topology of organometallic radicals how does coordination with transition metals affect...

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Department of Chemistry and Biochemistry

TRANSITION METAL-MEDIATED RADICAL REACTIONS

AND

DEVELOPMENT OF NOVEL THERAPEUTIC MEANS

FOR BREAST CANCER TREATMENT

GAGIK G. MELIKYAN

2009

Topology of Organometallic Radicals

CU

TM

X

X X

X X

X

π−β radical π−γ radical

σ−γ radicalσ−β radicalσ−α radical

π−α radical

transition metal-centered radical

X = C, Heteroatom, Metal; CU = η2-η6 Complexing Unit; TM = Transition Metal

σ-bonded ligand

π-bonded ligand

p-complexing unit-based radical

X

π−δ radical

Review: G. G. Melikyan. Ligand-Based Organometallic Radical Chemistry: an Emerging Interdisciplinary Field in: Frontiers in Organometallic Chemistry. Ed. M. A. Cato, Nova Science Publishers, 2006, Ch.7, 155 - 190.

How does coordination with transition metals affect reactivity&stereoelectronic parameters of propargyl

cation&radical?

+

.

Organic species Organometallic species

+

Co Co

OC

OC

OC

CO

CO

CO

Co Co

OC

OC

OC

CO

CO

CO

.

+

+

.

Alternative Strategies for Generation of Co2(CO)6 - Complexed Propargyl Radicals

Co CoOC

OCOC

CO

COCO

Co CoOC

OCOC

CO

COCO

Co CoOC

OCOC

CO

COCO

Na-Ph2COTHF and like molecules

radical additionto double bond

cathodeZn or Spontaneous

conversion of cation to radicals

Co

Tetrahydrofuran-Mediated Generation and Stereoselective Coupling of Cobalt-Complexed Propargyl Radicals

HBF4 / / CH2Cl2

path aone-step protocol

path btwo-step protocol

stereoselective intermolecularradical dimerization

OH

Co2(CO)6

O

Co2(CO)6

.

Co 2(CO)6

+ BF4-

HBF4O

/ CH2Cl2

Co2(CO)6

.Co2(CO)6

(CO)6Co2

Co2(CO)6

d,l : meso, 95 : 5

THF: Synthetic Profile

KNOWN:

1) TO BE A GOOD SOLVENT FOR

ORGANOMETALLIC REACTIONS;

2) TO BE A LIGAND CAPABLE OF

COORDINATING TO A VACANT

COORDINATION SITES IN

TRANSITION METAL COMPLEXES;

3) TO ACT AS AN H-ATOM DONOR

IN RADICAL REACTIONS;

4) TO SERVE AS A DONOR OF HYDRIDE IONS;

5) TO UNDERGO A NUCLEOPHILIC RING-

OPENING IN THE PRESENCE OF LEWIS ACIDS.

NOT KNOWN:

1) TO MEDIATE, INITIATE, OR

CATALYZE RADICAL REACTIONS

IN ORGANIC OR ORGANOMETALLIC

CHEMISTRY.

Understanding THF-Mediated Radical Reaction:Hydride Ion Transfer versus Direct Single Electron Reduction

H

M = Co2(CO)6

+

+

+

+Ph

O+ O

Ph

O+

Ph H

Ph H

+

Ph

+

OPh

H

+OH

+

Ph

HIT

M

H+

M

WM

M

M

M

M

M

+Ph

M

Toure, P.; Myer, S.; Melikyan, G. G. Interaction of Propargyl Cation with Tetrahydrofuran: Thermodynamics, Kinetics, and Biological Relevance. J. Phys. Chem. A, 2001, 105, 4579-4584.

hydride-ion transfer

mechanism

single-electrontransfer

Mechanistic studies: A. stoichiometry of the process; B. measurement of the kinetic isotope effect (KIE) in the competitive setting (THF-d0 and THF-d8); C. measurement of the kinetic isotope effect (KIE) in the noncompetitive setting (THF-d0 and THF-d8); D. ligand substitution experiments with 13CO; E. kinetic studies with model compounds - Co2(CO)6-complexed 1-phenyl-2-propyne, tetrahydrothiophene, cobalt-alkyne anchored tetrahydropyran; F. ab initio calculations.

