 1 P 2 glycal P 1 P 2 1,2-epoxyglycal H P 3 P 4 P 1 P 2 P 3 H P 4 []... P 1 P 2 P 5 P 6 P 3 H P 4 H P 5 P 6 H P 1 P 2 P 3 H P 4 = H 2 C HC Si(iPr) 2 n P = protecting group Randolph, J. T.; McClure, K. F.; Danishefsky, S. J. J. Am. Chem. Soc. 1995, 117, 5712.
24 Tetrasaccharide Synthesis Using Glycal Assembly CH 2 Cl 2 H ZnCl 2, THF H Bn = H H H 1. 2., CH 2 Cl 2 Bn Bn H ZnCl 2, THF H repeat H = H 2 C HC n Si(iPr) 2 Bn Bn 74% overall yield Randolph, J. T.; McClure, K. F.; Danishefsky, S. J. J. Am. Chem. Soc. 1995, 117, 5712.
25 Choice of Glycosylating Agents Bn Bn Lev 1. DMD 2. HP()(Bu) 2 3. PivCl, DMAP Bn Bn Lev Piv P(Bu)2 Bn Bn Bn Ac H K 2 C 3, Cl 3 CCN Bn Bn Bn Ac NH CCl 3 Ac = Bn = N Piv = tbu Lev = DMAP = N Plante,. J.; Andrade, R. B.; Seeberger, P. H. rg. Lett. 1999, 1, 211. Schmidt, R. R. Angew. Chem. Int. Ed. Engl. 1986, 25, 212.
26 The ctenediol Linker 1. TMSTf Cl H 2. Bn Bn Lev Piv P(Bu)2 Bn Bn Piv Bn Merrifield's resin Bn Bn Lev Piv R 1. NBS 2. RH Bn Bn H 2 C CH 2 Lev Piv Cl Cl PCy 3 Ru PCy 3 Ph Merrifield's resin = H 2 C HC n Cl NBS = Br N Lev = Piv = Cy = tbu Andrade, R. B.; Plante,. J.; Melean, L. G.; Seeberger, P. H. rg. Lett. 1999, 1, 1811.
27 Automated Solid Phase Synthesis of Protected b-phytoalexin Elicitor (PE) Lev = Piv = tbu Bn Bn Bn Bn Bn Lev Bn Bn Piv Bn Bn Bn Piv Bn Bn Piv Bn Bn Piv Bn = Plant glucan oligosaccharide. Induce plant to produce antibiotic phytoalexin. Plante,. J.; Palmacci, E. R.; Seeberger, P. H. Science 2001, 291, 1523.
28 Automated Solid Phase Synthesis of Protected b-phytoalexin Elicitor (PE) H Bn Bn Piv H Deprotection H 2 NNH 2 Coupling TMSTf Bn Bn Lev Piv 3 equiv. P(Bu)2 Bn Bn Lev Piv Lev = Piv = tbu Bn = Plante,. J.; Palmacci, E. R.; Seeberger, P. H. Science 2001, 291, 1523.
29 Automated Solid Phase Synthesis of Protected b-phytoalexin Elicitor (PE) Bn Bn Bn Bn Bn Bn Bn H H Piv Piv Bn Bn Piv Deprotection H 2 NNH 2 Coupling TMSTf Bn Bn Bn Bn Bn 10 equiv. Lev Piv P(Bu)2 Bn Bn Bn Bn Bn Lev Piv Bn Bn Piv Lev = Piv = Bn = tbu Plante,. J.; Palmacci, E. R.; Seeberger, P. H. Science 2001, 291, 1523.
30 Automated Solid Phase Synthesis of Protected b-phytoalexin Elicitor (PE) H Bn Bn Bn Bn Piv Bn Bn Bn Bn Bn Bn Bn Bn H Piv Bn Piv Bn Bn Piv Bn Piv Deprotection H 2 NNH 2 Coupling TMSTf Bn Bn Lev Piv 10 equiv. P(Bu)2 Bn Bn Bn Bn Bn Bn Lev Piv Bn Piv Bn Bn Piv Lev = Piv = Bn = tbu Plante,. J.; Palmacci, E. R.; Seeberger, P. H. Science 2001, 291, 1523.
