Phenylethylene glycol-derived LpxC inhibitors with diverse Zn2+-binding groups

Tetrahedron xxx (xxxx) xxx

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Tetrahedron

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Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-

binding groups

a

€

Magdalena Galster , Marius Loppenberg , Fabian Galla , Frederik Borgel ,

,

c

,

f,

, d, *

Oriana Agoglitta ^{b d}, Johannes Kirchmair ^{e g}, Ralph Holl ^c

^aInstitute of Pharmaceutical and Medicinal Chemistry, University of Münster, Corrensstr. 48, 48149 Münster, Germany

^bNRW Graduate School of Chemistry, University of Münster, Germany

^cInstitute of Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany

^dGerman Center for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-Riems, Germany

^eCenter for Bioinformatics (ZBH), University of Hamburg, Bundesstr. 43, 20146 Hamburg, Germany

^fDepartment of Chemistry, University of Bergen, N-5020 Bergen, Norway

^gComputational Biology Unit (CBU), University of Bergen, N-5020 Bergen, Norway

a r t i c l e i n f o

a b s t r a c t

The Zn^2þ-dependent bacterial deacetylase LpxC is a promising target for the development of novel an-

tibiotics. Most of the known LpxC inhibitors carry a hydroxamate moiety as Zn^2þ-binding group. How-

ever, hydroxamic acids generally exhibit poor pharmacokinetic properties. (S)-N-Hydroxy-2-{2-hydroxy-

1-[4-(phenylethynyl)phenyl]ethoxy}acetamide (3) is a known phenylethylene glycol derivative potently

inhibiting LpxC with a K_iof 66 nM. In vitro experiments have conﬁrmed in silico predictions that the

hydroxamate moiety of 3 is indeed metabolically labile. In this study, several strategies were explored to

replace the hydroxamate moiety by other Zn^2þ-binding groups while maintaining target activity. In total,

15 phenylethylene glycol derivatives with diverse Zn^2þ-binding groups like carboxylate, hydrazide,

carboxamide, sulfonamide, vicinal diol, thiol, thioester, and hydroxypyridinone moieties were prepared

in divergent syntheses. However, their biological evaluation revealed that the replacement of the

hydroxamate moiety of 3 by any of the investigated Zn^2þ-binding groups is detrimental for LpxC

inhibitory and antibacterial activity.

Article history:

Received 19 October 2018

Received in revised form

29 November 2018

Accepted 7 December 2018

Available online xxx

Keywords:

Antibacterials

LpxC inhibitors

Hydroxamic acids

Metabolic stability

Zn^2þ-chelating groups

1. Introduction

promising target for the development of antibiotics, selectively

combating Gram-negative bacteria [5]. The enzyme, which is highly

After iron, zinc is the second most abundant transition metal in

all living organisms, including animals, plants, and microorgan-

isms, with Zn^2þ-containing enzymes constituting the largest cate-

gory of metalloproteins [1]. Many of these enzymes are involved in

biological processes also associated with the propagation of various

diseases, like cancer, arthritis, hypertension, and bacterial in-

fections, thus making them attractive targets for drug therapy [2].

In the design and development of inhibitors of these enzymes, their

metal ion cofactor has frequently been targeted by chelating groups

[3,4].

conserved among Gram-negative bacteria, is involved in the

biosynthesis of lipid A. Lipid A is essential for growth and viability

of Gram-negative bacteria as it constitutes the hydrophobic

membrane anchor of lipopolysaccharides, representing the main

component of the outer monolayer of the outer membrane of these

germs [6]. LpxC plays a central role in lipid A biosynthesis, cata-

lyzing its ﬁrst irreversible step, which in E. coli is the deacetylation

of UDP-3-O-[(R)-3-hydroxymyristoyl]-N-acetylglucosamine (1,

Scheme 1) [7,8]. The enzyme's catalytic Zn^2þ-ion is located at the

bottom of the ~20 Å deep, conical active site cleft, where it is co-

ordinated by one aspartate and two histidine residues. From this

active site, an approximately 15 Å long, hydrophobic tunnel leads

outwards, which encloses the 3-O-[(R)-3-hydroxymyristoyl] sub-

stituent of the enzyme's natural substrate during catalysis [9,10].

Various structural classes of LpxC inhibitors have been

described in the patent and non-patent literature [5,11]. Most of the

The Zn^2þ-dependent bacterial deacetylase LpxC represents a

* Corresponding author. Institute of Organic Chemistry, University of Hamburg,

Martin-Luther-King-Platz 6, 20146 Hamburg, Germany.

E-mail address: ralph.holl@chemie.uni-hamburg.de (R. Holl).

https://doi.org/10.1016/j.tet.2018.12.011

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M. Galster et al. / Tetrahedron xxx (xxxx) xxx

assay (IC₅₀¼ 0.48 M, K_i¼ 66 nM) as well as in the performed disc

m

diffusion assays (Table 1) [38]. Therefore, the compound should be

further investigated. In this work, the results of in silico and in vitro

experiments on the metabolism of hydroxamic acid 3 are reported.

In addition, a systematic study of alternative metal binding groups

is described, in which the hydroxamate moiety of 3 was replaced by

various other Zn^2þ-binding groups that are part of effective in-

hibitors of other Zn^2þ-dependent enzymes [24,39e45]. Thus a

carboxylic acid, a hydrazide, several amides and sulfonamides,

vicinal diols, a thiol, a thioester, and hydroxypyridinone derivatives

were synthesized and tested for antibacterial activity.

Scheme 1. LpxC-catalyzed deacetylation of UDP-3-O-[(R)-3-hydroxymyristoyl]-N-

acetylglucosamine (1).

2. Results and discussion

2.1. Prediction of the metabolism of 3

described inhibitors share common structural features like a Zn^2þ

-

binding group as well as a structural element addressing the en-

zyme's hydrophobic tunnel [5,11,12]. The vast majority of the re-

The susceptibility of 3 toward human cytochrome P450 (CYP)-

mediated metabolism was investigated with FAME 2, a random

forest-based predictor of sites of metabolism [46]. FAME 2 assigned

a moderate likelihood of metabolism (0.602; values ranging from

0 to 1, with higher values indicating higher probabilities of atoms

being sites of metabolism) to the para-position of the terminal

phenyl moiety (Fig. 2). This is interpreted as a moderate likelihood

for a hydroxylation to happen at this atom position. All other atom

positions were predicted as stable in the context of CYP

metabolism.

The most likely human metabolites of 3 resulting from phase I

and phase II metabolism were predicted with SyGMa [47]. SyGMa

assigns to all predicted metabolites an empirical probability score,

which represents the proportion of correctly predicted metabolites

of the training set. For 3, SyGMa predicts four metabolites with a

score greater than 0.09 (Fig. 2): two glucuronic acid conjugates (4,

7) and two carboxylic acid metabolites (5, 6).

ported LpxC inhibitors uses a hydroxamate moiety as the Zn^2þ

binding group.

-

Although a hydroxamate moiety is found in some approved

drugs, like the histone deacetylase inhibitors vorinostat, pan-

obinostat, and belinostat, the clinical effectiveness of hydroxamic

acids is generally limited by their inadequate selectivity for Zn^2þ

-

ions and poor pharmacokinetics [13e18]. The unfavorable phar-

macokinetic properties of hydroxamic acids result from poor oral

bioavailability as well as high clearance due to rapid metabolism via

conjugate formation (glucuronidation and sulfation), reduction,

and hydrolytic cleavage, the latter leading to the release of toxic

hydroxylamine [19e26].

In case of numerous Zn^2þ-containing target enzymes, inhibitors

have been developed which exhibit alternative Zn^2þ-binding

groups with more favorable pharmacological and pharmacokinetic

properties [13,19,24,27,28]. However, in the case of LpxC inhibitors,

only a few inhibitors that do not contain the Zn^2þ-chelating

hydroxamate moiety have been reported so far [29e37].

2.2. In vitro metabolism using rat liver microsomes

Recently, we have reported on a series of benzyloxyacetohy-

droxamic acids as inhibitors of LpxC, with the most potent com-

pound, 3 (Fig. 1), exhibiting promising activities in the enzyme

To identify the metabolically labile positions of hydroxamic acid

3 in vitro, the compound was incubated with NADPH (for CYP-

mediated phase I metabolism) and UDPGA (for UGT-mediated

Fig. 1. Structure of hydroxamic acid 3 and alternative Zn^2þ-binding groups.

