Structural Modifications of the Antiinflammatory Oxicam Scaffold and Preparation of Anticancer Organometallic Compounds

Article

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Cite This: Organometallics XXXX, XXX, XXX −XXX

Structural Modiﬁcations of the Antiinﬂammatory Oxicam Scaﬀold

and Preparation of Anticancer Organometallic Compounds

Adnan Ashraf,^†,‡Farhana_‡Aman,^‡Sanam Mova_†ssaghi,^†Ayesh_†a Zafar,^†Mario Kubanik,^†

§

́

̈

Waseeq Ahmad Siddiqui, Johannes Reynisson, Tilo Sohnel, Stephen M. F. Jamieson,

Muhammad Hanif,*^,†and Christian G. Hartinger*^,†

^†School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand

^‡Department of Chemistry, University of Sargodha, Sargodha 40100, Pakistan

^§Auckland Cancer Society Research Centre, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand

S

* Supporting Information

ABSTRACT: Nonsteroidal antiinﬂammatory drugs (NSAIDs) have

chemopreventive eﬀects in several cancer types, and the oxicam-based

NSAIDs meloxicam and piroxicam exhibit potential to treat cancer. We

prepared a series of novel oxicams and coordinated them to Ru^II(cym)Cl

and Os^II(cym)Cl moieties (η⁶-p-cymene = cym). The oxicam ligands

acted either as monodentate N-donors or bidentate N,O-chelators,

depending upon the ligand structure as well as reaction conditions such

as the pH value and solvent used in the reaction. The cytotoxic activity

of the complexes toward carcinoma cells was investigated. The isoxazolyl

motif-containing ligand 1 and its complexes with Ru^II(cym)Cl 1a and

the Os analogue 1b proved to have anticancer activity with IC₅₀values in

a range similar to that observed for the Ru^IIIinvestigational drug IT-139, and in general the Os compounds were equally or even

slightly more potent than the Ru derivatives. Since meloxicam is known as a selective inhibitor of COX-2, molecular docking

studies were carried out to understand the possible interactions of the compounds with COX-2, where the organic ligands gave

higher scores than their organometallic counterparts.

group and more selectively bind to COX-2. Lombardino et al.

developed the oxicams as non-carboxylic acid-containing

antiinﬂammatory agents,¹¹⁻¹³and prominent examples of

oxicams are piroxicam, meloxicam, isoxicam, lornoxicam, and

sulfoxicam. Some of them are highly eﬀective and have longer

plasma half-lives. These oxicams are widely used drugs for the

treatment of a variety of inﬂammatory and rheumatic diseases

in humans.

In recent years, a variety of antiinﬂammatory drugs have

been coordinated to metal centers to achieve synergistic

eﬀects. Such strategies often resulted in enhanced biological

activity in comparison to the parent drugs. For example, the

Pt¹⁴and Co²complexes of acetylsalicylic acid derivatives

demonstrated promising antiproliferative properties. Dyson

and co-workers recently reported organo-Ru and -Os comp-

lexes bearing modiﬁed indomethacin and diclofenac. Some of

the complexes showed enhanced antiproliferative properties

and better tumor selectivity in comparison to the original

drugs.¹⁵We and others have demonstrated that anti-

inﬂammatory oxicams can act as versatile ligands.^16,17We

carried out coupling of these bioactive ligands with Ru(cym)

and Os(cym) chlorido moieties to develop new bioorgano-

metallics, and their activity against diﬀerent cancer cell lines

INTRODUCTION

■

Nonsteroidal antiinﬂammatory drugs (NSAIDs) are widely used

for the treatment of a range of acute and chronic inﬂammatory

diseases. Some NSAIDs, such as aspirin, diclofenac, naproxen,

and ibuprofen, are available over the counter for short-term use

as analgesic, antipyretic, and antiinﬂammatory agents.¹⁻³Some

of these NSAIDs have shown signiﬁcant advantages in terms of

prevention and inhibition of various cancers. Recent studies have

demonstrated the tumor-preventive eﬀects of aspirin.⁴Prolonged

use of aspirin has been suggested to reduce the risk of colon,

gastrointestinal, lung, ovarian, and breast cancer.⁵⁻⁸The mode

of action of these NSAIDs is associated with the inhibition of the

enzymes cyclooxygenase-1 (COX-1) and -2 (COX-2). The

isoform COX-1 is present in most tissues and is responsible for

the synthesis of prostaglandins, which is important for normal

cell function. On the other hand, COX-2 is an inducible isoform

and is primarily produced in response to inﬂammatory mediators

or growth factors. Most NSAIDs nonspeciﬁcally inhibit COX-1

over COX-2, which results in adverse eﬀects associated with the

use of these drugs.^1,3,9Moreover, these carboxylate-containing

NSAIDs undergo facile elimination by glucuronide and/or

sulfate conjugation. This causes short plasma half-lives and

hence aﬀects the long-term treatment of diseases such as chronic

arthritis.¹⁰

These implications prompted research on the design of

antiinﬂammatory drugs which are devoid of a carboxylic acid

Received: October 14, 2018

A

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Scheme 1. Synthetic Route to Novel Oxicams with Diﬀerent Substituents in Positions 2 and 3 and Their Organo-Ru and -Os

a

Compounds

a

When the ligands are coordinated bidentately to Ru or Os centers, the latter are labeled a and b, while in complexes where the ligands are

coordinated monodentately Ru complexes are denoted as a and c and the Os derivatives as b and d.

was established.¹⁷These compounds exhibited low to

moderate anticancer activity, which in some cases was

dependent on the lipophilicity of the oxicam ligand.

NMR spectra of 1−6, the peaks assigned to the protons of the

pyridyl (1, 3, 4) and indazole rings (5 and 6) were observed

in the ranges of 8.5−7.1 and 8.5−7.3 ppm, respectively.

The signals of the methyl protons in 2, 3, and 5 appeared in

the aliphatic region at 2.48, 2.88, and 2.89 ppm, respectively.

The methylene protons of the pyridyl moieties in 3 and 4 were

identiﬁed at 4.52 and 4.50 ppm, while the methylene protons

of the benzyl group in position 2 of the thiazine rings in 1, 2, 4,

and 6 were diastereotopic and were observed as two doublets

in the ranges of 4.50−4.67 and 4.32−4.44 ppm, with geminal

coupling constants of 14 Hz.

The ESI-MS results conﬁrmed the formation of the oxicam

derivatives with the m/z values of the pseudomolecular ion

peaks corresponding to [M + Na]⁺for 1, 2, and 4−6 and

[M + H]⁺for 1 and 3.

Single crystals of 3 suitable for X-ray diﬀraction analysis

were grown by slow evaporation of a solution in hot methanol.

Crystal structure data and selected bond lengths are given in

Tables S1 and S2. Intramolecular hydrogen bonds were formed

between the carbonyl oxygen atoms and the hydroxyl group in

position 4, with an O2H···O1 distance of 1.778 Å. Inter-

molecular H bonds were present between the amidate

hydrogen and the oxygen atom of the sulfonyl group (NH···

O4S 2.181 Å; Figure 1).

The oxicams 1−6 were converted to organometallic Ru and

Os complexes. The coordination mode of ditopic oxicams can

be controlled as monodentate or bidentate by the reaction

conditions such as the pH value and solvent.¹⁷When 1−6

were reacted with [M(cym)Cl₂]₂dimers in DCM without

deprotonating the acidic proton of the OH in position 4 of the

benzothiazine, all heterocyclic ligands coordinated exclusively

monodentately through their N-donors to the Ru and Os

centers and gave complexes 1c,d, 2c,d, 3a−c, and 4a−6a.

Activating the OH in position⁴by deprotonation with sodium

methoxide in methanol resulted in bidentate coordination to

Ru and Os to yield 1a,b and 2a,b.

The oxicams comprise a 1,2-benzothiazine 1,1-dioxide core and

varying aromatic heterocyclic substituents at the 3-carboxamide

position: e.g., 2-pyridyl in piroxicam, 2-thiazolyl in meloxicam,

and 3-(5-methyl)-isoxazolyl in isoxicam. The presence of these

heteroaryl substituents resulted in enhanced antiinﬂammatory

activity^18,19and binding aﬃnity of the drugs to the active site

of the target enzyme.^13,20Keeping this in mind, we aimed to

modulate the pharmacological properties of the oxicam

scaﬀold through the modiﬁcation of its backbone as well as

the amide moiety.¹⁷The synthesized ligands derived from the

antiinﬂammatory drugs piroxicam and isoxicam were then used

to prepare their organo-Ru and -Os complexes. The chemical

and biological properties of these oxicams and their organo-

metallic compounds were evaluated with regard to their

stability and their tumor-inhibiting potency as well as potential

target interaction.

RESULTS AND DISCUSSION

■

Analogues of the anti inﬂammatory drugs piroxicam, meloxicam,

and isoxicam were prepared for coordination to Ru and Os. The

precursor (1,1,3-trioxo-1,3-dihydro-1λ⁶-benzo[d]isothiazol-2-yl)-

acetic acid methyl ester (I) was prepared in excellent yield

from commercially available sodium saccharin.²¹In a Gabriel−

Colman-type ring expansion the ﬁve-membered isothiazole

ring was converted to a six-membered thiazine ring to give

methyl 4-hydroxy-2H-1,2-benzothiazine-3-carboxylate 1,1-di-

oxide (II).²²The latter was subjected to methyl or benzyl

alkylation to prepare compounds IIIa,b. They were treated

with the heterocycle amines 2-pyridineamine, 5-methyl-3-

isoxazolamine, 4-pyridinylmethanamine, and 1H-indazol-6-

amine in reﬂuxing xylene to give the desired ligands 1−6

(Scheme 1). The formation of these compounds was

1

conﬁrmed by NMR spectroscopy and ESI-MS. In the H

B

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and C-6′ in 3a−c and 4a. In the case of 1a,b and 2a,b,

considerable downﬁeld shifts were observed for C-4 (154−149

ppm) and C-11 (176−170 ppm) while C-2′ was less aﬀected

(169−165 ppm). These factors support the involvement of the

pyridyl nitrogen and carbonyl oxygen atoms in the complex

formation. The ESI-mass spectra of all complexes gave base

peaks with m/z values attributable to [M − X]⁺ions. The

observed m/z values were in close agreement with the

theoretical values and conﬁrm the structures proposed. The

low solubility of 5a prevented us from recording a ¹³C{¹H}

NMR spectrum, and in some cases the quaternary carbon

atoms were not detected due to low solubility.

Single crystals of 2b, 3c, and 4a were analyzed by X-ray

diﬀraction and demonstrated pseudo-octahedral geometry at

the metal center with a piano-stool conﬁguration characteristic

of these half-sandwich organometallics. In 2b, oxicam 2

coordinated to Os as an anionic N,O-chelator, forming a six-

membered ring through the amidate oxygen and endocyclic

nitrogen atoms of the isoxazole moiety (Figure 2). In the

Figure 1. Molecular structure of 3 drawn at the 50% probability level.

Inter- and intramolecular H bonds are indicated as dashed lines.

The compounds were characterized by diﬀerent analytical

methods. The infrared spectra of the complexes were

compared with those of the ligands. For complexes with

monodentately bound oxicams, the hydroxyl groups resulted in

broad bands in the range 3100−2700 cm⁻¹. Such bands were

absent in the spectra recorded for 1a,b and 2a,b, as the hydroxyl

group was deprotonated and its oxygen atom was coordinated

to the metal center. The CN stretching frequency in 1a,b

and 2a,b shifted from 1576 to 1569−1559 cm⁻¹, indicating the

involvement of this group in coordination.

1

The H NMR spectra of 1a,b and 2a,b did not contain

signals for the OH group due to the involvement of the

O atom in coordination to the metal center. However, the OH

group appeared in the range of 11.8−11.2 ppm in complexes

with monodentately coordinated oxicams. The NH signals

were observed to shift downﬁeld from 9.5−8.7 to 11.8−

11.2 ppm in the monodentate complexes 1c,d and 2c,d in

comparison to the respective ligands. No NH signals were

found for 1a,b and 2a,b, possibly due to H/D exchange in

CDCl₃. In comparison to the ligands 1 and 2, a considerable

downﬁeld shift was observed for the H-6′ proton signal next to

the pyridyl nitrogen due to the coordination of the pyridyl N

atom to the metal center. The formation of the six-membered

ring with the metal ion through the amidate oxygen and

isoxazole nitrogen in 2a,b stabilizes the molecule and also

induces a shift of the H-4′ proton signal. In the osmium comp-

lexes 1b,d and 2b,d the cymene aromatic protons appeared

in the range of 6.6−5.7 ppm while for the Ru counterparts

these protons resonated slightly upﬁeld (6.2−5.2 ppm).

In complexes with an N-benzyl group, the methylene protons

were diastereotopic and the signals split into two doublets.

In the monodentate complexes 3a−c and 4a, two signals

were observed for H-2′/H-6′ (8.8−8.2 ppm) and H-3′/H-5′

(7.3−7.0 ppm) and were signiﬁcantly shifted downﬁeld in

comparison to the spectra of 3 and 4. Similarly in 5b and 6a,

H-1′ and H-3′ were directly inﬂuenced by coordination of the

metal ion and showed a considerable downﬁeld shift in

comparison to 5 and 6. Compound 5a showed very limited

solubility in solvents other than DMSO, in which it may

however undergo ligand exchange reactions, as often observed

for monodentate N-donor ligands coordinated to Ru(arene)

moieties.

