Synthesis and antibacterial activity of novel C12 ethyl ketolides

Bioorganic & Medicinal Chemistry 14 (2006) 5592–5604

Synthesis and antibacterial activity of novel C₁₂ethyl ketolides

Matthew T. Burger,^*Christy Hiebert, Mehran Seid, Daniel T. Chu, Lynn Barker,

Mike Langhorne, Ribhi Shawar, Jolene Kidney, Manoj C. Desai and Jacob J. Plattner

Chiron Corporation, Biopharma Research, 4560 Horton Street, Emeryille, CA 94608-2916, USA

Received 27 March 2006; revised 12 April 2006; accepted 13 April 2006

Available online 11 May 2006

Abstract—A novel series of C₁₂ethyl erythromycin derivatives have been discovered which exhibit in vitro and in vivo potency

against key respiratory pathogens, including those resistant to erythromycin. The C₁₂modiﬁcation involves replacing the natural

C

₁₂methyl group in the erythromycin core with an ethyl group via chemical synthesis. From the C₁₂ethyl macrolide core, a series

of C₁₂ethyl ketolides were prepared and tested for antibacterial activity against a panel of relevant clinical isolates. Several com-

pounds were found to be potent against macrolide-sensitive and -resistant bacteria, whether resistance was due to ribosome meth-

ylation (erm) or eﬄux (mef). In particular, the C₁₂ethyl ketolides 4k,4s,4q,4m, and 4t showed a similar antimicrobial spectrum and

comparable activity to the commercial ketolide telithromycin. The in vivo eﬃcacy of several C₁₂ethyl ketolides was demonstrated in

a mouse infection model with Streptococcus pneumoniae as pathogen.

1. Introduction

macrolide-resistant pathogens by chemical manipulation

of erythromycin A. The novel cores we have targeted

diﬀer from erythromycin in the substitution of the natu-

ral C₁₂methyl group (C₂₁) by nonpolar groups other

than methyl. Nonpolar substitutions were targeted to

maintain the known overall hydrophobic nature of the

bottom face of the macrocycle.^8,9Since the erythromy-

cin core serves as the synthetic starting point for the sec-

ond and third generation macrolide antibiotics currently

in clinical use (clarithromycin, azithromycin, roxithro-

mycin, and the new ketolide telithromycin) as well as

many currently in preclinical research, such novel C₁₂

modiﬁed macrolide cores, could provide access to many

of the semi-synthetic derivatives that erythromycin has

been converted into, as well as new derivatives all

together. Recently, we reported on novel C₁₂vinyl keto-

lides which possess potent in vitro and in vivo antibacte-

rial properties against macrolide-resistant organisms.¹⁰

We report herein on the preparation of a novel C₁₂ethyl

macrolide core, the conversion of this core into the

ketolide class of macrolides, and on the in vitro and in -

vivo antibacterial properties of the resulting C₁₂ethyl

ketolides.¹¹

The macrolide antibiotic erythromycin A has been used

successfully clinically for over 40 years to treat upper

and lower respiratory tract infections. In recent decades,

to address shortcomings of erythromycin A,¹second-

generation macrolides (clarithromycin,²azithromycin,³

and roxithromycin⁴) have been developed and used clin-

ically. Resistance to the second generation macrolides

has emerged, with resistance most commonly being con-

ferred by ribosomal mutation (erm) or by eﬄux (mef)

mechanisms.⁵To overcome this resistance a third gener-

ation of macrolide antibiotics known as ketolides

[telithromycin⁶and cethromycin (ABT-773)⁷] has

recently been developed. In these molecules the C₃cladi-

nose sugar of erythromycin A is removed and replaced

with a C₃ketone group. Additionally, a heterocycle is

tethered to the macrolide core, introducing an addition-

al binding contact at the target ribosome (Fig. 1).

In our laboratories we have been conducting research

toward producing novel macrolide cores that exhibit po-

tent in vitro and in vivo antibacterial properties against

2. Chemistry

Keywords: Ketolide; Macrolide; Ketolide antibiotic; Macrolide antibi-

otic; Antiinfective; Antibiotic.

*

Synthetic modiﬁcations of erythromycin have been pur-

sued by numerous investigators attempting to prepare

Corresponding author. Tel.: +1 510 923 3537; fax: +1 510 923

3360; e-mail: matthew_burger@chiron.com

doi:10.1016/j.bmc.2006.04.032

M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

5593

Figure 1. Clinically utilized macrolides.

chemical derivatives with improved proﬁles and biolog-

ical activity. The addition of a single methyl group onto

the C₆hydroxyl of erythromycin A greatly improved the

acid stability and pharmacokinetic properties resulting

in the development of clarithromycin, which has found

widespread use clinically. Modiﬁcations involving the

C₁₁and C₁₂hydroxyl groups have been extensively

explored,¹²which in conjunction with modiﬁcations of

the C₃cladinose moiety, eventually yielded the recently

approved C₁₁, C₁₂cyclic carbamate, C₃oxo ketolide teli-

thromycin. Similar modiﬁcations in conjunction with a

C₆O-alkyl modiﬁcation led to the discovery of the

ketolide ABT-773. Additional modiﬁcations that have

been reported include 4⁰⁰carbamate macrolides,¹³keto-

lides containing nonnatural C₁₃substituents obtained

via alteration of the biosynthetic pathway of erythromy-

cin A¹⁴and C₆–C₁₁bridged ketolides.¹⁵

The C₁₂vinyl ketolides we have recently reported on

were obtained from chemical manipulation of the eryth-

romycin A macrolide; a key synthetic intermediate en

route to these C₁₂vinyl ketolides is the C₁₂–C₂₁exocy-

clic alkenyl macrolide 1, (Fig. 2). The double bond in

1 has proven to be a versatile intermediate for incorpo-

rating many novel groups at the C₁₂position of the mac-

rolide. In addition to dihydroxylation which ultimately

led to the C₁₂vinyl macrolide core, the alkenyl macro-

lide 1 can be ozonized yielding a C₁₂ketone¹⁶as well

as stereoselectively epoxidized yielding a C₁₂–C₂₁

epoxide. In all three chemical transformations, chemis-

Figure 2. Chemical manipulations of erythromycin derived C₁₂,C₂₁alkene 1.

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M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

try performed at the C₁₂–C₂₁bond yields products con-

taining a handle upon which further chemistry can be

performed to introduce unnatural C₁₂substituents into

the erythromycin core.

methyl group was achieved by opening the epoxide with

dimethylcuprate. Upon treating the resulting C₁₂ethyl

macrolide with pyridinium para-toluene sulfonate at

68 ꢁC the cyclic acetonide was deprotected, and the C₉

hydroxyl of the resulting triol was oxidized selectively

by Dess–Martin periodinane¹⁸at ꢀ10 ꢁC yielding

macrolide diol 2a.

The synthetic route for accessing C₁₂ethyl modiﬁed

macrolides and ketolides via the epoxidation product

of macrolide 1 is outlined in Scheme 1. The synthetic

details are as follows. Starting from clarithromycin,

the protected C₁₂–C₂₁alkenyl macrolide 1 was prepared

in four steps as previously described.¹⁰Treatment of

macrolide 1 with meta-chloroperoxybenzoic acid results

in epoxidation of the C₁₂–C₂₁alkene as well as oxidation

of the tertiary amine. We were unable to avoid the unde-

sired nitrogen oxidation. Initially, we found that the

N-oxide could be conveniently reduced under mild

conditions by treating with isopropanol and catalytic

tetrapropylperruthenate in dichloromethane in the pres-

ence molecular sieves.¹⁷Eventually, we found on scaleup

that the N-oxide could be eﬃciently reduced by treating

with sodium thiosulfate in a tetrahydrofuran–water

solution to yield the desired C₁₂–C₂₁epoxide. The epox-

idation is stereoselective and occurs from the beta face

of the macrocycle, vide infra. Introduction of the C₂₁

The structural assignment for the newly created C₁₂

stereocenter was initially supported by comparing the

NMR spectral data of macrolide 2a with the bisbenzoy-

lated clarithromycin 2b,¹⁰which diﬀer only by having a

methyl or ethyl at the C₁₂position. Further support for

this structural assignment came from preparing the

epimeric C₁₂ethyl C₉, C₁₁acetonide macrolide core

whose X-ray structure was solved.¹⁹

The C₁₂ethyl macrolide 2a was converted to a series of

C₁₂ethyl ketolides as follows. Mesylation of the C₁₁

hydroxyl of macrolide 2a was achieved by treating with

mesyl chloride in pyridine. Analysis by ¹³C NMR sug-

gests that the C₁₁mesylated 2a exists predominantly as

a C₁₂OH C₉cyclic hemiketal; a C₉ketone resonance

above 200 ppm is lacking, but a hemiketal resonance

Scheme 1. Synthesis of C₁₂ethyl ketolides. Synthesis of C₁₂ethyl ketolides. Reagents and conditions: (i)–(iv)ref10. (v) a—MCPBA, CH₂Cl₂b—

NaHSO₃, THF/H₂O, 83%; (vi) Me₂CuLi, Et₂O, ꢀ78 to 0 ꢁC, 80%; (vii) PPTS, 68 ꢁC, MeCN–H₂O (2:1) 55%; (viii) Dess–Martin periodinane,

CH₂Cl₂, ꢀ10 ꢁC, 67%; (ix) MsCl, pyridine, 69%; (x) a—DBU, acetone, 4 h, rt; b–66 ꢁC, 12 h, 98%; (xi) HCl, H₂O, MeOH, 40 ꢁC, 82%; (xii) Dess–

Martin periodinane, CH₂Cl₂, 94%; (xiii) CDI, THF, NaH, 0 ꢁC; (xiv) a—amine, MeCN, H₂O, 60 ꢁC, 14 h; b—MeOH, 65 ꢁC, 12 h, 20–45%.

M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

5595

distinct from the anomeric sugars is evident at

108.5 ppm. The C₁₁mesylated macrolide was then con-

verted to the corresponding enone by treatment with

DBU in acetone ﬁrst at room temperature and then at

reﬂux. This transformation we believe proceeds ﬁrst by

the C₁₂hydroxyl displacement of the C₁₁mesylate yield-

ing an intermediate C₁₁–C₁₂epoxide that upon heating

in the presence of DBU allows for C₁₀deprotonation

and elimination/opening of the epoxide to yield the

desired enone. A single enone isomer was produced in

compound 4k, which has the same alkyl tethered group

oﬀ the cyclic carbamate as telithromycin, the peaks for

the macrocycle core excluding resonances for the C₁₂

methyl or ethyl group are practically identical.²¹

Additionally, all ketolides exhibited the C₁₁H singlet

at ca. 3.7 ppm characteristic of C₁₁–C₁₂carbamates with

natural C₁₀conﬁguration.^12a

3. Results and discussion

3.1. In vitro evaluation

1

this reaction as judged by H NMR. Acidic hydrolysis

removes the cladinose group, which was oxidized when

subjected to Dess–Martin periodinane yielding the C₁₂

ethyl macrolide enone 3. Deprotonation of the C₁₂

hydroxyl of enone 3 with sodium hydride in the presence

of carbonyldiimidazole yielded the corresponding C₁₂

imidazoyl carbamate which upon reaction with an

excess of side chain amine,²⁰and deprotection of the

desosamine benzoate by heating in methanol yielded

the C₁₂ethyl ketolides 4. Typical unoptimized yields of

ﬁnal ketolide 4 from enone 3 were of the order of 20–

45%. The C₁₂ethyl ketolides (4a–t) prepared and report-

ed are illustrated in Figure 3.

The C₁₂ethyl ketolides prepared were assayed in a

primary panel against a number of strains of Staphy-

lococcus aureus, Staphylococcus epidermidis, Enterococ-

cus faecalis, Streptococcus pyogenes, S. pneumoniae

and Haemophilus inﬂuenzae. Included among the

strains of S. pneumoniae were erythromycin-resistant

strains containing mef and erm genes. Telithromycin

and clarithromycin were used as comparators in all as-

says. The in vitro antibacterial activity is reported as

the minimum inhibitory concentration (MIC) in

micrograms per milliliter as determined by the broth

microdilution method.²²The MIC data in Tables 1

and 2 indicate that C₁₂ethyl ketolides in general

The structural assignments of the ﬁnal ketolides were

supported by NMR comparison to telithromycin. For

Figure 3. Structures of C₁₂ethyl ketolides.