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

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3

Table 1

Results of the biological evaluation of the synthesized inhibitors with various Zn^2þ-binding groups. n. d.: not determinable. *: not soluble in the assay buffer at a concentration

of 200 M.

m

compound

zone of inhibition [mm]

MIC [

m

g/mL]

enzyme assay

R¼

E. coli BL21

E. coli

D22

E. coli BL21

E. coli

D22

IC₅₀

[

m

M]

K_i[mM]

3 [38]

9.5 0.4

20.5 0.2

64

4

0.48 0.23

0.066 0.032

13

14

<6

>64

>200

e

15

16

7.3 1.2

9.8 1.0

7.7 1.5

>64

>200

>20*

e

<6

20

22

<6

>64

>200

e

25

27

12.0 2.0

13.8 1.4

>64

64

n.d.

e

<6

>64

>20*

29

31

33

<6

8.7 0.6

7.7 0.6

<6

>64

>200

>20*

>200

e

7.0 1.0

<6

38 (de ¼ 60%)

39 (de ¼ 20%)

7.8 1.6

8.0 1.7

8.7 1.5

8.5 0.9

>64

>200

e

compound

zone of inhibition [mm]

MIC [

m

g/mL]

enzyme assay

R ¼

E. coli

BL21

E. coli

D22

E. coli

BL21

E. coli

D22

IC₅₀

[

m

M]

K_i[mM]

50

<6

>64

>200

e

(continued on next page)

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M. Galster et al. / Tetrahedron xxx (xxxx) xxx

Table 1 (continued )

compound

zone of inhibition [mm]

MIC [

m

g/mL]

enzyme assay

R¼

E. coli BL21

<6

E. coli

D22

E. coli BL21

>64

E. coli

D22

IC₅₀

[

mM]

K_i[mM]

51

<6

>64

>200

e

53

<6

>64

>200

e

compound

zone of inhibition [mm]

MIC [

m

g/mL]

enzyme assay

R ¼

E. coli

BL21

E. coli

D22

E. coli

BL21

E. coli

D22

IC₅₀

[

m

M]

K_i[mM]

57

<6

>64

>200

e

58 [38]

10.6 0.4

13.2 1.6

32

2

>200

e

phase II metabolism) in the presence of a suspension of rat liver

microsomes (Fig. 3).

enantiomerically pure form via a described procedure starting from

4-bromostyrene (8) [38]. In order to establish the lipophilic side

chain of the compounds, a Sonogashira coupling of aryl bromide 9

with phenylacetylene was performed to yield diphenylacetylene

derivative 10. Subsequently, the MOM protective group of ester 10

was cleaved under acidic conditions. When performing the reaction

in ethanol, ethyl ester 12 was obtained. The use of methanol as

solvent led to an additional transesteriﬁcation, yielding methyl

ester 11. Whereas the saponiﬁcation of ester 12 gave carboxylic acid

13, the aminolyses of esters 11 and 12 with ammonia and hydrazine

yielded primary amide 14 and hydrazide 15, respectively [48,49].

Finally, amide 16 was obtained by coupling carboxylic acid 13 with

1,2-phenylenediamine in the presence of the carboxyl activating

agent EDCI hydrochloride and N-hydroxysuccinimide [19,50,51].

In order to access thiol derivatives 20 and 22, ester 10 was

reduced with DIBAL to yield primary alcohol 17 (Scheme 3) [52].

Subsequently, the alcohol was mesylated and the resulting meth-

anesulfonic acid ester 18 was subjected to a nucleophilic substitu-

tion with thioacetic acid to obtain thioester 19 [53,54]. The removal

of the MOM protective group of thioester 19 under acidic condi-

tions also led to the cleavage of the compound's thioester moiety,

thus yielding thiol 20. In order to obtain thioester 22, at ﬁrst, the

MOM protective group of mesylate 18 was cleaved and thereafter a

nucleophilic substitution with thioacetic acid was performed.

The primary amine 24 (Scheme 3) represents an important in-

termediate in the synthesis of the envisaged carboxamide and

sulfonamide derivatives. The compound could be accessed via a

Gabriel synthesis. Thus, mesylate 18 was subjected to a nucleophilic

substitution with potassium phthalimide, yielding N-alkylph-

thalimide 23, which was subsequently cleaved with methylamine

to give primary amine 24 [55]. Additionally, the MOM protective

group of compound 24 was removed under acidic conditions

yielding amine 25, which was also tested for antibacterial and LpxC

Furthermore, experiments with 3 and the rat liver microsome

suspension alone as well as with the addition of only one of the

cofactors have been performed. All samples were analyzed by LC-

MS. Suggestions on the chemical structure of the formed metabo-

lites were made based on their exact masses and retention times

(Fig. 4).

When investigating the phase I metabolism of 3, the formation

of carboxylic acid 6 (3-NH) was observed. Whereas only traces of

carboxylic acid 6 were found upon incubation of 3 in PBS buffer pH

7.4 for 120 min, the addition of the rat liver microsome suspension

caused a hydrolytic cleavage of the hydroxamate moiety, irre-

spective of the absence or presence of the cofactor NADPH.

In the performed phase II metabolism study of 3, conjugate

formation yielded glucuronide 3 þ Glu, which is most probably

compound 4, exhibiting a glucuronidated hydroxamate moiety.

The formation of monooxygenated products or metabolites

arising from combined phase I and phase II biotransformation re-

actions could not be observed. Although these experiments were

performed with rat liver microsomes rather than with human

materials, the observations are in good agreement with the in silico

predictions. Both the carboxylic acid metabolite 6 and the glucur-

onic acid metabolite 4 were predicted with SyGMa as two out of

four metabolites. The transformation of the para-position of the

terminal phenyl moiety, predicted by FAME 2 with a moderate

likelihood, could not be experimentally conﬁrmed. However, it is

plausible that such a metabolite is formed in humans.

2.3. Chemistry

The envisaged carboxylic acid derivatives 13, 14, 15 and 16 were

synthesized from ester 9 (Scheme 2), which can be accessed in

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Fig. 2. Predictions of sites of metabolism with FAME 2 and of metabolites with SyGMa. The circle in the center compound (parent) indicates the most likely labile atom position

related to CYP-mediated metabolism. The numbers report the scores (probabilities) assigned by FAME 2 or SyGMa. Note that scores from FAME 2 and SyGMa are not directly

comparable. In the case of SyGMa they should primarily be considered as a means for ranking metabolites.

Fig. 3. HPLC chromatogram of the incubation of 3 with a rat liver microsome suspension, NADPH/H^þand UDPGA. EICs: blue (m/z 486.1414 0.05), green (310.1091 0.05), red

(295.0991 0.05), gradient elution (HPLC method 3), MS-detection in negative ion polarity.

inhibitory activity.

Subsequently, primary amine 24 was coupled with pyrrole-2-

carboxylic acid to give carboxamide 26 and reacted with mesyl

chloride, triﬂyl chloride, and tosyl chloride to yield sulfonamides

28, 30, and 32, respectively (Scheme 4) [56]. These compounds

were ﬁnally deprotected under acidic conditions, giving access to

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Fig. 4. Suggested structures of the observed phase I- and phase II-metabolites of hydroxamic acid 3.

Scheme 2. Reagents and conditions: (a) phenylacetylene, Pd(PPh₃)₄, CuI, NEt₃,

D, 16 h, 99%; (b) HCl, MeOH or EtOH, rt, 16 h, 11 86%, 12 84%; (c) NaOH, THF, rt, 16 h, 82%; (d) aq. NH₃,

rt, 16 h, 75%; (e) H₂NNH₂, EtOH, 37%; (f) EDCI hydrochloride, N-hydroxysuccinimide, 1,2-phenylenediamine, CH₂Cl₂, rt, 16 h, 29%.

alcohols 27, 29, 31, and 33.

hydroxamic acid 3 and which is also accessible from 4-

In order to obtain vicinal diols 38 and 39, secondary alcohol 34,

which is another intermediate of the described synthesis of

bromostyrene (8) [38], was reacted with allyl bromide to give

allyl ether 35 (Scheme 5). The latter was subjected to a Sonogashira

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Scheme 3. Reagents and conditions: (a) DIBAL, CH₂Cl₂, rt, 30 min, 77%; (b) mesyl chloride, NEt₃, DMAP, CH₂Cl₂, rt, 2.5 h, 69%; (c) thioacetic acid, NEt₃, DMF, rt, 16 h, 67%; (d) HCl,

MeOH, rt, 16 h, 53%; (e) HCl, MeOH, rt, 16 h, 87%; (f) thioacetic acid, NEt₃, DMF, rt, 16 h, 72%; (g) potassium phthalimide, DMF, 80 ^ꢀC, 3 h, 84%; (h) H₂NCH₃, EtOH, 70 ^ꢀC, 16 h, 82%; (i)

HCl, EtOH, rt, 16 h, 41%.