31 Automated Solid Phase Synthesis of Protected b-phytoalexin Elicitor (PE) Cleavage Bn Bn H Lev Bn Bn Bn Bn Piv Bn Bn Bn Bn Bn Bn Bn Piv Bn Bn Bn Bn Piv Bn Piv Bn Bn Bn Piv Cl Deprotection Cl PCy 3 Ru PCy 3 Ph H 2 C CH 2 Bn Bn Bn Bn Bn Lev Bn Bn Piv Bn Bn Bn Bn Piv Bn Piv Bn Bn Piv Coupling TMSTf Bn Bn Bn Bn Bn Lev = Piv = Bn = 10 equiv. Lev Piv P(Bu)2 tbu Plante,. J.; Palmacci, E. R.; Seeberger, P. H. Science 2001, 291, 1523.
32 Coupling Cycle For Phosphate Donors Step Function Reagent Time/min 1 Couple 5 equiv. donor and 5 equiv. TMSTf 30 2 Wash CH 2 Cl Couple 5 equiv. donor and 5 equiv. TMSTf 30 4 Wash 1:9 (MeH : CH 2 Cl 2 ) 4 5 Wash THF 4 6 Wash 3:2 (pyridine : acetic acid) 3 7 Deprotection 2 x 20 equiv. H 2 NNH Wash 3:2 (pyridine : acetic acid) 3 9 Wash 1:9 (MeH : CH 2 Cl 2 ) 4 10 Wash 0.2 M acetic acid in THF 4 11 Wash THF 4 12 Wash CH 2 Cl 2 6 Each cycle: 3 hours Plante,. J.; Palmacci, E. R.; Seeberger, P. H. Science 2001, 291, 1523.
33 (a) (b) (c) Bz Bz Bn Fmoc Ac Ac Bz Bz TBDPS = Fmoc = DMTST = H Bz TBDPS Ac Bz Ac TBDPS Bz SPh SPh SPh Si(Ph) 2 (tbu) N 2 Me Tf Me S S Me Solid Phase Synthesis of Protected b-phytoalexin Elicitor a, DMTST, then Et 3 N, DMTST, then HF/pyr., DMTST, then HF/pyr. Ac Ac Ac Ac Ac Ac Bn H Ac Ac Bn TBDPS Bz Bz Bz Ac Ac Bz Bz Bz Bz Ac Bz Ac Bn Ac Ac Ac Ac Ac Ac Ac Ac Bn Ac Ac Bz Bz Ac Bz Bz Bz Ac Bz Ac Bn Bn Bz Bz Bz Bz Bz Bz Nicolaou, K. C.; Winssinger, N.; Pastor, J.; DeRoose, F. J. Am. Chem. Soc. 1997, 119, 449. N 2 Bz Bz Bz hv b Bz Ac Ac Ac Ac Ac Ac Ac Bn H Ac Bz H Bz Bz Bz 20% overall yield c Bz Bz Bz N 2 N 2 N 2
34 Automated vs. Non-Automated Syntheses Ac Bn Bn Bn Bn Bn Lev Bn Bn Piv Bn Bn Bn Piv Bn Bn Piv Bn Bn Piv Ac Ac Ac Ac Ac Ac Ac Bn Ac Ac Bz Bz Bz Ac Bz Ac Bn Bz Bz Bz Bz Ac automated (Seeberger) non-automated (Nicolaou) automated labor intensive 10 machine hours 122 reaction hours 80% yield 20% yield Plante,. J.; Palmacci, E. R.; Seeberger, P. H. Science 2001, 291, Nicolaou, K. C.; Winssinger, N.; Pastor, J.; DeRoose, F. J. Am. Chem. Soc. 1997, 119, 449.