Mechanism of THF-Mediated Radical Reaction

Ar

H+ O HAr

O O HAr

O

>36e -

37e -

Ar

+

Ar

H

Ar

Ar

2O

+

HAr

+

+

+ +1/2

+1/2O

O HAr

O

+1/2

+1/2

+

+

Ar

+

1) - 12CO;2) + 13CO

Ar

+

clus te r-to-ligand SET

Co2(CO)6 (CO)6Co2

(CO)6Co2

Co2(12CO)5(13CO)

Co2(CO)6

Co2(CO)6

(CO)6Co2

(CO)6Co2

Co2(CO)6

(CO)6Co2Co2(12CO)6

Melikyan, G. G.; Villena, F.; Florut, A.; Sepanian, S.; Sarkissian, H.; Rowe, A.; Toure, P.; Mehta, D.; Christian, N.; Myer, S.; Miller, D.; Scanlon, S.; Porazik, M.; Gruselle, M. Tetrahydrofuran-Mediated Stereoselective Radical C-C Bond Formation in Dicobalthexacarbonyl-Propargyl Complexes. Organometallics 2006, 25, 4680-4690.

Unorthodox Radical Chemistry

Ar

.+.

+

Ar

+

Ar

+

donor acceptor acceptor-derived s pec ies

donor-derived s pec ies

Ar

+ +

Ocatalys t

Co2(CO)6Co2(CO)6Co2(CO)6 Co2(CO)6

+

Ar

+

donor accep tor

Ar

+O

catalys t for s te reos e lec tive rad ical d imerization

Ar

ArCo2(CO)6 Co2(CO)6 (CO)6Co2

Co2(CO)6

Spontaneous Generation of Cobalt- Complexed Propargyl Radicals

+ CH2Cl2 20°C

.spontaneous radical generation

OH CH2Cl2 20°C

+

R1 R1 R1

R1

R1

R2 R2 R2 R2 R2 R2 R2 R2

R2 R2

R1 = R2 = H; R1 = OMe, R2 = H; R1 = R2 = OMe.

etherCo2(CO)6

HBF4

BF4-

Co2(CO)6 Co2(CO)6 Co2(CO)6

Co2(CO)6

Co2(CO)6 Co2(CO)6

Co2(CO)6

(CO)6Co2

9-12h

Gagik G. Melikyan, Ferdinand Villena, Steve Sepanian, Michelle Pulido, Hagop Sarkissian and Arthur Florut. Spontaneous Generation and Stereoselective Coupling of Co2(CO)6-Complexed Propargyl Radicals. Organic Letters, 2003, 5, 3395-3397.

slow cluster-to-ligand reduction

Tentative Mechanism of Spontaneous Reaction

Scheme 2

(OC)3Co Co(CO)3

+

Co(CO)3(OC)3Co

+

cluster-to-clusterreduction

Co(CO)3

+

(CO)3Co Co(CO)3(CO)3Co

+alignment of a filleddz2 metal orbital andan empty p-orbital

Co(CO)3(CO)3Co

dz2-p SET

Co(12CO)3-m(13CO)m(13CO)n(12CO)3-nCo

+

6 (37e-)

13CO

9 (n+m≥4)1 (36e-)

1 (36e-)

3 (36e-)7 (37e-)

- 12CO

d,l-2

1.dz2-p SET2.dimerization

d,l-8 (n+m≥4)

dimerization

(OC)3Co Co(CO)3

Co(CO)3(OC)3Co

(13CO)n(12CO)3-nCo Co(12CO)3-m(13CO)m

Co(12CO)3-m(13CO)m(13CO)n(12CO)3-nCo

The Effect of Temperature Upon Reaction Rate

(CO)6Co2

Co2(CO)6

Co2(CO)6

Co2(CO)6

Gagik G. Melikyan, Boghos Mikailian, Ruth Sepanian, Pogban Toure. High-Temperature Reaction of a Co2(CO)6-Complexed Propargyl Cation. J. Organomet. Chem. 2009, 694,785-794.