Scheme 4. Reagents and conditions: (a) pyrrole-2-carboxylic acid, EDCI hydrochloride, HOBt, NEt₃, CH₂Cl₂, rt, 16 h, 87%; (b) H^þ, MeOH, rt, 82%; (c) mesyl chloride, NEt₃, CH₂Cl₂, rt,

16 h, 79%; (d) HCl, MeOH, rt, 16 h, 85%; (e) triﬂyl chloride, NEt₃, CH₂Cl₂, rt, 16 h, 45%; (f) HCl, MeOH, rt, 16 h, 63%; (g) pTsCl, NEt₃, CH₂Cl₂, rt, 16 h, 85%; (h) HCl, MeOH, rt, 16 h, 89%.

coupling with phenylacetylene, yielding diphenylacetylene deriv-

ative 36. After cleavage of the MOM protective group, Sharpless

asymmetric dihydroxylations were performed with the resulting

with high enantioselectivities (ee > 97%) [38], the diastereomeric

excess of vicinal diols 38 (de ¼ 60%) and 39 (de ¼ 20%) was rather

poor.

alcohol 37 [57]. When AD-mix-

transformed into the (R)-conﬁgured vicinal diol 38, whereas the

use of AD-mix- should lead to the formation of the respective (S)-

conﬁgured vicinal diol 39. However, the diastereoselectivities of the

performed asymmetric dihydroxylations of allyl ether 37 were

relatively low. Whereas the reported Sharpless asymmetric dihy-

droxylations of 4-bromostyrene (8) had yielded the respective diols

a

was used, allyl ether 37 should be

Primary alcohol 41 was obtained from ether 35 via the hydro-

boration of its allyl substituent with 9-borabicyclononane (9-BBN)

followed by an oxidative workup with NaOH/H₂O₂, yielding prop-

anol derivative 40, and a subsequent Sonogashira coupling with

phenylacetylene (Scheme 5) [58,59].

b

Primary alcohols 17 and 41 were used as stating materials for

the synthesis of hydroxypyridinone derivatives (Scheme 6). Thus,

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Scheme 5. Reagents and conditions: (a) allyl bromide, LiHMDS, NBu₄I, THF, D, 16 h, 64%; (b) phenylacetylene, Pd(PPh₃)₄, CuI, NEt₃, D, 16 h, 86%; (c) HCl, MeOH, rt, 16 h, 91%; (d) AD-

mix-

a

, tBuOH/H₂O (1:1), 0 ^ꢀC, 16 h, 38 93%, de ¼ 60% or AD-mix-

b

, tBuOH/H₂O (1:1), 0 ^ꢀC, 16 h, 39 90%, de ¼ 20%; (e) 1. 9-BBN, THF, rt, 17.5 h, 2. MeOH, aq. NaOH, aq. H₂O₂, -25 ^ꢀC /

40 ^ꢀC, 99%; (f) phenylacetylene, Pd(PPh₃)₄, CuI, NEt₃,

D, 16 h, 78%.

Scheme 6. Reagents and conditions: (a) pTsCl, DMAP, NEt₃, CH₂Cl₂, rt, 42 86%, 43 82%; (b) NaN₃, DMSO,

D, 16 h, 44 92%, 45 90%; (c) BnBr, K₂CO₃, ACN, D, 16 h, 95%; (d) 1. polymer-

bound PPh₃, THF, H₂O, 2. 47, H₂O, 140 ^ꢀC, 7 d, 48 19%, 49 14%; (e) 1. HCl, MeOH, rt, 16 h, 2. H₂, Pd/C, MeOH, rt, 16 h, 50 27%, 51 26%.

the compounds were transformed into azides 44 and 45 via a

tosylation and a subsequent substitution with sodium azide. The

obtained azides 44 and 45 were subjected to a Staudinger reduction

and the intermediately formed primary amines were reacted with

benzyl-protected maltol (47) to yield pyridinone derivatives 48 and

49, respectively [60]. Subsequently, both protective groups should

be cleaved under acidic conditions. According to the literature, the

benzyl protective group of the pyridinone derivatives should be

removable under strongly acidic conditions [60]. However, these

conditions also led to the cleavage of the second benzyl ether

moiety within the molecules and consequently to a degradation of

the compounds. Thus, after the acid-catalyzed cleavage of the MOM

protective groups of pyridinone derivatives 48 and 49, their benzyl

groups were hydrogenolytically removed. However, under the

latter reaction conditions, the triple bonds of the compounds were

additionally hydrogenated, leading to the formation 1,2-

diphenylethane derivatives 50 and 51.

For a better comparability, when elucidating the effect of the

replacement of the hydroxamate group by a hydroxypyridinone

moiety, two additional compounds were synthesized. On the one

hand, the 1,2-diphenylethane-derived hydroxamic acid 53 was

prepared (Scheme 7). Staring from the described lactone 52 [38], at

ﬁrst, the hydrogenation of its acetylene moiety was performed,

followed by an aminolysis with hydroxylamine, yielding hydroxa-

mic acid 53.

On the other hand, diphenylacetylene derivative 57 was

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Scheme 7. Reagents and conditions: (a) 1. H₂, Pd/C, MeOH, rt, 16 h, 2. H₂NOH$HCl, NaOMe, MeOH, rt, 16 h, 52%.

synthesized (Scheme 8), which can be considered as

a

other of the investigated functional groups is detrimental for the

inhibitory activity toward LpxC. None of the assayed compounds

was able to inhibit the enzymatic activity of LpxC by more than half

at the highest concentrations tested. These data are in general

agreement with the observed antibacterial activities.

hydroxypyridinone-derived analogue of the described benzylox-

yacetohydroxamic acid 58 [38]. The reaction of 2-(4-bromophenyl)

ethylamine (54) with maltol derivative 47 yielded pyridinone de-

rivative 55. After a Sonogashira coupling with phenylacetylene, the

benzyl protective group was removed by heating pyridinone de-

rivative 56 under strongly acidic conditions to yield hydroxypyr-

idinone derivative 57.

Whereas carboxylic acid 13, amide 14, thiol 20 and thioester 22

did not show any antibacterial activity, neither in the disc diffusion

nor in the MIC assays, hydrazide 15 was found to be able to inhibit

the growth of both E. coli strains in the performed disc diffusion

assays. However, the diameters of the observed halos of inhibition

caused by this compound, which should be able to chelate the

catalytic Zn^2þ-ion of LpxC in a similar fashion as hydroxamic acid 3,

are considerably smaller compared to the ones caused by the latter

compound. Also 1,2-phenylenediamine derivative 16 as well as

vicinal diols 38 and 39 caused observable halos of inhibition,

particularly against the sensitive E. coli D22 strain. Whereas pyr-

role-2-carboxamide 27 was found to exhibit no antibacterial ac-

tivity, among the investigated sulfonamides 29, 31, and 33,

noticeable halos of inhibition were found for mesylamide 29 and

triﬂylamide 31. In contrast, no inhibition of bacterial growth was

observed for sulfonamide 33.

Surprisingly, primary amine 25 caused quite large halos of in-

hibition, which however did not translate into low MIC values. Due

to its primary amino group, the inhibitory activity of compound 25

could not be determined using the ﬂuorescence-based LpxC

enzyme assay. Thus, it still needs to be elucidated, whether the

observed antibacterial activity in the disc diffusion assays is due to

inhibitory activity of the compound toward LpxC or due to un-

speciﬁc cytotoxicity, the latter being indicated by halos of inhibition

of approximately the same size when being assayed against E. coli

BL21 and the sensitive E. coli strain D22.

2.4. Biological evaluation

In order to evaluate the antibacterial activities of the synthe-

sized compounds, disc diffusion tests with E. coli BL21 (DE3) and

the defective E. coli strain D22 [61], which is more sensitive towards

LpxC inhibition, were performed and the MIC (minimal inhibitory

concentration) values of the potential LpxC inhibitors were deter-

mined (Table 1). Additionally, a ﬂuorescence-based LpxC enzyme

assay was performed to test the inhibitory activity of the synthe-

sized compounds against the isolated enzyme [62]. In the LpxC

enzyme assay, puriﬁed E. coli LpxCC63A was employed, as the C63A

mutation lowers the undesired inﬂuence of Zn^2þ-concentration on

enzymatic activity [5,63]. The inhibition of the deacetylation of the

enzyme's natural substrate 1 (Scheme 1) caused by a certain con-

centration of the putative inhibitors (ranging from 0.2 nM to

200 mM) was determined by transforming the resulting deacety-

lated primary amine 2 into a ﬂuorescent isoindole with phtha-

laldehyde and 2-mercaptoethanol.

As under the conditions of the enzyme assay primary amine 25

gave a ﬂuorescent product itself, an IC₅₀value could not be deter-

mined for this compounds. For all the other phenylethylene glycol

derivatives the results of the enzyme assay clearly showed that the

replacement of the hydroxamate moiety of compound 3 by any

The hydroxypyridinone derivatives 50 and 51 also exhibit no

Scheme 8. Reagents and conditions: (a) H₂O, 140 ^ꢀC, 10 d, 60%; (b) phenylacetylene, Pd(PPh₃)₄, CuI, NEt₃, ACN,

D, 16 h, 67%; (c) aq. HCl, MeOH, D, 4 h, 60%.

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

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10

M. Galster et al. / Tetrahedron xxx (xxxx) xxx

antibacterial activity. However, their inactivity in the performed

assays could be attributed to their ﬂexible side chain, as the hy-

drogenation of the triple bond of the diphenylacetylene moiety also

led to the complete inactivity of hydroxamic acid 53. This ﬁnding is

in agreement with previous observations that in case of the ben-

zyloxyacetohydroxamic acids a long, linear, and rigid lipophilic side

chain is required for potent LpxC inhibitory activity [38,64].

Additional evidence that the replacement of the hydroxamate

group by a hydroxypyridinone moiety is unfavorable for the bio-

logical activity of the compounds is given by hydroxypyridinone

derivative 57, which, in contrast to benzyloxyacetohydroxamic acid

58, exhibits no antibacterial activity at the concentrations tested.

column: phenomenex Gemini^®

250 ꢃ 4.6 mm; ﬂow rate: 1.00 mL/min; injection volume: 5.0

detection at

10 mM ammonium formate ¼ 10: 90 with 0.1% formic acid; B:

acetonitrile: 10 mM ammonium formate ¼ 90: 10 with 0.1% formic

acid; gradient elution: (A %): 0e5 min: 100%, 5e15 min: gradient

from 100% to 0%, 15e20 min: 0%, 20e22 min: gradient from 0% to

100%, 22e30 min: 100%.

