Thesis Title

“Synthesis of Dendritic Bioprobes and Catalysis of Oxometallic species in Aerobic Oxidation and Nucleophilic Acyl Substitutions”
Thesis is divided into two chapters.
Chapter-I: Synthesis of Dendritic Bioprobes.
Chapter-II: Catalysis of Oxometallic species in Asymmetric Reactions and Nucleophilic Acyl Substitutions.
Chapter-I: Synthesis of Dendritic Bioprobes
This chapter is further divided into six sections.
Section 1: Nucleation of Au nanoparticles or ZnS/CdSe quantum dots inside the cage of organic ligand by Ring closing metathesis (RCM)
This section describes the stabilization strategy for Au nanoaprticles and CdSe/ZnS QDs by new netting process to efficiently lock Au or ZnS/CdSe nanoparticles (Scheme 1)
Scheme-1

in central core. The netting unit 2 was prepared from intermediate 1. Methyl gallate by benzylation with benzylbromide in the presence of a base K2CO3, subsequent double allylation with allyl bromide and K2CO3 gives the intermediate 1. The methyl ester was saponified in MeOH followed by the amidation gives required unit 2. The thiolate end in 2 for priming to the pyridine stabilized CdSe/ZnS or HAuCl4 in presence of NaBH4. The allyloxy units at both C3 and C5 positions of 2 were used for netting and corss-linking by ring closing metathesis by Grubb’s catalyst.1 The stabilization strategy presented here may be extended to be extended to other colloidal systems.

Section 2: Synthesis of biocompatible water-soluble pentaol or haxaol coated ZnS/CdSe shell/core type semiconductor quantum dots as fluorescent biological labels
Functionalized N-2-mercaptoethyl-gallamides bearing five2 or six hydroxyl units that are tethered with diethylene glycol ether(s) allow for transferring hydrophobically pyridine-

Scheme 2

capped ZnS/CdSe shell/core nanoparticles from an organic to an aqueous layer with intact fluorescent profiles. The required dendritic polyol units 6 (Scheme 2) or 10 (Scheme 3) were prepared from 5 or 9 by osmium catalyzed dihydroxylation respectively.

Scheme-3

Dendritic Nanohybrids in Proteomics

[Fig. 1: Sample: total protein of E. coli BL21(DE3) Protein extraction : acetone precipitate Protein conc. : 9.48 mg/mL Gel conc. : SDS-PAGE 12.5% Electrophoresis time : 80 min (at 100V)]
Subsequent unmasking of S-trityl group by TFA/Et3SiH, encapsulate the pyridine-stabilized ZnS/CdSe shell/core type quantum dots. The resultant bioprobes are very stable, water-soluble, dispersive, and narrowly distributed in size. The nanohybrids were studied in proteomics (Fig. 1). After endocytic uptake of nanohybrids, HeLa cancer cells were stably labeled for two days with no detectable effects on cell morphology or physiology. Notabley, we saw no discernible fluorescence loss of the QD labels: brightly fluorescent cells were visible during the entire imaging sequence (Fig. 2). This indicates QDs were taken up by the cells via endocytosis.3

Cellular Imaging studies

Fig. 2: Distribution of Penta-podal QDs in live HeLa cells. Uptake and transport of QDs with 10µL solution. The image Epifluorescence and confocal microscope image of cells 12 hours after being spontaneous uptake by cells.

Section 3: Hybridization of Gallactoside-capped gallamide Dendrons with CdSe/ZnS Core/Shell nanoparticles: Fluorescent, Nucleus Localization probes for Cancer cells
Mostly monomeric-carbohydrates are attached to nanoparticles.4 Moreover; the application of dendritic carbohydrate–conjugated quantum dots in biological assays has not been explored. This is the first example of dendritic gallactoside dendrimer ligand anchored to ZnS/CdSe quantum dots. The simple and convenient method for the construction of dendritic gallactoside gallamide ligand encapsulated CdSe/ZnS quanum dots. The key chemical transformation which allows facile synthesis of this dendritic ligand (15) from 14, is the copper (I)-catalyzed azide–alkyne cycloaddition, a click reaction.5a (Scheme 4). The 13 is readily prepared from methyl gallate by treatment with 12 in presence of K2CO3 in refluxed acetonitrile. The resultant bioprobes 16 are very stable, water-soluble, dispersive, and narrowly distributed in size, which might be of great potential for the investigation of the biofunctions of carbohydrates.5b

Scheme-4

16

Fig. 3: Distribution of nanohybrid-16 in COS-7 kidney cancer cells and A549 liver cancer cells.