Yield and d,l-Diastereoselectivity NOT CompromisedYield and d,l-Diastereoselectivity NOT Compromised

Temperature Time Yield d,l:meso de

20°C 11h 80.0% 94:6 88%

40°C 100min 93.0% 94:6 88%

83°C 6min 88.0% 92:8 84%

147°C 1min 84.0% 90:10 80%

(CO)6Co2

Co2(CO)6

(CO)6Co2

Co2(CO)6

d,l meso

High Temperature Reactions in Cobalt-Alkyne Chemistry

Neutral complexes:

1) Ligand substitution reactions converting Co2(CO)6-complexes to axially, or equatorially, substituted Co2(CO)5L and Co2(CO)4L2 complexes (50-80°C); 2) Pauson-Khand reaction converting cobalt-alkyne complexes to cyclopentenones (20-150°C).

Cationic complexes:

1) None.

One-Step, Tf2O-Mediated Radical Reaction

OH OCH2Cl2 20°C

OMe

OMe

CF3 S

O

O

O S

O

O

CF3

S

O

O

CF3

OMe

OMe

C-O bondheterolysis

O S

O

O

CF3

OMe

OMe

+

spontaneouscluster-to-ligand SET

OMe

OMe

OMe

OMe

OMe

OMe

Co2(CO)6

Co2(CO)6

Co2(CO)6

Co2(CO)6 Co2(CO)6 Co2(CO)6

d,l : meso, 99 : 1

OMe

OMe

OMe

OMe

Ce4+

Generation of Cobalt-Complexed Propargyl Cations under Acidic Conditions

1

CF3 S

O

O

O S

O

O

CF3

(OC)3Co

(CO)3Co

OH + HO S

O

O

CF3+

2

3

4

CH2Cl2 (OC)3Co

(CO)3Co

-O S

O

O

CF3+

(OC)3Co

(CO)3Co

Co(CO)3

Co(CO)3

CH2Cl2(OC)3Co

(CO)3Co

3

+ -OTf

cluster-to-cluster &cluster-to-π-ligand

SET

(OC)3Co

(CO)3Co

5 dl-6 (84-94%)

Table 1. Spontaneous, high temperature radical coupling of cobalt-complexed propragyl triflates.

Protocol

a The yields are calculated on the basis of the reaction stoichiometry that requires two equivalents of propargyl cations to form an equivalent of respective radicals. b Compound determining the acidity of the reaction medium.

T, °C

147°

Yield,b%

Reactiontime

1min1. method A

crude 6d,l:meso

94:6

Reactantcomposition

alcohol 1 + 2eqs Tf2O 21.0

Medium

acidic (TfOHb)

isolated 6d,l:meso

147° 6min2. method A 86:14alcohol 1 + 1eq Tf2O 30.2acidic (TfOHb)

83° 3min3. method B 88:12alcohol 1 + 1eq Me3SiOTf 81.2acidic (TfOHb/Me3SiOHb)

83° 3min4. method C 94:6Me ether 10 + 1eq Tf2O 82.2neutral

Generation of Cobalt-Complexed Propargyl Cations under Acidic Conditions:

An Alternative Approach

(OC)3Co

(CO)3Co

Co(CO)3

Co(CO)3

CH2Cl2(OC)3Co

(CO)3Co

3

+ -OTf


SET

(OC)3Co

(CO)3Co

5 dl-6 (84-94%)

1

(OC)3Co

(CO)3Co

OH +

(OC)3Co

(CO)3Co

OSiMe3 +

7

8

4

CH2Cl2Me3Si+ -OTf TfOH

CH2Cl2

(OC)3Co

(CO)3Co

+

3

9

Me3SiOH+ -OTf

Generation of Cobalt-Complexed Propargyl Cations under Neutral Conditions

Table 1. Spontaneous, high temperature radical coupling of cobalt-complexed propragyl triflates.