5

m

m C6-Phenyl 110 Å; LC Column

L;

¼ 254 nm for 20 min; solvents: A: acetonitrile:

m

l

4.2. Synthetic procedures

4.2.1. Ethyl (S)-2-{2-(methoxymethoxy)-1-[4-(phenylethynyl)

phenyl]ethoxy}acetate (10)

Under N₂atmosphere, copper(I) iodide (50 mg, 0.26 mmol),

tetrakis(triphenylphosphine)palladium(0) (200 mg, 0.18 mmol)

and phenylacetylene (0.27 mL, 250 mg, 2.5 mmol) were added to a

solution of 9 (610 mg, 1.8 mmol) in triethylamine (40 mL). The

mixture was heated to reﬂux and additional phenylacetylene

(0.27 mL, 250 mg, 2.5 mmol) was added. After stirring the mixture

under reﬂux conditions for 16 h, the solvent was evaporated and

the residue was puriﬁed by ﬂash column chromatography

(Ø ¼ 3 cm, h ¼ 15 cm, cyclohexane/ethyl acetate ¼ 8:2, V ¼ 20 mL)

to give 10 as yellowish oil (650 mg, 1.8 mmol, 99% yield). R_f¼ 0.68

3. Conclusions

In divergent syntheses, phenylethylene glycol derivatives

exhibiting various Zn^2þ-binding groups, like e.g. carboxylate, hy-

drazide, amide, sulfonamide, and thiol moieties, were obtained.

The biological evaluation of the synthesized compounds revealed

that the replacement of the hydroxamate moiety of compound 3 by

other Zn^2þ-binding groups is detrimental for the LpxC inhibitory

and antibacterial activity of the phenylethylene glycol derivatives.

For this reason, the metabolic stability of none of the newly syn-

thesized compounds exhibiting an alternative Zn^2þ-binding group

was investigated. Thus, hydroxamic acid 3, whose hydroxamate

moiety was shown by in silico predictions as well as by in vitro

experiments to be the major metabolically labile position of the

compound, still represents the most potent LpxC inhibitor of the

presented phenylethylene glycol derivatives. In consequence,

further efforts need to be undertaken to ﬁnd suitable Zn^2þ-binding

groups that can replace the hydroxamate moiety without causing a

loss of LpxC inhibitory and antibacterial activity.

(cyclohexane/ethyl acetate ¼ 2:1); speciﬁc rotation: ½a _D²⁰

¼ þ91.4

ꢁ

(3.5; CH₂Cl₂); ¹H NMR (CDCl₃):

d

[ppm] ¼ 1.26 (t, J ¼ 7.2 Hz, 3H,

CO₂CH₂CH₃), 3.29 (s, 3H, OCH₂OCH₃), 3.71 (dd, J ¼ 10.8/4.3 Hz, 1H,

OCHCH₂O), 3.84 (dd, J ¼ 10.8/7.2 Hz, 1H, OCHCH₂O), 3.99 (d,

J ¼ 16.3 Hz, 1H, OCH₂CO₂Et), 4.11 (d, J ¼ 16.3 Hz, 1H, OCH₂CO₂Et),

4.15e4.23 (m, 2H, CO₂CH₂CH₃), 4.64 (d, J ¼ 6.6 Hz, 1H, OCH₂OCH₃),

4.67 (d, J ¼ 6.6 Hz, 1H, OCH₂OCH₃), 4.69 (dd, J ¼ 7.2/4.3 Hz, 1H,

OCHCH₂O), 7.31e7.39 (m, 5H, H_arom.), 7.49e7.56 (m, 4H, H_arom.); ¹³

C

NMR (CDCl₃):

d

[ppm] ¼ 14.3 (1C, CO₂CH₂CH₃), 55.5 (1C,

OCH₂OCH₃), 61.0 (1C, CO₂CH₂CH₃), 66.5 (1C, OCH₂CO₂Et), 71.3 (1C,

OCHCH₂O), 81.4 (1C, OCHCH₂O), 89.1 (1C, C^C), 89.9 (1C, C^C),

96.7 (1C, OCH₂OCH₃), 123.3 (1C, C_arom.), 123.5 (1C, C_arom.), 127.4 (2C,

4. Experimental section

C

_arom.), 128.49 (1C, C_arom.), 128.50 (2C, C_arom.), 131.8 (2C, C_arom.),

4.1. Chemistry, general

131.9 (2C, C_arom.), 138.5 (1C, C_arom.), 170.3 (1C, CO₂Et); IR (neat): ṽ

[cm^ꢂ1] ¼ 2928, 1751, 1508, 1443, 1381, 1277, 1200, 1111, 1034, 918,

837, 756, 691; HRMS (m/z): [MþH]^þcalcd for C₂₂H₂₅O₅: 369.1697,

found: 369.1664; HPLC (method 1): t_R¼ 22.0 min, purity 97.5%.

Unless otherwise mentioned, THF was dried with sodium/

benzophenone and was freshly distilled before use. Thin layer

chromatography (TLC): Silica gel 60 F₂₅₄plates (Merck). Reversed

phase thin layer chromatography (RP-TLC): Silica gel 60 RP-18 F₂₅₄S

4.2.2. Methyl (S)-2-{2-hydroxy-1-[4-(phenylethynyl)phenyl]

ethoxy}acetate (11)

plates (Merck). Flash chromatography (FC): Silica gel 60, 40e64 mm

(Macherey-Nagel); brackets include: diameter of the column,

fraction size, eluent. Automatic ﬂash column chromatography:

Isolera™ One (Biotage^®); brackets include: eluent, cartridge-type.

Melting point: Melting point apparatus SMP 3 (Stuart Scientiﬁc),

10 (100 mg, 0.28 mmol) was dissolved in HCl-saturated meth-

anol (5 mL). The reaction mixture was stirred at ambient temper-

ature for 16 h. After addition of a saturated aqueous solution of

sodium bicarbonate and water, the mixture was extracted with

ethyl acetate (3ꢃ). The combined organic layers were dried over

sodium sulfate, ﬁltered, and the solvent was removed in vacuo. The

residue was puriﬁed by ﬂash column chromatography (Ø ¼ 2 cm,

h ¼ 17 cm, cyclohexane/ethyl acetate ¼ 8:2 / 2:1, V ¼ 10 mL) to

give 11 as colorless oil (73 mg, 0.24 mmol, 86% yield). R_f¼ 0.21

uncorrected. Optical rotation

a [deg] was determined with a

Polarimeter 341 (Perkin Elmer); path length 1 dm, wavelength

589 nm (sodium D line); the unit of the speciﬁc rotation ½a _D²⁰

ꢁ

[deg ^.

mL ^.dm^{ꢂ1 .}g^ꢂ1] is omitted; the concentration of the sample c [mg ^.

mL^ꢂ1] and the solvent used are given in brackets. ¹H NMR

(400 MHz), ¹³C NMR (100 MHz): Agilent DD2 400 MHz spectrom-

(cyclohexane/ethyl acetate ¼ 2:1); speciﬁc rotation: ½a _D²⁰

¼ þ175.9

ꢁ

eter;

d in ppm related to tetramethylsilane. IR: IR Prestige-21

(3.4; CH₂Cl₂); ¹H NMR: (CD₃OD):

d

[ppm] ¼ 3.63 (dd, J ¼ 11.8/4.0 Hz,

(Shimadzu). APCI/LC-MS: MicrOTOF-QII (Bruker). HPLC methods

for the determination of product purity: Method 1: Merck Hitachi

Equipment; UV detector: L-7400; autosampler: L-7200; pump: L-

7100; degasser: L-7614; column: LiChrospher^®60 RP-select B

1H, OCHCH₂OH), 3.72 (s, 3H, OCH₂CO₂CH₃), 3.74 (dd, J ¼ 11.8/7.4 Hz,

1H, OCHCH₂OH), 4.04 (d, J ¼ 16.3 Hz, 1H, OCH₂CO₂CH₃), 4.11 (d,

J ¼ 16.3 Hz, 1H, OCH₂CO₂CH₃), 4.54 (dd, J ¼ 7.4/4.0 Hz, 1H, OCH-

CH₂OH), 7.34e7.40 (m, 5H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_4-(phenyl-

_{ethynyl)phenyl}, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.47e7.55 (m, 4H, 3⁰-

(5

injection volume: 5.0

m

m); LiChroCART^®250-4 mm cartridge; ﬂow rate: 1.00 mL/min;

mL; detection at

l

¼ 210 nm for 30 min; sol-

H_{4-(phenylethynyl)phenyl}

,

5⁰-H_{4-(phenylethynyl)phenyl}

,

2⁰⁰-H_phenyl

,

6⁰⁰-

vents: A: water with 0.05% (V/V) triﬂuoroacetic acid; B: acetonitrile

with 0.05% (V/V) triﬂuoroacetic acid: gradient elution: (A %):

0e4 min: 90%, 4e29 min: gradient from 90% to 0%, 29e31 min: 0%,

31e31.5 min: gradient from 0% to 90%, 31.5e40 min: 90%. Method

2: Merck Hitachi Equipment; UV detector: L-7400; pump: L-6200A;

H

_phenyl); ¹³C NMR (CD₃OD):

d

[ppm] ¼ 52.4 (1C, CO₂CH₃), 67.2 (1C,

OCH₂CO₂CH₃), 67.4 (1C, OCHCH₂OH), 84.7 (1C, OCHCH₂OH), 89.8

(1C, C^C), 90.4 (1C, C^C), 124.46 (1C, C_arom.), 124.48 (1C, C_arom.),

128.4 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 129.5

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11

(1C, C-4⁰⁰_phenyl), 129.6 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 132.5 (2C, C_arom.),

132.7 (2C, C_arom.), 140.0 (1C, C-1⁰_{4-(phenylethynyl)phenyl}), 172.8 (1C,

CO₂CH₃); IR (neat): ṽ [cm^ꢂ1] ¼ 3456, 2951, 1740, 1508, 1439, 1408,

1377, 1215, 1126, 1053, 833, 756, 691; LCMS (m/z): [MþNa]^þcalcd

for C₁₉H₁₈NaO₄: 333.1097, found: 333.1097; HPLC (method 1):

t_R¼ 21.1 min, purity 95.7%.

