photolabile protecting groups (plpg): synthetic …...requirements for plpgs •a functionalized...

Photolabile Protecting Groups (PLPG): Synthetic and Biological Applications

Carmin BurrellOctober 15, 2008

First Examples: Cbz-glycine

Zweifel, G. S.; Nantz, M. H.; Modern Organic Synthesis: An Introduction; University Freeman: New York, 2007, 60.

Barltrop, J. A.; Schofield, P.; Tetrahedron Lett., 1962, 16, 697-699.

HN

O

OHO

O H2NOH

OH2, Pd/C

orLi°, NH3

orHBr

HN

O

OHO

O H2N OH

Ohν (254 nm)

Med. P Hg lamp

30 min, H2O75%

First Examples: o-Nitrobenzylesters

Leighton, P. A.; Lucy, F. A., J. Chem. Phys., 1934, 2, 756-759.Barltrop, J.A.; Plant, P. J.; Schofield, P.; Chem Comm, 1966, 22, 822-823.

NO2

H

O

acetonehν (>280nm)

Med. P Hg LampPyrex Filter

NO

OH

O

NO2

H

O

O2N

H

O

hν

(>280nm)

NO2

H

O

O2N

H

O

NO2

H

O

NO

H

OHHO

NO

OH

O

First Examples: o-Nitrobenzylesters

Barltrop, J.A.; Plant, P. J.; Schofield, P.; Chem Comm, 1966, 22, 822-823.

R

OHNO2

R'

O

CCl4hν (>280nm)

Med. P Hg lampPyrex Filter

HO

O

R'

N O

O

R

R R' Time(hr) Yield

H Ph 2.5 17

Ph Ph 2.5 90

Ph C15H31 3.0 95

Ph CH2Ph 4.0 87

Mechanism of Deprotection

Barton, D. H. R.; Chow, Y. L.; Cox, A.; Kirby, G. W.; Tetrahedron Lett., 1962, 23, 1055-1057.

NO

OO

R

N O

O

H

R

NOH

O

CR

OHNO

hνR'

OH

O R'

O

O R'

O

OR'

O

H

transfer HO R'

ON O

R

OR

Excitation - Jablonski Diagram

• Excitation promotes a HOMO electron to the LUMO

• Rearrangement occurs to cleave the PLPG

Laimgruber, S.; Schreier, W. J.; Schrader, T.; Koller, F.; Zinth, W.; Gilch, P.; Angew. Chem. Int. Ed. 2005, 44, 7901-7904.

Excitationfemto(10-15s)

InternalconversionVibrational relaxation

Intersystem crossing

Fluorescencenano (10-9s)

Phosphorescence≥micro (10-6s)

pico 10-12sS2

S1

S0

T1

Applications of PLPGs - Synthesis of (-)-Diazonamide A

HN

O

Me Me

HN

OHO

Me MeN

O

O NH NH

O

N Cl

Cl

(-)-Diazonamide A

Snider, B. B.; Busuyek, M. V.; Tetrahedron, 2001, 57, 3301-3307.Li, J.; Jeong, S.; Esser, L.; Harran, P. G.; Angew. Chem. Int. Ed. 2001, 40, 4765-4769.

Li, J.; Jeong, S.; Esser, L.; Harran, P. G.; Angew. Chem. Int. Ed. 2001, 40, 4765-4769.

HN

O

Me Me

HN

OHO

Me MeN

O

O NH NH

O

N Cl

Cl

(-)-Diazonamide A


HN

OCbzHN

MeMe

O

N

OHOPh

CN

OHBr

o-NO2C6H4CH2Br

K2CO3, NaI, DMF52%

HN

OCbzHN

MeNa

O

N

OHOPh

CN

OBr

NO2

Applications of PLPGs - Synthesis of (-)-Diazonamide A HN

O

Me Me

HN

OHO

Me MeN

O

O NH NH

O

N Cl

Cl

(-)-Diazonamide A


HN

OCbzHN

MeMe

O

N

OHOPh

CN

OBr

NO2

Cl3CCO2H

HN

OCbzHN

MeMe

O

N

OPh

OBr

NO2

O

O



HN

O

Me Me

HN

OHO

Me MeN

O

O NH NH

O

N Cl

Cl

(-)-Diazonamide A

HN

OCbzHN

MeMe

O

N

OPh

OBr

NO2

O

O

NH

NHAlMe2

1.3 eq, toluene/CH2Cl20°C→RT

83% (2 steps)