Figure 2. Molecular structure of one of the two enantiomers of 2b

drawn at the 50% probability level with the oxicam acting as a

bidentate ligand and intramolecular H bonding shown between the

amide NH and the carbonyl O2 atom.

molecular structures of 3c and 4a the oxicams were exclusively

bound as neutral monodentate ligands (Figures 3 and 4),

coordinated to the metal centers through their pyridyl nitrogen

atoms.

The M−cym_centroiddistances were 1.653, 1.664, and 1.660 Å

in 2b, 3c, and 4a, respectively, and these and other bond

lengths around the metal center were comparable to those

reported earlier for related complexes.^23,24The M−N bond

lengths were slightly shorter at 2.052(7) and 2.105(2) Å for 2b

and 4a with its bi- or monodentate ligands coordinated to the

Os centers, respectively, in comparison to that for the Ru

compound 3c at 2.123(3) Å. The remaining coordination sites

at the metal center were completed by chlorido as well as

O donors of either oxicam in the case of 2b or oxalato for 3c.

In contrast to 3c and 4a, in the structure of 2b the O1−C11

and O2−C4 bond lengths show double-bond character while

the connecting carbon backbone has more single-bond

character, suggesting delocalization of the electron density

(Supporting Information), as observed for related structures.¹⁷

Intramolecular hydrogen bonding was observed in the

molecular structures between the carbonyl oxygen atom O2

and the amidate hydrogen with a O2···HN2 distance of 1.848 Å

for 2b. In the case of 3c and 4a, hydrogen bonds were observed

between the amidate carbonyl O1 and O2−H at 1.774 and

In the ¹³C{¹H} NMR spectra of the complexes, considerable

shifts were observed for carbon atoms close to the N-donor

atoms coordinated to the metal centers. This caused, for

example, slight downﬁeld shifts for the signals assigned to C-2′

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occurred during the 72 h incubation period. These ﬁndings

indicate that these reactions would not inﬂuence the outcome

of biological experiments. Furthermore, replacing the chlorido

leaving groups with oxalato as in 3c resulted in high stability of

the metal complex in comparison to the chlorido analogues

1

(for a comparison of the H NMR spectra for 3a and 3c in

DMSO after 2 and 24 h, respectively, see Figure S1). The

replacement of labile ligands with stronger, bidentate ligands is

another strategy to overcome the degradation of organo-

metallic compounds in aqueous environments.²⁵

Anticancer Activity. There is emerging evidence that

NSAIDs such as aspirin and meloxicam can play a role in the

prevention and inhibition of tumors.⁴⁻⁸The coordination of

NSAIDs to bioactive metal ions has resulted in promising

anticancer eﬀects.^2,14Therefore, the antiproliferative potential

of the novel oxicams and their organometallic compounds was

tested in human colorectal carcinoma (HCT116), non-small-

cell lung carcinoma (NCI-H460), cervical carcinoma (SiHa),

and human colon adenocarcinoma (SW480) cell lines using

the sulforhodamine B (SRB) assay (Table 1). The new

Figure 3. Molecular structure of 3c drawn at the 50% probability

level. The neutral oxicam coordinated to the metal center in

monodentate fashion. The intramolecular H bonding is shown

between the amide carbonyl oxygen atom O1 and the enolic OH

group, while the amide proton interacts with the oxalato ligand.

Table 1. In Vitro Anticancer Activity (Mean IC₅₀Values

Standard Deviations) of New Oxicam Derivatives 1−3 and

Their Organometallic Compounds in Comparison to

Investigational Ru Drug Candidates in Human Colorectal

(HCT116), Non-Small-Cell Lung (NCI-H460), Colon

(SW480),and Cervical (SiHa) Carcinoma Cell Lines

(Exposure Time 72 h)

Figure 4. Molecular structure of 4a drawn at the 50% probability level.

The neutral oxicam coordinated to Ru in a monodentate fashion. The

intramolecular H bonding is shown between the amide carbonyl oxygen

atom O1 and the enolic O2−H group, while the amide proton N2−H

interacts with the chlorido ligand Cl1 (not shown).

IC₅₀(μM)

compound

NCI-H460

85

SiHA

6

HCT116

SW480

124

1

5

93

90

2

3

105 11

>300

79 19

155

>300

67

7

142

>300

70

7

53

>300

81

1

1.807 Å, respectively. Intermolecular hydrogen bonds were also

formed by the amidate hydrogen N2−H with an oxygen atom of

the oxalato coligand (3c) or the chlorido leaving group (4a)

with distances of 2.161 and 2.382 Å, respectively. Similar

observations were made for related complexes.¹⁷

1a

1b

1c

1d

2a

2b

2c

2d

3a

3b

3c

7

9

4

5

4

3

61

6

69

64

63

>150

102

>150

101

>150

89

98 22

>200

>225

>270

>150

97

The heterocyclic thiazine ring was found to be nonplanar with

regard to the benzene ring. The nitrogen atom of thiazine was

signiﬁcantly out of plane, and the torsion angles (C10−C9−

SO₂−N1) were 36.64, 37.35, 40.05, and 34.96° for 3, 2b, 3c and

4a, respectively. These torsion angles are in a range similar to

that observed for other oxicam complexes.^25,26In 2b and 4a,

the benzyl substituent at the ring nitrogen formed π-stacking

interactions with the oxicam phenyl ring and the shortest C···C

distances were observed at 3.443 and 3.353 Å, respectively.

Stability in DMSO and Aqueous Solution. Due to

limited solubility in aqueous solution, compounds tested in

biological experiments are usually ﬁrst dissolved in DMSO and

then diluted with cell culture media to reach ﬁnal concen-

trations of ≤1% DMSO. However, DMSO can act as a ligand

and, therefore, the stability of the complexes 1a−d, 2a−d, and

6

2

9

5

7

93 14

>200

>225

93

92

>200

>225

>270

394 70

>300

>200

>225

>270

346 48

>300

>270

441 46

>300

a

[Ru(cym)Cl₂]₂

RAPTA-C

NAMI-A

NKP-1339 (IT-139) 92 27

Taken from ref 26.

433 28

>300

102

7

100

7

84 15

a

oxicams 1 and 2, which are analogous to low-cytotoxicity

piroxicam³¹and its derivative isoxicam, respectively, were

moderately active against all these cell lines. The IC₅₀values of

1 were in a similar range in all of the cell lines, while 2 was

more, though still moderately, potent against SW480 cells. The

organo-Ru and -Os compounds 1a,b were equally or slightly

more cytotoxic in comparison to their ligand 1 and 2a,b. A

comparison of the eﬀect of the metal ion reveals that the Os

complexes (1b and 2b) were equally or slightly more active in

comparison to their Ru counterparts (1a and 2a). All of the

complexes in which the oxicams were featured as monodentate

ligands, i.e., 1c,d, 2c,d, and 3a−c, were not active. For at least

1

3a−c was evaluated in DMSO-d₆by H NMR spectroscopy

1

over a period of 96 h. The H NMR spectra of compounds

1c,d, 2c,d, and 3a,c revealed an immediate exchange of the

monodentately coordinated oxicam ligands with DMSO, as

observed for related complexes with monodentate nitrogen

donor ligands (Figure S1).^23,24,27However, 1a,b and 2a,b

bearing the oxicams as anionic N,O-chelators were stable in

DMSO for 24 h. After 24 h, coordination of DMSO was

observed along with cleavage of the cym ligand.^{17,25,28−30}This

eﬀect was signiﬁcantly suppressed in DMSO-d₆/D₂O (5/95),

where predominantly chlorido/aqua ligand exchange reactions

D

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the compounds with the ligand coordinated monodentately, this

is likely a result of the low stability due to fast ligand exchange in

aqueous DMSO solution. Because of low solubility, oxicams

4−6 and their respective organo-Ru complexes 4a−6a were not

tested.

Overall, the N-benzyl-substituted oxicam 1 analogous to

piroxicam and its metal complexes 1a,b showed moderate

cytotoxicity which is in a range similar to that observed

for other investigational Ru drug candidates such as the

ruthenium(III) complexes NAMI-A and NKP-1339 (IT-139).

Low cytotoxic activity is often observed for organo-Ru^II

compounds. An excellent example is RAPTA-C, which is not

cytotoxic against primary tumors but displayed remarkable

antimetastatic as well as antiangiogenic properties in vivo.^32,33

Similarly, NSAIDs have low toxicity and therefore it is not

surprising that especially the complexes that are unstable under

the conditions used would result in low antiproliferative activity.

Molecular Modeling. To explain the ﬁndings from the

cytotoxicity assays in cancer cell lines and to estimate the

likelihood of binding of active ligands 1−3 and their Ru/Os

complexes 1a,b, 2a,b, and 3a to COX-2 as the target for

oxicams, docking studies were conducted with a crystal

structure of COX-2 with cocrystallized meloxicam.^20,34

Meloxicam was docked into the binding pocket as a positive

control, and a very good ﬁt with the crystallized structure was

found. The predicted scores for oxicams 1−3 were similar to or

higher than those of the known drug meloxicam, suggesting

possible binding to COX-2 (Table S3). All of the structures

were found inserted deep into the lipophilic pocket and

showed overlap with the conﬁguration of meloxicam, with the

3 derivative, however, slightly shifted away from the binding

site in comparison to the oxicam scaﬀold of the other ligands.

The best predicted binding modes and hydrogen bond

interactions of 1−3 (Figure S2) closely resembled that of

cocrystallized meloxicam.²⁰

As Gold Score (GS) is the only scoring function able to treat

metal complexes,²⁵it was used in the docking of the Ru and Os

compounds. For this purpose, the GS parameter ﬁle was

modiﬁed to include the parameters of Ru and Os which are not

included in the GOLD database.³⁵The docked conﬁguration

of the active derivative 1a into the binding site is shown in

Figure 5. Due to steric constraints, 1a did not ﬁt into the

binding pocket of COX-2 but occupied a cleft exposed to the

water environment (Figure 5A). Compound 1a was found to

be in lipophilic contact with Lys83, Pro86, and Val89 through its

isopropyl group and benzyl moieties, respectively (Figure 5B).

When 1b and 2a,b were docked, similar binding poses and

interactions were observed. However, complex 3a extends

signiﬁcantly in one dimension and therefore was able to reach

deep into the binding pocket (Figure 5C). Notably, all of the

metal complexes gave lower GS scores in comparison to their

ligands (Table S3). As the cytotoxic activity of 1a is higher

than that of the corresponding ligand 1, there may be other

factors that account for the antiproliferative potency.

Figure 5. Docked conﬁgurations of 1a and 3a in the binding site of

COX-2 (PDB ID: 4M11). (A) Lipophilic contacts are depicted as

purple dotted lines between 1a and the amino acids Lys83, Pro86, and

Val89. (B) Compound 1a is shown in the binding pocket with the

protein surface rendered. It occupies a cleft exposed to the water

environment. Blue depicts hydrophilic areas on the surface, while

hydrophobic areas are shown in brown/white. (C) Complex 3a in the

binding pocket with the protein surface rendered overlaid with the

cocrystallized meloxicam in green.

the reaction conditions, such as pH or nature of solvent, while

3−6 coordinated as monodentate ligands to the metal centers.

Organo-Ru and -Os complexes 1c,d, 2c,d, and 3a−6a bearing

oxicams coordinated in a monodentate fashion turned out to

be less stable and immediately underwent ligand exchange

reactions with DMSO. In contrast, the organometallics 1a,b

and 2a,b with the oxicam ligands bound as anionic bidentate

chelators were stable in DMSO for at least 24 h and for an

even longer time in aqueous solutions.

Oxicams 1 and 2 were moderately cytotoxic against cancer

cells. Interestingly, 2 was most potent against human colon

adenocarcinoma SW480 cells. Coordination of 1 to Ru(cym)

and Os(cym) led to the most cytotoxic organometallics of this

series with IC₅₀values in the range of 61−81 μM for 1a,b in

diﬀerent cancer cells. The Os complexes showed equal or

slightly better cytotoxicity proﬁles in comparison to their Ru

counterparts.

CONCLUSIONS

■

The coordination of antiinﬂammatory drugs to bioactive metal

ions has given rise to compounds with tumor-inhibiting pro-

perties, thus opening the possibility to design multitargeted

anticancer drugs. Inspired by these studies, we prepared novel

anti inﬂammatory oxicams which were utilized to obtain organo-

Ru and -Os complexes. The oxicams 1 and 2 exhibited either

monodentate or bidentate coordination modes depending on

Since oxicams are known inhibitors of COX-2, the

interactions of selected oxicams and their organo-Ru and -Os

E

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complexes were studied by molecular modeling. Oxicams 1−3

demonstrated binding interactions similar to those observed

for the known drug meloxicam, while organometallic com-

pounds gave lower scores than the oxicams alone. As the

binding pocket of COX-2 lies deep in the enzyme and is also

size-restricted, this may limit the access of the bulky organo-Ru

and -Os compounds and other modes of action than COX-2

inhibition may play a role in inducing anticancer activity.