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M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

Table 1. In vitro properties [MIC (lg/mL)] of C₁₂ethyl ketolides

Strains

4a

4b

4c

4d

4e

4f

4g

4h

4i

4j

teli

0.1–0.2

>50

0.1–0.2

clari

0.4–0.78

>50

0.2–0.4

S. aureus_29213

S. aureus_33591

0.2

>50

0.4

>50

0.4

>50

0.2

>50

0.2

0.1

>50

0.1

0.78

>50

0.4

1.56

>50

1.56

>50

0.78

0.2

>50

0.2

0.78

>50

0.78

S. epidermidis_14990

S. epidermidis f50654

E. faecalis _29212

E. faecalis_bc11148–2

S. pyogenes_8668

0.2

0.1

0.4

0.2

0.1

0.2

0.1

60.05

25

0.78

0.1

0.78

0.2

1.56

0.1

0.2

0.1

0.78

0.2

0.1–0.2

60.05–0.1

0.4

0.2–0.4

0.78–1.56

1.56

6.25

0.78

12.5

0.1

3.13

0.1

1.56

0.1

50

3.13

>50

60.05 60.05 60.05 60.05 60.05

60.05 60.05 60.05

60.05

>50

S. pneumo_49619

60.05 60.05 60.05 60.05 60.05 60.05 60.05 60.05 60.05 60.05 60.05

S. pneumo_297–749

S. pneumo_280–962

S. pneumo_Erm 6849

S. pneumo_Mef 5654

S. pneumo_Mef S 3427

H. inﬂuenzae_49247

H. inﬂuenzae_2762

0.78

0.4

0.2

0.4

0.4 >50

3.13

0.4

3.13

0.78

0.2

0.78

0.2

0.4

3.13

0.78

0.1

0.1–0.4

0.78

0.2

1.56

0.2

0.78

0.1

0.4

0.4–0.78

0.1–0.2

6.25–12.5

0.1

3.13

60.05 60.05

60.05

3.13

3.13–6.25

6.25–12.5

0.78–3.13

3.13

6.25

1.56

6.25

0.78

3.13

0.2

3.13

6.25

1.56

3.13

1.56

3.13

1.56

3.13–6.25

0.4–1.56

—

Table 2. In vitro properties [MIC (lg/mL)] of C₁₂ethyl ketolides

Strains

4k

4l

4m

0.4

>50

0.2

4n

4o

4p

4q

4r

4s

4t

S. aureus_29213

S. aureus_33591

0.4

>50

0.2

0.4

>50

0.2

0.1

>50

0.1

0.2

>50

0.4

>50

0.2

>50

0.2

0.4

>50

0.2

>50

0.2

0.78

>50

0.4

S. epidermidis_14990

S. epidermidis f50654

E. faecalis _29212

E. faecalis_bc11148–2

S. pyogenes_8668

0.4

0.1

3.13

0.2

0.1

0.4

0.2

0.1

0.2

0.1

0.2

0.1

0.4

0.1

60.05

1.56

0.4

3.13

0.78

60.05

0.4

3.13

60.05

0.78

1.56

60.05

0.2

0.78

60.05

0.78

0.4

0.78

0.4

60.05

0.4

60.05

1.56

60.05

6.25

60.05

>50

60.05

0.2

60.05

0.78

0.1

S. pneumo_49619

S. pneumo_297–749

S. pneumo_280–962

S. pneumo_Erm 6849

S. pneumo_Mef 5654

S. pneumo_Mef S 3427

H. inﬂuenzae_49247

H. inﬂuenzae_2762

0.4

0.1

0.78

0.2

0.4

0.1

0.78

0.2

0.78

0.2

0.4

0.1

0.78

0.2

0.4

60.05

3.13

0.1

3.13

6.25

0.4

6.25

1.56

3.13

0.78

6.25

0.78

6.25

1.56

3.13

0.78

6.25

1.56

—

possess potent antibacterial activity against a range of

pathogens. The spectrum is similar to that of

telithromycin, and like telithromycin, the C₁₂ethyl

ketolides are potent against the mef and erm gene con-

taining S. pneumoniae strains that clarithromycin is

not active against. The overall activity spectrum of

the C₁₂ethyl ketolides can be attenuated by the nat-

ure of the heterocycle tethered to the C₁₁, C₁₂carba-

mate. All of the heterocyclic moieties on the C₁₂ethyl

ketolides reported here are tethered to the C₁₁at-

tached nitrogen via a four-atom spacer. The heterocy-

clic moieties can be divided into 6,6 and 5,6

heteroaromatic fused bicycles or 5,6 or 6,6 unfused

biaryl systems.

are ﬁve- to tenfold less potent than telithromycin

against S. aureus, S. epidermidis, E. faecalis, and the

erm gene containing S. pneumoniae strain. When the

4-quinolyl group is tethered via a butyl group as in

C₁₂ethyl ketolide 4i the activity against S. aureus,

S. epidermidis, and the erm gene containing S. pneu-

moniae strain is comparable to that of telithroycin

but the activity against E. faecalis is 100-fold less that

of than telithromycin. A slight but less pronounced

improvement in potency is evident switching to the

butyl tethered 2-quinolyl in C₁₂ethyl ketolide 4f rela-

tive to 4g. For azabenzimidazole tethered C₁₂ethyl

ketolides 4a,4c, and 4d the activity is comparable to

that of telithromycin for all strains, being only two-

to fourfold less potent against S. aureus, S. epidermi-

dis, and the erm gene containing S. pneumoniae strain.

The incorporation of the gem dimethyl groups into

azabenzimidazole tethered 4d seems to improve the

activity against E. faecalis relative to azabenzimidazole

tethered 4b. The azaindole tethered C₁₂ethyl ketolide

4e is equipotent to telithromycin in all strains tested,

except for E. faecalis and the erm gene containing S.

pneumoniae strain where it is at least 50-fold less

potent.

A general trend that appears for the C₁₂ethyl

ketolides with tethered heteroaromatic fused bicycles

is potency similar to telithromycin versus S. aureus,

S. pyogenes, susceptible S. pneumoniae,mef gene

containing S. pneumoniae strains and H. inﬂuenzae,

and weaker potency relative to telithromycin against

S. epidermidis, E. faecalis, and the erm gene contain-

ing S. pneumoniae strain. C₁₂ethyl ketolides with teth-

ered quinolines in particular have weakened activity

regardless of the nature of the four-atom tether. With

an N-methyl group inserted in the four-atom tether,

quinolyl tethered C₁₂ethyl ketolides 4g,4h, and 4j

A general trend that appears for the C₁₂ethyl keto-

lides with tethered 5,6 or 6,6 unfused biaryl systems

M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

5597

from Table 2 is potency similar to telithromycin ver-

sus all pathogens in the primary panel. The C₁₂ethyl

ketolide 4k, with the same tethered imidazoyl pyridyl

bicycle as telithromycin, is essentially equipotent with

telithromycin. Substitution on the pyridyl group of

this bicycle with methyl 4l, ﬂuoro 4m, methoxy 4o

and chloro 4n is tolerated, albeit with a four- to eight-

fold decrease in potency against E. faecalis. The C₁₂

ethyl ketolide 4r containing a tethered 4-(4⁰-pyridyl)

imidazolyl group is tenfold less potent against

E. faecalis and 100-fold less potent against the erm

gene containing S. pneumoniae strain than both the

4-(3⁰-pyridyl) imidazolyl containing 4k and telithromy-

cin. Replacing the pyridyl group of the tethered biaryl

moiety with phenyl, pyrimidyl, and pyrazinyl groups is

tolerated as C₁₂ethyl ketolides 4s,4p, and 4q are equi-

potent with telithromycin, with the exclusion of slight-

ly elevated (2-fold) S. aureus and E. faecalis MIC

values. Compound 4t, in which a 6,6 bipyridyl system

is connected to the macrolide core via a four-atom

aminomethyl containing tether, exhibits a balanced

antibacterial proﬁle also comparable to that of

telithromycin.

lides has been demonstrated within the range of

telithromycin.

5. Experimental

5.1. Antibiotics

All new synthetic compounds tested were dissolved in

95% ethanol and further diluted with sterile deionized

water as were telithromycin (internal synthesis), erythro-

mycin (Sigma, St. Louis, MO), and clarithromycin

(internal synthesis). Drug stocks were stored at

ꢀ80 ꢁC, protected from light.

5.2. Bacterial strains

Bacterial strains were cultivated from ꢀ80 ꢁC frozen

stocks by two consecutive overnight passages at 35 ꢁC

on 5% blood agar (Remel, Lenexa, KS). Chocolate agar

(Remel) was used for H. inﬂuenzae strains H. inﬂuenzae,

S. pneumoniae and S. pyogenes were incubated in 5–10%

CO₂.

3.2. In vivo evaluation

Type/quality control strains were received from the

American Type Culture Collection (ATCC; Rockville,

MD). Clinical isolates collected in 2001 of S. pneumo-

niae, H. inﬂuenzae, and S. aureus were received from

Focus Technologies, Inc., VA, and The Jones Group,

JMI Laboratories, IA. Other isolates were supplied by

Childrens’ Hospital Medical Center, Seattle, WA; Har-

borview Medical Center, Seattle, WA; University Health

Systems, San Antonio, TX; and Henry Ford Hospital,

Detroit, MI.

The in vivo properties of several C₁₂ethyl ketolides were

assessed in a mouse infection model with S. pneumoniae

as the pathogen. Compounds were administered via the

oral route and telithromycin was used as the control.

The ED₅₀values determined for compounds 4d,4l,4m,

and 4t are listed in Table 3.

Telithromycin was always the most potent compound in

these experiments. Compounds 4t,4l, and 4m were two

to threefold less potent, while 4d was ﬁvefold less potent

than telithromycin.

5.3. Susceptibility testing

The in vitro antibacterial activity is reported as the min-

imum inhibitory concentration (MIC) in micrograms

per milliliters as determined by the broth microdilution

method in accordance with the Clinical Laboratory

Standards Institute (CLSI, formerly NCCLS) guide-

lines.²²In brief, organism suspensions were adjusted to

a 0.5 McFarland standard to yield a ﬁnal inoculum

between 3· 10⁵and 5· 10⁵CFU/mL. The inoculum

was made in sterile, cation adjusted Mueller–Hinton

Broth (CAMHB) for all but S. pneumoniae (CAMHB

with 3% lysed horse blood) and H. inﬂuenzae (haemoph-

ilus test medium). All inoculated microdilution trays

were incubated in ambient air at 35 ꢁC for 18–24 h ex-

cept for S. pneumoniae and H. inﬂuenzae (both at 5–

10% CO₂). Following appropriate incubation, the MIC

was deﬁned as the lowest concentration of the drug that

prevented visible growth. Performance of the antibiotics

on the test trays was monitored by the use of ATCC

quality control strains with a deﬁned MIC spectrum,

in accordance with CLSI guidelines.²³

4. Conclusion

The replacement of the C₁₂methyl group of erythromy-

cin with a C₁₂ethyl group and the conversion of the

resulting macrolide core into the ketolide class of anti-

bacterials have been described. The C₁₂ethyl group

was installed by a methylcuprate opening of a C₁₂–C₂₁

macrolide epoxide. The C₁₂ethyl ketolides prepared

possess potent antibacterial properties in vitro against

key respiratory pathogens including those resistant to

erythromycin, with several of the compounds reported

exhibiting properties in the range of telithromycin. In

a mouse infection model with S. pneumonia as the path-

ogen in vivo eﬃcacy with several of the C₁₂ethyl keto-

Table 3. In vivo eﬃcacies of C₁₂ethyl ketolides and telithromycin in

mice

Compound

ED₅₀(mg/kg)

Telithromycin

4t

3.7

7.0

5.4. In Vivo therapeutic eﬃcacy

4l

9.6

8.0

Test compounds were prepared using sterile saline as the

diluent. The pH was adjusted using 1 N acetic acid to a

range of pH 5.0–5.6. A single 100 times LD₅₀dose of

4m

4d

18.9

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M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

S. pneumoniae PGO #4716 was injected by the intraperi-

toneal route (500 lL) to CF-1 mice. Groups of ﬁve fe-

male CF-1 mice were treated via oral gavage over a

ﬁve-dose range (1, 5, 10, 25, and 50 mg/kg) with test

compounds at 1 and 5 h post-infection and observed

for the following ﬁve days. All untreated mice suc-

cumbed to the infection and died within 24 h. Eﬃcacy,

reported as ED₅₀, is deﬁned as the eﬃcacious dose which

protects 50% of the infected mice from mortality.