HN

OCbzHN

MeMe

O

N

OHOPh

OBr

NO2

HN

O

NH



HN

O

Me Me

HN

OHO

Me MeN

O

O NH NH

O

N Cl

Cl

(-)-Diazonamide A

HN

OCbzHN

MeMe

O

N

OHOPh

OBr

NO2

HN

O

NH

5 mol% nPr4NRuO41.5 eq NMO

4 Å MS, CH2Cl278%

HN

OCbzHN

MeMe

O

N

OOPh

OBr

NO2

HN

O

NH


HN

O

Me Me

HN

OHO

Me MeN

O

O NH NH

O

N Cl

Cl

(-)-Diazonamide A


HN

OCbzHN

MeMe

O

N

OOPh

OBr

NO2

HN

O

NH

350nm, 3x10-2Mdegassed dioxane

excess Ac2O, py,DMAP, CH2Cl2, 85%

HN

OCbzHN

MeMe

O

N

OPh

OBr

HN

O

NH

OAc

Requirements for PLPGs

• A Functionalized Aromatic System

• Substituents can allow for use of a specific wavelength radiation

• Stabilize the radicals or ions created after excitation

• Fast Rate of Cleavage

• Reduce the time needed for deprotection

• High quantum yields

Photolabile Protecting Groups (PLPGs)

Wang, P.; Wang, Y.; Hu, H.; Spencer, C.; Liang, X.; Pan, L. J. Org. Chem. 2008, 73, 6152-6157.

Kitani. S.; Sugawara, K.; Tsutsumi, K.; Morimoto, T.; Kakiuchi, K.; ChemComm.

2008, 2103-2105.

Furuta, T.; Wang, S. S.; Dantzker, J. L.; Dore, T. M.; Bybee, W. J.; Callaway, E. M.; Denk, W.; Tsien, R. Y.; Proc. Natl.

Acad. Sci. 1999, 96, 1193-1200.

MeO

OMe

O O

PhPh S

O

OO O

R R'

OR

O

O

OR

OMe

MeO

NO2 O

MeO

MeO MeO

OR

O

OR

Pirrung, M.C.; Bradley, J. C., J. Org. Chem., 1995, 60,

1116-1117.


OMe N NO2

π→π∗ λmax (nm) 184 217 251 252n→π* λmax (nm) 269 299 330

Lambert, J. B.; Shurvell, H. F.; Lightner, D. A.; Cooks, R. G.; Organic Structural Spectroscopy, Prentice-Hall: New Jersey,1998, 289.


• A Functionalized Aromatic System

• Substituents can allow for use of a specific wavelength radiation

• Fast Rate of Cleavage

• Reduce the time needed for deprotection

• High quantum yields

Wang, P.; Wang, J.; Hu, H.; Spencer, C.; Liang, X.; Pan, L. J. Org. Chem. 2008, 73, 6152-6157.Anslyn, E. V.; Dougherty, D. A.; Modern Physical Organic Chemistry; University Science Books: Sausalito,

California, 2006, 971.

OMe

O OH Ph

MeO

OMe

O O

PhPh

H Ph

MeO

2Φ = 0.03

3Φ = 0.17

Chlorophyll Φ= 0.25

Rhodopsin Φ= 0.66

Requirements for PLPGsNumber of molecules that undergo cleavage

Total number of photons absorbedQuantum Yield = Φ =

0 < Φ < 1

Sheenan, J.C.; Wilson, R. M., J. Am. Chem. Soc., 1964, 86, 5277-5281.Sheenan, J. C.; Wilson, R. M.; Oxford, A. W, J. Am. Chem. Soc., 1971, 93, 7222-7228

Dimethoxybenzoin Carbonates

Φ= 0.64

MeO

OMe

O

OAc MeCNhν (360nm)

Rayonet reactorpyrex filters

7min, N2

O

MeO

OMe

HOAc

99%

O

X

R2

R1

R3

R4

benzenehν (>280nm)

Med. P Hg lampPyrex Filter

OR2

R1 R3

R4

R1 R2 R3 R4 X Time (hr) Yield H H H H OAc 17 15 H H H H Cl 18 1 OMe H OMe H OAc 17 46

Pirrung, M.C.; Bradley, J. C., J. Org. Chem., 1995, 60, 1116-1117.