Overall, the mode of coordination and the nature of the

metal ion and ligand have clear eﬀects on the cytotoxicity of

the compounds and their interactions with COX-2. The organo-

Os complexes showed anticancer activity which is similar to or

better than that of the investigational drug NKP-1339 (IT-139),

which is in clinical trials.

IIIb as a white precipitate, which was ﬁltered and dried

at room temperature. Yield: 59% (0.81 g, white), FTIR

(KBr, cm⁻¹): 2958 (CH), 1645 (CO), 1440 (CH def, 1348,

1174 (SO₂). ¹H NMR (400.13 MHz, CDCl₃, 25 °C): δ 11.77

(s, 1H, OH), 7.79−7.72 (m, 2H, H-8, H-5), 7.69−7.64

(m, 2H, H-6, H-7), 7.06−7.02 (m, 1H, H-5″), 6.99−6.96

(m, 2H, H-4′′, H-6′′), 6.91−6.89 (m, 2H, H-3′′, H-7′′), 4.61

(s, 2H, H-1′′), 3.93 (s, 3H, H-Me) ppm. ¹³C{¹H} NMR

(100.61 MHz, CDCl₃, 25 °C): δ 168.5 (C-11), 158.7 (C-4),

137.3 (C-2″), 132.9 (C-6), 132.7 (C-7), 132.5 (C-9), 129.2

(C-4′′, C-6′′), 127.9 (C-10), 127.6 (C-3′′, C-7′′), 127.4

(C-5′′), 126.0 (C-5), 122.5 (C-8), 106.7 (C-3), 54.3 (C-1′′),

53.0 (C-Me) ppm.

General Procedure for the Synthesis of Oxicam Derivatives

1−6. A suspension of IIIa or IIIb (1 equiv) and a heterocyclic amine

(1.05 equiv) was subjected to reﬂux in xylene (150 mL) for 24−72 h

in the presence of molecular sieves (4 Å). After completion of the

reaction, xylene was removed, which yielded a solid product. This was

washed with n-hexane and recrystallized in methanol to isolate the

oxicam-based ligands 1−6 in a manner similar to that reported for

related compounds.¹⁹

EXPERIMENTAL SECTION

■

Materials and Methods. All the reactions were carried out under

inert conditions. All of the reagents and chemicals were of analytical

grade and were used as received from commercial suppliers.

Chloroacetic acid, sodium metal, and benzyl chloride were purchased

from Sharlu, and 2-aminopyridine, 5-amino-3-methylisoxazole,

4-pyridinylmethanamine, 1H-indazol-6-amine, and OsO₄were

purchased from Sigma-Aldrich. RuCl₃·xH₂O was purchased from

Precious Metals Online. (1,1,3-Trioxo-1,3-dihydro-1λ⁶-benzo[d]-

isothiazol-2-yl)acetic acid methyl ester (I),²¹methyl 4-hydroxy-2H-

1,2-benzothiazine-3-carboxylate 1,1-dioxide (II),²²methyl 4-hydroxy-

2-methyl-2H-benzo[e][1,2]thiazine-3-carboxylate 1,1-dioxide

(IIIa),³⁶bis[dichlorido(cym)ruthenium(II)],³⁷and bis[dichlorido-

(cym)osmium(II)]³⁸were synthesized according to literature

procedures.

2-Benzyl-N-(pyridin-2-yl)-4-hydroxy-2H-benzo[e][1,2]thiazine-3-

carboxamide 1,1-Dioxide (1).

High-resolution mass spectra were recorded on a Bruker micro-

TOF-Q II electrospray ionization (ESI) mass spectrometer in positive

Compound 1 was synthesized by following the general

procedure using IIIb (3.00 g, 8.7 mmol) and 2-aminopyridine

(0.82 g, 8.7 mmol). Yield: 56% (2.00 g, oﬀ-white). Mp: 157−158

°C. MS (ESI⁺): m/z 430.0826 [M + Na]⁺, calcd 430.0832; m/z

408.1006 [M + H]⁺, calcd 408.1018; calcd 406.0867. Anal.

Found: C, 61.85; H, 4.38; N, 10.22; S, 7.99. Calcd for

C₂₁H₁₇N₃O₄S: C, 61.90; H, 4.21; N, 10.31; S, 7.87. FT-IR

1

ion mode. H and ¹³C{¹H} NMR spectra were recorded on Bruker

DRX 400 MHz NMR spectrometers at ambient temperature at

400.13 (¹H) and 100.61 MHz (¹³C{¹H}), and 2D NMR data were

collected in a gradient-enhanced mode. ¹H and ¹³C{¹H} NMR

chemical shifts are reported vs SiMe₄and were determined by

reference to the residual solvent peaks. All compounds were analyzed

1

via multinuclear 2D (¹H−¹H COSY, H−¹³C HSQC, and HMBC)

(KBr, cm⁻¹): ν

̃

3381, 3309 (NH), 3050−2700 (OH), 1622

(CO), 1576 (CN), 1438 (CH def, 1346, 1160 (SO₂). ¹H

NMR spectroscopic experiments, allowing unambiguous assignments

of the resonances. Elemental analyses were carried out on an Exeter

Analytical Inc. CE-440 Elemental Analyzer.

NMR (400.13 MHz, CDCl₃, 25 °C): δ 13.32 (s, 1H, OH),

3

4

8.70 (s, 1 H, NH), 8.34 (dd, J_{(H6′,H5′)}= 5 Hz, J_{(H6′,H4′)}

=

The X-ray diﬀraction data of crystals of 3, 2b, 3c, and 4a were

collected on a Bruker Smart APEX II diﬀractometer with graphite-

monochromated Mo Kα radiation (λ_Mo= 0.71073 Å) at 100 K

(see Table S1 for the measurement parameters). Data reduction was

carried out using the SAINT program.³⁹Semiempirical absorption

corrections were applied on the basis of equivalent reﬂections using

SADABS.⁴⁰The structure solution and reﬁnements were performed

with the SHELXS-97 and SHELXL-2013 program packages.⁴¹

Synthesis of Compound IIIb.

3

1 Hz, H-6′), 8.16 (d, J_(H3′,H4)= 7 Hz, 1H, H-3′), 7.77−7.71

(m, 2H, H-8, H-4′), 7.67 (dd, ³J_(H5,H6)= 8 Hz, ⁴J_(H5,H7)= 1 Hz,

3

4

1H, H-5), 7.57 (td, J_{(H6,H7)/(H6,H5)}= 8 Hz, J_(H6,H8)= 1 Hz,

1H, H-6), 7.52 (td, ³J_{(H7,H6)/(H7,H8)}= 8 Hz, ⁴J_(H7,H5)= 1 Hz,1H,

H-7), 7.11−7.09 (m, 1H, H-5′), 7.06−7.04 (m, 2H, H-4″,

H-6′′), 6.99−6.95 (m, 3H, H-3′′, H-5′′, H-7′′), 4.64

2

(d, J_{(H1″A,H1′′B)}= 14 Hz, 1H, H-1″A), 4.44 (d, J_{(H1″B,H1′′B)}

=

14 Hz, 1H, H-1″B) ppm. ¹³C{¹H} NMR (100.61 MHz,

CDCl₃, 25 °C): δ 166.9 (C-11), 159.2 (C-4), 150.2 (C-2′),

140.0 (C-6′), 137.6 (C-2″), 134.8 (C-7), 134.5 (C-4′), 133.6

(C-6), 132.3 (C-9), 131.9 (C-10), 129.7 (C-4′′, C-6′′), 127.8

(C-5′′), 127.4 (C-3′′, C-7′′), 126.1 (C-5), 122.4 (C-8), 119.8

(C-5′), 116.4 (C-3′), 113.8 (C-3), 54.8 (C-1′′) ppm.

2-Benzyl-N-(5-methylisoxazol-3-yl)-4-hydroxy-2H-benzo[e][1,2]-

thiazine-3-carboxamide 1,1-Dioxide (2).

Benzyl chloride (0.45 mL, 3.92 mmol) was added to a solution

of methyl 4-hydroxy-2H-benzo[e][1,2]thiazine-3-carboxylate

1,1-dioxide (II; 1 g, 3.92 mmol) and sodium hydroxide

(0.47 g, 11.75 mmol) in methanol (35 mL).²¹The reaction

mixture was allowed to react at room temperature for 12 h

under a nitrogen atmosphere. After completion of the reaction,

the reaction mixture was acidiﬁed with 10% HCl. This yielded

Compound 2 was synthesized by following the general procedure

using IIIb (3.00 g, 8.67 mmol) and 5-methylisoxazol-3-amine

F

DOI: 10.1021/acs.organomet.8b00751

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

(0.85 g, 8.67 mmol). Yield: 74% (2.66 g, oﬀ-white). Mp: 193−

195 °C. MS (ESI⁺): m/z 434.0774 [M + Na]⁺, calcd 434.0781.

Anal. Found: C, 58.65; H, 4.22; N, 10.03; S, 7.99. Calcd for

C₂₀H₁₇N₃O₅S: C, 58.38; H, 4.16; N, 10.21; S, 7.79. FT-IR

C₂₂H₁₉N₃O₄S·1.25CH₂Cl₂: C, 52.92; H, 4.11; N, 7.96; S, 6.08.

FTIR (KBr, cm⁻¹): 3450, 3330 (NH), 3100−2850 (OH),

1606 (CO), 1596 (CN), 1416 (CH def), 1341, 1171

1

(SO₂). H NMR (400.13 MHz, CDCl₃, 25 °C): δ 14.13

3

(KBr, cm⁻¹): ν

̃

3153 (NH), 3063−2850 (OH), 1642 (CO),

(s, 1H, OH), 9.45 (t, J_(HNH,H11′)= 6 Hz, 1H, H-NH), 8.56−

3

1606 (CN), 1541 (NH def), 1424 (CH def), 1341, 1174

8.55 (m, 2H, H-2′, H-6′), 7.73−7.70 (dd, J_(H8,H7)= 8 Hz,

1

3

³J_(H8,H6)= 1 Hz, 1H, H-8), 7.68−7.64 (td, J_{(H6,H7)/(H6,H5)}

=

(SO₂). H NMR (400.13 MHz, CDCl₃, 25 °C): δ 13.18

3

8 Hz, ³J_(H₃_6,H8)= 1 Hz, 1H, H-6), 7.60−7.56 (td, ³J_{(H7,H8)/(H7,H5)}

(s, 1H, OH), 9.25 (s, 1H, H-NH), 7.77 (dd, J_(H8,H7)= 8 Hz,

⁴J_(H8,H5)= 1 Hz, 1H, H-8), 7.67 (dd, ³J_(H5,H6)= 8 Hz, ⁴J_(H5,H7)

=

3

= 8 Hz, J_(H7,H5)= 1 Hz, 1H, H-7), 7.49−7.47 (dd, J_(H5,H6)

=

3

4

3

1 Hz,1H, H-5), 7.58 (td, J_{(H7,H8)/(H7,H6)}= 8 Hz, J_(H7,H5)

8 Hz, J_(H5,H7)= 1 Hz, 1H, H-5), 7.34−7.32 (m, 2H, H-5′,

H-3′), 7.03−6.99 (m, 1H, H-5″), 6.94−6.90 (m, 2H, H-4′′,

H-6′′), 6.82−6.80 (m, 2H, H-3′′, H-7′′), 4.55 (s, 2H, H-1′′),

4.50 (m, 2H, H-11′) ppm. ¹³C{¹H} NMR (100.61 MHz,

CDCl₃, 25 °C): δ 169.1 (C-11), 159.3 (C-4), 150.29 (C-2′,

C-6′), 146.3 (C-4′), 136.8 (C-2″), 132.6 (C-7), 132.0 (C-6),

132.2 (C-9), 130 (C-4′′, C-6′′), 128.8 (C-10), 128.7 (C-5′′),

128.3 (C-3′′, C-7′′), 126.5 (C-5), 123.8 (C-8), 122.4 (C-3′,

3

4

1 Hz, H-7), 7.52 (td, J_{(H6,H7)/(H6,H5)}= 8 Hz, J_(H6,H8)= 1 Hz,

H-6), 7.04−7.00 (m, 5H, H-3″, H-4′′, H-5′′, H-6′′, H-7′′),

6.68 (d, ⁴J_{(H4′,H6′)}= 1 Hz, 1H, H-4′), 4.60 (d, ²J_{(H1″A,H1′′B)}= 14

2

Hz, 1H, H-1″A), 4.42 (d, J_{(H1″A,H1′′B)}= 14 Hz, 1H, H-1″B),

2.48 (s, 3H, H-6′) ppm. ¹³C{¹H} NMR (100.61 MHz, CDCl₃,

25 °C): δ 170.5 (C-3′), 167.1 (C-11), 161.1 (C-4), 157.0

(C-5′), 137.5 (C-2″), 132.5 (C-6), 132.3 (C-7), 131.1 (C-9),

130.3 (C-4′′, C-6′′), 128.7 (C-5′′), 128.4 (C-10), 128.1

(C-3′′, C-7′′), 126.5 (C-5), 123.8 (C-8), 107.8 (C-3), 96.5

(C-4′), 57.2 (C-1′′), 12.8 (C-6′) ppm.

C-5′), 108.4 (C-3), 57.3 (C-1′′), 42.2 (C-11′) ppm.