1H), 4.80–4.85 (m, 2H), 4.48–4.56 (m, 1H), 4.13 (d,

J = 3.3, 1H), 4.08 (d, J = 1.8, 1H), 3.90–4.00 (m, 1H),

3.77 (d, J = 6.3, 1H), 3.56 (s, 3H), 3.29 (s, 3H), 3.14–

3.20 (m, 1H), 2.95–3.03 (m, 2H), 2.67 (d, J = 5.4, 1H),

2.53–2.57 (m, 1H), 2.49 (d, J = 15.0, 1H), 2.33 (s, 6H),

2.03–2.10 (m, 3H), 1.41–1.77 (m, 7H), 1.30 (s, 3H),

1.27 (s, 3H), 1.22 (d, J = 6.3, 3H), 1.21 (s, 3H), 1.17

(d, J = 6.3, 3H), 1.15 (d, J = 6.9, 3H), 1.00 (d, J = 6.6,

3H), 0.97 (s, 3H), 0.96 (d, J = 6.3, 3H), 0.84 (t, J = 7.5,

3H), 0.73 (d, J = 7.5, 3H). ¹³C NMR (CDCl₃) d 175.5,

166.2, 165.3, 133.3, 132.5, 130.9, 129.9, 129.6, 128.3,

128.1, 100.8, 100.3, 95.2, 79.9, 79.2, 79.1, 78.2, 76.9,

73.1, 72.3, 67.6, 66.8, 63.8, 63.4, 57.9, 49.8, 49.6, 46.0,

44.1, 43.5, 40.9, 35.1, 33.4, 31.7, 31.4, 26.9, 23.6, 21.3,

21.1, 20.4, 18.5, 16.5, 13.5, 11.1, 10.0. HPLC:

t_R= 25.18 min. HRMS (ESI⁺) m/z [M+H]⁺calcd for

C₅₅H₈₁NO₁₅: 996.5678. Found: 996.5676.

5.5. General

All reagents used were of commercial quality and all

reactions were carried out using commercially available

1

anhydrous solvents from Aldrich, Acros or VWR. H

(300 MHz) and ¹³C (75 MHz) NMR spectra were

recorded on either a Varian Unity 300 or Varian Mercu-

ry 300 spectrometer, using CDCl₃or CD₃OD solutions.

Chemical shifts (d) are reported in parts per million

(ppm) referenced at 7.26 ppm (CDCl₃) or 3.30 (CD₃OD)

for ¹H NMR and 77.0 ppm (CDCl₃) for ¹³C NMR.

Coupling constants (J) are given in hertz, with the

abbreviations s, d, dd, t, q, and m referring to singlet,

doublet, doublet of doublets, triplet, quartet, and multi-

plet. Elemental analyses were performed at Desert Ana-

lytics (Tuscon, AZ). Mass spectral data were recorded

on either a Hewlett Packard 1100 MSD {50 V, 30 ꢁC,

electrospray ionization conditions (ESI+)} or Micro-

mass ZQ LC/MS {50 V, 30 ꢁC, electrospray ionization

conditions (ESI+)} systems. High-resolution mass spec-

tra were obtained on a Q-STAR quadrupole-TOF-MS

(Applied Biosystems Inc.) in ESI+ mode. HPLC reten-

tion times are reported using a Column Engineering

Reliasil BDX C18, 5 lM, 4.6 · 100 mm column, where

elution takes place with a 40 min gradient at 4 mL/min

of 2–98% solvent A, where solvent A is MeCN with

0.1% TFA and solvent B is H₂O with 0.1%TFA.

Stage vi. An oven-dried 500 mL two-necked ﬂask

equipped with a 14/20 side arm connection to the man-

ifold was cooled under Ar. An internal thermometer was

inserted and CuBr dimethyl sulﬁde complex (28.4 g,

138.6 mmol) was added. The system was evacuated un-

der high vacuum and purged with Ar three times. Dieth-

yl ether (200 mL) was added and the heterogeneous

solution was cooled in a ꢀ78 ꢁC bath. Methyl lithium

(180.0 mL, 277.1 mmol) was added via syringe with

the internal temperature 6 ꢀ60 ꢁC. The solution was

held in the ꢀ78 ꢁC bath for 10 min after the addition

and then the bath was removed. Upon warming to

ꢀ20 ꢁC, a homogeneous solution resulted. The solution

was then held at ꢀ20 ꢁC. An oven-dried 1000 mL three-

necked ﬂask equipped with a 14/20 side arm connection

to the manifold and an overhead mechanical stirrer was

cooled under Ar. C₁₂, C₂₁epoxide (27.6 g, 27.7 mmol)

was added and the system was evacuated under high

vacuum and purged with Ar three times. Diethyl ether

was added (400 mL), the solution was cooled to

at 0 ꢁC, and the epoxide was stirred (the solution is a

heterogeneous slurry). The cuprate solution was then

cannulated into the slurry of epoxide with the internal

temperature of the epoxide solution staying 60 ꢁC.

The resultant light yellow heterogeneous solution was

held at 0–5 ꢁC for 12 h with mechanical stirring.

NH₄Cl_(satd)(200 mL) was added to stop the reaction,

with the internal temperature 610 ꢁC. The reaction mix-

ture was diluted with ethyl acetate (2 L) and washed

with NH₄Cl_(satd)(3· 1 L), NaCl_(satd)(1 L), dried over

MgSO₄, ﬁltered, concentrated, and dried in vauo yield-

ing the crude C₁₂ethyl, hydroxy macrolide (26.87 g,

ca. 80% pure by LC) as a white solid. An analytical

sample was obtained by puriﬁcation through SiO₂chro-

matography (20–25% acetone/hexanes with 0.1% trieth-

ylamine). MS (ESI): 1012.9 (MH⁺). ¹H NMR (CDCl₃) d

8.00–8.04 (m, 4H), 7.52–7.63 (m, 2H), 7.40–7.49 (m,

4H), 5.32 (dd, J = 10.2, 3.0, 1H), 5.15 (br s, 1H), 5.05

(d, J = 7.5, 1H), 4.93 (d, J = 10.2, 1H), 4.8 (br s, 1H),

4.48–4.56 (m, 1H), 4.16 (s, 1H), 4.02–4.12 (m, 1H),

3.85 (d, 5.7, 1H), 3.78 (br s, 1H), 3.59 (s, 3H), 3.36 (t,

J = 3.9, 1H), 3.33 (s, 3H), 2.98–3.08 (m, 1H), 2.48–2.55

(m, 2H), 2.34 (s, 6H), 2.12–2.22 (m, 1H), 1.44–1.96 (m,

10H), 1.38 (s, 3H), 1.32 (s, 3H), 1.21 (s, 3H), 1.20 (s,

3H), 1.16 (d, J = 7.2, 3H), 1.14 (d, J = 6.3, 3H), 1.07

5.6. Compound 2a

Stage v. To 2⁰,4⁰⁰OBz, C₉, C₁₁-dimethylketal, C_12,21al-

kene macrolide 1¹⁰(20.0 g, 20.4 mmol) in dichlorometh-

ane (204 mL) at 0 ꢁC was added 3-chloroperoxybenzoic

acid (17.6 g, 45.5 mmol). After stirring for 30 min at

0 ꢁC, the ice bath was removed and the solution was stir-

red at rt for 21 h. Cyclohexene (10 mL, 100 mmol) was

added and the solution was stirred for an additional

15 h. The dichloromethane was removed by rotary evap-

oration (not to dryness). The solution was diluted with

ethyl acetate (400 mL) and washed with NaHCO_3(satd)

(7· 125 mL) and NaCl_(satd)(1· 125 mL), dried over

MgSO₄, ﬁltered, concentrated, and dried in vacuo yield-

ing the product epoxide, N-oxide as a white solid, 20.5 g

(99% yield). This material was dissolved in 2:1 THF/

H₂O (100 mL) and to this solution was added 2 M NaH-

SO_3(aq)(100 mL). The solution was vigorously stirred

for 30 min, diluted with ethyl acetate (400 L), and was

washed with NaHCO_3(satd)(4· 125 mL), and NaCl_(satd)

(125 ml), dried over MgSO₄, concentrated, and dried

in vacuo yielding the product epoxide (16.75 g, 83%)

as a white solid. MS (ESI): 996.8 (MH⁺). ¹H NMR

(CDCl₃) d 8.00–8.04 (m, 4H), 7.20–7.62 (m, 6H), 5.20–

5.30 (m, 1H), 4.97 (d, J = 8.1, 1H), 4.93 (d, J = 9.9,

M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

5599

(d, J = 6.6, 3H), 0.92–1.03 (m, 9H), 0.83 (t, J = 7.5, 3H),

0.75 (d, J = 7.5, 3H). ¹³C NMR (CDCl₃) d 176.3, 166.3,

165.2, 133.3, 132.4, 130.9, 129.9, 129.6, 129.5, 128.3,

128.1, 100.6, 99.9, 95.2, 80.3, 79.6, 79.1, 78.9, 77.3,

76.2, 73.2, 72.4, 67.5, 63.8, 63.4, 49.4, 44.6, 43.8, 40.9,

35.1, 32.4, 32.3, 31.8, 30.8, 28.0, 26.0, 24.1, 23.7, 21.4,

21.1, 20.1, 18.6, 17.4, 16.9, 14.1, 11.5, 10.2. HPLC:

t_R= 27.47 min. HRMS (ESI⁺) m/z [M+H]⁺calcd for

C₅₆H₈₅NO₁₅: 1012.5991. Found: 1012.6016.

3H), 3.10 (s, 1H), 3.02 (s, 3H), 2.88–3.01 (m, 2H),

2.76–2.81 (m, 1H), 2.54–2.62 (m, 1H), 2.47 (d,

J = 15.0, 1H), 2.32 (s, 6H), 1.40–1.98 (m, 10H), 1.38

(s, 3H), 1.22 (s, 3H), 1.19–1.21 (m, 6H), 1.13 (d,

J = 6.9, 3H), 1.11 (d, J = 6.9, 3H), 0.93 (d, J = 6.3,

3H), 0.88 (t, J = 7.8, 3H), 0.81 (t, J = 7.5, 3H), 0.70 (d,

J = 7.8, 3H). ¹³C NMR (CDCl₃) d 219.5, 175.4, 165.9,

165.3, 133.2, 132.4, 130.8, 129.8, 129.5, 129.4, 128.2,

128.0, 100.2, 95.7, 80.5, 78.9, 78.3, 77.9, 77.7, 75.7,

73.5, 72.9, 72.5, 68.0, 67.5, 63.7, 63.5, 50.6, 49.7, 45.1,

44.9, 41.0, 38.6, 38.3, 37.7, 35.4, 31.8, 25.0, 21.9, 21.4,

20.0, 18.6, 18.1, 16.1, 12.5, 11.0, 9.5, 9.1. HPLC:

t_R= 23.56 min. HRMS (ESI⁺) m/z [M+H]⁺calcd for

C₅₃H₇₉NO₁₅: 970.5522. Found: 970.5521.