Protocol

a The yields are calculated on the basis of the reaction stoichiometry that requires two equivalents of propargyl cations to form an equivalent of respective radicals. b Compound determining the acidity of the reaction medium.

T, °C

147°

Yield,b%

Reactiontime

1min1. method A

crude 6d,l:meso

94:6

Reactantcomposition

alcohol 1 + 2eqs Tf2O 21.0

Medium

acidic (TfOHb)

isolated 6d,l:meso

147° 6min2. method A 86:14alcohol 1 + 1eq Tf2O 30.2acidic (TfOHb)

83° 3min3. method B 88:12alcohol 1 + 1eq Me3SiOTf 81.2acidic (TfOHb/Me3SiOHb)

83° 3min4. method C 94:6Me ether 10 + 1eq Tf2O 82.2neutral

10

(OC)3Co

(CO)3Co

O +

2

CH2Cl2

(OC)3Co

(CO)3Co

+

3

12

Me F3C S

O

O

O S

O

O

CF3

(OC)3Co

(CO)3Co

OS

Me

CF3

O

O

+O S

O

O

CF3

_

O S

O

O

CF3

_

11

+ O S

O

O

CF3Me

Expanding Reagent Base: Trifluoroacetic Anhydride vs Triflic Anhydride

10

CF3 CO

O CO

CF3

(OC)3Co

(CO)3Co

OMe13

14

CH2Cl2(OC)3Co

(CO)3Co

-O C

O

CF3+

83°C, 6min

MeO CO

CF3

15

(OC)3Co

(CO)3Co

Co(CO)3

Co(CO)3

CH2Cl2


SET

(OC)3Co

(CO)3Co

5 6 (dl:meso, 84:16)

Expanding Substrate Base of Spontaneous Radical Reaction

(OC)3Co

(CO)3Co

OMe

10

(OC)3Co

(CO)3Co

Co(CO)3

Co(CO)3

6 24

Substrate Bis-cluster Organic productc

(OC)3Co

(CO)3Co

OMe

16

(OC)3Co

(CO)3Co

Co(CO)3

Co(CO)3

19 25

(OC)3Co

(CO)3Co

OMe

17

(OC)3Co

(CO)3Co

Co(CO)3

Co(CO)3

20 26

MeO MeO

OMe

MeO

OMe

(OC)3Co

(CO)3Co

OMe

(OC)3Co

(CO)3Co

Co(CO)3

Co(CO)3

21 27

MeO MeO

OMe

MeO

OMe

18

dl : mesoratio

94 : 6a

97 : 3a

89 : 11b

95 : 5a

a Chromatographically separable. b Chromatographically inseparable. c Only major dl-diastereomers were decomplexed with ceric ammonium nitrate.

OMe

MeO MeO

OMe

MeO

OMe

MeO

OMe

MeO

OMe

Can the New Method for Cation Generation Handle Acid-Sensitive Moieties?

H O

Co2(CO)8

Co2(CO)6

(CO)6Co2

Co2(CO)6Osodium

acetylide

O- Na+

O

CH3I

OCH3

O

OCH3

OTf2O

O

O

Ce4+

O

O

enzymatic debenzylation

OH

OH

O

O

O

O

O

O

O

O

acetals,1,3-dioxolanes

o-benzyloxymoiety

How Free the Cobalt-Complexed Radicals Are?