314.1387, found: 314.1416; HPLC (method 2): t_R¼ 17.0 min, purity

98.0%.

4.2.5. (S)-2-{2-Hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}

acetamide (14)

An emulsion of 11 (55 mg, 0.18 mmol) in ammonia solution (ca.

25% NH₃, 4 mL) was stirred at ambient temperature overnight. The

formed precipitate was ﬁltered off, washed with water (3ꢃ) and

dried in a desiccator for 7 d to give 14 as colorless solid (40 mg,

4.2.3. Ethyl (S)-2-{2-hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}

acetate (12)

0.14 mmol, 75% yield). R_f

¼

0.34 (dichloromethane/meth-

10 (120 mg, 0.31 mmol) was dissolved in HCl-saturated ethanol

(4 mL). The reaction was stirred at ambient temperature for 16 h.

After addition of a saturated aqueous solution of sodium bicar-

bonate and water, the mixture was extracted with ethyl acetate

(3ꢃ). The combined organic layers were dried over sodium sulfate,

ﬁltered, and the solvent was removed in vacuo. The residue was

puriﬁed by ﬂash column chromatography (Ø ¼ 2 cm, h ¼ 15 cm,

cyclohexane/ethyl acetate ¼ 8:2 / 2:1, V ¼ 10 mL) to give 12 as

yellowish oil (84 mg, 0.26 mmol, 84% yield). R_f¼ 0.14 (cyclohexane/

anol ¼ 9:1); melting point: 139 ^ꢀC; speciﬁc rotation: ½a ²_D⁰

¼ þ127.1

ꢁ

(2.9; CH₃OH); ¹H NMR: (CD₃OD):

d

[ppm] ¼ 3.64 (dd, J ¼ 11.9/

3.5 Hz, 1H, OCHCH₂OH), 3.71 (dd, J ¼ 11.9/8.0 Hz, 1H, OCHCH₂OH),

3.81 (d, J ¼ 15.7 Hz, 1H, OCH₂CONH₂), 3.93 (d, J ¼ 15.7 Hz, 1H,

OCH₂CONH₂), 4.51 (dd, J ¼ 8.0/3.5 Hz, 1H, OCHCH₂OH), 7.33e7.41

(m, 5H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}, 3⁰⁰-H_phenyl

,

5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.48e7.56 (m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}

5⁰-H_{4-(phenylethynyl)phenyl}, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl); ¹³C NMR: (CD₃OD):

ethyl acetate ¼ 3:1); speciﬁc rotation: ½a _D²⁰

¼ þ156.2 (2.6; CH₂Cl₂);

ꢁ

d

[ppm] ¼ 67.4 (1C, OCHCH₂OH), 69.0 (1C, OCH₂CONH₂), 85.3 (1C,

¹H NMR (CDCl₃):

d

[ppm] ¼ 1.29 (t, J ¼ 7.2 Hz, 3H, CO₂CH₂CH₃), 3.65

OCHCH₂OH), 89.7 (1C, C^C), 90.5 (1C, C^C), 124.5 (1C, C_arom.),

124.6 (1C, C_arom.), 128.2 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_4-(phenyl-

_{ethynyl)phenyl}), 129.5 (1C, C-4⁰⁰_phenyl), 129.6 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl),

132.5 (2C, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl), 132.8 (2C, C-3⁰_{4-(phenylethynyl)phenyl}

(dd, J ¼ 11.8/3.2 Hz, 1H, OCHCH₂OH), 3.76 (dd, J ¼ 11.8/8.8 Hz, 1H,

OCHCH₂OH), 3.94 (d, J ¼ 16.8 Hz, 1H, OCH₂CO₂Et), 4.20 (d,

J ¼ 16.8 Hz, 1H, OCH₂CO₂Et), 4.21e4.28 (m, 2H, CO₂CH₂CH₃), 4.52

(dd, J ¼ 8.8/3.2 Hz, 1H, OCHCH₂OH), 7.29e7.39 (m, 5H, 2⁰-H_4-(phe-

_{nylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-

H_phenyl), 7.50e7.56 (m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_4-(phenyl-

,

C-5⁰_{4-(phenylethynyl)phenyl}), 139.7 (1C, C-1⁰_{4-(phenylethynyl)phenyl}), 175.6

(1C, CONH₂); IR (neat): ṽ [cm^ꢂ1] ¼ 3348, 3194, 2978, 2913, 1686,

1655, 1597, 1504, 1412, 1331, 1238, 1107, 1076, 1049, 833, 756, 691;

LCMS (m/z): [MþH]^þcalcd for C₁₈H₁₈NO₃: 296.1281, found:

296.1289; HPLC (method 2): t_R¼ 16.2 min, purity 97.2%.

,

2⁰⁰-H_phenyl

,

6⁰⁰-H_phenyl);

¹³C

NMR

(CDCl₃):

ethynyl)phenyl

d

[ppm] ¼ 14.3 (1C, CO₂CH₂CH₃), 61.5 (1C, CO₂CH₂CH₃), 66.5 (1C,

OCH₂CO₂Et), 67.3 (1C, OCHCH₂OH), 84.6 (1C, OCHCH₂OH), 89.0 (1C,

C^C), 90.0 (1C, C^C), 123.2 (1C₀, C-1⁰⁰_phenyl), 123.6 (1C, C-4⁰_4-(phe-

,

C-6⁰_4-(phenyl-

4.2.6. (S)-2-{2-Hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}

acetohydrazide (15)

_{nylethynyl)phenyl}), 126.9 (2C, C-2 _{4-(phenylethynyl)phenyl}

_{ethynyl)phenyl}), 128.51 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 128.53 (1C, C-

4⁰⁰_phenyl), 131.8 (2C, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl), 132.0 (2C, C-3⁰_4-(phenyl-

_{ethynyl)phenyl}, C-5⁰_{4-(phenylethynyl)phenyl}), 137.9 (1C, C-1⁰_{4-(phenylethynyl)}

_phenyl), 171.3 (1C, CO₂Et); IR (neat): ṽ [cm^ꢂ1] ¼ 3437, 2970, 1736,

1508, 1443, 1381, 1215, 1126, 949, 837, 756, 691; LCMS (m/z):

[MþH]^þcalcd for C₂₀H₂₁O₄: 325.1434, found: 325.1469; HPLC

(method 1): t_R¼ 22.1 min, purity 97.7%.

After heating a solution of hydrazine monohydrate (98%,

0.20 mL, 210 mg, 4.1 mmol) in ethanol (6 mL) to reﬂux for 5 min, a

solution of 12 (170 mg, 0.54 mmol) in ethanol (6 mL) was added and

the mixture was heated to reﬂux for 75 min and then stirred at

ambient temperature overnight. After removing the solvent in

vacuo, the residue was puriﬁed by ﬂash column chromatography (1.