Stage vii. To crude C₉, C₁₁ketal, C₁₂ethyl, C₁₂hydroxy

macrolide (6.65 g, 6.57 mmol) in 2:1 acetonitrile/water

(130 mL) was added pyridinium para-toluene sulfonate

(8.25 g, 32.9 mmol). The solution was heated in a

70 ꢁC oil bath for 48 h. Upon cooling, the reaction

was diluted with ethyl acetate (1.5 L) and washed with

NaHCO_3(satd)(2· 300 mL), NaCl_(satd)(300 mL), dried

over MgSO₄, ﬁltered, and concentrated. Puriﬁcation

by ﬂash chromatography (15% acetone/hexanes with

0.1% triethylamine) yielded the C₁₂ethyl, C₉, C₁₁, C₁₂

triol macrolide (3.52 g, 55% yield) as a white solid. MS

(ESI): 972.8 (MH⁺). ¹H NMR (CDCl₃) d 7.98–8.04

(m, 4H), 7.42–7.64 (m, 6H), 5.76 (d, J = 9.6, 1H), 5.18

(dd, J = 11.4, 1.8, 1H), 5.15 (m, 1H), 5.09 (d, J = 4.8,

1H), 4.95 (d, J = 7.5, 1H), 4.94 (d, J = 9.6, 1H), 4.42–

4.54 (m, 1H), 4.48 (s, 1H), 3.91 (br s, 1H), 3.79 ( d,

J = 6.0, 1H), 3.72 (d, J = 9.9, 1H), 3.52 (s, 3H), 3.33

(s, 3H), 3.27–3.33 (m, 1H), 3.06 (s, 1H), 2.79–2.90 (m,

1H), 2.48 (d, J = 15.0, 1H), 2.42 (s, 6H), 2.06–2.16 (m,

1H), 1.72–1.98 (m, 6H), 1.40–1.60 (m, 7H), 1.35 (s,

3H), 1.19–1.22 (m, 9H), 1.10 (d, J = 6.9, 3H), 0.94 (d,

J = 7.2, 3H), 0.93 (d, J = 5.7, 3H), 0.75–0.82 (m, 6H),

0.66 (d, J = 7.2, 3H). ¹³C NMR (CDCl₃) d 174.9,

166.2, 165.3, 133.5, 132.8, 130.4, 129.6, 128.5, 128.3,

99.7, 96.0, 82.6, 80.2, 78.8, 78.3, 78.0, 76.2, 72.9, 72.0,

70.6, 67.3, 63.6, 50.6, 49.5, 45.1, 38.1, 35.2, 34.5, 34.3,

32.3, 31.9, 25.3, 22.3, 21.3, 21.2, 20.1, 18.6, 17.2, 16.3,

11.0, 9.8, 8.8. HPLC: t_R= 22.84 min. HRMS (ESI⁺)

m/z [M+H]⁺calcd for C₅₃H₈₁NO₁₅: 972.5678. Found:

972.5687.

5.7. Compound 3

Stage ix. To C₁₂ethyl, C₉keto, C₁₁, C₁₂diol macrolide

(3.75 g, 3.87 mmol) in pyridine (18 mL) at 0 ꢁC was add-

ed methanesulfonyl chloride (1.5 mL, 19.3 mmol) via

syringe over 5 min. The solution was stirred for 18 h

as the solution warmed to rt. Upon concentrating and

drying in vacuo, the material was taken up in ethyl ace-

tate (750 mL) and washed with NaHCO_3(satd)

(2· 250 mL). The combined aqueous layers were back

extracted with ethyl acetate (500 mL) and the combined

organic layers were then washed with NaCl_(satd)

(100 mL), dried over MgSO₄, ﬁltered, and concentrated.

Puriﬁcation by ﬂash chromatography (20–25% acetone/

hexanes with 0.1% triethylamine) yielded the C₁₂ethyl,

C₉keto, C₁₁OMs, C₁₂hydroxy macrolide (2.81 g,

69% yield) as a white solid. MS (ESI): 1048.8 (MH⁺).

¹H NMR (CDCl₃) d 8.02–8.14 (m, 4H), 7.54–7.64 (m,

2H), 7.42–7.51 (m, 4H), 5.20 (dd, J = 10.5, 2.7, 1H),

5.03(dd, J = 10.8, 7.8, 1H), 4.90–4.96 (m, 2H), 4.71 (d,

J = 7.5, 1H), 4.60 (d, J = 1.8, 1H), 4.54–4.60 (m, 1H),

3.98 (d, J = 9.9, 1H), 3.74 (d, J = 6.3, 1H), 3.46–3.54

(m, 1H), 3.39 (s, 3H), 3.22–3.28 (m, 1H), 3.22 (s, 3H),

2.82–2.92 (m, 1H), 2.58–2.65 (m, 1H), 2.46 (d,

J = 14.7, 1H), 2.30–2.38 (m, 1H), 2.30 (s, 3H), 2.27 (s,

6H), 1.88–2.25 (m, 3H), 1.35–1.75 (m, 8H), 1.20–1.26

(m, 12H), 1.08–1.11 (m, 6H), 1.01 (d, J = 6.0, 3H),

0.92–0.98 (m, 6H), 0.77 (t, J = 7.2, 3H). ¹³C NMR

(CDCl₃) d 175.3, 166.1, 164.7, 133.1, 132.6, 130.3,

129.8, 129.6, 129.5, 128.2, 128.1, 108.5 (C9 hemiketal),

101.3, 97.5, 90.6, 86.4, 79.3, 79.2, 79.1, 77.6, 74.5, 73.0,

72.4, 68.5, 63.4, 63.2, 50.2, 49.8, 46.8, 46.2, 40.7, 39.6,

38.3, 37.8, 35.6, 31.9, 31.4, 28.8, 22.6, 21.5, 21.3, 21.2,

18.4, 17.9, 16.2, 15.5, 10.8, 10.7, 7.3. HPLC:

t_R= 22.54 min. HRMS (ESI⁺) m/z [M+H]⁺calcd for

C₅₄H₈₁NO₁₇S: 1048.5297. Found: 1048.5260.

Stage viii. To C₁₂ethyl, C₉, C₁₁, C₁₂triol macrolide

(3.52 g, 3.62 mmol) in dichloromethane (72 mL) at

ꢀ5 ꢁC was added Dess–Martin periodinane (1.84 g,

4.35 mmol). The solution was stirred for 5 min and then

was placed in a ꢀ10 ꢁC refrigerator. After standing

for 22 h, more Dess–Martin periodinane (80 mg,

0.19 mmol) was added and the solution stood in the

ꢀ10 ꢁC refrigerator for an additional 8 h. The solution

was diluted with ethyl acetate (1 L) and washed with

1:1 10% Na₂S₂O₃/NaHCO_3(satd)(2· 200 mL). The com-

bined aqueous layers were back extracted with ethyl ace-

tate (4· 200 mL) and the combined organic layers were

then washed with NaCl_(satd)(200 mL), dried over

MgSO₄, ﬁltered, and concentrated. Puriﬁcation by ﬂash

chromatography (15% acetone/hexanes with 0.1% tri-

ethylamine) yielded the C₁₂ethyl, C₉keto, C₁₁, C₁₂diol

macrolide 2a (2.37 g, 67% yield) as a white solid. MS

(ESI): 970.8 (MH⁺). ¹H NMR (CDCl₃) d 8.00–8.04

(m, 4H), 7.54–7.64 (m, 2H), 7.41–7.49 (m, 4H), 5.03–

5.10 (m, 2H), 4.91–4.98 (m, 3H), 4.42–4.52 (m, 1H),

3.84–3.92 (m, 1H), 3.82 (s, 1H), 3.76 (d, J = 6.9, 1H),

3.68 (d, J = 1.2, 1H), 3.63 (d, J = 6.3, 1H), 3.53 (s,

Stage x. To C₁₂ethyl, C₉, C₁₁OMs, C₁₂OH macrolide

(3.73 g, 3.56 mmol) in acetone (49 mL) was added DBU

(650 lL, 4.34 mmol). The solution was stirred for 5 h at

rt and then for 40 h at 60 ꢁC. The solution was diluted

with ethyl acetate (1.5 L), washed with H₂O (2 ·

400 mL), NaHCO_3(satd)(400 mL), NaCl_(satd)(300 mL),

dried over MgSO₄, ﬁltered, concentrated, and dried in

vacuo yielding the C₁₂ethyl, C₉, C₁₀, C₁₁enone, C₁₂

OH macrolide (3.32 g, 98% yield) as an oﬀ white solid.

MS (ESI): 952.8 (MH⁺). ¹H NMR (CDCl₃) d 8.00–

8.04 (m, 4H), 7.52–7.63 (m, 2H), 7.40–7.49 (m, 4H),

5600

M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

6.34 (s, 1H), 5.05–5.11 (m, 2H), 4.91–4.95 (m, 2H), 4.86

(d, J = 7.2, 1H), 4.46–4.54 (m, 1H), 3.74–78

(m, 2H), 3.62 (d, 6.6, 1H), 3.51 (s, 3H), 2.96–3.14 (m,

3H), 3.03 (s, 3H), 2.66–2.74 (m, 1H), 2.45 (d, J = 15.0,

1H), 2.31 (s, 6H), 2.10–2.20 (m, 1H), 1.96 (s, 3H),

1.40–1.94 (m, 10), 1.17–1.21 (m, 12H), 0.96 (d, J = 6.3,

3H), 0.88 (t, J = 7.2, 3H), 0.83 (t, J = 7.2, 3H), 0.74 (d,

7.5, 3H). ¹³C NMR (CDCl₃) d 207.4, 175.6, 166.2,

165.3, 139.3, 139.2 133.4, 132.6, 130.9, 129.9, 129.7,

129.6, 128.4, 128.2, 100.7, 95.6, 80.5, 79.4, 78.9, 78.8,

77.5, 76.1, 73.0, 72.4, 67.8, 63.8, 63.5, 50.3, 49.7, 44.9,

40.9, 40.1, 39.9, 35.4, 31.7, 28.5, 22.7, 21.3, 20.2, 19.7,

18.3, 15.2, 14.1, 10.8, 9.9, 7.8. HPLC: t_R= 23.38 min.

HRMS (ESI⁺) m/z [M+H]⁺calcd for C₅₃H₇₇NO₁₄:

952.5416. Found: 952.5437.

10.8, 7.7. HPLC: t_R= 18.06 min. HRMS (ESI⁺) m/z

[M+H]⁺calcd for C₃₈H₅₇NO₁₀: 688.4055. Found:

688.4033.

5.8. Compounds 4a–t

Stage xiv. To a solution of C₁₂ethyl, C₉, C₁₀, C₁₁enone,

C₃oxo, C₁₂OH macrolide 3 (12.48 g, 18.2 mmol) and

carbonyldiimidazole (7.37 g, 45.5 mmol) in tetrahydro-

furan (180 mL) at 0 ꢁC was added sodium hydride,

60% dispersion in mineral oil (1.09 g, 27.3 mmol). After

stirring for 7 h, while still at 0 ꢁC, NaHCO_{3 (satd)}(5 mL)

was added cautiously to quench the excess hydride. The

mixture was then diluted with ethyl acetate (600 mL),

was washed with NaHCO_3(satd)(4· 200 mL), with

NaCl_(satd)(200 mL), dried over MgSO₄, ﬁltered, concen-

trated, and dried in vacuo yielding crude C₁₂ethyl C₉,

C₁₀, C₁₁enone, C₃oxo, C₁₂OCO imidazoyl macrolide

(14.6 g). The crude material was used in the next step

without further puriﬁcation. MS (ESI): 782.5 (MH⁺)

and 688.5 (hydrolyzed MH⁺).

Stage xi. To C₁₂ethyl, C₉, C₁₀, C₁₁enone, C₁₂OH mac-

rolide (5.84 g, 6.13 mmol) in acetonitrile (80 mL) was

added 3 M HCl_(aq)(40 mL). After standing for 22 h,

the solution was diluted with ethyl acetate (1.4 L) and

washed with NaHCO_3(satd)(2· 400 mL), with NaCl_(satd)

(300 mL), dried over MgSO₄, ﬁltered, and concentrated.