Section 4: Dendritic crown ether-capped ZnS/CdSe Core/Shell nanoparticles: Potential fluorescent bioprobes to study the Transmembrane Profiles
The novel 12-crown-4 dendritic ligand 17 was prepared via Cu(I) catalysed Click chemistry from 14. Funcationalization of ZnS/CdSe QDs with 12-crwon-4 dendritic ligand has achieved,6 to investigate the multiple binding studies with Li+ ions in H2O.7 When treated with kidney cancer cells, the nanohybrid-18 induce facile endocytic uptake, which opens up a new entry in the field of cell-biology for studying dynamic transmembrane behaviors.
Scheme-5

18

Fig. 4: Distribution of nanohybrid-18 in live COS-7 cells. Uptake and transport of QDs with 10µL solution.

Section 5: Doubly Ortho-linked Quinoxaline and 3/4-diarylaminopyridine Hybrid as Donor-type Optoelectronic Capping Materials for ZnS/CdSe shell/core nanocrystals
Using Nitrogen donars as binding group, we have created monomeric Q-pyridine –CdSe/ZnS nanocrystal complexes. The new design allows the simple synthesis of surfactant 21 and 22 by Palladium catalyzed coupling reaction of 20 (Q-H)8 with 4-bromo pyridine or 3-bromo pyridine respectively (Scheme 6). The single crystal structures and optoelectronic properties of Q-H-py wrapped ZnS/CdSe nanohybrids are promising for application9 in OLEDs and photovoltaic cells.10

Scheme-6

Section 6: Hydrophobic Nanocrystals coated with Amphiphilic Tetraol and Tetraphosphonic and Tetra carboxylic acid: A general route to water soluble CdSe/ZnS and Pd nanoparticles
We have developed a simple synthetic method for preparation of tetraol (24) or tetraacid (25 or 26) dendritic ligand from 23. This can be used to transfer various nanoparticles11

Scheme-7

from organic solvents to water. The aqueous nanoparticles have physical properties and reactivities similar to those in organic solvents. The wrapping such type of gallamide dendritic ligand around Pd nanoparticles may further enhance the stability.12 The Pd nanoparticles could be useful for C-C bond formation reaction like as Suzuki reaction, Heck coupling.

Chapter-II: Catalysis of Oxometallic species in Aerobic Oxidation and Nucleophilic Acyl Substitutions
This chapter is further divided into two sections.
Section 1: Direct Atom-Efficient Esterification between Carboxylic Acids and Alcohols Catalyzed by Amphoteric, Water-Tolerant TiO(acac)2
The esterification of carboxylic acids with different functionalized alcohols is one of the most important and commonly used transformations in organic synthesis. A diverse array of oxometallic species were examined as catalysts for a test direct condensation of benzoic acid and 2-phenylethanol in 1:1 stoichiometry. Besides Group IVB MOCl2-xH2O and TiOX2-xH2O, Group VB VOCl2-xTHF and Group IVB TiO(acac)2 were found to be

Scheme-8

the most efficient and water-tolerant catalysts for the test reaction. The new neutral catalytic protocol with the optimal TiO(acac)2, tolerates many stereo/electronic structural variations in both (di)acid (1o-3o alkyl and aryl) and (di)alcohol (1o, 2o alkyl, and aryl) components with high chemoselectivity.13