4-Hydroxy-N-(1H-indazol-6-yl)-2-methyl-2H-benzo[e][1,2]-

thiazine-3-carboxamide 1,1-Dioxide (5).

2-Methyl-4-hydroxy-1,1-dioxo-1,2-dihydro-1λ⁶-benzo[e][1,2]-

thiazine-3-carboxylic Acid (Pyridin-4-ylmethyl)amide (3).

Compound 5 was synthesized by following the general

procedure using IIIa (3.00 g, 11.14 mmol) and 6-amino-

indazole (1.49 g, 11.14 mmol). Yield: 65% (2.10 g, oﬀ-white).

MS (ESI⁺): m/z 393.0628 [M + Na]⁺, calcd 393.0633. Anal.

Found: C, 55.42; H, 3.72; N, 15.21; S, 8.45. Calcd

for C₁₇H₁₄N₄O₄S: 55.13; H, 3.81; N, 15.13; S, 8.66. FTIR

(KBr, cm⁻¹): 3399, 3268 (NH), 3100−2850 (OH), 1607

(CO), 1594 (CN), 1468 (CH def), 1335, 1173 (SO₂).

¹H NMR (400.13 MHz, DMSO-d₆, 25 °C): δ 14.08 (s, 1H,

OH), 13.07 (s, 1H, H1′), 10.39 (s, 1H, NH), 8.09 (s, 1H,

H-3′), 8.06−8.04 (m, 2H, H-4′, H-7′), 7.93−7.86 (m, 3H,

H-8, H-6, H-7), 7.76−7.74 (d, ³J_(H5,H6)= 9 Hz,1H, H-5), 7.51−

Compound 3 was synthesized by following the general procedure

using IIIa (0.60 g, 3.72 mmol) and 4-pyridylmethylamine (0.60 g,

5.58 mmol). Yield: 58% (0.70 g, oﬀ-white). Mp: 196−197 °C.

MS (ESI⁺): m/z 346.0850 [M + H]⁺, calcd 346.0862. Anal.

Found: C, 55.89; H, 4.48; N, 12.17; S, 9.13. Calcd for

1

C₁₆H₁₅N₃O₄S: C, 55.64; H, 4.38; N, 12.17; S, 9.28. H NMR

(400.13 MHz, CDCl₃, 25 °C): δ 13.39 (s, 1H, OH), 8.58−8.57

3

(m, 2H, H-2′, H-6′), 8.05−8.03 (dd, J₍₃_H8,H7)

=

4

8 Hz, J_(H8,H5)= 1 Hz 1H, H-8), 7.85−7.83 (dd, J_(H5,H6)

3

4

7 Hz, ⁴J_(H5,H7)= 1 Hz 1H, H-5), 7.78−7.74 (td, ³J_{(H6,H5)/(H6,H7)}

7.48 (dd, J_{(H5′,H4′)}= 9 Hz, J_{(H5′,H7′)}= 2 Hz, 1H, H-6′), 2.89

(s, 3H, H-1″) ppm. ¹³C{¹H} NMR (100.61 MHz, DMSO-d₆, 25

°C): δ 167.3 (C-11), 157.3 (C-4), 140.0 (C-8′), 135.2 (C-5′),

134.3 (C-9), 133.6 (C-3′), 133.5 (C-7), 133.1 (C-6), 127.9

(C-10), 126.3 (C-5), 124.2 (C-8), 120.4 (C-4′), 120.2 (C-9′),

4

8 Hz, J_{(H6, H8 )}= 1 Hz, 1H, H-6), 7.73−7.69

3

4

(td, J_{(H7,H8)/(H7,H6)}= 8 Hz, J_(H7,H5)= 1 Hz, 1H, H-7), 7.39 (t,

³J_(HNH,H11′)= 6 Hz, 1H, H-NH), 7.23 (d, ³J_{(H7,H8)/(H7,H6)}= 5 Hz,

2H, H-3′, H-5′), 4.52 (d, 2H, H-11′), 2.88 (s, 3H, H-1″) ppm.

¹³C{¹H} NMR (100.61 MHz, CDCl₃, 25 °C): δ 169.0 (C-11),

116.4 (C-5′), 111.7 (C-3), 102.6 (C-7′), 39.5 (C-1″) ppm.

2-Benzyl-4-hydroxy-N-(1H-indazol-6-yl)-2H-benzo[e][1,2]-

thiazine-3-carboxamide 1,1-Dioxide (6).

157.8 (C-4), 150.6 (C-2′, C-6′), 146.8 (C-4′), 133.5 (C-7), 132.6

(C-6), 128.8 (C-9), 128.8 (C-10), 127.0 (C-5), 125.0 (C-8),

122.5 (C-3′, C-5′), 111.5 (C-3), 42.4 (C-1″), 40.1 (C-11′) ppm.

2-Benzyl-4-hydroxy-N-(pyridin-4-ylmethyl)-2H-benzo[e][1,2]-

thiazine-3-carboxamide 1,1-Dioxide (4).

Compound 6 was synthesized by following the general

procedure using IIIb (3.00 g, 8.7 mmol) and 6-aminoindazole

(1.16 g, 8.7 mmol). Yield: 77% (2.80 g, oﬀ-white). MS (ESI⁺):

m/z 469.0938 [M + Na]⁺, calcd 469.0941. Anal. Found: C,

61.57; H, 4.22; N, 12.23; S, 6.87. Calcd for C₂₃H₁₈N₄O₄S: C,

61.87; H, 4.06; N, 12.55; S, 7.18. FTIR (KBr, cm⁻¹): 3350

(NH), 3050−2800 (OH), 1636 (CO), 1592 (CN), 1455

(CH def), 1334, 1168 (SO₂). ¹H NMR (400.13 MHz, CDCl₃,

25 °C): δ 13.51 (s, 1H, OH), 10.20 (s, 1H, H-1′), 8.11 (s, 1H,

H-3′), 8.02−8.0 (m, 2H, NH, H-4′), 7.8.6−7.82 (m, 2H, H-8,

Compound 4 was synthesized by following the general

procedure using IIIb (3.00 g, 8.7 mmol) and 4-amino-

methylpyridine (0.94 g, 8.7 mmol). Yield: 27% (1.00 g, oﬀ-

white). MS (ESI⁺): m/z 444.0978 [M + Na]⁺, calcd 444.0988.

Anal. Found: C, 52.63; H, 3.75; N, 8.20; S, 6.01. Calcd for

G

DOI: 10.1021/acs.organomet.8b00751

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Organometallics

Article

Chlorido(2-benzyl-4-oxido-N-(pyridin-2-yl)-2H-benzo[e][1,2]-

thiazine-3-carboxamide 1,1-dioxide)(cym)osmium(II) (1b).

H-5), 7.66−7.61 (m, 3H, H-7′, H-6, H-7), 7.22−7.20 (m, 2H,

H-4″, H-6′′), 7.15−7.12 (m, 3H, H-3′′, H-5′′, H-7′′), 6.68−

3

4

6.66 (dd, J_{(H5′,H4′)}= 9 Hz, J_{(H5′,H7′)}= 2, 1H, H-5′), 4.67

(d, ²J_(H12a,H12b)= 14 Hz, 1H, H-1″), 4.32 (d, ²J_{(H1″A,H1′′B)}= 14

Hz, 1H, H-1″) ppm. ¹³C{¹H} NMR (100.61 MHz, CDCl₃, 25

°C): δ = 167.2 (C-11), 159.7 (C-4), 140.5 (C-8′), 136.7

(C-13), 135.3 (C-6′), 135.1 (C-3′), 132.9 (C-7), 132.7 (C-9),

132.2 (C-6), 130 (C-4″, C-6′′), 128.9 (C-5′′), 128.8 (C-10),

128.7 (C-3′′, C-7′′), 126.7 (C-5), 124.1 (C-8), 121.4 (C-4′),

120.7 (C-9′), 115.3 (C-5′), 109.5 (C-3), 100.6 (C-7′), 57.98

(C-1′′) ppm.

General Procedure for the Synthesis of Complexes 1a,b

and 2a,b. Sodium methoxide was added to a suspension of ligand 1

or 2 in methanol (30 mL) under inert conditions to give a light yellow

solution. After 1/2 h of stirring at room temperature, [M(cym)Cl₂]₂

was added and the reaction mixture was stirred for a further 4 h. After

completion of the reaction, the solvent was evaporated. The reaction

mixture was dissolved in DCM and the solution ﬁltered to remove

excess inorganic salts. The ﬁltrate was concentrated to obtain a

precipitate, which was collected by ﬁltration and washed with diethyl

ether to isolate the product.²⁵

Complex 1b was synthesized by following the general

procedure using 1 (41 mg, 0.10 mmol), sodium methoxide

(7 mg, 0.12 mmol), and [Os(cym)Cl₂]₂(39 mg, 0.10 mmol).

Yield: 62% (50 mg, pale yellow solid), MS (ESI⁺): m/z

732.1568 [M − Cl]⁺, calcd 732.1572. Anal. Found: C, 48.71;

H, 3.79; N, 5.61; S, 4.38. Calcd for C₃₁H₃₀ClN₃O₄OsS: C,

48.59; H, 3.95; N, 5.48; S, 4.18. FT-IR (KBr, cm⁻¹): ν

̃

3150

(NH), 1613 (CO), 1568 (CN), 1530 (NH def), 1466

(CH def), 1330, 1171 (SO₂). ¹H NMR (400.13 MHz, CDCl₃,

3

4

Chlorido(2-benzyl-4-oxido-N-(pyridin-2-yl)-2H-benzo[e][1,2]-

thiazine-3-carboxamide 1,1-dioxide)(cym)ruthenium(II) (1a).

25 °C): δ 8.55 (dd, J_{(H6′,H5′)}= 7 Hz, J_{(H6′,H4′)}= 1 Hz, 1H,

H-6′), 7.71 (td, ³J_{(H4′,H5′)/(H4′,H3′)}= 8 Hz, ⁴J_{(H4′,H6′)}= 2 Hz, 1H,

3

4

H-4′), 7.65 (dd, J_(H8,H7)= 8 Hz, J_(H8,H6)= 2 Hz, 1H, H-8),

3

4

7.62 (dd, J_(H5,H6)= 8 Hz, J_(H5,H7)= 2 Hz, 1H, H-5), 7.44

3

4

(td, J_{(H6,H7)/(H6,H5)}= 7 Hz, J_(H6,H4)= 1 Hz, 1H, H-6), 7.39

(td, ³J_{(H7,H8)/(H7,H6)}= 7 Hz, ⁴J_(H7,H5)= 1 Hz, 1H, H-7), 7.09−7.01

(m, 7H, H-3′, H-5′, H-3″, H-4′′, H-5′′, H-6′′, H-7′′), 6.22 (d,

³J_{(H13,H14)/(H17,H16)}= 6 Hz, 1H, H-13/H-17), 6.13

3

(d, J_{(H13,H14)/(H17,H16)}= 6 Hz, 1H, H-13/H-17), 5.89 (d,

³J_{(H14,H13)/(H16,H17)}= 6 Hz, 1H, H-14/H-16), 5.72 (d,

³J_{(H14,H13)/(H16,H17)}= 6 Hz, 1H, H-14/H-16), 4.89 (d,

²J_{(H1″A,H1′′B)}= 15 Hz, 1H, H-1″), 4.40 (d, J_{(H1″A,H1′′B)}= 15 Hz,

2

Complex 1a was synthesized by following the general

procedure using 1 (122 mg, 0.30 mmol), sodium methoxide

(19 mg, 0.36 mmol), and [Ru(cym)Cl₂]₂(92 mg, 0.15 mmol).

Yield: 75% (150 mg, orange crystals), MS (ESI⁺): m/z

700.0626 [M + Na]⁺, calcd 700.0587; m/z 642.1017

[M − Cl]⁺, calcd 642.1001. Anal. Found: C, 54.93; H, 4.81;

N, 5.86; S, 4.38. Calcd for C₃₁H₃₀ClN₃O₄RuS: C, 54.98; H,

1H, H-1″), 2.97−2.90 (m, 1H, H-20), 2.08 (s, 3H, H-18), 1.37

3

(d, J_{(H19,H20)/(H21,H20)}= 7 Hz, 3H, H-19/H-21), 1.35 (d,

³J_{(H19,H20)/(H21,H20)}= 7 Hz, 3H, H-19/H-21) ppm. ¹³C{¹H}

NMR (100.61 MHz, CDCl₃, 25 °C): δ 153.9 (C-6′), 149.7

(C-4), 139.9 (C-4′), 137.8 (C-2″), 134.1 (C-9), 133.7 (C-10),

131.6 (C-6), 130.8 (C-7), 130.2 (C-3′′/C-7′′), 130.1 (C-3′′/

C-7′′), 127.44 (C-4′′/ C-6′′), 127.1 (C-4′′/ C-6′′), 126.9 (C-5),

122.4 (C-8), 119.7 (C-3′), 115.2 (C-5′), 103.8 (C-3), 94.0

(C-12), 91.1 (C-15), 76.5 (C-13/C-17), 75.1 (C-13/C-17), 72.3

(C-14/C-16), 70.1 (C-14/C-16), 55.5 (C-1′′), 31.5 (C-20), 23.5

(C-19/C-21), 22.1 (C-19/C-21), 18.8 (C-18) ppm.