Puriﬁcation by ﬂash chromatography (30% acetone/hex-

anes with 0.1% triethylamine) yielded the C₁₂ethyl, C₉,

C₁₀, C₁₁enone, C₃, C₁₂diol macrolide (3.48 g, 82%

yield) as a white solid. MS (ESI): 690.4 (MH⁺). ¹H

NMR (CDCl₃) d 8.07–8.10 (m, 2H), 7.50–7.52 (m,

1H), 7.40–7.46 (m, 2H), 6.13 (s, 1H), 4.94–5.00 (m,

2H), 4.87 (d, J = 8.1, 1H), 3.87 (d, 3.0, 1H), 3.54–3.64

(m, 2H), 3.10 (s, 3H), 3.00–3.09 (m, 1H), 2.76–2.86 (m,

1H), 2.32–2.37 (m, 1H), 2.24 (s, 6H), 2.01 (s, 3H),

1.38–1.90 (m, 11H), 1.31 (s, 3H), 1.29 (d, J = 6.0, 3H),

1.21 (d, J = 6.6, 3H), 0.77–0.89 (m, 9H), 0.66 (d,

J = 6.9, 3H). ¹³C NMR (CDCl₃) d 207.5, 175.2, 165.5,

139.6, 138.3, 132.5, 130.6, 129.8, 128.1, 103.0, 89.0,

80.4, 79.6, 76.5, 76.4, 72.4, 69.3, 64.3, 48.9, 44.1, 40.8,

38.3, 38.1, 37.7, 30.8, 27.9, 21.7, 21.3, 20.0, 17.6, 14.4,

13.7, 10.7, 8.5, 8.2. HPLC: t_R= 15.67 min. HRMS

(ESI⁺) m/z [M+H]⁺calcd for C₃₈H₅₉NO₁₀: 690.4211.

Found: 690.4217.

Stage xv. Procedure A for ﬁnal C₁₂ethyl ketolide: C₁₂

ethyl imidazole carbamate macrolide (1 equiv) was add-

ed to amino tethered heterocycle (2.0 equiv);

a

10%water/acetonitrile solution was added such that the

concentration was 0.25 M. The solution was heated in

a 65 ꢁC oil bath for 12 h. Upon cooling the reaction mix-

ture was diluted with ethyl acetate and washed with

NaHCO_{3 (satd)}(3·), NaCl_(satd)(1·), dried over MgSO₄,

ﬁltered, and concentrated. To the crude material was

added methanol (5 mL/mmol) and the solution was

heated at 65 ꢁC for 16 h. Upon concentrating, the mate-

rial was puriﬁed by RP-HPLC and/or SiO₂chromato-

graphy (0–5% MeOH/DCM with 0.1% triethylamine)

yielding C₁₂ethyl ketolide.

5.8.1. Compound 4a. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-imi-

dazo[4,5-b]pyridin-3-yl-butylamine yielded 4a (20%

yield) as a white solid. MS (ESI): 800.7 (MH⁺).

HPLC: t_R= 12.34 min. ¹H NMR (CDCl₃) d 8.37

(dd, J = 4.8, 1.2, 1H), 8.10 (s, 1H), 8.04 (dd, J = 8.4,

1.5, 1H) 7.21 (dd, J = 8.4, 4.5, 1H), 4.93 (dd,

J = 10.8, 1.8, 1H), 4.23–4.42 (m, 4H), 3.84 (q,

J = 6.9, 1H), 3.52–3.72 (m, 3H), 3.66 (s, 1H), 3.25

(dd, J = 10.2, 7.2, 1H), 3.15–3.22 (m, 1H), 3.02–3.12

(m, 1H), 2.60 (s, 3H), 2.54–2.66 (m, 1H), 2.38 (s,

6H), 1.54–2.04 (m, 14H), 1.35 (d, J = 6.6, 3H), 1.33

(s, 3H), 1.21–1.28 (m, 9H), 1.15 (d, J = 7.2, 3H),

1.01 (d, J = 6.9, 3H), 0.84 (t, J = 7.5, 3H). Anal. Calcd

for C₄₂H₆₅N₅O₁₀: C, 63.06; H, 8.19; N, 8.75. Found:

C, 62.84; H, 7.86; N, 8.52.

Stage xii. To C₁₂ethyl, C₉, C₁₀, C₁₁enone, C₃, C₁₂diol

macrolide (3.48 g, 5.0 mmol) in dichloromethane

(100 mL) was added Dess–Martin Periodinane (3.39 g,

1.6 mmol). After stirring for 2 h, the solution was dilut-

ed with ethyl acetate (1.4 L) and washed with 1:1 10%

Na₂S₂O₃/NaHCO_3(satd)(2· 500 mL), with NaCl_(satd)

(300 mL), dried over MgSO₄, ﬁltered, and concentrated.

Puriﬁcation by ﬂash chromatography (30% acetone/hex-

anes with 0.1% triethylamine) yielded the C₁₂ethyl, C₉,

C₁₀, C₁₁enone, C₃oxo, C₁₂OH macrolide 3 (3.25 g,

94% yield) as a white solid. MS (ESI): 688.5 (MH⁺).

¹H NMR (CDCl₃) d 8.00–8.04 (m, 2H), 7.53–7.58 (m,

1H), 7.41–7.46 (m, 2H), 6.44 (s, 1H), 5.00–5.06 (m,

2H), 4.54 (d, J = 7.5, 1H), 4.14 (d, J = 9.0, 1H), 3.56–

3.62 (m, 2H), 2.78–3.13 (m, 3H), 2.75 (s, 3H), 2.25 (s,

6H), 1.96 (s, 3H), 1.64–1.84 (m, 7H), 1.35–1.55 (m,

2H), 1.25–1.29 (m, 9H), 1.17 (d, J = 8.1, 3H), 0.97 (d,

J = 7.2, 3H), 0.95 (t, J = 7.2, 3H), 0.85 (t, J = 7.5, 3H).

¹³C NMR (CDCl₃) d 209.9, 206.7, 169.6, 165.1, 140.8,

138.5, 132.7, 130.4, 129.7, 128.2, 101.8, 82.0, 79.9,

78.3, 76.4, 72.0, 69.2, 63.6, 51.3, 49.9, 47.4, 40.7, 31.7,

31.1, 28.5, 22.7, 20.9, 20.1, 19.3, 15.3, 14.6, 14.3, 13.5,

5.8.2. Compound 4b. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-imi-

dazo[4,5-b]pyridin-1-yl-butylamine yielded 4b (31%

yield) as a white solid. MS (ESI): 800.6 (MH⁺). HPLC:

t_R= 11.49 min. ¹H NMR (CDCl₃) d 8.54 (d, J = 4.8,

1H), 8.16 (s, 1H), 7.79 (dd, J = 8.1, 0.9, 1H) 7.21 (dd,

J = 8.4, 4.5, 1H), 4.90 (d, J = 9.0, 1H), 4.31 (d, J = 7.2,

1H), 4.20–4.26 (m, 2H), 3.85 (q, J = 6.9, 1H), 3.54–

3.76 (m, 3H), 3.67 (s, 1H), 3.30 (dd, J = 10.2, 7.5, 1H),

M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

5601

3.15–3.22 (m, 1H), 3.00–3.12 (m, 1H), 2.66–2.78 (m,

1H), 2.60 (s, 3H), 2.44 (s, 6H), 1.54–2.10 (m, 14H),

1.36 (d, J = 6.6, 3H), 1.34 (s, 3H), 1.21–1.30 (m, 9H),

1.14 (d, J = 6.6, 3H), 1.00 (d, J = 6.6, 3H), 0.81

(t, J = 7.5, 3H). Anal. Calcd for C₄₂H₆₅N₅O₁₀: C,

63.06; H, 8.19; N, 8.75. Found: C, 63.40; H, 7.78; N,

8.64.

¹H NMR (CDCl₃) d 8.04 (d, J = 8.1, 1H), 8.03 (d, 8.4,

1H), 7.76 (dd, J = 8.1, 1.5, 1H), 7.64–7.69 (m, 1H),

7.46–7.49 (m, 1H), 7.31 (d, J = 8.7, 1H), 4.98 (dd,

J = 8.4, 1.8, 1H), 4.28 (d, J = 6.9, 1H), 4.24 (d, J = 4.8,

1H), 3.83 (q, J = 6.9, 1H), 3.71 (s, 1H), 3.60–3.65

(m, 1H), 3.48–3.58 (m, 1H), 2.96–3.22 (m, 3H), 2.61 (s,

3H), 2.39–2.49 (m, 1H), 2.26 (s, 6H), 1.54–2.08 (m,

16H), 1.35 (d, J = 6.9, 3H), 1.33 (s, 3H), 1.21–1.28 (m,

9H), 1.15 (d, J = 76.9, 3H), 1.02 (d, J = 6.9, 3H), 0.85

(t, J = 7.5, 3H). Anal. Calcd for C₄₅H₆₇N₃O₁₀Æ1.2

H₂O: C, 65.02; H, 8.41; N, 5.06. Found: C, 65.01; H,

8.13; N, 4.99.

5.8.3. Compound 4c. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 2-imi-

dazo[4,5-b]pyridin-1-yl-4-methyl-pentylamine

yielded

4c (22% yield) as a white solid. MS (ESI): 828.7

(MH⁺). HPLC: t_R= 12.32 min. ¹H NMR (CDCl₃) d

8.55 (d, J = 3.9, 1H), 8.31 (s, 1H), 8.01 (d, J = 8.1, 1H)

7.23 (dd, J = 8.4, 4.8, 1H), 4.86 (d, J = 8.4, 1H), 4.44

(d, J = 7.2, 1H), 4.23 (d, J = 7.8, 1H), 3.82 (q, J = 6.6,

1H), 3.60 (s, 1H), 3.45–3.65 (m, 2H), 2.96–3.16 (m,

2H), 2.89 (s, 6H), 2.46–2.54 (m, 1H), 2.43 (s, 3H),

1.80–2.20 (m, 10H), 1.76 (s, 3H), 1.74 (s, 3H), 1.40–

1.72 (m, 8H), 1.20–1.36 (m, 15H), 1.09 (d, J = 6.6,

3H), 0.95 (d, J = 6.9, 3H), 0.84 (t, J = 7.2, 3H). Anal.

Calcd for C₄₄H₆₉N₅O₁₀Æ3.1H₂O: C, 59.78; H, 8.58; N,

7.93. Found: C, 59.73; H, 8.59; N, 8.28.

5.8.7. Compound 4g. Following procedure A using the

C

₁₂ethyl imidazolyl carbamate macrolide and N1-meth-

yl-N1-(quinolin-2-ylmethyl)ethane-1,2-diamine yielded

4g (13% yield) as a white solid. MS (ESI): 825.7

(MH⁺). HPLC: t_R= 14.94 min. ¹H NMR (CDCl₃) d

8.24 (d, J = 6.0, 1H), 8.13 (d, J = 8.1, 1H), 7.80–7.86

(m, 2H), 7.72–7.77 (m, 1H), 7.56–7.61 (m, 1H), 4.90

(d, J = 9.9, 1H), 4.39–4.54 (m, 2H), 4.37 (d, J = 7.2,

1H), 4.24 (d, J = 8.1, 1H), 3.86–4.12 (m, 2H), 3.80 (q,

J = 6.9, 1H), 3.69 (s, 1H), 3.58–3.66 (m, 1H), 3.12–3.54

(m, 4H), 2.98–3.06 (m, 1H), 2.73 (s, 9H), 2.63 (s, 3H),

2.50–2.58 (m, 1H), 1.40–2.12 (m, 10H), 1.23–1.33 (m,

15H), 1.15 (d, J = 6.9, 3H), 1.00 (d, J = 6.6, 3H), 0.79

(t, J = 7.2, 3H). Anal. Calcd for C₄₅H₆₈N₄O₁₀Æ2.2H₂O:

C, 62.49; H, 8.44; N, 6.48. Found: C, 62.48; H, 8.02;

N, 6.41.