Section 2: Synthesis of Dendrimer catalysts and it’s application towards catalysis and also for DNA cleavage
We demonstrate for the first time use of oxo-metallic species in dendrimer catalyst. This is simple and convenient method for the construction of dendritic gallamide catalyst. The key chemical transformation which allows facile synthesis of this dendritic ligand (29 or 30) from 28, is the copper (I)-catalyzed azide–alkyne cycloaddition, a click reaction.5a (Scheme 10). To check the feasibility of enhanced reactivity in a dendritic catalyst resulting from cooperative reactivity between catalytic units. Further exploration and optimization of such multimeric catalysts in related asymmetric reactions are ongoing.
The titled vanadyl(V) complexes14 serve as efficient reagents for cleaving supercoiled plasmid DNA by photoinitiation.15 We have shown the vanadyl Complexes, derived from 2-hydroxy-1-naphthaldehyde and L-phenylalanine, exhibits a unique wedge feature, inducing a site-selective photocleavage at the C22- T23 of the bulge backbone for a HIV-27 DNA system at 0.15 íM. Transient absorption experiments for corresponding Vanadyl complex indicate the involvement of LMCT with concomitant tautomerization, leading to an o-quinone-methide V-bound hydroxyl species responsible for the cleavage profiles. The use of dendrimer-Vanadyl complex for such DNA cleavage is underway.

Scheme 9

Scheme 10

Scheme-11

Thesis Title

“Synthesis of Dendritic Bioprobes and Catalysis of Oxometallic species in Aerobic Oxidation and Nucleophilic Acyl Substitutions”
Thesis is divided into two chapters.
Chapter-I: Synthesis of Dendritic Bioprobes.
Chapter-II: Catalysis of Oxometallic species in Asymmetric Reactions and Nucleophilic Acyl Substitutions.
Chapter-I: Synthesis of Dendritic Bioprobes
This chapter is further divided into six sections.
Section 1: Nucleation of Au nanoparticles or ZnS/CdSe quantum dots inside the cage of organic ligand by Ring closing metathesis (RCM)
This section describes the stabilization strategy for Au nanoaprticles and CdSe/ZnS QDs by new netting process to efficiently lock Au or ZnS/CdSe nanoparticles (Scheme 1)
Scheme-1

in central core. The netting unit 2 was prepared from intermediate 1. Methyl gallate by benzylation with benzylbromide in the presence of a base K2CO3, subsequent double allylation with allyl bromide and K2CO3 gives the intermediate 1. The methyl ester was saponified in MeOH followed by the amidation gives required unit 2. The thiolate end in 2 for priming to the pyridine stabilized CdSe/ZnS or HAuCl4 in presence of NaBH4. The allyloxy units at both C3 and C5 positions of 2 were used for netting and corss-linking by ring closing metathesis by Grubb’s catalyst.1 The stabilization strategy presented here may be extended to be extended to other colloidal systems.

Section 2: Synthesis of biocompatible water-soluble pentaol or haxaol coated ZnS/CdSe shell/core type semiconductor quantum dots as fluorescent biological labels
Functionalized N-2-mercaptoethyl-gallamides bearing five2 or six hydroxyl units that are tethered with diethylene glycol ether(s) allow for transferring hydrophobically pyridine-

Scheme 2

capped ZnS/CdSe shell/core nanoparticles from an organic to an aqueous layer with intact fluorescent profiles. The required dendritic polyol units 6 (Scheme 2) or 10 (Scheme 3) were prepared from 5 or 9 by osmium catalyzed dihydroxylation respectively.

Scheme-3

Dendritic Nanohybrids in Proteomics

[Fig. 1: Sample: total protein of E. coli BL21(DE3) Protein extraction : acetone precipitate Protein conc. : 9.48 mg/mL Gel conc. : SDS-PAGE 12.5% Electrophoresis time : 80 min (at 100V)]
Subsequent unmasking of S-trityl group by TFA/Et3SiH, encapsulate the pyridine-stabilized ZnS/CdSe shell/core type quantum dots. The resultant bioprobes are very stable, water-soluble, dispersive, and narrowly distributed in size. The nanohybrids were studied in proteomics (Fig. 1). After endocytic uptake of nanohybrids, HeLa cancer cells were stably labeled for two days with no detectable effects on cell morphology or physiology. Notabley, we saw no discernible fluorescence loss of the QD labels: brightly fluorescent cells were visible during the entire imaging sequence (Fig. 2). This indicates QDs were taken up by the cells via endocytosis.3

Cellular Imaging studies

Fig. 2: Distribution of Penta-podal QDs in live HeLa cells. Uptake and transport of QDs with 10µL solution. The image Epifluorescence and confocal microscope image of cells 12 hours after being spontaneous uptake by cells.