35 ther Protected ligosaccharides Synthesized with Automated Synthesizer Approach Bn Bn Bn Ac Bn Bn Bn Bn Bn n = 3, 74% yield (90% average yield per unit) n = 5, 42% yield (84% average yield per unit) n = 8, 34% yield (87% average yield per unit) Bn n polymannoside Bn Bn Bn Bn Bn Bn Bn Bn Ac Piv Bn Bn Bn 50% yield (84% average yield per unit) Leishmania tetrasaccharide TCAHN = Ac = Piv = N CCl 3 H tbu Bn Bn Bn Bn H TCAHN Bn Piv Piv Bn Bn Piv Bn Bn Piv Lewis x pentasaccharide 12.6% yield (66% average yield per unit) H Bn = Plante,. J.; Palmacci, E. R.; Seeberger, P. H. Science 2001, 291, Hewitt, M. C.; Seeberger, P. H. rg. Lett. 2001, 3, Love, K. R.; Seeberger, P. H. Angew. Chem. Int. Ed. 2004, 43, 602.
36 How About More Complex Molecules? AcHN H H H H H 2 C H H Sialyl Lewis x tetrasaccharide 4% overall yield in 8 steps (Denishefsky and Wong, 1992) H H H H H R NHAc H H H H H H H H AcNH H 2 C H H H H H R H H H H NHAc Fucosyl GM 1 5% overall yield in 15 steps (Denishefsky, 1999) Danishefsky, S. J.; Gervay, J.; Peterson, J. M.; McDonald, F. E.; Koseki, K.; riyama, T.; Griffith, D. A.; Wong, C.-H.; Dumas, D. P. J. Am. Chem. Soc. 1992, 114, Allen, J. R.; Danishefsky, S. J. J. Am. Chem. Soc. 1999, 121,
37 utline 1. Introduction 2. Solid Phase Approach: Automated ligosaccharide Synthesizer 3. Solution Phase Approach: ptimer ne-pot ligosaccharide Synthesis 4. Summary
38 Solution Phase: ptimer Programmed ne-pot ligosaccharide Synthesis Zhang, Z.; llmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov, T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734.
39 The Armed - Disarmed Concept Armed Disarmed React Faster React Slower H L H H H + L activator H + L L Mootoo, D. R.; Date, V.; Fraser-Reid, B. J. Am. Chem. Soc. 1988, 110, Linhorst, T. K. Essentials of Carbohydrate Chemistry and Biochemistry, Wiley-VCH: Weinheim, 2003.
40 Protecting Groups Control H EDG H EWG + L L activator H EDG H EWG + L H EDG EWG L EDG = electron donating group EWG = electron withdrawing group Mootoo, D. R.; Date, V.; Fraser-Reid, B. J. Am. Chem. Soc. 1988, 110, Linhorst, T. K. Essentials of Carbohydrate Chemistry and Biochemistry, Wiley-VCH: Weinheim, 2003.
41 Disaccharide Synthesis Using Protecting Groups Control armed disarmed Bn Bn Bz Bz Bn Bn + H Bz NBS Bn Bn Bn Bn Bz Bz Bz 62% yield a : b = 1 : 1 NBS = Bz = Br N Bz Bz H Bz Bz Bz is NT formed Bz Bn = Mootoo, D. R.; Date, V.; Fraser-Reid, B. J. Am. Chem. Soc. 1988, 110, 2662.
42 Disaccharide Synthesis Using Protecting Groups Control Br Bn Bn Bn Bn Br N Bn Bn Bn Bn Br Bn Bn Bn Bn H Bz = Bn Bn Bn Bn Bz Bz Bz Bz Bz Bz Bn = Mootoo, D. R.; Date, V.; Fraser-Reid, B. J. Am. Chem. Soc. 1988, 110, 2662.