5.8.4. Compound 4d. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-imi-

dazo[4,5-b]pyridin-1-yl-4-methyl-pentylamine

yielded

4d (33% yield) as a white solid. MS (ESI): 828.8

(MH⁺). HPLC: t_R= 13.68 min. ¹H NMR (CDCl₃) d

8.33 (dd, J = 4.5, 1.2, 1H), 8.09 (s, 1H), 8.02 (dd,

J = 7.8, 1.5, 1H) 7.19 (dd, J = 7.8, 4.5, 1H), 4.87 (dd,

J = 10.5, 1.8, 1H), 4.30 (d, J = 7.8, 1H), 4.22 (d, J =

8.1, 1H), 3.79 (q, J = 6.9, 1H), 3.61 (s, 1H), 3.52–3.60

(m, 1H), 3.44 (t, J = 7.5, 2H), 3.24 (dd, J = 10.2, 7.5,

1H), 2.98–3.14 (m, 2H), 2.50–2.65 (m, 1H), 2.45 (s,

3H), 2.37 (s, 6H), 2.15–2.35 (m, 2H), 1.85–2.05 (m,

4H), 1.80 (s, 6H), 1.45–1.78 (m, 8H), 1.33 (d, J = 6.9,

3H), 1.25–1.30 (m, 9H), 1.21 (t, J = 7.5, 3H), 1.12 (d,

J = 6.9, 3H), 0.96 (d, J = 6.9, 3H), 0.83 (t, J = 6.9,

3H). Anal. Calcd for C₄₄H₆₉N₅O₁₀Æ1.1H₂O: C, 62.35;

H, 8.47; N, 8.27. Found: C, 62.35; H, 8.13; N, 8.13.

5.8.8. Compound 4h. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and N1-meth-

yl-N1-(quinolin-3-ylmethyl)ethane-1,2-diamine yielded

4h (35% yield) as a white solid. MS (ESI): 825.7 MH⁺.

HPLC: t_R= 12.22 min. ¹H NMR (CDCl₃) d 8.84 (d,

J = 2.1, 1H), 8.12 (s, 1H), 8.08 (d, J = 8.1, 1H), 7.81

(d, J = 6.9, 1H), 7.63–7.69 (m, 1H), 7.48–7.54 (m, 1H),

5.08 (dd, J = 10.8, 2.4, 1H), 4.30 (d, J = 6.9, 1H), 4.24

(d, J = 8.4, 1H), 3.86–3.94 (m, 3H), 3.82 (q, J = 6.6,

1H), 3.68 (d, J = 13.2, 1H), 3.67 (s, 1H), 3.52–3.62 (m,

1H), 3.19–3.30 (m, 2H), 3.02–3.13 (m, 1H), 2.82–2.91

(m, 1H), 2.57–2.67 (m, 2H), 2.64 (s, 3H), 2.41 (s, 6H),

2.24 (s, 3H), 1.54–2.06 (m, 10H), 1.23–1.33 (m, 15H),

1.17 (d, J = 6.9, 3H), 1.05 (d, J = 6.9, 3H), 0.71 (t,

J = 7.2, 3H). Anal. Calcd for C₄₅H₆₈N₄O₁₀Æ1.5H₂O: C,

63.48; H, 8.40; N, 6.59. Found: C, 63.46; H, 8.00; N,

6.65.

5.8.5. Compound 4e. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-pyr-

rolo[3,2-b]pyridinylbutylamine yielded 4e (52% yield)

as a white solid. MS (ESI): 799.7 (MH⁺). HPLC:

1

t_R= 12.72 min. H NMR (CDCl₃) d 8.42 (dd, J = 4.8,

1.1, 1H), 7.67 (d, J = 7.8, 1H), 7.35 (d, J = 3.3, 1H)

7.08 (dd, J = 8.1, 4.5, 1H), 6.66 (d, J = 3.3, 1H), 4.93

(dd, J = 10.5, 1.8, 1H), 4.27 (t, J = 7.2, 1H), 4.15 (t,

7.2, 1H), 3.85 (q, J = 7.2, 1H), 3.52–3.68 (m, 3H), 3.66

(s, 1H), 3.16–3.22 (m, 2H), 3.03–3.13 (m, 1H), 2.59 (s,

3H), 2.42–2.52 (m, 1H), 2.29 (s, 6H), 1.45–1.25 (m,

12H), 1.38 (d, J = 6.6, 3H), 1.34 (s, 3H), 1.29 (d,

J = 7.5, 3H), 1.20–1.26 (m, 9H), 1.15 (d, J = 6.9, 3H),

1.00 (d, J = 6.9, 3H), 0.82 (t, J = 7.2, 3H). Anal. Calcd

for C₄₃H₆₆N₄O₁₀: C, 64.64; H, 8.33; N, 7.01. Found:

C, 64.24; H, 8.05; N, 6.87.

5.8.9. Compound 4i. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-(quino-

lin-4-yl)butan-1-amine yielded 4i (47% yield) as a white

solid. MS (ESI): 810.6 (MH⁺). HPLC: t_R= 13.57 min.

¹H NMR (CDCl₃) d 8.80 (d, J = 4.5, 1H), 8.11 (d,

J = 8.4, 1H), 8.06 (d, J = 8.4, 1H) 7.67–7.72 (m, 1H),

7.55–7.58 (m, 1H), 7.27 (d, J = 4.2, 1H), 4.98 (dd,

J = 10.5, 2.1, 1H), 4.29 (t, J = 7.5, 2H), 3.86 (q,

J = 6.9, 1H), 3.73 (s, 1H), 3.62–3.70 (m, 1H), 3.52–3.62

(m, 1H), 3.06–3.24 (m, 3H), 2.64 (s, 3H), 2.42–2.53 (m,

1H), 2.29 (s, 6H), 1.54–2.12 (m, 14H), 1.40 (d, J = 6.6,

3H), 1.36 (s, 3H), 1.21–1.32 (m, 9H), 1.18 (d, J = 6.9,

3H), 1.04 (d, J = 6.9, 3H), 0.84 (t, J = 7.2, 3H). Anal.

Calcd for C₄₅H₆₇N₃O₁₀Æ1.0H₂O: C, 65.25; H, 8.40; N,

5.07. Found: C, 65.21; H, 8.23; N, 5.18.

5.8.6. Compound 4f. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-(quino-

lin-2-yl)butan-1-amine yielded 4f (39% yield) as a white

solid. MS (ESI): 810.6 (MH⁺). HPLC: t_R= 13.20 min.

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M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

5.8.10. Compound 4j. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and N1-meth-

yl-N1-(quinolin-4-ylmethyl)ethane-1,2-diamine yielded

4j (20% yield) as a white solid. MS (ESI): 825.7

(MH⁺). HPLC: t_R= 12.00 min. ¹H NMR (CDCl₃) d

8.84 (d, J = 4.8, 1H), 8.18 (d, J = 8.1, 1H), 8.09 (d,

J = 8.7, 1H), 7.65–7.70 (m, 1H), 7.50–7.57 (m, 2H),

7.56–7.61 (m, 1H), 4.99 (dd, J = 10.8, 2.4, 1H), 4.31

(d, J = 8.1, 1H), 4.23 (d, J = 8.4, 1H), 4.06 (d, J = 5.4,

1H), 3.76–3.88 (m, 2H), 3.67 (s, 1H), 3.54–3.62 (m,

1H), 3.33 (dd, J = 10.2, 7.2, 1H), 3.20 (q, J = 6.9, 1H),

2.70–3.24 (m, 4H), 2.59 (s, 3H), 2.49 (s, 6H), 2.27 (s,

3H), 1.52–2.08 (m, 10H), 1.22–1.33 (m, 15H), 1.16 (d,

J = 7.2, 3H), 1.04 (d, J = 6.9, 3H), 0.67 (t, J = 7.2,

3H). Anal. Calcd for C₄₅H₆₈N₄O₁₀: C, 65.51; H, 8.31;

N, 6.79. Found: C, 65.94; H, 8.21; N, 6.66.

(d, J = 1.2, 1H), 7.29 (d, J = 1.2, 1H), 6.93 (dd,

J = 8.7, 2.7, 1H), 4.93 (dd, J = 11.1, 2.4, 1H), 4.32 (d,

J = 7.2, 1H), 4.24 (d, J = 8.9, 1H), 4.0 (t, J = 7.2, 2H),

3.85 (q, J = 6.9, 1H), 3.53–3.78 (m, 3H), 3.67 (s, 1H),

3.23 (dd, J = 9.9, 7.2, 1H), 3.19–3.23 (m, 1H), 3.04–

3.12 (m, 1H), 2.74–2.84 (m, 1H), 2.61 (s, 3H), 2.51 (s,

6H), 1.48–2.10 (m, 14H), 1.35 (d, J = 6.6, 3H), 1.23–

1.34 (m, 12H), 1.17 (d, J = 6.9, 3H), 1.02 (d, J = 6.9,

3H), 0.83 (t, J = 7.5, 3H). Anal. Calcd for

C₄₄H₆₆FN₅O₁₀Æ0.4H₂O: C, 61.56; H, 8.03; F, 2.27; N,

8.35. Found: C, 61.58; H, 7.71; F, 2.66; N, 7.95.

5.8.14. Compound 4n. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-[4-(6-

chloro-pyridin-3-yl)-imidazol-1-yl]-butylamine yielded

4n (15% yield) as a white solid. MS (ESI): 860.7

(MH⁺). HPLC: t_R= 13.18 min. ¹H NMR (CDCl₃) d

8.73 (d, J = 2.4, 1H), 8.05 (dd, J = 8.1, 2.4, 1H), 7.53

(d, J = 1.2, 1H) 7.33 (s, 1H), 7.31 (d, J = 7.2, 1H), 4.93

(dd, J = 10.5, 2.4, 1H), 4.29 (d, J = 6.9, 1H), 4.24 (d,

J = 8.7, 1H), 4.0 (t, J = 7.5, 2H), 3.85 (q, J = 6.9, 1H),

3.50–3.74 (m, 3H), 3.67 (s, 1H), 3.16–3.28 (m, 2H),

3.02–3.12 (m, 1H), 2.61 (s, 3H), 2.52–2.58 (m, 1H),

2.36 (s, 6H), 1.55–2.08 (m, 14H), 1.35 (d, J = 6.9, 3H),

1.33 (s, 3H), 1.22–1.29 (m, 9H), 1.16 (d, J = 6.6, 3H),

1.01 (d, J = 6.9, 3H), 0.83 (t, J = 7.5, 3H). Anal. Calcd

for C₄₄H₆₆ClN₅O₁₀Æ0.7H₂O: C, 60.12; H, 7.44; Cl,

3.89; N, 7.80. Found: C, 60.13; H, 7.54; Cl, 3.79; N,

7.83.

5.8.11. Compound 4k. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-(4-

(pyridin-3-yl)-1H-imidazol-1-yl)butan-1-amine yielded

4k (44% yield) as a white solid. MS (ESI): 826.7

(MH⁺). HPLC: t_R= 11.34 min. ¹H NMR (CDCl₃) d

8.96 (d, J = 1.5, 1H), 8.45 (dd, J = 4.8, 1.8, 1H), 8.08

(dt, J = 7.8, 1.8, 1H), 7.54 (d, J = 1.5, 1H) 7.33 (d,

J = 1.5, 1H), 7.26–7.30 (m, 1H), 4.94 (dd, J = 10.5, 2.1,

1H), 4.28 (d, J = 8.4, 1H), 4.24 (d, J = 9.0, 1H), 4.01

(t, J = 7.2, 2H), 3.85 (q, J = 6.6, 1H), 3.67 (s, 1H),

3.50–3.72 (m, 3H), 3.16–3.24 (m, 2H), 3.02–3.12 (m,

1H), 2.63 (s, 3H), 2.46–2.58 (m, 1H), 2.31 (s, 6H),

1.55–2.10 (m, 14H), 1.36 (d, J = 6.9, 3H), 1.34 (s, 3H),

1.22–1.30 (m, 9H), 1.16 (d, J = 6.9, 3H), 1.01 (d,

J = 6.6, 3H), 0.83 (t, J = 7.2, 3H). ¹³C NMR (CDCl₃)

d 216.1, 203.1, 169.5, 157.0, 147.3, 146.2, 138.8, 137.6,

131.8, 130.1, 123.3, 115.4, 103.8, 82.9, 79.5, 78.2, 70.3,

69.5, 65.8, 60.3, 51.3, 49.8, 47.7, 46.9, 44.9, 42.8, 40.2,

39.3, 38.6, 28.7, 28.6, 24.4, 23.3, 23.0, 21.2, 21.1, 19.8,

18.2, 15.8, 14.4, 14.3, 10.9, 9.7. Anal. Calcd for

C₄₄H₆₇N₅O₁₀: C, 63.98; H, 8.18; N, 8.48. Found: C,

64.34; H, 8.60; N, 8.10.