Radical dimer Zn-mediated, two step

THF-mediated, two-step

THF-mediated, one-step

Spontaneous, two-step

Tf2O-mediated, one-step

Co2(CO)6

(CO)6Co2

Co2(CO)6

(CO)6Co2

OMe

OMe

Co2(CO)6

(CO)6Co2

OMe

OMe

MeO

OMe

84 : 16 95 : 5 95 : 5 94 : 6

95 : 5 97 : 3 97 : 3

98 : 2 98 : 2 99 : 1

92 : 8

99 : 1

99 : 1

93 : 7

98 : 2 98 : 2 99 : 1 99 : 1Co2(CO)6

(CO)6Co2

MeO

OMe

Melikyan, G. G.; Deravakian, A.; Myer, S.; Yadegar, S.; Hardcastle, K. I.; Ciurash, J.; Toure, P. J. Organomet. Chem. 1999, 578, 68. Melikyan, G. G.; Sepanian, S.; Riahi, B.; Villena, F.; Jerome, J.; Ahrens, B.; McClain, R.; Hardcastle, K. I. J. Organomet. Chem. 2003, 683, 324. Melikyan, G. G.; Villena, F.; Sepanian, S.; Pulido, M.; Sarkissian, H.; Florut, A. Org. Lett. 2003, 5, 3395. Melikyan, G. G.; Villena, F.; Florut, A.; Sepanian, S.; Sarkissian, H.; Rowe, A.; Toure, P.; Mehta, D.; Christian, N. Organometallics 2006, 25, 4680.

Cobaltocene

62 : 38

Na/Ph2CO

71 : 29

OMe

OMe

OMe

OMe

(CO)6Co2

(CO)6Co2

67 : 33 4 : 96

Ratios of dl & meso Diastereomers

New Avenue: Cross-Coupling Radical Reactions

+

Co2(CO)6 Co2(CO)6

OMe

OH OH

HBF4+

Co2(CO)6 Co2(CO)6

OMe

++ e -

BF4- BF4

-

+

Co2(CO)6 Co2(CO)6

OMe

(CO)6Co2

Co2(CO)6

+

(CO)6Co2

Co2(CO)6

+

OMe

(CO)6Co2

Co2(CO)6

OMe

OMe

d,l+mes o d,l+mes o d,l+mes o

1.

Reduction method

Zn

2. Cp2Co

3. THF-mediated, one-s tepcoupling protocol4h

4. Tf2O-mediated, one-s tepcoupling protocol4g

22 40 38

33

d,l:mes o d,l:mes o d,l:mes o

83:17 88:12 88:12

26

19

78:22 38 2970:30 75:25

92:8 94:6 95:5

88:12 94:6 96:447 34

49 25

HOMO I HETERO HOMO II

+

Gagik G. Melikyan, Arthur Floruti, Lucin Devle tyan, Pogban Toure , Norman Dean, Louis Ca rlson. Cross -Coupling of Coba lt-Complexed Propargyl Radica ls : Meta l Core and α- and γ-Aryl-Induced Chemo- and Diastereoselectivity. Organometallics 2007, 26, 3173-3182.

Charge distribution and structural parameters derived from the PM3 and 3-21G* calculation.

++

OMe

+

MeO

+0.126233 +0.042917

+0.063326

-0.216264 -0.206424

-0.193875

1

1'

1

1'1

1'4'

4'

4'

HH

1"4"

+

Co CoOC COOC CO

OC CO

+

Co CoOC COOC CO

OC CO

OMe

+

Co CoOC COOC CO

OC CO

MeO

-0.029867+0.382988+0.004863

-0.086368

-0.404561 -0.421442 -0.472625 -0.479224 -0.422122 -0.433775

-0.266173-0.070943

1.464Å 1.405Å

1.340Å 1.408Å

1.463Å

1.340Å

1 1 1

23 23 23

1'

4'

1'

4'

1'

4'

H H

1"

4"

Synopsis of Cross-Coupling Radical Reactions

Ar

MAr

ArM

M

Ar

M

Ar''

Ar

Ar'M

M

Ar

ArM

M

Ar''Ar

ArM

M

Ar''Ar''

symmetrical d,l-dimers unsymmetrical d,l-dimersM = Co2(CO)6;Ar, Ar', Ar'' = Ph, 4-OMeC6H4.