43 Anomeric Reactivity Control H H + L 1 activator H H + H L 2 L 2 L 2 L 1 is better leaving group than L 2 Mootoo, D. R.; Date, V.; Fraser-Reid, B. J. Am. Chem. Soc. 1988, 110, Linhorst, T. K. Essentials of Carbohydrate Chemistry and Biochemistry, Wiley-VCH: Weinheim, 2003.
44 ne-pot Synthesis of Protected Ciclamycin S less reactive S Me + + TMS Bn most reactive S H Bn least reactive 0.05 equiv. TfH -78 o C S S + Bn H Bn Bn = S -70 o C Bn Bn Ciclamycin Ciclamycin 25% overall yield S Me S > >> S Raghavan, S.; Kahne, D. J. Am. Chem. Soc. 1993, 115, 1580.
45 Strategy for Sequential ne-pot Linear and Branched ligosaccharides Synthesis X most reactive donor H less reactive X H least reactive X H reducing end R R X most reactive donor H less reactive X H reducing end R R Zhang, Z.; llmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov, T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734.
46 ptimer Database of Thioglycosyl Donors Number in bracket represents the Relative Reactivity Value (RRV) Ritter, T. K.; Mong, K.-K. T.; Liu, H.; Nakatani, T.; Wong, C.-H. Angew. Chem. Int. Ed. 2003, 42, 4657.
47 ptimer Database of Thioglycosyl Donors Zhang, Z.; llmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov, T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734.
48 ptimer Database of Thioglycosyl Donors Ye, X.-S.; Wong, C.-H. J. rg. Chem. 2000, 65, 2410.
49 ptimer Database of Thioglycosyl Donors Ritter, T. K.; Mong, T. K.-K.; Liu, H.; Nakatani, T.; Wong, C.-H. Angew. Chem. Int. Ed. 2003, 42, 4657.
50 Relative Reactivity in Competitive Reactions donor (D 0 ) reference (R 0 ) SR SR NIS MeH (5eq.) Me Me product (D t ) reference product (R t ) HPLC analysis reference compound = Ac Ac Ac Ac STol NIS = I N Zhang, Z.; llmann, I. R.; Ye, X. -S.; Wischnat, R.; Baasov, T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734.
51 Relative Reactivity in Competitive Reaction RRV = k D k R = In([D t ]/[D 0 ]) In([R t ]/[R 0 ]) R 0 D 0 The result is normalized based on Ac Ac Ac Ac RRV = 1 STol R t D t t = 0h t = 2h Larger the number, higher the reactivity Zhang, Z.; llmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov, T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734.
52 Sequential ne-pot Synthesis of Globo H H H H H H H H H AcNH Globo H H H H H H Globo H 1% overall yield in 19 steps (Denishefsky, 1995) H H H H R Human breast tumor associated antigen. First total synthesis was reported by Danishefsky in 1995 using glycal assembly. Bilodeau, M. T.; Park, T. K.; Hu, S.; Randolph, J. T.; Danishefsky, S. J.; Livingston, P..; Zhang, S. J. Am. Chem. Soc. 1995, 117, 7840.
53 Sequential ne-pot Synthesis of Globo H H H H H H H H H H H AcNH H H Globo H H H H H H R ptimer Bn = Bn Bn Bz Bz NBz NBz ClBn = NBz = TrocHN = R = Cl N H N 2 CCl 3 Me Bn Bn Bn RRV = 72,000 H STol Bn TrocHN RRV = 6 Bn STol ClBn H Bn Bn (67% yield) Bn Bn Bn R Burkhart, F.; Zhang, Z.; Wacowich-Sgarbi, S.; Wong, C.-H. Angew. Chem. Int. Ed. 2001, 40, 1274.