5.8.15. Compound 4o. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-[4-(6-

methoxy-pyridin-3-yl)-imidazol-1-yl]-butylamine yield-

ed 4o (33% yield) as a white solid. MS (ESI): 856.7

(MH⁺). HPLC: t_R= 13.21 min. ¹H NMR (CDCl₃) d

8.51 (dd, J = 2.4, 0.9, 1H), 7.97 (dd, J = 8.7, 2.4, 1H),

7.50 (d, J = 1.2, 1H) 7.17 (d, J = 1.5, 1H), 6.75 (dd,

J = 8.7, 0.6, 1H), 4.93 (dd, J = 10.5, 2.1, 1H), 4.27 (d,

J = 7.5, 1H), 4.25 (d, J = 8.4, 1H), 3.98 (t, J = 7.5,

2H), 3.95 (s, 3H), 3.85 (q, J = 6.6, 1H), 3.48–3.76 (m,

3H), 3.68 (s, 1H), 3.15–3.24 (m, 2H), 3.02–3.12 (m,

1H), 2.63 (s, 3H), 2.40–2.48 (m, 1H), 2.26 (s, 6H),

1.54–2.08 (m, 14H), 1.36 (d, J = 6.9, 3H), 1.35 (s, 3H),

1.20–1.30 (m, 9H), 1.16 (d, J = 7.2, 3H), 1.01 (d,

J = 6.9, 3H), 0.83 (t, J = 7.5, 3H). Anal. Calcd for

C₄₅H₆₉N₅O₁₁Æ2.4H₂O: C, 60.07; H, 8.28; N, 7.79.

Found: C, 60.08; H, 8.19; N, 7.67.

5.8.12. Compound 4l. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-[4-(6-

methyl-pyridin-3-yl)-imidazol-1-yl]-butylamine yielded

4l (44% yield) as a white solid. MS (ESI): 840.7

(MH⁺). HPLC: t_R= 11.80 min. ¹H NMR (CDCl₃) d

8.83 (d, J = 2.1, 1H), 7.96 (dd, J = 7.8, 2.4, 1H), 7.52

(d, J = 1.5, 1H) 7.27 (d, J = 1.2, 1H), 7.15 (d, J = 8.1,

1H), 4.93 (dd, J = 10.5, 2.4, 1H), 4.28 (d, J = 7.2, 1H),

4.25 (d, J = 8.7, 1H), 4.0 (t, J = 7.2, 2H), 3.85 (q,

J = 6.9, 1H), 3.50–3.72 (m, 3H), 3.68 (s, 1H), 3.16–3.26

(m, 2H), 3.02–3.12 (m, 1H), 2.63 (s, 3H), 2.52–2.62 (m,

1H) 2.55 (s, 3H), 2.34 (s, 6H), 1.56–2.12 (m, 14H),

1.34–1.37 (m, 6H), 1.20–1.31 (m, 9H), 1.16 (d, J = 6.9,

3H), 1.01 (d, J = 6.9, 3H), 0.83 (t, J = 7.5, 3H). Anal.

Calcd for C₄₅H₆₉N₅O₁₀Æ1.7H₂O: C, 62.04; H, 8.39; N,

8.04. Found: C, 62.04; H, 8.16; N, 7.98.

5.8.16. Compound 4p. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-(4-Pyri-

mid-5-yl-imidazol-1-yl)-butylamine yielded 4p (27%

yield) as a white solid. MS (ESI): 827.7 (MH⁺). HPLC:

t_R= 11.45 min. ¹H NMR (CDCl₃) d 9.10 (s, 2H), 9.06 (s,

1H), 7.56 (d, J = 1.2, 1H) 7.40 (d, J = 1.5, 1H), 4.92 (dd,

J = 10.5, 2.1, 1H), 4.27 (d, J = 7.5, 1H), 4.23 (d, J = 9.3,

1H), 4.02 (t, J = 7.5, 2H), 3.84 (q, J = 6.9, 1H), 3.67 (s,

1H), 3.50–3.74 (m, 3H), 3.16–3.24 (m, 2H), 3.02–3.12

(m, 1H), 2.60 (s, 3H), 2.42–2.56 (m, 1H), 2.30 (s, 6H),

1.55–2.10 (m, 14H), 1.34–1.36 (m, 6H), 1.21–1.29 (m,

9H), 1.16 (d, J = 6.9, 3H), 1.01 (d, J = 6.9, 3H), 0.82

(t, J = 7.2, 3H). Anal. Calcd for C₄₃H₆₆N₆O₁₀Æ1.8H₂O:

C, 60.02; H, 8.17; N, 9.77. Found: C, 60.08; H, 8.44;

N, 9.47.

5.8.13. Compound 4m. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-[4-(6-

ﬂuoro-pyridin-3-yl)-imidazol-1-yl]-butylamine yielded

4m (27% yield) as a white solid. MS (ESI): 844.7

(MH⁺). HPLC: t_R= 12.60 min. ¹H NMR (CDCl₃) d

8.55 (d, J = 2.1, 1H), 8.18 (td, J = 8.4, 2.4, 1H), 7.52

M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

5603

5.8.17. Compound 4q. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-(4-

2.65 (s, 3H), 2.50–2.58 (m, 2H), 2.32 (s, 6H), 2.23 (s,

3H), 1.40–2.05 (m, 10H), 1.21–1.34 (m, 15H), 1.17 (d,

J = 6.6, 3H), 1.03 (d, J = 6.6, 3H), 0.64 (t, J = 7.2,

3H). Anal. Calcd for C₄₆H₆₉N₅O₁₀: C, 64.84; H, 8.16;

N, 8.22. Found: C, 64.42; H, 7.79; N, 8.15.

pyrazin-2-yl-imidazol-1-yl)-butylamine

yielded

4q

(29% yield) as a white solid. MS (ESI): 827.7 (MH⁺).

HPLC: t_R= 11.88 min. ¹H NMR (CDCl₃) d 9.19 (d,

J = 1.8, 1H), 8.44 (dd, J = 2.4, 1.2, 1H), 8.37 (d,

J = 2.7, 1H) 7.65 (d, J = 1.2, 1H), 7.56 (d, J = 1.5,

1H), 4.93 (dd, J = 10.8, 1.8, 1H), 4.28 (d, J = 7.5, 1H),

4.25 (d, J = 9.3, 1H), 4.03 (t, J = 7.5, 2H), 3.84 (q,

J = 6.9, 1H), 3.68 (s, 1H), 3.50–3.74 (m, 3H), 3.16–3.24

(m, 2H), 3.02–3.12 (m, 1H), 2.63 (s, 3H), 2.42–2.56 (m,

1H), 2.30 (s, 6H), 1.55–2.10 (m, 14H), 1.34–1.36 (m,

6H), 1.22–1.30 (m, 9H), 1.16 (d, J = 6.9, 3H), 1.01 (d,

J = 6.9, 3H), 0.84 (t, J = 7.2, 3H). Anal. Calcd for

C₄₃H₆₆N₆O₁₀Æ4.6H₂O: C, 56.73; H, 8.34; N, 9.24.

Found: C, 56.76; H, 8.46; N, 9.06.

Acknowledgments

We thank Dr. Xiadong Lin and Alice Rico for prepara-

tion of the epimeric C₁₂ethyl, C₁₂hydroxy, C₉, C₁₁ace-

tonide ketolide core and Dr. Fook S. Tham of

University of Riverside, CA, for solving its X-ray struc-

ture. We also thank Weiping Jia and Dr. Gavin Dollin-

ger of Chiron for analytical chemistry support.

Supplementary data

5.8.18. Compound 4r. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-(4-

(pyridin-4-yl)-1H-imidazol-1-yl)butan-1-amine yielded

4r (31% yield) as a white solid. MS (ESI): 826.7

(MH⁺). HPLC: t_R= 11.51 min. ¹H NMR (CDCl₃) d

8.56 (d, J = 4.8, 2H), 7.69 (d, J = 4.8, 1H), 7.55 (d,

J = 1.2, 1H), 7.49 (d, J = 1.2, 1H), 4.94 (dd, J = 10.5,

2.1, 1H), 4.35 (d, J = 7.2, 1H), 4.24 (d, J = 8.7, 1H),

4.02 (t, J = 7.2, 2H), 3.86 (q, J = 7.2, 1H), 3.67 (s, 1H),

3.56–3.74 (m, 3H), 3.40–3.46 (m, 1H), 3.16–3.24 (m,

1H), 3.0–3.10 (m, 1H), 2.64 (s, 3H), 2.59 (s, 6H), 1.58–

2.10 (m, 14H), 1.36 (d, J = 6.9, 3H), 1.30 (s, 3H),

1.24–1.30 (m, 9H), 1.17 (d, J = 6.9, 3H), 1.02 (d,

J = 6.6, 3H), 0.83 (t, J = 7.2, 3H). Anal. Calcd for

C₄₄H₆₇N₅O₁₀Æ3.5H₂O: C, 59.40; H, 8.39; N, 7.88.

Found: C, 59.41; H, 7.98; N, 7.63.

Synthesis and X-ray structure of the epimeric C₁₂ethyl,

C₁₂hydroxy, C₉, C₁₁acetonide macrolide, and ¹H NMR

spectra of ﬁnal ketolide 4k and telithromycin. Supple-

mentary data associated with this article can be found,

in the online version, at doi:10.1016/j.bmc.2006.04.032.

References and notes

1. (a)Macrolides: Chemistry, Pharmacology and Clinical

Uses; Bryskier, A. J., Butzler, J.-P., Neu, H. C., Tulkens,

P. M., Eds.; Arnette Blackwell: Paris, 1993; (b) New

Macrolides, Azalides, and Streptogramins in Clinical

Practice; Neu, H. C., Young, L. S., Zinner, S. H., Acar,

J. F., Eds.; Marcel Dekker: New York, 1995; (c) Kurath,

P.; Jones, P. H.; Egan, R. S.; Perun, T. J. Experentia 1971,

27, 362; (d) Krowicki, K.; Zamojski, A. J. Antibiot. 1974,

26, 569–574.

5.8.19. Compound 4s. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and 4-(4-

2. Morimoto, S.; Takahashi, Y.; Watanabe, Y.; Omura, S.

J. Antibiot. 1984, 37, 343–345.

phenyl-1H-imidazol-1-yl)butan-1-amine

yielded

4s

(42% yield) as a white solid. MS (ESI): 825.7 (MH⁺).

HPLC: t_R= 13.94 min. ¹H NMR (CDCl₃) d 8.96 (d,

J = 1.5, 1H), 8.45 (dd, J = 4.8, 1.8, 1H), 8.08 (dt,

J = 7.8, 1.8, 1H), 7.54 (d, J = 1.5, 1H) 7.33 (d, J = 1.5,

1H), 7.26–7.30 (m, 1H), 4.94 (dd, J = 10.5, 2.1, 1H),

4.28 (d, J = 8.4, 1H), 4.24 (d, J = 9.0, 1H), 4.01 (t,

J = 7.2, 2H), 3.85 (q, J = 6.6, 1H), 3.67 (s, 1H), 3.50–

3.72 (m, 3H), 3.16–3.24 (m, 2H), 3.02–3.12 (m, 1H),

2.63 (s, 3H), 2.46–2.58 (m, 1H), 2.31 (s, 6H), 1.55–2.10

(m, 14H), 1.36 (d, J = 6.9, 3H), 1.34 (s, 3H), 1.22–1.30

(m, 9H), 1.16 (d, J = 6.9, 3H), 1.01 (d, J = 6.6, 3H),

0.83 (t, J = 7.2, 3H). Anal. Calcd for C₄₅H₆₈N₄O₁₀Æ1.2-

H₂O: C, 63.85; H, 8.38; N, 6.62. Found: C, 63.86; H,

7.97; N, 6.39.