Section 3: Hybridization of Gallactoside-capped gallamide Dendrons with CdSe/ZnS Core/Shell nanoparticles: Fluorescent, Nucleus Localization probes for Cancer cells
Mostly monomeric-carbohydrates are attached to nanoparticles.4 Moreover; the application of dendritic carbohydrate–conjugated quantum dots in biological assays has not been explored. This is the first example of dendritic gallactoside dendrimer ligand anchored to ZnS/CdSe quantum dots. The simple and convenient method for the construction of dendritic gallactoside gallamide ligand encapsulated CdSe/ZnS quanum dots. The key chemical transformation which allows facile synthesis of this dendritic ligand (15) from 14, is the copper (I)-catalyzed azide–alkyne cycloaddition, a click reaction.5a (Scheme 4). The 13 is readily prepared from methyl gallate by treatment with 12 in presence of K2CO3 in refluxed acetonitrile. The resultant bioprobes 16 are very stable, water-soluble, dispersive, and narrowly distributed in size, which might be of great potential for the investigation of the biofunctions of carbohydrates.5b

Scheme-4

16

Fig. 3: Distribution of nanohybrid-16 in COS-7 kidney cancer cells and A549 liver cancer cells.

Section 4: Dendritic crown ether-capped ZnS/CdSe Core/Shell nanoparticles: Potential fluorescent bioprobes to study the Transmembrane Profiles
The novel 12-crown-4 dendritic ligand 17 was prepared via Cu(I) catalysed Click chemistry from 14. Funcationalization of ZnS/CdSe QDs with 12-crwon-4 dendritic ligand has achieved,6 to investigate the multiple binding studies with Li+ ions in H2O.7 When treated with kidney cancer cells, the nanohybrid-18 induce facile endocytic uptake, which opens up a new entry in the field of cell-biology for studying dynamic transmembrane behaviors.
Scheme-5

18

Fig. 4: Distribution of nanohybrid-18 in live COS-7 cells. Uptake and transport of QDs with 10µL solution.

Section 5: Doubly Ortho-linked Quinoxaline and 3/4-diarylaminopyridine Hybrid as Donor-type Optoelectronic Capping Materials for ZnS/CdSe shell/core nanocrystals
Using Nitrogen donars as binding group, we have created monomeric Q-pyridine –CdSe/ZnS nanocrystal complexes. The new design allows the simple synthesis of surfactant 21 and 22 by Palladium catalyzed coupling reaction of 20 (Q-H)8 with 4-bromo pyridine or 3-bromo pyridine respectively (Scheme 6). The single crystal structures and optoelectronic properties of Q-H-py wrapped ZnS/CdSe nanohybrids are promising for application9 in OLEDs and photovoltaic cells.10

Scheme-6

Section 6: Hydrophobic Nanocrystals coated with Amphiphilic Tetraol and Tetraphosphonic and Tetra carboxylic acid: A general route to water soluble CdSe/ZnS and Pd nanoparticles
We have developed a simple synthetic method for preparation of tetraol (24) or tetraacid (25 or 26) dendritic ligand from 23. This can be used to transfer various nanoparticles11

Scheme-7

from organic solvents to water. The aqueous nanoparticles have physical properties and reactivities similar to those in organic solvents. The wrapping such type of gallamide dendritic ligand around Pd nanoparticles may further enhance the stability.12 The Pd nanoparticles could be useful for C-C bond formation reaction like as Suzuki reaction, Heck coupling.