MeO

OMe

O

X

OH SH

MeO

OHOH

benzenehν (350nm)

Rayonet reactor1h, Ar

O

MeO

OMe

HX

88% 95% 90% 94%

Boudebous, H.; Košmrlj, B.; Šket, B.; Wirz, J., J. Phys. Chem. A., 2007, 111, 2811-2813.


MeO

OMe

O

OAcMeO

OMe

O

OAc

O

MeO

OMe

OAc

O

MeO

OMeH

O

MeO

OMe

HOAc

hν

New PLPGs - Thiochromone S,S Dioxide

Kitani, S.; Sugawara, K.; Tsutsumi, K.; Morimoto, T.; Kakiuchi, K. Chem. Comm. 2008, 18, 2103-2105.

S

O

O OR

OS

O

O OR

O

S

O

O OEt

O

hν (λ >280nm)ultra-high P Hg lamp

pyrex filter

CD3OD (2.0X10-2M)0.5h

S

O

O OEt

O>99%



S

O

OO O

OEt

O

EtOH>99%


pyrex filter

CD3OD (2.0X10-2M)0.5h



S

O

OO O

XR

OS

O

OO O

XR

O

S

O

O OO XR

O S

O

O O

CO2 HXR

H

hν (λ >280nm)

CD3OD

S

O

O OR

OS

O

O OR

O



S

O

OO O

O

O

CD3OD (2.0X10-2M)R S

O

O O

ROH

Alcohol Irradiation Time(h) Yield(%)EtOH 0.5 >99C8H17OH 0.5 >99

0.5 >99OH

1.0 97OH

OH 1.0 98

OH1.0 >99 (98)

OMeMe

HOH H

1.0 >99 (99)

O OMe

OAcAcOOAc

HO 0.5 >99 (99)

Alcohol Irradiation Time(h) Yield(%)


pyrex filter



S

O

OO O

N

O

CD3OD (2.0X10-2M)R S

O

O O

R'

R NH

R'

1.0 97

1.0 98

1.0 97

Amine Irradiation Time/h Yield(%)

C4H9NH2

Et2NHNH2

CO2Bn


pyrex filter



S

O

OO O

R

O

CD3OD (2.0X10-2M)RCOOH

S

O

O O

RCOOH Irradiation Time/h Yield(%)

C11H23COOH 1.0 >99

C17H35COOH 1.0 >99

1.0 >99COOH

COOH 1.0 >99


pyrex filter

New PLPGs - Ketones and AldehydesGeneration 1

• Ortho - meta effects on the excited state facilitate heterolytic cleavage

Zimmerman, H. E.; J. Am. Chem. Soc., 1995, 117, 8988-8991Wang, P.; Hu, H.; Wang, Y.; Org. Lett., 2007, 9, 2831-2833.

OMe

O OH H

OMe

O OH H

MeOO OH H

S1 S0

-0.181 -0.159

S1 S0

-0.193 -0.143

S1 S0

-0.168 -0.172

δ- δ- δ-

Mulliken Charges

Gaussian 03, Revision C.02 CIS/3-21G for excited states

HF/3-21G for geometry optimization

Excited State - Ortho - Meta Effect

Zimmerman, H. E., J. Am. Chem. Soc.,1995, 117, 8988-8991.

MO 1

MO 3

MO 5

MO 7

MO 2

MO 4

MO 6


• Ortho - meta effects on the excited state facilitate heterolytic cleavage

Zimmerman, H. E.; J. Am. Chem. Soc., 1995, 117, 8988-8991Wang, P.; Hu, H.; Wang, Y.; Org. Lett., 2007, 9, 2831-2833.

OMe

O OH H

OMe

O OH H

MeOO OH H

S1 S0

-0.181 -0.159

S1 S0

-0.193 -0.143

S1 S0

-0.168 -0.172

δ- δ- δ-

Mulliken Charges

Gaussian 03, Revision C.02 CIS/3-21G for excited states

HF/3-21G for geometry optimization

OMe

OCH2O

R1 R2

MeO

Wang, P.; Hu, H.; Wang, Y.; Org. Lett., 2007, 9, 2831-2833.