54 Sequential ne-pot Synthesis of Globo H Bn Bn Bn Bn H Bn Bz STol Bn Bz TrocHN NBz RRV = 72,000 NBz RRV = 6 STol ClBn NIS, TfH, CH 2 Cl 2 H Bn Bn Bn Bn Bn Bn R NIS = Bn = ClBn = Cl I N R = NBz = TrocHN = N H Me N 2 CCl 3 Bz Bn Bz Bz Bz Bn TrocNH Bn Bn Bn Globo H NBz ClBn Bn 41% yield Bn Bn Bn Bn Bn R H H H H H H H H H H AcNH H Globo H Globo H 20% overall yield H H H H H H R 1. Zn-AcH 2. Ac 2 -pyridine 3. NaMe-MeH 4. H 2 -Pd/C Burkhart, F.; Zhang, Z.; Wacowich-Sgarbi, S.; Wong, C.-H. Angew. Chem. Int. Ed. 2001, 40, 1274.
55 ther ligosaccharides Synthesized with ptimer H H H H H H AcHN H H H H H H AcNH H 2 C H H H 2 C H H H H NHAc H H H H H H H H H H Sialyl Lewis x hexasaccharide 8% overall yield in 2 one-pot reactions (cf. 4% overall yield in 8 steps) R Fucosyl GM 1 6% overall yield in 3 one-pot reaction (cf. 5% overall yield in 15 steps) NHAc H H H H H H R And more.. Zhang, Z.; Kikura, K.; Huang, X.-F.; Wong, C.-H. Can. J. Chem. 2002, 80, Mong, T. K.-K.; Lee, H.-K.; Duron, S. G.; Wong, C.-H. Proc. Natl. Acad. Sci. USA 2003, 100, 797.
56 Comparison of the Two Approaches Common Advantages: They both reduce labor cost. They both allow for high throughput synthesis of oligosaccharides Advantages for the one-pot approach over the automated synthesizer: It fundamentally helps planning of oligosaccharide synthesis It involves no intermediate deprotection Scale-up is possible
57 Heparin-Like ligosaccharides: A Synthetic Challenge H S 3 3 SHN H a C 2 H 3 S a S 3 3 SHN H 2 C S 3 H S 3 3 SHN iduronic acid Belongs to the family of glycosaminoglycans (GAG). Heparin is widely used as an anticoagulant. Jacquinet, J.-C.; Petitou, M.; Duchaussoy, P.; Lederman, I.; Choay, J.; Torri, G.; Sinay, P. Carbohydr. Res. 1984, 130, 221. Yu, H. N.; Furukawa, J.-I; Ikeda, T.; Wong, C.-H. rg. Lett. 2004, 6, 723. rgueira, H. A.; Bartolozzi, A.; Schell, P.; Litjens, R. E. J. N.; Palmacci, E. R.; Seeberger, P. H. Chem. Eur. J. 2003, 9, 140.
58 utline 1. Introduction 2. Solid Phase Approach: Automated ligosaccharide Synthesizer 3. Solution Phase Approach: ptimer ne-pot ligosaccharide Synthesis 4. Summary
59 Summary 1. Novel strategies towards oligosaccharide synthesis were discussed: - Solid Phase Automated ligosaccharide Synthesizer - Solution Phase ptimer ne-pot ligosaccharide Synthesis 2. From a chemical point of view, the reactivity based one-pot strategy makes the design of oligosaccharide synthesis easier.
60 Acknowledgement Prof. John Frost Dr. Karen Frost Prof. Chris Chang Prof. Babak Borhan Prof. Joan Broderick Frost Group
61 The End
62 Example in Calculating RRV 1: Ac Ac Ac Ac STol Lev H 40: PMB STol Bn Bn Bn Zhang, Z.; llmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov, T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734.
63 Accuracy Measurement of Calculated RRV Experimental values are shown without parentheses Calculated values are shown in parentheses Zhang, Z.; llmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov, T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734.
64 Relationship Between Relative Rates and Substrate Comsumption Zhang, Z.; llmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov, T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734.
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