Chapter-II: Catalysis of Oxometallic species in Aerobic Oxidation and Nucleophilic Acyl Substitutions
This chapter is further divided into two sections.
Section 1: Direct Atom-Efficient Esterification between Carboxylic Acids and Alcohols Catalyzed by Amphoteric, Water-Tolerant TiO(acac)2
The esterification of carboxylic acids with different functionalized alcohols is one of the most important and commonly used transformations in organic synthesis. A diverse array of oxometallic species were examined as catalysts for a test direct condensation of benzoic acid and 2-phenylethanol in 1:1 stoichiometry. Besides Group IVB MOCl2-xH2O and TiOX2-xH2O, Group VB VOCl2-xTHF and Group IVB TiO(acac)2 were found to be

Scheme-8

the most efficient and water-tolerant catalysts for the test reaction. The new neutral catalytic protocol with the optimal TiO(acac)2, tolerates many stereo/electronic structural variations in both (di)acid (1o-3o alkyl and aryl) and (di)alcohol (1o, 2o alkyl, and aryl) components with high chemoselectivity.13

Section 2: Synthesis of Dendrimer catalysts and it’s application towards catalysis and also for DNA cleavage
We demonstrate for the first time use of oxo-metallic species in dendrimer catalyst. This is simple and convenient method for the construction of dendritic gallamide catalyst. The key chemical transformation which allows facile synthesis of this dendritic ligand (29 or 30) from 28, is the copper (I)-catalyzed azide–alkyne cycloaddition, a click reaction.5a (Scheme 10). To check the feasibility of enhanced reactivity in a dendritic catalyst resulting from cooperative reactivity between catalytic units. Further exploration and optimization of such multimeric catalysts in related asymmetric reactions are ongoing.
The titled vanadyl(V) complexes14 serve as efficient reagents for cleaving supercoiled plasmid DNA by photoinitiation.15 We have shown the vanadyl Complexes, derived from 2-hydroxy-1-naphthaldehyde and L-phenylalanine, exhibits a unique wedge feature, inducing a site-selective photocleavage at the C22- T23 of the bulge backbone for a HIV-27 DNA system at 0.15 íM. Transient absorption experiments for corresponding Vanadyl complex indicate the involvement of LMCT with concomitant tautomerization, leading to an o-quinone-methide V-bound hydroxyl species responsible for the cleavage profiles. The use of dendrimer-Vanadyl complex for such DNA cleavage is underway.