O OH

OMe

O OH

OMe

O OH

MeO

Ph

Ph

Ph

hν (>280nm)Med P Hg lamp

pyrex sleeve

CD3CN/D2O (9:1)1hr

H Ph

O

H Ph

O

H Ph

O

50%

8%


pyrex sleeve

CD3CN/D2O (9:1)1hr


pyrex sleeve

CD3CN/D2O (9:1)1hr



R1

O

R2

hν (>280nm)Med. P Hg lamp

pyrex filterMeCN/H2O (4:1)

OMe

OH OHMeO

10 mol%, p-TsOH

OMe

O OR1 R2

MeO

Ph CHO

CHO

OPh MeO

O

O

16

Protection Yield: 92 99 93 91

Deprotection Yield: 81 79 86 93

Time (h): 4.0 0.5 3.0 3.5



O

MeO

OCHO

OMe

8



Time (min): 60 60 60 80

OMe

OH OH

PhPh

OMe

O OR1 R2

PhPh

Ph CHO

R1

O

R2


pyrex filterMeCN

10 mol%, p-TsOHOMe

O OR1 R2

PhPh

Wang, P.; Wang, J.; Hu, H.; Spencer, C.; Liang, X.; Pan, L. J. Org. Chem. 2008, 73, 6152-6157.

New PLPGs - Ketones and AldehydesOptimized System

OMe

OH OH

PhPh

MeOOH OH

OMe

1 2

OMe

MeOOH OH

PhPh

3

PPG Φ protection yield (%) deprotection yield (%) time (min)

1 0.03 92 81 2402 0.11 99 90 603 0.17 99 92 30



OMe

OH OHMeO

OMe

O OR1 R2

MeO

Ph CHO

CHO

OPh MeO

O

O

16



Time (h): 30 44 25 25

PhPh PhPh

R1

O

R2


pyrex filterMeCN/H2O 10%(v/v)

10 mol%, p-TsOH



OMe

MeOO OR1 R2

PhPh

hν

OMe

MeOO OR1 R2

PhPh

R1 R2O

OMe

MeOO

Ph

Ph

H2O

hν-H2O

OMe

MeOOH OH

PhPh


OMe

O O

PhPh

H Ph

MeO


Reagent Solvent Conditions %RecoveryPhLi THF -78 to 23°C, 6h 100LiAlH4 THF 23°C, 24h 100NaBH4 THF 23°C, 24h 100H2, Pd/C THF 23°C, 18h 100t-BuOK MeCN 23°C, 24h 100 80°C, 2h 100DDQ MeCN 23°C, 24h 100 80°C, 2h 94CAN MeCN 23°C, 24h 0 80°C, 2h 0AcOH MeCN 23°C, 24h 100 80°C, 2h 100TFA MeCN 23°C, 24h 100 80°C, 2h 91HCl (37%) MeCN 23°C, 24h 100 80°C, 2h 65pTsOH MeCN 23°C, 24h 47 80°C, 2h 0

New PLPGs - Ketones and AldehydesAmino Acetal


R1

R2

O OH Ph

H Ph

O

R1 R2 Yield Time Φ λmaxN(Me)2 H 99 16 0.13 327 OMe OMe 92 30 0.17 297

hν (>280nm)

Med. P Hg lamppyrex filter


Orthogonality Using PLPGs

N

O O

PhPh

OMe

O O

PhPh

H Ph

MeO

H Ph

hνMeCN/

H2O (1:1)

OMe

O O

PhPh

H Ph

MeO H Ph

O

350nm, 20min: 98% >89%

sunlight, 3h : 98% >96%



S

O

O O

OO O

OS

O

O O hν (λ >280nm)

CD3OD, 0.5h99%

S

O

O O

OOH

S

O

O O

CO2



mCPBA85%

S

O

O O

OOH

O O

hν (λ >280nm)

CD3OD, 0.5h99%

HO OHS

O

O O

CO2

>99% 85%

S

O

O O

OOH


Blanc, A.; Bochet, C. G., J. Org. Chem., 2002, 67, 5567-5577.