4.47; N, 6.21; S, 4.74. FT-IR (KBr, cm⁻¹): ν

̃

3150 (NH), 1611

(CO), 1569 (CN), 1503 (NH def), 1466 (CH def),

1

1328, 1170 (SO₂). H NMR (400.13 MHz, CDCl₃, 25 °C):

δ 8.55 (dd, ³J_{(H6′,H5′)}= 6 Hz, ⁴J₍₄_H6′,H4′)=1 Hz, 1H, H-6′), 7.74

3

(td, J_{(H4′,H5′)/(H4′,H3′)}= 9 Hz, J_{(H4′,H6′)}= 2 Hz, 1H, H-4′),

Chlorido(2-benzyl-N-(5-methylisoxazol-3-yl)-4-oxido-2H-benzo[e]-

[1,2]thiazine-3-carboxamide 1,1-dioxide)(cym)ruthenium(II) (2a).

3

7.65−7.61 (m, 2H, H-8, H-5), 7.41 (dtd, J_{(H6,H7)/(H‑6,H5)}

=

³J_{(H7,H8)/(H7,H6)}= 8 Hz, J_{(H6,H8)/(H7,H6)}= 8 Hz, H-6, H-7),

7.09−7.01 (m, 2H, H-3′, H-5′), 6.95−6.89 (m, 3H, H-4″,

H-5′′, H-6′′), 6.86−6.82 (m, 2H, H-3′′, H-7′′), 5.78−5.74

3

(m, 2H, H-13, H-17), 5.42 (d, J_{(H14,H13)/(H16,H17)}= 6 Hz,

3

1H, H-14/H-16), 5.22 (d, J_{(H14,H13)/(H‑16,H17)}= 6 Hz, 1H,

2

H-14/H-16), 4.91 (d, J_{(H1″A,H1′′B)}= 14 Hz, 1H, H-1″), 4.41

2

(d, J_{(H1″A,H1′′B)}= 14 Hz, 1H, H-1″), 3.11−3.08 (m, 1H,

H-20), 2.05 (s, 3H, H-18), 1.40 (d, ³J_{(H19,H20)/(H21,H20)}= 7 Hz,

3

3H, H-19/H-21), 1.36 (d, J_{(H19,H20)/(H21,H20)}= 7 Hz, 3H,

H-19/H-21) ppm. ¹³C{¹H} NMR (100.61 MHz, CDCl₃,

25 °C): δ 175.7 (C-11), 168.7 (C-2′), 153.78 (C-6′), 151.0

(C-4), 140.0 (C-4′), 139.7 (C-2″), 134.5 (C-9), 133.8 (C-10),

131.8 (C-6), 130.9 (C-7), 130.34 (C-3′′, C-7′′), 127.6 (C-4′′,

C-6′′), 127.2 (C-5), 122.5 (C-8), 119.8 (C-3′), 115.4 (C-5′),

104.8 (C-3), 104.1 (C-12), 98.0 (C-15), 85.3 (C-13/C-17),

83.8 (C-13/C-17), 81.6 (C-14/C-16), 79.6 (C-14/C-16),

66.2 (C-1′′), 31.2 (C-20), 22.2 (C-19/C-21), 22.1 (C-19/

C-21), 18.7 (C-18) ppm.

Complex 2a was synthesized by following the general

procedure using 2 (123 mg, 0.30 mmol), sodium methoxide

(19 mg, 0.36 mmol), and [Ru(cym)Cl₂]₂(92 mg, 0.15 mmol).

Yield: 73% (148 mg, yellow powder). MS (ESI⁺): m/z

646.0946 [M − Cl]⁺, calcd 646.0949. Anal. Found: C, 52.91;

H, 4.33; N, 6.12; S, 4.69. Calcd for C₃₀H₃₀ClN₃O₅RuS: C,

52.90; H, 4.44; N, 6.17; S, 4.71. FT-IR (KBr, cm⁻¹): ν

̃

3110

H

DOI: 10.1021/acs.organomet.8b00751

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

General Procedure for the Synthesis of Complexes 1c,d,

2c,d, 3a,b, 4a, 5a,b, and 6a. Oxicam 1−6 and [M(cym)X₂]₂

(M = Ru, Os) were dissolved in dichloromethane at room

temperature. The reaction mixture was subjected to stirring for 4 h

under anhydrous conditions. After completion of the reaction, the

volume of the solvent was reduced to approximately 5 mL and diethyl

ether was added to precipitate the product. The solid was collected by

ﬁltration, washed with ethyl ether, and dried under vacuum.

(NH), 1590 (CO, CN), 1540 (NH def), 1428 (CH def),

1

1323, 1169 (SO₂). H NMR (400.13 MHz, CDCl₃, 25 °C):

3

4

δ 7.63 (dd, J_(H8,H7)= 8 Hz, J_(H8,H5)= 1 Hz, 1H, H-8), 7.56

3

4

(dd, J_(H5,H6)= 8 Hz, J_(H5,H7)= 1 Hz, 1H, H-5), 7.40

3

4

(td, J_{(H6,H7)/(H6,H5)}= 8 Hz, J_(H6,H8)= 1 Hz, H-6), 7.35

3

4

(td, J_{(H7,H8)/(H7,H6)}= 8 Hz, J_(H7,H5)= 1 Hz, H-7), 7.09−7.07

(m, 2H, H-4″, H-6′′), 6.92−6.85 (m, 3H, H-5′′, H-3′′, H-7′′),

3

5.88 (s, 1H, H-4′), 5.64 (d, J_{(H13,H14)/(H17,H16)}= 5 Hz,1H,

Dichlorido(2-benzyl-N-(pyridin-2-yl)-4-hydroxy-2H-benzo[e]-

[1,2]thiazine-3-carboxamide 1,1-dioxide)(cym)ruthenium(II) (1c).

3

H-13/H-17), 5.59 (d, J_{(H13,H14)/(H16,H17)}= 5 Hz,1H, H-13/

3

H-17), 5.46 (d, J_{(H14,H13)/(H17,H16)}= 6 Hz, 2H, H-14, H-16),

2

4.85 (d, J_{(H1″A,H1′′B)}= 15 Hz, 1H, H-1″), 4.47 (d, J_{(H1″A,H1″B)}

= 15 Hz, 1H, H-1″), 3.05−2.98 (m, 1H, H-20), 2.49 (s, 3H,

3

H-6′), 2.32 (s, 3H, H-18), 1.37 (d, J_{(H19,H20)/(H21,H20)}= 7 Hz,

3

3H, H-19/H-21), 1.36 (d, J_{(H19,H20)/(H21,H20)}= 7 Hz, 3H,

H-19/H-21) ppm. ¹³C{¹H} NMR (100.61 MHz, CDCl₃, 25 °C):

δ 171.9 (C-3′), 171.1 (C-11), 165.5 (C-5′), 153.4 (C-4), 139.4

(C-2″), 133.8 (C-9), 133.4 (C-10), 131.3 (C-6), 130.4 (C-7),

130.0 (C-4′′, C-6′′), 127.1 (C-3′′, C-7′′), 127.1 (C-5′′), 126.8

(C-5), 122.1 (C-8), 105.7 (C-3), 103.5 (C-12), 98.0 (C-15), 97.4

(C-4′), 83.0 (C-13/C-17), 82.2 (C-13/C-17), 82.0 (C-14/C-16),

81.1 (C-14/C-16), 54.5 (C-1′′), 31.0 (C-20), 22.5 (C-19/C-21),

22.2 (C-19/C-21), 18.4 (C-18), 12.8 (C-6′) ppm.

Complex 1c was synthesized following the general procedure

using 1 (122 mg, 0.30 mmol) and [Ru(cym)Cl₂]₂(92 mg, 0.15

mmol). Yield: 61% (130 mg, orange crystals). ESI-MS: m/z

678.0784 [M − Cl]⁺, calcd 678.0766. Anal. Found: C, 52.13;

H, 4.47; N, 5.61; S, 4.26. Calcd for C₃₁H₃₁Cl₂N₃O₄RuS: C,

Chlorido(2-benzyl-N-(5-methylisoxazol-3-yl)-4-oxido-2H-benzo-

[e][1,2]thiazine-3-carboxamide 1,1-dioxide)(cym)osmium(II) (2b).

52.17; H, 4.38; N, 5.89; S, 4.49. FT-IR (KBr, cm⁻¹): ν

̃

3465

(NH), 3100−2700 (OH), 1626 (CO), 1559 (CN), 1432

(CH def), 1340, 1174 (SO₂). ¹H NMR (400.13 MHz, CDCl₃,

25 °C): δ 13.50 (s, 1H, OH), 11.80 (s, 1H, NH), 9.24

3

4

(dd, J_{(H6′,H5′)}= 6 Hz, J_{(H6′,H4′)}= 1 Hz, 1H, H-6′), 8.01

3

(d, J_{(H43′,H4′)}= 8 Hz, 1H, H-3′), 7.82 (td, J₍₃_{H4′,H5′)/(H4′,H3′)}

=

8 Hz, J_{(H4′,H6′)}= 1 Hz, 1H, H-4′), 7.78 (d, J_(H8,H7)= 7 Hz,

3

1H, H-8), 7.41 (d, J_(H5,H6)= 8 Hz, 1H, H-5), 7.57

3

4

(td, J_{(H7,H8)/(H7,H6)}= 8 Hz, J_(H7,H5)= 1 Hz, 1H, H-7), 7.49

3

4

(td, J_{(H6,H7)/(H6,H5)}= 8 Hz, J_(H6,H4)= 1 Hz, 1H, H-6), 7.18−

Complex 2b was synthesized following the general procedure

using ligand 2 (123 mg, 0.30 mmol), sodium methoxide

(19 mg, 0.36 mmol), and [Os(cym)Cl₂]₂(118 mg,

0.15 mmol). Yield: 82% (190 mg, light yellow). MS (ESI⁺):

m/z 736.1528 [M − Cl]⁺, calcd 736.1515. Anal. Found: C,

46.85; H, 3.94; N, 5.53; S, 4.27. Calcd for C₃₀H₃₀ClN₃O₅OsS:

7.15 (m, 1H, H-5′), 6.98−6.91 (m, 5H, H-4″, H-6′′, H-5′′,

3

H-3′′, H-7′′), 6.15 (d, J_{(H13,H14)/(H‑17/H16)}= 6 Hz, 1H, H-13/

3

H-17), 5.61 (d, J_{(H13,H14)/(H‑17/H16)}= 6 Hz, 1H, H-13/H-17),

3

5.51 (d, J_{(H14,H13)/(H‑16/H17)}= 6 Hz, 1H, H-14/H-16), 5.43

3

(d, J_{(H14,H13)/(H‑16/H17)}= 6 Hz, 1H, H-14/H-16), 5.01

2

(d, J_{(H1″A,H1′′B)}= 14 Hz, 1H, H-1″), 4.44 (d, J_{(H1″A,H1′′B)}

=

C, 46.78; H, 3.93; N, 5.45; S, 4.16. FT-IR (KBr, cm⁻¹): ν

̃

3100

14 Hz, 1H, H-1″), 2.95−2.88 (m, 1H, H-20), 1.86 (s, 3H, H-

3

(NH), 1600 (CO, CN), 1566 (NH def), 1488 (CH def),

18), 1.36 (d, J_{(H19,H20)/(H21,H20)}= 7 Hz, 3H, H-19/H-21), 1.27

1

(d, J_{(H19,H20)/(H21,H20)}= 7 Hz, 3H, H-19/H-21) ppm. ¹³C{¹H}

3

1327, 1170 (SO₂). H NMR (400.13 MHz, CDCl₃, 25 °C):

3

4

δ 7.63 (dd, J_(H8,H7)= 8 Hz, J_(H8,H5)= 1 Hz, 1H, H-8), 7.57

NMR (100.61 MHz, CDCl₃, 25 °C): δ 168.0 (C-11), 162.4

(C-4), 154.6 (C-6′), 153.5 (C-2′), 139.4 (C-4′), 138.0 (C-2″),

132.3 (C-6, C-7), 131.1 (C-9), 130.6 (C-4′′, C-6′′), 128.5

(C-10), 128.3 (C-5′′), 127.7 (C-3′′, C-7′′), 126.4 (C-8), 123.4

(C-5), 121.0 (C-5′), 119.9 (C-3′), 107.4 (C-3), 101.9 (C-12),

98.8 (C-15), 85.7 (C-13/C-17), 84.3 (C-13/C-17), 81.1 (C-14/

C-16), 80.9 (C-14/C-16), 57.1 (C-1′′), 30.8 (C-20), 22.5

3

4

(dd, J_(H5,H6)= 8 Hz, J_(H5,H7)= 1 Hz, 1H, H-5), 7.42

(td, J_{(H6,H7)/(H6,H5)}= 8 Hz, J_(H6,H8)= 1 Hz, H-6), 7.35

(td, J_{(H7,H8)/(H7,H6)}= 8 Hz, J_(H7,H5)= 1 Hz, H-7), 7.11−7.09

(m, 2H, H-4″, H-5′′), 6.94−6.85 (m, 3H, H-5′′, H-3′′, H-7′′),

5.95−5.91 (m, 3H, H-4′, H-13, H-17), 5.75 (d, ³J_{(H14,H13)/(H16,H17)}

= 6 Hz, 1H, H-14/H-16), 5.72 (d, ³J_{(H14,H13)/(H16,H17)}= 6 Hz, 1H,

3

4

3

4

2

H-14/H-16), 4.85 (d, J_{(H1″A,H1′′B)}= 15 Hz, 1H, H-1″), 4.43

(C-19, C-21), 18.3 (C-18) ppm.