3. (a) Bright, G.; Nage, A.; Bordner, J.; Desai, K.;

Dibrino, J.; Nowakowska, J.; Vincent, L.; Watrous,

R.; Sciavolino, F.; English, A.; Retsema, J.; Anderson,

M.; Brennan, L.; Borovoy, R.; Cimchowsji, C.; Faiella,

J.; Girard, A.; Girard, D.; Herbert, C.; Manousos, M.;

Mason, R. J. Antibiot. 1988, 41, 1029–1047; (b)

Retsema, J. A.; Girard, A. E.; Schekly, W.; Manousos,

M.; Anderson, M. R.; Bright, G. M.; Borovoy, R. J.;

Brennan, L. A.; Mason, R. Antimicrob. Agents Chemo-

ther. 1987, 31, 1939–1947.

4. (a) Chantot, J.-F.; Bryskier, A.; Gasc, J.-C. J. Antibiot.

`

1986, 39, 660–668; (b) Gasc, J. C.; Gouin d’Ambrieres, S.;

Lutz, A.; Chantot, J. F. J. Antibiot. 1991, 44, 313–330.

5. (a) Leclercq, Q.; Courvalin, P. Antimicrob. Agents Che-

mother. 1991, 35, 1267–1272; (b) Leclercq, Q.; Courvalin,

P. Antimicrob. Agents Chemother. 1991, 35, 1273–1276; (c)

Sutcliﬀe, J.; Tait-Kamradt, A.; Wondrack, L. Antimicrob.

Agents Chemother. 1996, 40, 1817–1824.

5.8.20. Compound 4t. Following procedure A using the

C₁₂ethyl imidazolyl carbamate macrolide and N1-

[3,3⁰]bipyridinyl-5-ylmethyl-N1-methyl-ethane-1,2-di-

amine yielded 4t (43% yield) as a white solid. MS (ESI):

852.7 (MH⁺). HPLC: t_R= 10.10 min. ¹H NMR (CDCl₃)

d 8.87 (d, J = 2.7, 1H), 8.71 (d, J = 2.4, 1H), 8.63 (dd,

J = 4.8, 1.5, 1H), 8.51 (d, J = 1.5, 1H), 7.93–7.98 (m,

2H), 7.40 (dd, J = 8.1, 4.8, 1H), 5.04 (dd, J = 10.5, 2.4,

1H), 4.28 (d, J = 7.5, 1H), 4.24 (d, J = 8.4, 1H), 3.78–

3.94 (m, 4H), 3.65 (s, 1H), 3.48–3.58 (m, 2H), 3.18–

3.24 (m, 2H), 3.02–3.10 (m, 1H), 2.78–2.90 (m, 1H),

6. (a) Agouridas, C.; Denis, A.; Auger, J. M.; Benedetti, Y.;

Bonnefoy, A.; Bretin, F.; Chantot, J. F.; Dussarat, A.;

`

Fromentin, C.; D’Ambrieres, S. G.; Lachaud, S.; Laurin,

P.; Le Martret, O.; Loyau, V.; Tessot, N. J. Med. Chem.

1998, 41, 4080–4100; (b) Denis, A.; Agouridas, C.;

Auger, J.-M.; Benedetti, Y.; Bonnefoy, A.; Bretin, F.;

Chantot, J.-F.; Dussarat, A.; Fromentin, C.; D’Ambri-

eres, S. G.; Lachaud, S.; Laurin, P.; Martret, O. L.;

Loyau, V.; Tessot, N.; Pejac, J.-M.; Perron, S. Bioorg.

Med. Chem. Lett. 1999, 9, 3075–3080.

5604

M. T. Burger et al. / Bioorg. Med. Chem. 14 (2006) 5592–5604

7. Ma, Z.; Clark, R. F.; Brazzale, A.; Wang, S.; Rupp, M. J.;

Conference on Antimicrobial Agents and Chemotherapy,

San Diego, Ca., 2002; Abst F-1662; (b) Abbanat, D.;

Ashley, G.; Foleno, B.; Fu, H.; Hilliard, J.; Li, Y.; Licari,

P.; Macielag, M.; Melton, J.; Monteenegro, D.; Raina,

D.; Stryker, S.; Wira, E. J.; Bush, K. 43rd Interscience

Conference on Antimicrobial Agents and Chemotherapy,

Chicago, Ill. 2003; Abst F-1203; (c) Ashley, G. W.; Li,

Y.; 44th Interscience Conference on Antimicrobial

Agents and Chemotherapy, Washington D.C., 2004;

Abst F-1409.

Li, L.; Griesgraber, G.; Zhang, S.; Yong, H.; Phan, L. T.;

Nemoto, P. A.; Chu, D. T.; Plattner, J. J.; Zhang, X.;

Zhong, P.; Cao, Z.; Nilius, A. M.; Shortridge, V. D.;

Flamm, R.; Mitten, M.; Meulbroek, J.; Ewing, P.; Alder,

J.; Or, Y. S. J. Med. Chem. 2001, 44, 4137–4156.

8. (a) Harris, D. R.; McGeachin, S. G.; Mills, H. H.

Tetrahedron Lett. 1965, 679–685; (b) Awan, A.; Brennan,

R. J.; Regan, A. C.; Barber, J. J. Chem. Soc., Chem.

Commun. 1995, 1653–1654; (c) Bertho, G.; Ladam, P.;

Gharbi-Benarous, J.; Delaforge, M.; Girault, J.-P. Int. J.

Biol. Macromol. 1998, 22, 103–127; (d) Bertho, G.;

Gharbi-Benarous, J.; Delaforge, M.; Girault, J.-P. Bioorg.

Med. Chem. 1998, 6, 209–221; (e) Awan, A.; Brennan, R.

J.; Regan, A. C.; Barber, J. J. Chem. Soc., Perkin Trans. 2

2000, 1645–1652.

9. Studies have suggested that the hydrophobic nature of the

macrolide bottom face is maintained in the ketolides (a)

Bertho, G.; Gharbi-Benarous, J.; Delaforge, M.; Lang, C.;

Parent, A.; Girault, J.-P. J. Med. Chem. 1998, 41, 3373–

3386; (b) Evrard-Todeschi, N.; Gharbi-Benarous, J.;

Gaillet, C.; Verdier, L.; Bertho, G.; Lang, C.; Parent, A.;

Girault, J.-P. Bioorg. Med. Chem. 2000, 8, 1579–1597.

10. Burger, M. T.; Lin, X.; Chu, D. T.; Hiebert, C.; Rico, A.;

Seid, M.; Carroll, G.; Barker, L.; Huh, K.; Langhorne,

M.; Shawar, R.; Kidney, J.; Young, K.; Anderson, S.;

Desai, M. C.; Plattner, J. J. J. Med. Chem. 2006, 49, 1730–

1743.

15. (a) Or, Y. S.; Wang, G.; Phan, L. T.; Niu, D.; Vo, N. H.;

Qiu, Y.; Wang, Y.; Busuyek, M.; Hou, Y.; Peng, Y.; Kim,

H.; Liu, T.; Farmer, Jay J.; Xu, G.. U.S Patent #

6,878,691 B2. April 12, 2005; (b) Scorneaux, B.; Arya, A.;

Polemeropoulos, A.; Lillard, M.; Han, F.; Amsler, K.;

Sonderfan, A.; Wang, G.; Wang, Y.; Peng, Y.; Xu, G.;

Kim, H.; Lien, T.; Phan, L.; Or, Y. T. 43rd Interscience

Conference on Antimicrobial Agents and Chemotherapy,

Chicago, Ill. 2003; Abst F-1191.

16. From the C₁₂ketone, C₁₂hydrogen and C₁₂CF₃groups

can be introduced into the macrolide core. Xiadong Lin,

Georgia Carrol and Alice Rico unpublished results.

17. Griﬃth, W. F.; Ley, S. V.; Whitcombe, G. P.; White, A.

D. J. Chem. Soc., Chem. Commun. 1987, 1625–1627.

18. Martin, J. C.; Dess, D. B. J. Am. Chem. Soc. 1991, 113,

7277–7287.

19. The epimeric C₁₂ethyl C₁₂hydroxy macrolide core was

prepared by Dr. Xiadong Lin and Alice Rico by ethylg-

rignard addition to the corresponding C₁₂ketone macro-

lide. The X-ray structure of the ethyl grignard product was

determined by Dr. Fook Tham, UC Riverside. See the

supplementary material for details. Crystallographic data

for this structure has been deposited with the Cambridge

Crystallographic Data Centre as supplementary publica-

tion nos. CCDC 604208.

20. (a) Sidechains for compounds 4c,4d,4l,4m,4n,4o,4p,4q, and

4t were prepared as described in Ref. 10. Sidechains for

compounds 4e,4g,4h,4j, and 4r were prepared using the

methods described in Ref. 10; (b) Sidechains for com-

pounds 4a,4b,4i,4k, and 4s were prepared as described in

Ref. 6a; (c) The sidechain for compound 4f was prepared

as in Agouridas, Constantin; Chantot, Jean-Francois;

Denis, Alexis; Gouin d’Ambrieres, Solange; Le Martret,

Odile. Eur. Pat. Appl. (1995) EP 680967 A1 19951108.

21. For 4k and telithromycin ¹H NMR spectra, see supple-

mentary material.

11. Lin, X.; Burger, M.; Chu, D.; Rico, A.; Hiebert, C.; Seid,

M.; Carroll, G.; Barker, L.; Shawar, R. 43rd Interscience

Conference on Antimicrobial Agents and Chemotherapy,

Chicago, Ill. 2003; Abst F-1201.

12. (a) Baker, W. R.; Clark, J. D.; Stephens, R. L.; Kim, K. H.

J. Org. Chem. 1988, 53, 2340–2345; (b) Fernandes, P. B.;

Baker, W. R.; Freiberg, L. A.; Hardy, D. J.; McDonald,

E. J. Antimicrob. Agents Chemother. 1989, 33, 78–81; (c)

Elliott, R. L.; Pireh, D.; Griesgraber, G.; Nilius, A. M.;

Ewing, P. J.; Bui, M. H.; Raney, P. M.; Flamm, R. K.;

Kim, K.; Henry, R. F.; Chu, D. T. W.; Plattner, J. J.; Or,

Y. S. J. Med. Chem. 1998, 41, 1651–1659; (d) Griesgraber,

G.; Kramer, M. J.; Elliott, R. L.; Nilius, A. M.; Ewing, P.

J.; Raney, P. M.; Bui, M.-H.; Flamm, R. K.; Chu, D. T.

W.; Plattner, J. J.; Or, Y. S. J. Med. Chem. 1998, 41, 1660–

1670; (e) Hunziker, D.; Wyss, P. C.; Angehrn, P.; Mueller,

A.; Marty, H. P.; Halm, R.; Kellenberger, L.; Bitsch, V.;

Biringer, G.; Arnold, W.; Sta¨mpﬂi, A.; Schmitt-Hoﬀmann,

A.; Cousot, D. Bioorg. Med. Chem. 2004, 12, 3503–3519.

13. Su, W. G.; Smyth, K. T.; Rainville, J. P.; Kaneko, T.;

Sitcliﬀe, J. S.; Brennan, L. A.; Duignan, J. M.; Girard, A.

E.; Finegan S. M.; Cimochowski, C. R. 38th Interscience

Conference on Antimicrobial Agents and Chemotherapy

1998; Abst F-122.

22. NCCLS. 2003. Methods for Dilution Antimicrobial Sus-

ceptibility Tests for Bacteria that Grow Aerobically;

Approved Standard—6th ed. NCCLS document M7-A6.

NCCLS, Wayne, PA 19807, USA.

23. NCCLS. 2003. Performance Standards for Antimicrobial

Susceptibility Testing; Approved Standard—14th ed.

NCCLS document M100-S13. NCCLS, Wayne, PA

19807, USA.

14. (a) Macielag, M.; Abbanat, D.; Ashley, G.; Foleno, B.;

Fu, H.; Li, Y.; Wira, E.; Bush, K. 42nd Interscience

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Synthesis and antibacterial activity of novel C12 ethyl ketolides

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