OMe

MeO O

O O

O

O

O2N OMe

OMen

hν, thenCH2N2

420 nm254 nm

MeO

O

O

O

O2N OMe

OMen

OMe

MeO O

O O

OMe

On

n 254 nm 420 nm (%) (%)

0 86 671 94 832 94 853 96 854 78 875 92 70

Summary of Uses of PLPGs in Synthesis• o-Nitrobenzyl is most widely used and has been

applied to total syntheses

• Thiochromone systems could be an alternative although optimization required

• Acetal protection system for aldehydes and ketones is groundbreaking

• Proof of orthogonality makes PLPG more practical

R

OHNO2

R'

O

S

O

OO O

O

OR

OMe

MeOO OR1 R2

PhPh

Caged Biomolecules

• PLPG inactivates the biomolecule until irradiated

• Biomolecules that have been caged include:

• neurotransmitters, ATP, Pi, Glutamate

• An effective method to elucidate cellular functions of biomolecules

• Release occurs on a biologically relevant time scale as compared to diffusion (temporal resolution)

• Release can be controlled to a specific area (spacial resolution)

Furuta, T.; Wang, S. S.; Dantzker, J. L.; Dore, T. M.; Bybee, W. J.; Callaway, E. M.; Denk, W.; Tsien, R. Y.; Proc. Natl. Acad. Sci. 1999, 96, 1193-1200.

Caged Biomolecules - C. Elegans

Li, H.; Avery, L.; Denk, W.; Hess, G. P., Proc. Natl. Acad. Sci. USA, 1997, 94, 5912-5916.

Caged Biomolecules - C. Elegans

Li, H.; Avery, L.; Denk, W.; Hess, G. P., Proc. Natl. Acad. Sci. USA, 1997, 94, 5912-5916.

NO2

COO-

O

O

NH3+

COO-

NO

COO-

O HO

OCOO-

NH3+hν

Light Triggered Molecule-Scale Dosing

McCoy, C. P.; Rooney, C.; Edwards, C. R.; Jones, D. S.; Gorman, S. P.; J. Am. Chem. Soc. 2007, 129, 9572-9573.

O

O

OCH3

OCH3O

O

O

OCH3

OCH3O

O

O

OCH3

OCH3O

O O

OAcetylsalicylic acid Ibuprofen

Ketoprofen

Light Triggered Molecule-Scale Dosing

OOCH3

OCH3

O

O

OCH3

OCH3O

Ibuprofen

hν (365 nm)Hg lamp

quartz cuvette

HO

O

McCoy, C. P.; Rooney, C.; Edwards, C. R.; Jones, D. S.; Gorman, S. P.; J. Am. Chem. Soc. 2007, 129, 9572-9573.

0

30

60

90

0 10 20 30 40

Yie

ld o

f Ib

upro

fen

(%)

Time (min)

Off

Off

Off

Off

OffOff

On

On

On

On

OnOn

Taxol® Prodrug

Skwarczynski, M.; Sohma, Y.; Noguchi, M.; Kimura, M.; Hayashi, Y.; Hamada, Y.; Kiso, Y.; Kimura, T.; J. Med. Chem. 2005, 48, 2655-2666.

OO

O

O

O

HO

O

OH

OH

O

OO

O O

H2N

OHO

O

O

HO

O

OH

OH

O

OO

O O

NH

O

Isotaxel0.45 mg/mL

Taxol®2.5 x 10-4 mg/mL

Skwarczynski, M.; Noguchi, M.; Hirota, S.; Sohma, Y.; Kimura, T.; Hayashi, Y.; Kiso, Y.; Bioorg. Med. Chem. Lett. 2006, 16, 4492-4496.

ON O

O

NHO

OO

O

O

O

HO

O

OH

OH

O

OO

O O

HCl

OO

O

O

O

HO

O

OH

OH

O

OO

O O

H2N

Isotaxel0.45 mg/mL

430 nm

diode laser

Phototaxel< 2.5 x 10-4 mg/mL

Taxol® Prodrug

0

20

40

60

80

100

0 5 10 15 20 25 30

Time (min)

(%)

Skwarczynski, M.; Noguchi, M.; Hirota, S.; Sohma, Y.; Kimura, T.; Hayashi, Y.; Kiso, Y.; Bioorg. Med. Chem. Lett. 2006, 16, 4492-4496.