2

(d, J_{(H1″A,H1′′B)}= 15 Hz, 1H, H-1″), 2.91−2.84 (m, 1H, H-20),

Dichlorido(2-benzyl-N-(pyridin-2-yl)-4-hydroxy-2H-benzo[e]-

[1,2]thiazine-3-carboxamide 1,1-dioxide)(cym)osmium(II) (1d).

Complex 1d was synthesized following the general procedure using

1 (41 mg, 0.10 mmol) and [Os(cym)Cl₂]₂(39 mg, 0.05 mmol).

Yield: 77% (62 mg, greenish yellow precipitate). MS (ESI⁺): m/z

768.1319 [M − Cl]⁺, calcd 768.1322. Anal. Found: C, 46.61; H, 3.91;

N, 5.12; S, 4.01. Calcd for C₃₁H₃₁Cl₂N₃O₄OsS: C, 46.38; H, 3.89; N,

2.48 (s, 3H, H-6′), 2.37 (s, 3H, H-18), 1.35 (d, ³J_{(H19,H20)/(H21,H20)}

= 7 Hz, 3H, H-19/H-21), 1.33 (d, ³J_{(H19,H20)/(H21,H20)}= 7 Hz, 3H,

H-19/H-21) ppm. ¹³C{¹H} NMR (100.61 MHz, CDCl₃, 25 °C):

δ 171.7 (C-3′), 170.8 (C-11), 165.5 (C-5′), 151.5 (C-4), 139.6

(C-2″), 133.7 (C-9), 133.0 (C-10), 131.5 (C-6), 130.7 (C-7),

130.1 (C-4′′, C-6′′), 127.3 (C-3′′, C-7′′), 127.2 (C-5′′), 126.9

(C-5), 122.2 (C-8), 105.8 (C-3), 97.9 (C-4′), 93.9 (C-12), 89.5

(C-15), 74.8 (C-13/C-17), 73.6 (C-13/C-17), 73.3 (C-14/C-16),

71.9 (C-14/C-16), 54.5 (C-1′′), 31.5 (C-20), 23.1 (C-19/C-21),

22.6 (C-19/C-21), 18.7 (C-18), 12.8 (C-6′) ppm.

5.23; S, 3.99. FT-IR (KBr, cm⁻¹): ν

̃

3100 (NH), 2960−2750 (OH),

1630 (CO), 1559 (CN), 1431 (CH def), 1344, 1174 (SO₂). ¹H

NMR (400.13 MHz, CDCl₃, 25 °C): δ 13.45 (s, 1H, OH), 11.66 (s,

1H, H-NH), 9.16 (dd, ³J_{(H6′,H5′)}= 6 Hz, ⁴J_{(H6′,H4′)}= 1 Hz, 1H, H-6′),

7.99 (d, ³J_{(H3′,H4′)}= 8 Hz, 1H, H-3′), 7.79−7.73 (m, 2H, H-5, H-4′),

I

DOI: 10.1021/acs.organomet.8b00751

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

127.4 (C-3′′, C-7′′), 126.1 (C-5), 123.2 (C-8), 107.2 (C-3),

104.1 (C-12), 99.8 (C-4′), 99.7 (C-15), 83.7 (C-13/C-17),

83.6 (C-13/C-17), 82.0 (C-14/C-16), 81.3 (C-14/C-16), 57.3

(C-1′′), 30.9 (C-20), 22.4 (C-19/C-21), 22.3 (C-19/C-21),

19.0 (C-18), 13.0 (C-6′) ppm.

Dichlorido(2-benzyl-N-(5-methylisoxazol-3-yl)-4-hydroxy-2H-

benzo[e][1,2]thiazine-3-carboxamide 1,1-dioxide)(cym)osmium(II)

(2d).

3

4

7.63 (dd, J_(H5,H6)= 7 Hz, J_(H5,H7)= 1 Hz, 1H, H-8), 7.58 (td,

³J_{(H7,H8)/(H7,H6)}= 8 Hz, J_(H7,H5)= 1 Hz, 1H, H-7), 7.50 (td,

4

³J_{(H6,H5)/(H6,H7)}= 8 Hz, J_(H6,H4)= 1 Hz, 1H, H-6), 7.17 (td,

4

³J_{(H5′,H6′)/(H5′/H4′)}= 6 Hz, ³J_{(H5′,H3′)}= 1 Hz, 1H, H-5′), 7.01−6.90 (m,

5H, H-4″, H-6′′, H-5′′, H-3′′, H-7′′), 6.57 (d, ³J_{(H13,H14)/(H17,H16)}= 5

3

Hz, 1H, H-13/H-17), 6.03 (d, J_{(H13,H14)/(H17,H16)}= 5 Hz, 1H, H-13/

3

H-17), 5.91 (d, J_{(H14,H13)/(H16,H17)}= 6 Hz, 2H, H-14, H-16), 4.99

2

(d, J_{(H1″A,H1′′B)}= 14 Hz, 1H, H-1″), 4.42 (d, J_{(H1″A,H1′′B)}= 14 Hz,

1H, H-1″), 2.85−2.75 (m, 1H, H-20), 1.87 (s, 3H, H-18), 1.35

Complex 2d was synthesized by following the general

procedure using 2 (123 mg, 0.30 mmol) and [Os(cym)Cl₂]₂

(119 mg, 0.15 mmol). Yield: 87% (210 mg, light yellow). MS

(ESI⁺): m/z 830.0845 [M + Na]⁺, calcd 830.0848; m/z

772.1228 [M − Cl]⁺, calcd 772.1228; m/z 646.0946 [M − 2Cl

− H]⁺, calcd 646.0949. Anal. Found: C, 44.51; H, 3.92; N,

5.35; S, 3.85. Calcd for C₃₀H₃₁Cl₂N₃O₅OsS: C, 44.66; H, 3.87; N,

3

(d, J_{(H19,H20)/(H21,H20)}= 7 Hz, 3H, H-19/H-21), 1.27 (d,

³J_{(H19,H20)/(H21,H20)}= 7 Hz, 3H, H-19/H-21) ppm. ¹³C{¹H} NMR

(100.61 MHz, CDCl₃, 25 °C): δ 167.8 (C-11), 162.4 (C-4), 154.3

(C-6′), 152.8 (C-2′), 139.5 (C-4′), 138.0 (C-13), 132.3 (C-6, C-7),

131.0 (C-9), 130.6 (C-4″, C-6′′), 128.5 (C-10), 128.4 (C-5′′), 127.7

(C-3′′, C-7′′), 126.4 (C-8), 123.5 (C-5), 120.9 (C-5′), 119.7 (C-3′),

107.4 (C-3), 92.7 (C-12), 90.8 (C-15), 77.9 (C-13, C-17), 72.5

(C-14/C-16), 72.0 (C-14/C-16), 57.1 (C-1′′), 31.2 (C-20), 22.8

(C-19/C-21), 22.7 (C-19/C-21), 18.4 (C-18) ppm.

5.21; S, 3.97. FT-IR (KBr, cm⁻¹): ν

̃

3199 (NH), 3050−2700

(OH), 1642 (CO), 1606 (CN), 1541 (NH def), 1485

(CH def), 1341, 1174 (SO₂). ¹H NMR (400.13 MHz, CDCl₃,

25 °C): δ 13.05 (s, 1H, OH), 11.48 (s, 1H, H-NH), 7.67

Dichlorido(2-benzyl-N-(5-methylisoxazol-3-yl)-4-hydroxy-2H-

benzo[e][1,2]thiazine-3-carboxamide 1,1-dioxide)(cym)ruthenium-

(II) (2c).

3

4

(d, J_(H8,H7)= 7 Hz, J_(H8,H5)= 1 Hz, 1H, H-8), 7.49−7.43

(m, 2H, H-6, H-5), 7.36 (td, ³J_{(H7,H8)/(H7,H6)}= 8 Hz, ⁴J_(H7,H5)

=

1 Hz, H-7), 7.07 (s, 1H, H-4′), 6.90−6.79 (m, 5H, H-5″,

H-3′′, H-4′′, H-6′′, H-7′′), 6.01 (d, ³J_{(H13,H14)/(H17,H16)}= 5 Hz,

3

1H, H-13/H-17), 5.99 (d, J_{(H13,H14)/(H17,H16)}= 5 Hz, 1H,

H-13/H-17), 5.85−5.81 (m, 2H, H-14, H-16), 5.05

2

(d, J_{(H1″A,H1′′B)}= 15 Hz, 1H, H-1″), 4.73 (d, J_{(H1″A,H1′′B)}

=

15 Hz, 1H, H-1″), 2.95−2.88 (m, 1H, H-20), 2.54 (s, 3H,

H-6′), 2.31 (s, 3H, H-18), 1.32−1.29 (m, 6H, H-19/H-21)

ppm. ¹³C{¹H} NMR (100.61 MHz, CDCl₃, 25 °C): δ

170.2 (C-3′), 167.5 (C-11), 162.2 (C-4), 158.6 (C-5′),

139.1 (C-2″), 132.0 (C-6), 132.0 (C-7), 131.3 (C-9), 130.6

(C-4′′, C-6′′), 128.5 (C-10), 127.9 (C-5′′), 127.3 (C-3′′,

C-7′′), 126.2 (C-5), 123.2 (C-8), 107.3 (C-3), 100.1 (C-4′),

94.7 (C-12), 91.6 (C-15), 76.1 (C-13/C-17), 75.8 (C-13/

C-17), 73.2 (C-14/C-16), 72.6 (C-14/C-16), 57.6 (C-1′′),

31.1 (C-20), 22.8 (C-19/C-21), 22.5 (C-19/C-21), 18.9

Complex 2c was synthesized by following the general

procedure using 2 (123 mg, 0.30 mmol) and [Ru(cym)Cl₂]₂

(92 mg, 0.15 mmol). Yield: 84% (199 mg, orange precipitate).

MS (ESI⁺): m/z 740.0295 [M + Na]⁺, calcd 740.0302; m/z

682.0711 [M − Cl]⁺, calcd 682.0716; m/z 646.0946 [M − 2Cl

− H]⁺, calcd 646.0949. Anal. Found: C, 50.35; H, 4.38; N,

5.77; S, 4.57. Calcd for C₃₀H₃₁Cl₂N₃O₅RuS: C, 50.21; H, 4.35;

(C-18), 12.8 (C-6′) ppm.

Dichlorido[2-methyl-N-(pyridin-4-ylmethyl)-4-hydroxy-2H-

benzo[e][1,2]thiazine-3-carboxamide 1,1-dioxide](cym)ruthenium-

(II) (3a).

N, 5.86; S, 4.47. FT-IR (KBr, cm⁻¹): ν

̃

3209 (NH), 3064−

2700 (OH), 1639 (CO), 1608 (CN), 1543 (NH def),

1

1428 (CH def), 1341, 1174 (SO₂). H NMR (400.13 MHz,

CDCl₃, 25 °C): δ 13.05 (s, 1H, OH), 11.27 (s, 1H, H-NH),

3

7.68 (d, J_(H8,H7)= 8 Hz, 1H, H-8), 7.49−45 (m, 2H, H-6, H-

5), 7.60 (td, ³J_{(H7,H8)/(H7,H6)}= 8 Hz, ⁴J_(H7,H5)= 1 Hz, H-7), 7.04

(s, 1H, H-4′), 6.91−6.78 (m, 5H, H-5″, H-3′′, H-4′′, H-6′′, H-

3

7′′), 5.71 (d, J_{(H13,H14)/(H16,H17)}= 5 Hz, 1H, H-13/H-17),

3

5.62 (d, J_{(H13,H14)/(H16,H17)}= 5 Hz, 1H, H-13/H-17), 5.47−

2

5.46 (m, 2H, H-14, H-16), 5.03 (d, J_{(H1″A,H1′′B)}= 15 Hz,

1H, H-1″), 4.65 (d, J_{(H1″,H1′′B)}= 15 Hz, 1H, H-1″), 3.11−

2

Compound 3a was synthesized by following the general

procedure using 3 (138 mg, 0.40 mmol) and [Ru(cym)Cl₂]₂

(123 mg, 0.20 mmol). Yield: 65% (168 mg, orange powder).

mp 222−225 °C. MS (ESI⁺): m/z 580.0842 [M − 2Cl − H]⁺,

calcd 580.0844. Anal. Found: C, 47.98; H, 4.58; N, 6.45; S,

4.62, Calcd for C₂₆H₂₉Cl₂N₃O₄RuS·0.75H₂O: C, 47.93; H,

3.05 (m, 1H, H-20), 2.54 (s, 3H, H-6′), 2.29 (s, 3H, H-18),

1.34−1.31 (m, 6H, H-19/H-21) ppm. ¹³C{¹H} NMR (100.61

MHz, CDCl₃, 25 °C): δ 171.0 (C-3′), 167.5 (C-11), 162.1

(C-4), 159.5 (C-5′), 139.1 (C-2″), 131.9 (C-6), 131.7 (C-7),

131.4 (C-9), 130.5 (C-4′′, C-6′′), 128.4 (C-10), 127.8 (C-5′′),

J

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Organometallics XXXX, XXX, XXX−XXX