References

1. (a) Wedland, M. S.; Zimmerman, S.C. J. Am. Chem. Soc. 1999, 121, 1389. (b) Guo,
W.; Li, J. J.; Wang, Y. A.; Peng, X. J. Am. Chem. Soc. 2003, 125, 3901.
2. Chen, C.-T.; Pawar, V. D.; Munot, Y. S.; Chen, C.-C.; Hsu, C.-J. Chem. Commun.
2005, 2483.
3. (a) Bruchez, M.;mMoranne, M.; Gin, P. ; Weiss, Alivisatos, A. P.; Science, 1998, 281,
2013. (b) Chan, W. C.; Nie, S. M. Science, 1998, 281, 2016.
4. (a) Chen, Y.; Ji, T.; Rosenwig, Z, Nano. Lett. 2003, 3, 581; (b) Osaki, F.; Kanamori,
T.; Sando, S.; Sera, T.; Aoyama, Y., J. Am. Chem. Soc. 2004, 126, 6520; (c) Xie, M.;
Liu, H. –H.; Chen, P.; Zhang, Z. –L.; Wang, X. –H.; Xie, Z. -X.; Du, Y. –M.; Pan, B.
–Q.; Pang, D. W. Chem. Commun. 2005, 5518. (d) A. G. Barrientos, A. G. ; De la.
Fuente, J. M. ; Rojas, T. S. ; Fernandez, A.; Penades, S. Chem. Eur. J. 2003, 9, 1909.
(e) Lin, C. C. ; Yah, Y. –C. ; Yang, C. –Y. ; Chen, C.-L. ; Chen, G. –F. ; Chen, C. –
C, ; Wu, Y. –C. J. Am. Chem. Soc. 2002, 124, 3508.
5. (a) Z. P. Demko and K. B. Sharpless, Angew. Chem. Int. Ed. 2002, 41, 2113. (b) to be
communicated 2006.
6. (a) Chen, C. -Y.; Cheng, C. -T.; Lai, C. -W.; Wu, P. -W.; Wu. K.-C.; Chou, P.-T.;
Chou, Y.-H.; Chiu, H.-T. Chem Commun. 2006, 263 .(b) Lin, S. Y., Liu, S. W. Lin, C.
M. Chen, C.H. Anal Chem. 2002, 74, 330.
7. to be communicated.
8. Chen, C.-T.; Lin, J.-S.; Moturu, V. R. K. Murthy.: Lin, Y. –W.; Yi, W.; Tao, Y.-T.;
Chein, C. –H. Chem. Commun. 2005, 31, 3980.
9. (a) Milliron, D. J; Alivisatos, A.. P.; Pitois, C.; Edder, C.; Frechet, J. M. J. Advan.
Mater. 2003, 12, 58. (b) Huynh, W. U.; Peng, X.; Alivisatos, A. P. Adv. Mater. 1999,
11, 923. (c) Geenham, N. C.; Peng, X.; Alivisatos, A. P. Phys Rev. B 1996, 54, 17628
10. to be communicated.
11. (a) Kim, S. –W.; Kim, S.; Tracy, J. B.; Jasanoff, A.; Bawendi, M. G. J. Am. Chem.
Soc. 2005, 127, 4556. (b)
12. (a) Bruce, J. I.; Chanbron, J.-C.; Koll, P.; Sauvage, J.-P. J. Chem.Soc., Perkin Trans.
1 2002, 1226. (b) Kaes, C.; Hosseini, M. W.; De Cian, A.; Fischer, J. Tetrahedron
Lett. 1997, 38, 3901. (c) Mendoza, J.; Mesa, E.; Rodriguez-Ubis, J.; Vasquez, P.;
Vogtle, F.; Windschief, P.; Rissanen, K.; Lehn, J.-M.; Lilienbaum, P.; Ziessel, R.
Angew. Chem. Int. Ed. Engl. 1991, 30, 1331. (d) Romero, F. M.; Ziessel, R.
Tetrahedron Lett. 1994, 5, 9203. (e) Baxter, P. N. M. J. Org. Chem. 2000, 65, 1257.
(f) to be communicated.
13. (a) Chen, C.-T.; Kuo, J.-H.; Ku, C.-H.; Weng, S.-S.; Liu, C.-Y. J. Org. Chem.
2005, 70, 1328. (b) Chen, C. –T.; Munot, Y. S. J. Org. Chem. 2005, 70, 8625
14. (a) Radodevich, A. T.; Musich, C.; Toste, F. D. J. Am. Chem. Soc. 2005, 127, 1090.
(b) Weng, S. –S.; Shen, M. –W.; Kao, J. –Q.; Munot, Y. S. Chen, C. –T. Proc. Natl.
Acad. Sci. USA, 2006, 103, 3522.(c) Chen, C.-T.; Kuo, J.-H.; Pawar, V. D.; Munot,
Y. S.; Weng, S.-S.; Ku, C.-H.; Liu, C.-Y. J. Org. Chem. 2005, 70, 1188.
15. (a) Chen, C.-T.; Lin, J.-S.; Kuo, J.-H.; Weng, S.-S.; Cuo, T.-S.; Lin, Y.-W.; Cheng,
C.-C.; Huang, Y.-C.; Yu, J.-K.; Chou, P.-T. Org. Lett. 2004, 6, 4471. (b) Hon, S.-W.;
Li, C.-H.; Kuo, J.-H.; Barhate, N. B.; Liu, Y.-H.; Wang, Y.; Chen, C.-T. Org. Lett.
2001, 3, 869. (c) Barhate, N. B.; Chen, C.-T. Org. Lett. 2002, 4, 2529. (d) Annis, D.
A.; Jacobsen, E. N. J. Am. Chem. Soc. 1999, 121, 707.