Ar'

M

cobalt-complexed propargyl radicals

homo coupling crosscoupling

Intramolecular Cyclizations: Topology

n

m

R R

n = 2 - 6 m = 2 - 4

Co2(CO)6(CO)6Co2

Co2(CO)6(CO)6Co2

Intramolecular Radical Cyclizations: an Easy Access to 1,5-Cyclodecadiynes

R1=R2=R3=H; R1=i-Pr, R2=R3=H; R1=OMe, R2=R3=H; R1=R2=OMe, R3=H; R1=R2=R3=OMe.

2BF4-

d,l- / meso-

OHOH

(CO)6Co2R1

R2

R3

R3

R1

R2

R1

R2

R3

R3

R1

R2

R1

R2

R3

R3

R1

R2

R1

R2

R3

R3

R1

R2

R1

R2

R3

R3

R1

R2

- 2H2O

HBF4(12eqs)

Zn(100eqs)

Ce4+

(9-12eqs)

(CO)6Co2

(CO)6Co2

(CO)6Co2 (CO)6Co2

(CO)6Co2

(CO)6Co2

(CO)6Co2

Melikyan, G. G.; Wild, C.; Toure, P. Intramolecular Radical Cyclizations of Co2(CO)6-Complexed Propargyl Radicals: Facile Entry to d,l- and meso-1,5-Cyclodecadiynes. Organometallics 2008, 27, 1569-1581.

Diastereoselectivity of Intramolecular Cyclizations

Substrates

1

2

3

4

d,l:mesoa

5

26

Products

16

17

18

19

20

29

54:46

80:20

Relativechromatographic

mobility

inseparable

inseparable

inseparable

separable

separable

separable

d,l:mesob

a Diastereomeric ratios of the crude products. b Diastereomeric ratios of the isolated cobalt complexes. c Pure d,l- and meso-diastereomers were isolated by chromatographic means. d Only individual d,l-diastereomers were decomplexed with ceric ammonium nitrate. e dl-/meso-16 was equal to 80:20.

- c

d,l:meso

100:0d

Decomplexedproducts

21

22

23

24

25

30

- c

- c

100:0d

100:0d

67:33

80:20

67:33

67:33

68:32

66:34

80:20

84:16e

80:20

73:27

Substitutionpattern

0-

4-

4-

3,4-

3,4,5-

3,4,5-

OHOH

(CO)6Co2

R1

R2

R3

R3

R1

R2(CO)6Co2

(CO)6Co2 R1

R2

R3

R3

R1

R2

(CO)6Co2

R1

R2

R3

R3

R1

R2

CH/pi-Coordination Leading to meso-Diastereomer

(CO)6Co2

H

H

OMeOMe

OMe

O

HH

H

3'4'

OMeOMe

C2v1'

5'