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4.49; N, 6.45; S, 4.92. ¹H NMR (400.13 MHz, CDCl₃, 25 °C):

3

δ 13.33 (brs, 1H, O−H), 8.87 (d, J_{(H2′,H3′)/(H6′,H5′)}= 5 Hz,

3

4

2H, H-2′, H-6′), 8.04−8.02 (dd, J_(H8,H7)= 8 Hz, J_(H8,H6)= 2

Hz, 1H, H-8), 7.91−7.89 (dd, ³J_(H5,H6)= 7 Hz, ⁴J_(H5,H7)= 2 Hz,

3

4

1H, H-5), 7.78−7.74 (td, J_{(H6,H7)/(H6,H5)}= 9 Hz, J_(H6,H8)

=

1 Hz, 1H, H-6), 7.74−7.70 (td, ³J_{(H7,H8)/(H7,H6)}= 9 Hz, ⁴J_(H5,H7)

= 1 Hz, 1H, H-7), 7.21−7.19 (m, 2H, H-3′, H-5′), 5.43 (d,

³J_{(H13,H14)/(H17,H16)}= 6 Hz, 2H, H-13, H-17), 5.21 (d,

³J_{(H13,H14)/(H16,H17)}= 6 Hz, 2H, H-14, H-16), 4.50 (brs, 2H,

H-11′), 3.03−2.95 (m, 1H, H-20), 2.94 (s, 3H, H-1″), 2.08 (s,

reaction mixture was stirred for 20 h at room temperature, and the

volume of the solvent was reduced under vacuum. Precipitation was

induced by adding diethyl ether. The product was ﬁltered, washed

with diethyl ether, and dried under vacuum. Bright yellow crystals

suitable for X-ray diﬀraction analysis were obtained by slow diﬀusion

of diethyl ether into solution of compound in methanol. Yield: 76%

(405 mg, bright yellow powder). Mp: 183−194 °C. MS (ESI⁺): m/z

692.0616 [M + Na]⁺, calcd 692.0617. Anal. Found: C, 47.75; H, 4.30;

N, 6.00; S, 4.61. Calcd for C₂₈H₂₉N₃O₈RuS·0.5CH₂Cl₂: C, 48.13; H,

4.25; N, 5.91; S, 4.51. ¹H NMR (400.13 MHz, CDCl₃, 25 °C): δ 13.7

3

3H, H-18), 1.31 (d, J_{(H19,H20)/(H21,H20)}= 7 Hz, 6H, H-19, H-

21) ppm. ¹³C{¹H} NMR (100.61 MHz, CDCl₃, 25 °C): δ

169.1 (C-11), 157.5 (C-4), 154.3 (C-2′, C-6′), 150.3 (C-4′),

135.1 (C-9), 133.1 (C-6), 132.4 (C-7), 129.1 (C-10), 126.8

(C-5), 124.9 (C-8), 123.9 (C-3′, C-5′), 111.8 (C-3), 104.0

(C-15), 97.5 (C-12), 83.2 (C-14, C-16), 82.5 (C-13, C-17),

41.8 (C-11′), 40.5 (C-1″), 31.0 (C-20), 22.6 (C-19, C-21),

3

(brs, 1H, OH), 9.07 (t, J_{(H10′,H11′)}= 7 Hz,1H, NH), 8.23

3

18.5 (C-18) ppm.

(d, J_{(H2′,H3′)/(H6′,H5′)}= 6 Hz, 2H, H-2′, H-6′), 8.04 (dd, J_(H8,H7)

=

7 Hz, ⁴J_(H8,H6)= 1 Hz, 1H, H-8), 7.91 (dd, ³J_(H5,H6)= 7 Hz, ⁴J_(H5,H7)

2 Hz,1H, H-5), 7.75 (td, J_{(H6,H7)/(H6,H5)}= 8 Hz, J(H6,H8) = 2 Hz,

Dichlorido[2-methyl-N-(pyridin-4-ylmethyl)-4-hydroxy-2H-

benzo[e][1,2]thiazine-3-carboxamide 1,1-dioxide](cym)osmium(II)

(3b).

3

4

3

1H, H-6), 7.71 (td, J_{(H7,H8)/(H7,H6)}= 9 Hz, J_{(H7,H8)/(H7,H6)}= 8 Hz,

⁴J_(H7,H5)= 2 Hz, 1H, H-7), 7.24 (d, J_{(H3′,H2′)/(H5′,H6′)}= 6 Hz, 2H,

3

H-3′, H-5′), 5.56 (d, J_{(H13,H14)/(H17,H18)}= 6 Hz, 2H, H-13, H-17),

3

5.42 (d, J_{(H14,H13)/(H16,H17)}= 6 Hz, 2H, H-14, H-16), 2.94−2.86

(m, 4H, H-1″, H-20), 2.18 (s, 3H, H-18), 2.16 (s, 2H, H-11′), 1.33

(d, ³J_{(H19,H20)/(H21,H20)}= 7 Hz, 6H, H-19, H-21) ppm. ¹³C{¹H} NMR

(100.61 MHz, CDCl₃, 25 °C): δ 169.1 (C-11), 157.4 (C-4), 152.0

(C-2′, C-6′), 151.8 (C-4′), 134.8 (C-9), 132.8 (C-10), 132.0 (C-8),

128.9 (C-5), 126.5 (C-6), 124.4 (C-7), 124.1 (C-3′, C-5′), 111.5

(C-3), 102.1 (C-13, C-17), 96.7 (C-14, C-16), 81.9 (C-12), 81.2

(C-15), 41.5 (C-11′), 39.8 (C-1″), 30.9 (C-20), 22.5 (C-19, C-21),

17.9 (C-18) ppm.

Compound 3b was synthesized by following the general

procedure using 3 (138 mg, 0.40 mmol) and [Os(cym)Cl₂]₂

(158.2 mg, 0.20 mmol). Yield: 74% (220 mg, yellow powder).

Mp: 220−228 °C. MS (ESI⁺): m/z 670.1424 [M − 2Cl − H]⁺,

calcd 670.1415. Anal. Found: C, 42.17; H, 3.92; N, 5.68; S,

4.28, Calcd for C₂₆H₂₉Cl₂N₃O₄SOs: C, 42.16; H, 3.95; N,

5.67; S, 4.33. ¹H NMR (400.13 MHz, CDCl₃, 25 °C): δ 13.42

Dichlorido(2-benzyl-4-hydroxy-N-(pyridin-4-ylmethyl)-2H-

benzo[e][1,2]thiazine-3-carboxamide 1,1-dioxide)(cym)ruthenium-

(II) (4a).

3

(s, 1H, OH), 8.72 (d, J_{(H2′,H3′)/(H6′,H5′)}= 7 Hz, 2H, H-2′, H-

6′), 8.01−7.99 (dd, ³J_(H7,H8)= 7 Hz, ⁴J_(H6,H8)= 2 Hz, 1H, H-8),

7.89−7.87 (dd, ³J_(H5,H6)= 7 Hz, ⁴J_(H5,H7)= 2 Hz,1H, H-5), 7.84

(t, ³J_{(H10′,H11′)}= 7 Hz, 1H, NH), 7.76−7.72 (td, ³J_{(H6,H7)/(H6,H5)}

4

= 9 Hz, J_(H6,H8)= 2 Hz, 1H, H-6), 7.72−7.68

3

4

(td, J_{(H7,H8)/(H7,H6)}= 9 Hz, J_(H7,H5)= 1 Hz, 1H, H-7), 7.17

3

(d, J_{(H3′,H2′)/(H5′,H6′)}= 6 Hz, 2H, H-3′, H-5′), 5.85 (d,

³J_{(H13,H14)/(H17,H16)}= 6 Hz, 2H, H-13, H-17), 5.57 (d,

³J_{(H14,H13)/(H16,H17)}= 6 Hz, 2H, H-14, H-16), 4.52 (brs, 2H,

H-11′), 2.93 (s, 3H, H-1″), 2.85−2.80 (m, 1H, H-20), 2.03

Compound 4a was synthesized by following the general

procedure using 4 (169 mg, 0.40 mmol) and [Ru(cym)Cl₂]₂

(123 mg, 0.20 mmol). Yield: 68% (198 mg, yellow powder).

MS (ESI⁺): m/z 750.0507 [M + Na]⁺, calcd 750.0510. Anal.

Found: C, 45.35; H, 4.00; N, 4.50; S, 3.34. Calcd for

C₃₂H₃₃Cl₂N₃O₄RuS·2CH₂Cl₂: C, 45.50; H, 4.16; N, 4.68; S,

3.57. FTIR (KBr, cm⁻¹): 3298, 3188 (NH), 1650 (CO),

3

(s, 3H, H-18), 1.30 (d, J_{(H19,H20)/(H21,H20)}= 7 Hz, 6H, H-19,

H-21) ppm. ¹³C{¹H} NMR (100.61 MHz, CDCl₃, 25 °C): δ

169.1 (C-11), 157.6 (C-4), 154.1 (C-2′, C-6′), 150.2 (C-4′),

135.0 (C-9), 133.2 (C-6), 132.5 (C-7), 129.0 (C-10), 126.9

(C-5), 124.9 (C-8), 123.9 (C-3′, C-5′), 111.7 (C-3), 94.4

(C-15), 88.9 (C-12), 75.2 (C-14, C-16), 73.4 (C-13, C-17),

41.6 (C-11′), 40.4 (C-1″), 31.2 (C-20), 22.9 (C-19, C-21),

1

1577 (CN), 1455 (NH def), 1333, 1180 (SO₂). H NMR

(400.13 MHz, CDCl₃, 25 °C): δ 13.52 (s, 1H, OH), 8.78−

3

8.77 (d, J_{(H2′,H‑3′)/(H6′,H‑5′)}= 6 Hz, 2H, H-2′, H-6′), 7.84

18.5 (C-18) ppm.

(s, 1H, NH), 7.72−7.70 (dd, ³J_(H8,H7)= 8 Hz, ⁴J_(H8,H6)= 1 Hz,

Oxalato[2-methyl-N-(pyridin-4-ylmethyl)-4-hydroxy-2H-benzo-

[e][1,2]thiazine-3-carboxamide 1,1-dioxide](cym)ruthenium(II)

(3c). Silver oxalate (291 mg, 0.96 mmol) and [Ru(cym)Cl₂]₂(245

mg, 0.40 mmol) were added to 20 mL of deionized H₂O, and the

mixture was stirred for 24 h in the dark. The reaction mixture was

ﬁltered through Celite under suction to yield water-soluble, red

[Ru(cym)(oxalato)(H₂O)]. The water was removed, and the

compound was dissolved in dry methanol (15 mL). Compound 3

(276 mg, 0.80 mmol) was dissolved in DCM (5 mL) and added to

the methanol solution of the organoruthenium compound. The

3

4

1H, H-8), 7.60−7.58 (dd, J_(H5,H6)= 8 Hz, J_(H5,H7)= 1 Hz,

3

4

1H, H-5), 7.54−7.50 (td, J_{(H6,H5)/(H6,H7)}= 8 Hz, J_(H6,H8)= 1

3

4

Hz, 1H, H-6), 7.48−7.44 (td, J_{(H7,H8)/(H7,H6)}= 8 Hz, J_(H7,H5)

= 1 Hz, 1H, H-7), 7.11−7.09 (d,³J_{(H5′,H6′)/(H3′,H2′)}= 6 Hz, 2H,

H-3′, H-5′), 7.04−6.94 (m, 5H, H-4″, H-6′′, H-3′′, H-7′′,

H-5′′), 5.49−5.45 (m, 2H, H-13, H-17), 5.22−5.21 (m, 2H,

H-14, H-16), 4.70−4.24 (m, 4H, H-1′′, H-11′), 3.03−2.96

(m, 1H, H-20), 2.04 (s, 3H, H-18), 1.33−1.31 (m, 6H, H-19,

H-21) ppm. ¹³C{¹H} NMR (100.61 MHz, CDCl₃, 25 °C): δ

K

DOI: 10.1021/acs.organomet.8b00751

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Sulforhodamine B Cytotoxicity Assay. HCT116 and NCI-

H460 cells were supplied by ATCC, while SiHa cells were supplied by

Dr. David Cowan, Ontario Cancer Institute, Canada. Cells were

grown in αMEM (Life Technologies) supplemented with 5% fetal calf

serum (Moregate Biotech) at 37 °C in a humidiﬁed incubator with

5% CO₂. Cells were seeded at 750 (HCT116, NCI-H460) and 4000

(SiHa) cells/well in 96-well plates and left to settle for 24 h.