Ø ¼ 2 cm, h ¼ 15 cm, ethyl acetate/methanol ¼ 100:0 / 10:1,

V ¼ 10 mL; 2. Ø ¼ 2 cm, h ¼ 15 cm, dichloromethane/meth-

anol ¼ 98:2 / 95:5, V ¼ 10 mL) to give 15 as colorless solid (61 mg,

0.20 mmol, 37% yield). R_f¼ 0.23 (ethyl acetate/methanol ¼ 10:1);

4.2.4. (S)-2-{2-Hydroxy-1-[4-(phenylethynly)phenyl]ethoxy}acetic

acid (13)

melting point: 104 ^ꢀC; speciﬁc rotation: ½a ²_D⁰

¼ þ106.5 (3.0;

ꢁ

12 (310 mg, 0.95 mmol) was dissolved in THF (3 mL) and a 1 M

aqueous solution of NaOH (10 mL) was added. The reaction was

stirred at ambient temperature for 16 h. Then the mixture was

acidiﬁed with a 1 M aqueous solution of HCl and extracted with

ethyl acetate (3ꢃ). The combined organic layers were dried over

sodium sulfate, ﬁltered, and the solvent was removed in vacuo to

give 13 as a colorless solid (230 mg, 0.78 mmol, 82% yield). R_f¼ 0.41

(dichloromethane/methanol ¼ 9:1); melting point: 122 ^ꢀC; speciﬁc

CH₃OH); ¹H NMR (DMSO‑d₆):

d

[ppm] ¼ 3.41e3.64 (m, 2H, OCH-

CH₂OH), 3.78 (d, J ¼ 14.8 Hz, 1H, OCH₂CONH), 3.85 (d, J ¼ 14.8 Hz,

1H, OCH₂CONH), 4.20e4.55 (m, 2H, CONHNH₂), 4.45 (dd, J ¼ 7.3/

3.4 Hz, 1H, OCHCH₂OH), 5.21e5.34 (m, 1H, OCHCH₂OH), 7.32e7.49

(m, 5H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}, 3⁰⁰-H_phenyl

,

5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.49e7.63 (m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}

5⁰-H_{4-(phenylethynyl)phenyl}

,

2⁰⁰-H_phenyl

,

6⁰⁰-H_phenyl), 9.19 (s, 1H,

rotation:

½

a ²_D⁰

ꢁ

¼

þ87.3 (2.2; CH₂Cl₂); ¹H NMR (CD₃OD):

CONHNH₂); ¹³C NMR (DMSO‑d₆):

d

[ppm] ¼ 65.5 (1C, OCHCH₂OH),

67.7 (1C, OCH₂CONH), 83.2 (1C, OCHCH₂OH), 89.2 (1C, C^C), 89.3

(1C, C^C), 121.7 (1C, C-4⁰_{4-(phenylethynyl)phenyl}), 122.2 (1C, C-1⁰⁰_phenyl),

127.3 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 128.76

(2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 128.80 (1C, C-4⁰⁰_phenyl), 131.3 (2C, C_arom.),

131.4 (2C, C_arom.), 139.5 (1C, C-1⁰_{4-(phenylethynyl)phenyl}), 168.0 (1C,

CONHNH₂); IR (neat): ṽ [cm^ꢂ1] ¼ 3294, 2909, 1651, 1632, 1535,

1508, 1443, 1335, 1119, 1049, 833, 756, 691; LCMS (m/z): [MþH]^þ

calcd for C₁₈H₁₉N₂O₃: 311.1390, found: 311.1384; HPLC (method 1):

t_R¼ 17.4 min, purity 95.7%.

d

[ppm] ¼ 3.63 (dd, J ¼ 11.8/3.9 Hz, 1H, OCHCH₂OH), 3.74 (dd,

J ¼ 11.8/7.5 Hz,1H, OCHCH₂OH), 3.99 (d, J ¼ 16.5 Hz,1H, OCH₂CO₂H),

4.08 (d, J ¼ 16.5 Hz, 1H, OCH₂CO₂H), 4.54 (dd, J ¼ 7.5/3.9 Hz, 1H,

OCHCH₂OH), 7.30e7.41 (m, 5H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_4-(phe-

_{nylethynyl)phenyl}, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.45e7.59 (m, 4H,

3⁰-H_{4-(phenylethynyl)phenyl}

,

, ,

5⁰-H_{4-(phenylethynyl)phenyl}2⁰⁰-H_phenyl6⁰⁰-

H

_phenyl); ¹³C NMR (CD₃OD):

d

[ppm] ¼ 67.1 (1C, OCH₂CO₂H), 67.4

(1C, OCHCH₂OH), 84.7 (1C, OCHCH₂OH), 89.8 (1C, C^C), 90.4 (1C,

C^C), 124.47 (1C, C_arom.), 124.49 (1C, C_arom.), 128.4 (2C, C-2⁰_4-(phe-

_{nylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 129.5 (1C, C-4⁰⁰_phenyl), 129.6

(2C, C-3⁰⁰₀_phenyl, C-5⁰⁰_phenyl), 132.5 (2C, C_arom.), 132.7 (2C, C_arom.), 140.0

(1C, C-1 _{4-(phenylethynyl)phenyl}), 174.2 (1C, OCH₂CO₂H); IR (neat): ṽ

[cm^ꢂ1] ¼ 2978, 2889, 1739, 1597, 1508, 1385, 1242, 1126, 1072, 1053,

953, 833, 752, 687; LCMS (m/z): [M þ NH₄]^þcalcd for C₁₈H₂₀NO₄:

4.2.7. (S)-N-(2-Aminophenyl)-2-{2-hydroxy-1-[4-(phenylethynyl)

phenyl]ethoxy}acetamide (16)

Under N₂atmosphere, 1-ethyl-3-(3-dimethylaminopropyl)car-

bodiimide (EDCI) hydrochloride (65 mg, 0.34 mmol), N-

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

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M. Galster et al. / Tetrahedron xxx (xxxx) xxx

hydroxysuccinimide

(39 mg,

0.34 mmol)

and

1,2-

[cm^ꢂ1] ¼ 3429, 2927, 2882, 1597, 1508, 1443, 1408, 1343, 1211, 1150,

1107, 1030, 918, 833, 756, 691; HRMS (m/z): [MþH]^þcalcd for

phenylenediamine (37 mg, 0.34 mmol) were added to a solution

of 13 (100 mg, 0.34 mmol) in dry dichloromethane (15 mL). The

reaction mixture was stirred under N₂atmosphere (balloon) at

ambient temperature for 16 h. Then water was added and the

mixture was extracted with dichloromethane (3ꢃ). The combined

organic layers were dried over sodium sulfate, ﬁltered, and the

solvent was removed in vacuo. The residue was puriﬁed by ﬂash

column chromatography (Ø ¼ 2 cm, h ¼ 20 cm, dichloromethane/

methanol ¼ 100:0 / 9:1, V ¼ 20 mL) to give 16 as yellowish solid

(38 mg, 0.10 mmol, 29% yield). R_f¼ 0.23 (cyclohexane/ethyl ace-

C₂₀H₂₃O₄: 327.1591, found: 327.1563; HPLC (method 1):

t_R¼ 21.4 min, purity 99.3%.

4.2.9. (S)-2-{2-(Methoxymethoxy)-1-[4-(phenylethynyl)phenyl]

ethoxy}ethyl methanesulfonate (18)

Under N₂atmosphere, triethylamine (1.6 mL, 1.2 g, 12 mmol),

DMAP (140 mg, 1.2 mmol) and methanesulfonyl chloride (0.9 mL,

1.3 g, 12 mmol) were added to a solution of 17 (1.9 g, 5.9 mmol) in

dry dichloromethane (100 mL). The reaction was stirred for 2.5 h at

ambient temperature. Then water and a saturated aqueous solution

of sodium bicarbonate were added and the mixture was extracted

with dichloromethane (3ꢃ). The combined organic layers were

dried over sodium sulfate, ﬁltered, and the solvent was evaporated

in vacuo. The residue was puriﬁed by ﬂash column chromatography

(Ø ¼ 6 cm, h ¼ 15 cm, cyclohexane/ethyl acetate ¼ 8:2 / 2:1,

V ¼ 50 mL) to give 18 as colorless solid (1.7 g, 4.1 mmol, 69% yield).

R_f¼ 0.22 (cyclohexane/ethyl acetate ¼ 2:1); melting point: 59 ^ꢀC;

tate ¼ 1:2); melting point: 134 ^ꢀC; speciﬁc rotation: ½a ²_D⁰

¼ þ115.2

ꢁ

(2.5; CH₂Cl₂); ¹H NMR (CD₃OD):

d

[ppm] ¼ 3.70 (dd, J ¼ 11.9/3.2 Hz,

1H, OCHCH₂OH), 3.76 (dd, J ¼ 11.9/8.5 Hz, 1H, OCHCH₂OH), 4.00 (d,

J ¼ 15.8 Hz, 1H, OCH₂CONH), 4.17 (d, J ¼ 15.8 Hz, 1H, OCH₂CONH),

4.65 (dd, J ¼ 8.5/3.2 Hz, 1H, OCHCH₂OH), 6.74 (td, J ¼ 7.6/1.4 Hz, 1H,

5⁰⁰⁰-H_{2-aminophenyl}), 6.88 (dd, J ¼ 8.0/1.4 Hz, 1H, 3⁰⁰⁰-H_{2-aminophenyl}),

7.05 (ddd, J ¼ 8.0/7.4/1.5 Hz, 1H, 4⁰⁰⁰-H_{2-aminophenyl}), 7.24 (dd, J ¼ 7.8/

1.5 Hz, 1H, 6⁰⁰⁰-H_{2-aminophenyl}), 7.34e7.40 (m, 3H, 3⁰⁰-H_phenyl, 5⁰⁰-

H_phenyl, 4⁰⁰-H_phenyl), 7.42e7.46 (m, 2H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-

H_{4-(phenylethynyl)phenyl)}, 7.49e7.54 (m, 2H, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl),

speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ27.4 (2.4; CH₂Cl₂); ¹H NMR (CD₂Cl₂):

d

[ppm] ¼ 3.05 (s, 3H, OSO₂CH₃), 3.28 (s, 3H, OCH₂OCH₃), 3.63 (dd,

7.54e7.58 (m, 2H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl)}

¹³C NMR (CD₃OD):