ON O

O

NHO

OO

O

O

O

HO

O

OH

OHO

OO

O O

HCl

2

OHO

O

O

HO

O

OH

OHO

OO

O O

NH

O

1

ON O

OH5

Taxol® Prodrug

= 1= 2= 5

Skwarczynski, M.; Noguchi, M.; Hirota, S.; Sohma, Y.; Kimura, T.; Hayashi, Y.; Kiso, Y.; Bioorg. Med. Chem. 2008, 16, 5389-5397.

Taxol® Prodrug

ON O

O

NHO

OO

O

O

O

HO

O

OH

OH

O

OO

O O

NHO

N

NH

ON

3 HCl

OO

O

O

O

HO

O

OH

OH

O

OO

O O

H2N

Isotaxel0.45 mg/mL

365 nm

UV lamp

Phototaxel 2> 100mg/mL

0

20

40

60

80

100

0 10 20 30 40 50 60

Time (min)

(%)

Skwarczynski, M.; Noguchi, M.; Hirota, S.; Sohma, Y.; Kimura, T.; Hayashi, Y.; Kiso, Y.; Bioorg. Med. Chem. 2008, 16, 5389-5397.

ON O

O

NHO

OO

O

O

O

HO

O

OH

OH

O

OO

O O

NHO

N

NH

ON

3 HCl

Phototaxel

OHO

O

O

HO

O

OH

OHO

OO

O O

NH

O

Taxol®

Taxol® Prodrug

= Taxol®

= Phototaxel

UV Damage

• Preceding PLPGs required 280 - 365nm radiation for cleavage

Matsumura, Y.; Ananthaswamy, H. N.; Toxicol. Appl. Pharmacol. 2004, 195, 298-308.

X-Rays Visiblelight

100 150 200 250 300 350 400Wavelength (nm)

Ultraviolet radiation

UVC UVB UVA

UV Damage

Matsumura, Y.; Ananthaswamy, H. N.; Toxicol. Appl. Pharmacol. 2004, 195, 298-308.

Acute UV

Sunburn, Suntan, Epidermal Hyperplasia

DNA damage

Immune Suppression

p53 induction

Cell cycle controlApoptosis

DNA Repair

Maintenance of genomic stabilityDNA replication and repairAngiogenesis inhibition

Chronic UV

Skin aging (Photoaging)

DNA damage accumulation

Immune suppression

Genetic mutations

Skin carcinogenesis

Two Photon Excitation

• Maria Göppert-Mayer first described non-linear optics - 1931

• Theodore Maiman developed the ruby laser -1960

• W. Kaiser and C. B. G. Garrett observed two photon excited fluorescence in CaF2:Eu2+ crystals- 1961

• Janis Valdemanis and R. L. Fork described multiphoton microscopy - 1980s

• D. E. Spence, P. N. Kean and W. Sibbert developed Ti-sapphire femtosecond laser - 1990

Masters, B.R.; So, P. T. C., Microscopy Research and Technique, 2004, 63, 3-11.


Oheim, M.; Michael, D. J.; Geisbauer, M.; Madsen, D.; Chow, R. H.; Adv. Drug Deliv. Rev., 2006, 58, 788–808

S0

S1

S2

T1

Exci

tatio

n

Fluo

resc

ence

Phos

phor

esce

nce

IC

ISC

UVOne Photon Excitation

S0

S1

S2

T1

Exci

tatio

n

Fluo

resc

ence

Phos

phor

esce

nce

IC

ISC

IRTwo Photon Excitation

VirtualState


• Utilizes IR radiation instead of UV

• Requires concentrated photons and provides increased spacial and temporal control of excitation

• Not sensitive to scattering

• No out-of-focus absorption

• Photobleaching and photodamage is limited to the location of excitation

• Increases Depth Penetration

Piston, D. W.; Adv. Drug Deliv. Rev., 2006, 58, 770-772.


Released Biomolecule PLPGCaged

Biomolecule

Two Photon ExcitationOne Photon Two Photon

UV IR


Oheim, M.; Michael, D. J.; Geisbauer, M.; Madsen, D.; Chow, R. H.; Adv. Drug Deliv. Rev., 2006, 58, 788–808.