Compounds were added to the plates in a series of 3-fold dilutions in

0.5% DMSO at the highest concentration for 72 h before the assay

was terminated by addition of 10% trichloroacetic acid (Merck

Millipore) at 4 °C for 1 h. Cells were stained with 0.4%

sulforhodamine B (Sigma-Aldrich) in 1% acetic acid for 30 min in

the dark at room temperature and then washed with 1% acetic acid to

remove unbound dye. The stain was dissolved in unbuﬀered Tris base

(10 mM; Serva) for 30 min on a plate shaker in the dark and

quantitated on a BioTek EL808 microplate reader at an absorbance of

490 nm with a reference wavelength of 450 nm to determine the

percentage of cell-growth inhibition by determining the absorbance of

each sample relative to a negative (no inhibitor) and a no-growth

control (day 0).

IC₅₀values were calculated with SigmaPlot 12.5 (Systat Software

Inc.) using a three-parameter logistic sigmoidal dose−response curve

between the calculated growth inhibition and the compound

concentration. The presented IC₅₀values are the mean of at least 3

independent experiments, where 10 concentrations were tested in

duplicate for each compound.

Molecular Modeling. The compounds were docked to the crystal

structure of COX-2 (PDB ID 4M11, resolution 2.45 Å),²⁰which was

obtained from the Protein Data Bank (PDB).^42,43The program

Scigress Ultra version FJ 2.6⁴⁴was used to prepare the crystal

structure for docking. Hydrogen atoms were added, and the

cocrystallized meloxicam was removed as well as crystallographic

169.0 (C-11), 159.3 (C-4), 154.45 (C-2′, C-6′), 149.9 (C-4′),

137.5 (C-2″), 132.2 (C-7), 131.7 (C-9), 131.5 (C-6), 130.2

(C-4′′, C-6′′), 128.9 (C-10), 128.4 (C-5′′), 127.8 (C-3′′,

C-7′′), 126.2 (C-5), 123.7 (C-3′, C-5′), 123.3 (C-8), 107.8

(C-3), 103.8 (C-1), 97.3 (C-15), 83.0 (C-13, C-17), 82.2

(C-14, C-16), 56.9 (C-1′′), 41.5 (C-11′), 30.8 (C-18), 22.4

(C-20), 22.3 (C-19), 18.3 (C-21) ppm.

Dichlorido(4-hydroxy-N-(1H-indazol-6-yl)-2-methyl-2H-benzo-

[e][1,2]thiazine-3-carboxamide 1,1-dioxide)(cym)ruthenium(II)

(5a).

Compound 5a was synthesized by following the general

procedure using 5 (148 mg, 0.40 mmol) and [Ru(cym)Cl₂]₂

(123 mg, 0.20 mmol). Yield: 34% (92 mg, yellow powder). MS

(ESI⁺): m/z 641.0551 [M − Cl]⁺, calcd 641.0563. Anal.

Found: C, 44.01; H, 3.93; N, 7.31; S, 4.01. Calcd for

C₂₇H₂₈Cl₂N₄O₄RuS·CH₂Cl₂: C, 44.16; H, 3.97; N, 7.36; S,

4.21. FTIR (KBr, cm⁻¹): 3337, 3253 (NH), 3100−2750

(OH), 1617 (CO), 1585 (CN), 1443 (CH def), 1330,

1180 (SO₂). ¹H NMR (400.13 MHz, DMSO-d₆, 25 °C): 14.09

(s, 1H, OH), 13.07 (s, 1H, H-1′), 10.40 (s, 1H, NH), 8.10−

8.06 (m, 3H, H-3′, H-4′, H-7′), 7.97−7.89 (m, 3H, H-8, H-6,

3

H-7), 7.76 (d, J_(H5,H6)= 9 Hz,1H, H-5), 7.51−7.49

3

4

(dd, J_{(H5′,H4′)}= 9 Hz, J_{(H5′,H7′)}= 1 Hz,1H, H-5′), 5.83

3

(d, J_{(H14,H13)/(H16,H17)}= 6 Hz, 2H, H-14, H-16), 5.79

(d, J_{(H13,H14)/(H17,H16)}= 6 Hz, 2H, H-13, H-17), 2.91 (s, 3H,

3

H-1″), 2.89−2.82 (m, 1H, H-20), 2.10 (s, 3H, H-18), 1.21

3

(d, J_{(H19,H20)/(H21,H20)}= 7 Hz, 6H, H-19, H-21) ppm.

Dichlorido(2-benzyl-4-hydroxy-N-(1H-indazol-6-yl)-2H-benzo[e]-

[1,2]thiazine-3-carboxamide 1,1-dioxide)(cym)ruthenium(II) (6a).

Compound 6a was synthesized by following the general procedure

using 6 (134 mg, 0.30 mmol) and [Ru(cym)Cl₂]₂(123 mg, 0.20

mmol). Yield: 45% (113 mg, pale yellow powder). MS (ESI⁺): m/z

717.0869 [M − Cl]⁺, calcd 717.0876. Anal. Found: C, 52.93; H, 4.25;

N, 7.41; S, 4.31. Calcd for C₃₃H₃₂Cl₂N₄O₄RuS: C, 52.66; H, 4.29; N,

7.44; S, 4.26. FTIR (KBr, cm⁻¹): 3347, 3257 (NH), 1610 (CO),

1587 (CN), 1447 (CH def), 1333, 1160 (SO₂). ¹H NMR (400.13

MHz, CDCl₃, 25 °C): δ 13.49 (s, 1H, OH), 11.58 (s, 1H, H-1′), 8.39

(s, 1H, H-3′), 8.25 (s, 1H, NH), 7.85−7.79 (m, 2H, H-8, H-5), 7.64−

7.59 (m, 3H, H-7′, H-6, H-7), 7.36−7.33 (d, ³J_{(H4′,H5′)}= 9 Hz, 1H, H-

4′), 7.17−7.14 (m, 2H, H-4″, H-6′′), 7.07−7.05 (m, 3H, H-5′′, H-3′′,

H-7′′), 6.89−6.87 (dd, ³J_{(H5′,H4′)}= 9 Hz, ⁴J_{(H5′,H7′)}= 1 Hz, 1H, H-5′),

5.69−5.66 (m, 2H, H-14, H-16), 5.48−5.47 (m, 2H, H-13, H-17),

4.61−4.46 (m, 2H, H-1″), 3.07−3.0 (m, 1H, H-20), 2.21 (s, 3H, H-

18), 1.32−1.26 (m, 6H, H-19, H-21) ppm. ¹³C{¹H} NMR (100.61

MHz, CDCl₃, 25 °C): δ 167.2 (C-11), 160.0 (C-4), 141.1 (C-8′),

140.7 (C-3′), 136.9 (C-2″), 136.8 (C-6′), 132.8 (C-7), 132.2 (C-9),

132.1 (C-6), 130.2 (C-4′′, C-6′′), 128.8 (C-5′′), 128.7 (C-10), 128.4

(C-3′′, C-7′′), 126.3 (C-5), 123.9 (C-8), 120.6 (C-9′), 120.5 (C-4′),

116.3 (C-5′), 108.9 (C-3), 104.2 (C-15), 99.9 (C-7′), 98.7 (C-12),

83.6 (C-14, C-16), 82.6 (C-13, C-17), 57.8 (C-1′′), 31.5 (C-20), 22.6

(C-19, C-21), 19.2 (C-18) ppm.

water molecules. The Scigress software suite was also used to build

the inhibitors and the MM2⁴⁵force ﬁeld to optimize the structures.

The center of the binding pocket was defned as the position of

the hydroxyl oxygen atom in meloxicam (x = 67.830, y = 15.016,

z = 24.355)²⁵with 20 Å radius. Fifty docking runs were allowed for

each ligand with defult search eﬃciency (100%). The basic amino

acids ^L-lysine and L-arginine were defned as protonated. Furthermore,

L-aspartic and L-glutamic acids were assumed to be deprotonated. The

GoldScore (GS),³⁴ChemScore (CS),^46,47Chem Piecewise Linear

Potential (ChemPLP),⁴⁸and Astex Statistical Potential (ASP)⁴⁹

scoring functions were implemented to validate the predicted binding

modes and relative energies of the ligands using the GOLD v5.4

software suite. The parameter ﬁle for GS was augmented for Ru and

Os according to Sciortino et al.³⁵Meloxicam was redocked into the

binding pocket using the four scoring functions and correlated to the

cocrystallized conformation. The root-mean-square deviation between

the heavy atoms of the cocrystallized ligand and its docked

counterparts was as follows: ChemPLP, 1.03 Å; ASP, 1.62 Å; CS,

1.74 Å; GS, 1.20 Å.

Stability in DMSO and Aqueous Solution. For stability studies

in DMSO-d₆, 1a−d, 2a−d, and 3a−c (1−2 mg/mL) were dissolved

in DMSO-d₆and ¹H NMR spectra were recorded after 0.5, 6, 24, 48,

and 72 h at room temperature on a Bruker Avance AV 300

spectrometer at a 300.13 (¹H) MHz operating frequency. For

hydrolytic stability assaying, 1a−d, 2a−d, and 3a−c (1−2 mg/mL)

were dissolved in DMSO-d₆/D₂O (10/90) and ¹H NMR spectra were

measured after 0.5, 6, 24, 48, and 72 h at room temperature.

ASSOCIATED CONTENT

* Supporting Information

The Supporting Information is available free of charge on the ACS

Publications website at DOI: 10.1021/acs.organomet.8b00751.

■

S

NMR spectra, X-ray crystallographic data, and molecular

modeling data (PDF)

L

DOI: 10.1021/acs.organomet.8b00751

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(12) Luger, P.; Daneck, K.; Engel, W.; Trummlitz, G.; Wagner, K.

Structure and physicochemical properties of meloxicam, a new

NSAID. Eur. J. Pharm. Sci. 1996, 4, 175−187.

Accession Codes

CCDC 1872872−1872875 contain the supplementary crys-

tallographic data for this paper. These data can be obtained

free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by

emailing data_request@ccdc.cam.ac.uk, or by contacting The

Cambridge Crystallographic Data Centre, 12 Union Road,

Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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̆

(15) Paunescu, E.; McArthur, S.; Soudani, M.; Scopelliti, R.; Dyson,

AUTHOR INFORMATION

■

P. J. Nonsteroidal Anti-inflammatory−Organometallic Anticancer

Corresponding Authors

*M.H.: e-mail, m.hanif@auckland.ac.nz.

Compounds. Inorg. Chem. 2016, 55, 1788−1808.

(16) Raja, M. U.; Tauchman, J.; Therrien, B.; Suss-Fink, G.; Riedel,

T.; Dyson, P. J. Arene ruthenium and pentamethylcyclopentadienyl

rhodium and iridium complexes containing N,O-chelating ligands

derived from piroxicam: Synthesis, molecular structure and

cytotoxicity. Inorg. Chim. Acta 2014, 409, 479−483.

*C.G.H.: e-mail, c.hartinger@auckland.ac.nz; web, http://

hartinger.auckland.ac.nz; tel, +64 9 3737 599 ext. 83220.

ORCID

Muhammad Hanif: 0000-0002-2256-2317

Christian G. Hartinger: 0000-0001-9806-0893

Notes

(17) Aman, F.; Hanif, M.; Kubanik, M.; Ashraf, A.; Sohnel, T.;

Jamieson, S. M. F.; Siddiqui, W. A.; Hartinger, C. G. Anti-

Inflammatory Oxicams as Multi-donor Ligand Systems: pH- and

Solvent-Dependent Coordination Modes of Meloxicam and Pirox-

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(18) Lombardino, J. G.; Wiseman, E. H. Sudoxicam and Related N-

Heterocyclic Carboxamides of 4-Hydroxy-2H-1,2-Benzothiazine 1,1-

Dioxide - Potent Nonsteroidal Antiinflammatory Agents. J. Med.

Chem. 1972, 15, 848−849.

(19) Lombardino, J. G.; Wiseman, E. H.; Chiaini, J. Potent

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(20) Xu, S.; Hermanson, D. J.; Banerjee, S.; Ghebreselasie, K.;

Clayton, G. M.; Garavito, R. M.; Marnett, L. J. Oxicams Bind in a

Novel Mode to the Cyclooxygenase Active Site via a Two-water-

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(21) Lombardino, J. G.; Wiseman, E. H.; Mclamore, W. M.

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(22) Schapira, C. B.; Perillo, I. A.; Lamdan, S. 3-Oxo-1,2-

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(23) Babak, M. V.; Plazuk, D.; Meier, S. M.; Arabshahi, H. J.;

Reynisson, J.; Rychlik, B.; Blauz, A.; Szulc, K.; Hanif, M.; Strobl, S.;

Roller, A.; Keppler, B. K.; Hartinger, C. G. Half-Sandwich

Ruthenium(II) Biotin Conjugates as Biological Vectors to Cancer

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(24) Moon, S.; Hanif, M.; Kubanik, M.; Holtkamp, H.; Sohnel, T.;

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The authors declare no competing ﬁnancial interest.

ACKNOWLEDGMENTS

■

We thank the University of Auckland and the Higher

Education Commission of Pakistan for research project

NRPU 20-1582 and IRSIP (F.A. and A.A.), the Austrian

̈

Science Fund (Schrodinger fellowship to M.H.), and COST

CM1105 for ﬁnancial support. The authors are grateful to

Tanya Groutso for collecting the X-ray crystal data and Tony

Chen for ESI-MS analyses.

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Structural Modifications of the Antiinflammatory Oxicam Scaffold and Preparation of Anticancer Organometallic Compounds

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