[ppm] ¼ 67.3 (1C, OCHCH₂OH), 69.6 (1C,

;

J ¼ 10.9/4.1 Hz, 1H, OCHCH₂O), 3.65e3.71 (m, 2H, OCH₂CH₂OS) 3.74

(dd, J ¼ 10.9/7.4 Hz, 1H, OCHCH₂O), 4.32e4.37 (m, 2H, OCH₂CH₂OS),

4.56 (dd, J ¼ 7.4/4.1 Hz, 1H, OCHCH₂O), 4.60 (d, J ¼ 6.5 Hz, 1H,

OCH₂OCH₃), 4.62 (d, J ¼ 6.5 Hz, 1H, OCH₂OCH₃), 7.32e7.40 (m, 5H,

d

OCH₂CONH), 85.7 (1C, OCHCH₂OH), 89.7 (1C, C^C), 90.6 (1C, C^C),

118.5 (1C, 3⁰⁰⁰-C_{2-aminophenyl}), 119.5 (1C, 5⁰⁰⁰-C_{2-aminophenyl}), 124.2 (1C,

1⁰⁰⁰-C_{2-aminophenyl}), 124.5 (1C, C-1⁰⁰_phenyl), 124.7 (1C, C-4⁰_4-(phenyl-

_{ethynyl)phenyl}), 127.1 (1C, 6⁰⁰⁰-C_{2-aminophenyl}), 128.3 (2C, C-2⁰_4-(phenyl-

_{ethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 128.5 (1C, 4⁰⁰⁰-C_{2-aminophenyl}),

129.5 (1C, C-4⁰⁰_phenyl), 129.6 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 132.5 (2C, C-

2⁰⁰_phenyl, C-6⁰⁰_phenyl), 132.8 (2C, C-3⁰_{4-(phenylethynyl)phenyl}, C-5⁰_4-(phenyl-

_{ethynyl)phenyl}), 139.6 (1C, C-1⁰_{4-(phenylethynyl)phenyl}), 143.2 (2⁰⁰⁰-C_2-

_aminophenyl), 171.4 (1C, CONH); IR (neat): ṽ [cm^ꢂ1] ¼ 3472, 3383,

3310, 2924, 2866, 1663, 1616, 1531, 1504, 1458, 1335, 1312, 1269,

1111, 1057, 833, 748, 691; LCMS (m/z): [MþH]^þcalcd for

2⁰-H_{4-(phenylethynyl)phenyl}

, , ,

6⁰-H_{4-(phenylethynyl)phenyl}3⁰⁰-H_phenyl5⁰⁰-

H_phenyl, 4⁰⁰-H_phenyl), 7.50e7.57 (m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-

H_{4-(phenylethynyl)phenyl}, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl); ¹³C NMR (CD₂Cl₂):

d

[ppm] ¼ 38.1 (1C, OSO₂CH₃), 55.6 (1C, OCH₂OCH₃), 67.7 (1C,

OCH₂CH₂OS), 70.2 (1C, OCH₂CH₂OS), 72.0 (1C, OCHCH₂O), 82.3 (1C,

OCHCH₂O), 89.5 (1C, C^C), 90.1 (1C, C^C), 97.2 (1C, OCH₂OCH₃),

123.6 (1C, C_arom.), 123.7 (1C, C_arom.), 127.7 (2C, C-2⁰_{4-(phenylethynyl)}

_phenyl, C-6⁰_{4-(phenylethynyl)phenyl}), 128.98 (1C, C-4⁰⁰_phenyl), 128.99 (2C,

C-3₀⁰⁰_phenyl, C-5⁰⁰_phenyl), 132.1 (2C, C_arom.), 132.2 (2C, C_arom.), 139.6 (1C,

C-1 _{4-(phenylethynyl)phenyl}); IR (neat): ṽ [cm^ꢂ1] ¼ 2932, 1508, 1443,

1350, 1173, 1107, 1034, 1018, 968, 914, 833, 799, 756, 691; LCMS (m/

z): [MþH]^þcalcd for C₂₁H₂₅O₆S: 405.1366, found: 405.1365; HPLC

(method 1): t_R¼ 22.9 min, purity 99.7%.

C

₂₄H₂₃N₂O₃: 387.1703, found: 387.1719; HPLC (method 2):

t_R¼ 17.4 min, purity 97.7%.

4.2.8. (S)-2-{2-(Methoxymethoxy)-1-[4-(phenylethynyl)phenyl]

ethoxy}ethan-1-ol (17)

4.2.10. (S)-S-{2-[2-(Methoxymethoxy)-1-(4-[phenylethynyl]

phenyl)ethoxy]ethyl} ethanethioate (19)

Under N₂atmosphere, a 1.2 M solution of diisobutylaluminium

hydride in toluene (14 mL, 17 mmol) was added to a solution of 10

(2.8 g, 7.6 mmol) in dry dichloromethane (100 mL). The mixture

was stirred at ambient temperature. After 30 min the reaction was

terminated by adding a saturated aqueous solution of Rochelle salt

(50 mL). Then diethyl ether (100 mL) was added and the mixture

was vigorously stirred until two clear layers appeared. The aqueous

layer was extracted with ethyl acetate (3ꢃ). The combined organic

layers were dried over sodium sulfate, ﬁltered, and the solvent was

removed in vacuo. The residue was puriﬁed by ﬂash column chro-

matography (Ø ¼ 6 cm, h ¼ 15 cm, cyclohexane/ethyl ace-

tate ¼ 8:2 / 100% ethyl acetate, V ¼ 50 mL) to give 17 as colorless

oil (1.9 g, 5.9 mmol, 77% yield). R_f¼ 0.41 (cyclohexane/ethyl ace-

Triethylamine (40

tion of 18 (97 mg, 0.24 mmol) in DMF (10 mL). Then thioacetic acid

(20 L, 19 mg, 0.25 mmol) was added dropwise to the mixture. The

mL, 26 mg, 0.26 mmol) was added to a solu-

m

reaction was stirred at ambient temperature for 16 h. After the

addition of water, the mixture was extracted with ethyl acetate

(3ꢃ). The combined organic layers were dried over sodium sulfate,

ﬁltered, and the solvent was removed in vacuo. The residue was

puriﬁed by ﬂash column chromatography (Ø ¼ 2 cm, h ¼ 15 cm,

cyclohexane/ethyl acetate ¼ 10:1 /8:2, V ¼ 10 mL) to give 19 as

reddish oil (61 mg, 0.16 mmol, 67% yield). R_f¼ 0.38 (cyclohexane/

ethyl acetate ¼ 8:2); speciﬁc rotation: ½a _D²⁰

¼ þ81.7 (2.6; CH₂Cl₂);

ꢁ

¹H NMR (CD₂Cl₂):

d

[ppm] ¼ 2.31 (s, 3H, SCOCH₃), 3.01e3.14 (m, 2H,

tate ¼ 1:1); speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ56.8 (3.1; CH₂Cl₂); ¹H NMR

OCH₂CH₂S), 3.27 (s, 3H, OCH₂OCH₃), 3.44e3.57 (m, 2H, OCH₂CH₂S),

3.60 (dd, J ¼ 10.8/4.3 Hz, 1H, OCHCH₂O), 3.71 (dd, J ¼ 10.8/7.2 Hz,

1H, OCHCH₂O), 4.51 (dd, J ¼ 7.2/4.3 Hz, 1H, OCHCH₂O), 4.59 (d,

J ¼ 6.5 Hz, 1H, OCH₂OCH₃), 4.62 (d, J ¼ 6.5 Hz, 1H, OCH₂OCH₃),

(CDCl₃):

d

[ppm] ¼ 3.34 (s, 3H, OCH₂OCH₃), 3.51 (ddd, J ¼ 10.7/6.0/

3.8 Hz, 1H, HOCH₂CH₂O), 3.63 (ddd, J ¼ 10.7/5.4/3.3 Hz, 1H,

HOCH₂CH₂O), 3.66 (dd, J ¼ 10.9/3.7 Hz, 1H, OCHCH₂O), 3.71e3.78

(m, 3H, HOCH₂CH₂O, OCHCH₂O (1H)), 4.58 (dd, J ¼ 8.0/3.7 Hz, 1H,

OCHCH₂O), 4.67 (s, 2H, OCH₂OCH₃), 7.31e7.37 (m, 5H, H_arom.),

7.32e7.40 (m, 5H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}

,

7.51e7.55 (m, 4H, H_arom.); ¹³C NMR (CDCl₃):

d

[ppm] ¼ 55.5 (1C,

3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.50e7.57 (m, 4H, 3⁰-H_4-(phenyl-

_{ethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl); ¹³C

OCH₂OCH₃), 62.0 (1C, HOCH₂CH₂O), 70.9 (1C, HOCH₂CH₂O), 72.1

(1C, OCHCH₂O), 81.8 (1C, OCHCH₂O), 89.1 (1C, C^C), 89.8 (1C,

C^C), 96.9 (1C, OCH₂OCH₃), 123.2 (1C, C_arom.), 123.3 (1C, C_arom.),

127.0 (2C, C_arom.), 128.47 (1C, C_arom.), 128.49 (2C, C_arom.), 131.8 (2C,

NMR (CD₂Cl₂):

d

[ppm] ¼ 29.6 (1C, OCH₂CH₂S), 30.9 (1C, SCOCH₃),

55.6 (1C, OCH₂OCH₃), 68.5 (1C, OCH₂CH₂S), 71.9 (1C, OCHCH₂O),

81.9 (1C, OCHCH₂O), 89.6 (1C, C^C), 89.9 (1C, C^C), 97.2 (1C,

OCH₂OCH₃), 123.3 (1C, C_arom.), 123.7 (1C, C_arom.), 127.7 (2C, C-2⁰_4-

C

_arom.), 131.9 (2C, C_arom.), 139.3 (1C, C_arom.); IR (neat): ṽ

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

https://doi.org/10.1016/j.tet.2018.12.011

M. Galster et al. / Tetrahedron xxx (xxxx) xxx

13

z): [MþH]^þcalcd for C₁₉H₂₁O₅S: 361.1104, found: 361.1126; HPLC

(method 1): t_R¼ 21.3 min, purity 99.7%.