Denk, W.; Helmchen, F.; Nature Methods, 2005, 12, 932-940.

One Photon Two Photon UV IR


• Confocal microscopy depth in brain tissue: 50 - 100μm

• Used for imaging of slices of the brain tissue

• Two Photon Excitation depth in brain tissue: up to 1mm

• Could lead to excitation deeper in a tumor

Denk, W.; Helmchen, F.; Nature Methods, 2005, 12, 932-940.

Coumarin Derivatives

Givens, R. S.; Matuszewski, B., J. Am. Chem. Soc., 1984, 106, 6860-6861.Furuta, T.; Toriagai, H.; Sugimoto, M.; Iwamura, M., J. Org. Chem., 1995, 60, 3953-3956.

OH3CO O

CH2OP(OC2H5)2

O

hν (360nm)

Nu OH3CO O

CH2Nu

Nu = CH3OH, piperidine, cysteine, tyrosine, α-chymotrypsin

OH3CO O

PO

O

O

O OO

N

NN

N

NH2

PO

O

O

O OHO

N

NN

N

NH2

cAMP

Dioxane/Water (1:1)hν (340nm)

Xe lamp1h, Ar, 90%



MeO

MeO

O

OCO2

NH3NO2

1 α-DMNB-gluO

OAc

HO O2

O

OAc

O O3

Cl

Cmpd Φ(365nm) ∂u(740nm (GM)) ∂u(800nm (GM))1 0.006

2 0.025 1.07 ± 0.05 0.13 ± 0.001

3 0.01 1.07 ± 0.07 0.34 ± 0.02

Cross Sectional Area of Uncaging (δu)

• Measures the efficiency of the chromophore to absorb two photons

• 1δu = 10-50 cm4s/photon = 1GM

• Dependent on:

• Cross-sectional area of the chromophore

Albota, M., et. al.; Science, 1998, 281, 1653-1656.



MeO

MeO

O

OCO2

NH3NO2

1 α-DMNB-gluO

OAc

HO O2

O

OAc

O O3

Cl

Cmpd Φ(365nm) ∂u(740nm (GM)) ∂u(800nm (GM))1 0.006

2 0.025 1.07 ± 0.05 0.13 ± 0.001

3 0.01 1.07 ± 0.07 0.34 ± 0.02



Cmpd Φ(365nm) ∂u(740nm (GM)) ∂u(800nm (GM))4 0.037 1.99 ± 0.09 0.42 ± 0.01

5 0.065 0.96 ± 0.05 3.1 ± 0.2

6 0.019 0.89 ± 0.24 0.42 ± 0.11

7 0.019 0.95 ± 0.21 0.37 ± 0.06

O

OAc

O O4

Br

O

OAc

O O5

Br

Br

Br

OO

Br

OHN

O

CO2

O

CO2

7 Bhc-gluOO

Br

O

OCO2

O

NH3

6



= 1=7

0

20

40

60

80

100

0 10 20 30 40 50 60

Time (min)

(%)

MeO

MeO

O

OCO2

NH3NO2

1 α-DMNB-gluOO

Br

OHN

O

CO2

O

CO2

7 Bhc-glu

Coumarin Derivatives - Mechanism of Cleavage

Schmidt, R.; Geisser, D.; Hagen, V.; Bendig, J., J. Phys. Chem. A., 2007, 111, 5768-5774.

OH3CO O

OR

OH3CO O

C OR

OH3CO O

CH2OH

HOR

333nmHH

OH3CO O

CH2H2OOR

SET

Conclusions

• Usage is an attractive alternative to classical protecting groups

• Technique is still in its infancy and further optimization is required before wide spread usage

• Has the potential to revolutionize drug delivery systems

• Combined application with fiber optics to target tumors

Acknowledgements

• Dr. Babak Borhan

• Dr. Ned Jackson

• Dr. Petr Klan

• Toyin, Aman, Arvind, Camille, Dan, Calvin, Xiaoyong, Mercy, Roozbeh, Atefeh, Sarah, Sing, Wenjing, Xiaofei, Chryssoula

• All of you for your attention

photolabile protecting groups (plpg): synthetic …...requirements for plpgs •a functionalized...

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