ring A

ring B

T-shapedcoordination

(CO)6Co2

X-Ray Structures of 1,5-Alkadiynes & 1,5-Cycloalkadiynes

(CO)6Co2

(CO)6Co2

O

O

O

O

O

O

(CO)6Co2

(CO)6Co2



O

O

O

O

O

O

OMe

OMe

OMe

OMe

MeO

MeO

Synthetic PotentialX

X

X=OMe,OEt,OBn

X

X

X=OMe;Y=OMe

Y

Y

X

X

X=OMe,OBn;Y=OMe;Z=OMe;R=H,Et

Y

Y

Z

Z

X

X

X=OMe;Y=OMe,OH

Y

Y

X

X

X=OMe;Y=OMe

Y

Y

X

X

Z

Y

Z

Y

X,Y,Z=H,OMe,iPr;R=H,OMe,OH

R

R

X

Z

Y

X,Y,Z=H,OMe;R=H,CN,COOMe,F

R

X

X,Y,Z=OH,Me

X

Y

Z

Z

X

Y

X,Y,Z=H,OMe

R

R

*

*

X

X

Z

Y

Z

Y

X,Y,Z=H,OMe

Y

Y=OMe

Y Z

C8-C10

X

X

Z

Y

Z

Y

X,Y,Z=H,OMe

2-6

2-6

Functional Group Tolerance

O

methoxy

O

ethoxy

O

benzyloxy benzenering

naphthalenering

n

alkyl

Br

bromine

CF3

trifluoromethyl

CURRENT

PROSPECTIVE

OO

acetal ester

O OR

keto

O R

cyano

N

acetal

O O

The Concept of Controlling the Concentration of Female Hormones

O

O

4-androstene3,17-dione

HO

cholesterol

hormonecascade aromatase

O

HO

estrone (E1)

dehydrogenase dehydrogenase

OH

HO

estrogen (E2)

OH

O

testosterone

aromatase

female hormones causing

breast cancer

Can Radical Dimers Compete with Testosterone for an Enzymatic Site?

OH

O

testosteronevolume 384.5Å3

5.44Å

10.61Å

dl-3,4-Di(4'-hydroxyphenyl)-1,5-hexadiynevolume 331.1Å3

5.48Å

11.92Å

OH

OH

Aromatase Inhibitors (AIs): What is on the Market?

O

O

O

O

OH

N O

H

O

H2N

N

N

CN

exemestane formestane aminoglutethimide

fadrozole

Deficiencies: (1) design; (2) toxicity; (3) lack of enzyme selectivity; (4) estrogenicity.

What is needed: (1) alternative design; (2) low toxicity; (3) high enzyme selectivity; (4) zero estrogenicity.

N

N NN

N

anastrozole;Arimidex

N

N

NN

N

letrozole;Fumara

DNA Cleaving Agents of New Topology

Z

Y

X

X

Y

ZZ

Y

X

X

Y

Z

DNAstrand

cancer cell

death

cycloaromatization

Enediynes, potential anticancer agents

X,Y,Z=H,Alk,Alkoxy

Z

Y

X

X

Y

Z

Z

Y

X

X

Y

Z

Z

Y

X

X

Y

Z

Z

Y

X

X

Y

Z

H

H

H-atom abstractionfrom 4'/1' positions

of ribose ring

Melikyan Research Group Spring 2009



ACKNOWLEDGEMENTS Graduate Students UnderGraduate Students Bobby Riahi Fred Amiryan Nolan Christian Maria Porazik Ferdinand Villena Todd Monroe Louis Lurie John Jerome Kevin Paulsen Linda Hayrapetian Brian Ahrens Stephanie Scanlon Steven Myer Eric Steele Lisa Barron Michelle Pulido Sam Yadegar Asatour Deravakian Stephen Bright Randolph McClain Christopher Wild Michael Conn Aram Arakelyan Hagop Sarkissian Arthur Floruti John Matchett Lucin Devletyan Nino Nezami Louis Carlson Paul Mikaelian Anasheh Justin Molnar Aaron Rowe Keith Stancu Babakhanian Ruth Sepanian Ryan Spencer

C O L L A B O R A T I O N Dr. Pogban Toure, Computational Chemistry (CSUN, Northridge) Dr. Kenneth Hardcastle, X-Ray Crystallography (Emory University, Atlanta)

$$$ NSF ACS PRF Office of Research & Sponsored Projects NATO College of Science and Mathematics U.S. Civilian Research Development Foundation California State University Northridge Hewlett Packard University Corporation

topology of organometallic radicals how does coordination with transition metals affect...

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