_{(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 128.9 (1C, C-4⁰⁰_phenyl),

129.0 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 132.1 (4C, C-3⁰_{4-(phenylethynyl)phenyl}

,

C-5⁰_{4-(phenylethynyl)phenyl}, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl), 140.3 (1C, C-1⁰_4-(phe-

_{nylethynyl)phenyl}), 195.7 (1C, SCOCH₃); IR (neat): ṽ [cm^ꢂ1] ¼ 2928,

1690, 1508, 1443, 1354, 1103, 1034, 953, 918, 837, 756, 691, 625;

LCMS (m/z): [MþH]^þcalcd for C₂₂H₂₅O₄S: 385.1468, found:

385.1456; HPLC (method 1): t_R¼ 24.7 min, purity 98.1%.

4.2.13. (S)-S-(2-{2-Hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}

ethyl) ethanethioate (22)

Triethylamine (90

mL, 65 mg, 0.64 mmol) and thioacetic acid

(46 L, 49 mg, 0.64 mmol) were added to a solution of 21 (120 mg,

m

0.32 mmol) in DMF (10 mL). The reaction mixture was stirred at

ambient temperature overnight. Then water was added and the

mixture was extracted with ethyl acetate (3ꢃ). The combined

organic layers were dried over sodium sulfate, ﬁltered, and the

solvent was removed in vacuo. The residue was puriﬁed by ﬂash

column chromatography (Ø ¼ 2 cm, h ¼ 15 cm, cyclohexane/ethyl

acetate ¼ 8:2, V ¼ 10 mL) to give 22 as reddish oil (78 mg,

0.23 mmol, 72% yield). R_f¼ 0.33 (cyclohexane/ethyl acetate ¼ 3:1);

4.2.11. (S)-2-(2-Mercaptoethoxy)-2-[4-(phenylethynyl)phenyl]

ethan-1-ol (20)

19 (58 mg, 0.15 mmol) was dissolved in HCl-saturated methanol

(7.5 mL). The reaction was stirred at ambient temperature for 16 h.

After addition of a saturated aqueous solution of sodium bicar-

bonate and water, the mixture was extracted with ethyl acetate

(3ꢃ). The combined organic layers were dried over sodium sulfate,

ﬁltered, and the solvent was removed in vacuo. The residue was

puriﬁed by automatic ﬂash column chromatography (100% H₂O /

100% ACN, Biotage^®SNAP KP-C18-HS 12 g, V ¼ 20 mL) to give 20 as

colorless oil (25 mg, 0.08 mmol, 53% yield). R_f¼ 0.21 (cyclohexane/

speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ109.5 (9.0; CH₂Cl₂); ¹H NMR (CD₂Cl₂):

d

[ppm] ¼ 2.32 (s, 3H, SCOCH₃), 3.05e3.16 (m, 2H, OCH₂CH₂S),

3.46e3.66 (m, 4H, OCH₂CH₂S, OCHCH₂O), 4.44 (dd, J ¼ 7.7/4.2 Hz,

1H, OCHCH₂O), 7.30e7.40 (m, 5H, H_arom.), 7.50e7.57 (m, 4H, H_arom.);

ethyl acetate ¼ 3:1); speciﬁc rotation: ½a _D²⁰

¼ þ99.0 (1.7; CH₃OH);

ꢁ

¹³C NMR (CD₂Cl₂):

d

[ppm] ¼ 29.7 (1C, OCH₂CH₂S), 31.0 (1C,

¹H NMR (CD₃OD):

d

[ppm] ¼ 2.64e2.72 (m, 2H, OCH₂CH₂SH), 3.53

SCOCH₃), 67.5 (1C, OCHCH₂O), 68.4 (1C, OCH₂CH₂S), 83.6 (1C,

OCHCH₂O), 89.5 (1C, C^C), 90.0 (1C, C^C), 123.5 (1C, C_arom.), 123.7

(1C, C_arom.), 127.5 (2C, C_arom.), 128.96 (1C, C_arom.), 128.98 (2C, C_arom.),

132.1 (2C, C_arom.), 132.2 (2C, C_arom.), 139.5 (1C, C_arom.), 195.8 (1C,

SCOCH₃); IR (neat): ṽ [cm^ꢂ1] ¼ 3429, 2866, 1686, 1508, 1393, 1350,

1099, 1042, 953, 833, 756, 691, 625; LCMS (m/z): [MþH]^þcalcd for

(t, J ¼ 6.4 Hz, 2H, OCH₂CH₂SH), 3.59 (dd, J ¼ 11.7/4.1 Hz, 1H, OCH-

CH₂O), 3.67 (dd, J ¼ 11.7/7.5 Hz, 1H, OCHCH₂O), 4.44 (dd, J ¼ 7.5/

4.1 Hz,1H, OCHCH₂O), 7.34e7.41 (m, 5H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-

H_{4-(phenylethynyl)phenyl}, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.48e7.54

(m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}, 2⁰⁰-H_phenyl

,

6⁰⁰-H_phenyl); ¹³C NMR (CD₃OD):

d

[ppm] ¼ 24.9 (1C, OCH₂CH₂SH),

C₂₀H₂₁O₃S: 341.1206, found: 341.1218; HPLC (method 1):

t_R¼ 22.7 min, purity 97.2%.

67.6 (1C, OCHCH₂OH), 72.4 (1C, OCH₂CH₂SH), 84.4 (1C, OCH-

CH₂OH), 89.9 (1C, C^C), 90.2 (1C, C^C), 97.2 (1C, OCH₂OCH₃),124.2

(1C, C_arom.), 124.6 (1C, C_arom.), 128.3 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-

4.2.14. (S)-2-(2-{2-(Methoxymethoxy)-1-[4-(phenylethynyl)

phenyl]ethoxy}ethyl)isoindoline-1,3-dione (23)

6⁰_{4-(phenylethynyl)phenyl}), 129.46 (1C, C-4⁰⁰_phenyl), 129.54 (2C, C-3⁰⁰

,

phenyl

C-5⁰⁰_phenyl), 132.5 (2C, C_arom.), 132.6 (2C, C_arom.), 141.2 (1C, C-1⁰_4-

_{(phenylethynyl)phenyl}); IR (neat): ṽ [cm^ꢂ1] ¼ 3402, 2866, 2558, 1682,

1504, 1443, 1393, 1339, 1177, 1096, 1034, 833, 752, 691; LCMS (m/z):

[MþH]^þcalcd for C₁₈H₁₉O₂S: 299.1100, found: 299.1131; HPLC

(method 1): t_R¼ 22.4 min, purity 95.8%.

Potassium phthalimide (840 mg, 4.5 mmol) was added to a so-

lution of 18 (1.7 g, 4.1 mmol) in DMF (55 mL). The mixture was

stirred at 80 ^ꢀC for 3 h. After cooling the reaction mixture to

ambient temperature, water was added and the mixture was

extracted with ethyl acetate (3ꢃ). The combined organic layers

were dried over sodium sulfate, ﬁltered, and the solvent was

evaporated in vacuo. The residue was puriﬁed by ﬂash column

chromatography (Ø ¼ 6 cm, h ¼ 15 cm, cyclohexane/ethyl ace-

tate ¼ 8:2 / 2:1, V ¼ 50 mL) to give 23 as colorless oil (1.6 g,

3.4 mmol, 84% yield). R_f¼ 0.26 (cyclohexane/ethyl acetate ¼ 3:1);

4.2.12. (S)-2-{2-Hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}ethyl

methanesulfonate (21)

18 (190 mg, 0.46 mmol) was dissolved in HCl-saturated meth-

anol (5 mL). The reaction was stirred at ambient temperature for

16 h. After addition of a saturated aqueous solution of sodium bi-

carbonate and water, the mixture was extracted with ethyl acetate

(3ꢃ). The combined organic layers were dried over sodium sulfate,

ﬁltered, and the solvent was removed in vacuo. The residue was

puriﬁed by ﬂash column chromatography (Ø ¼ 2 cm, h ¼ 15 cm,

cyclohexane/ethyl acetate ¼ 3:1 /1:2, V ¼ 10 mL) to give 21 as

colorless oil (150 mg, 0.40 mmol, 87% yield). R_f¼ 0.21 (cyclohexane/

speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ7.6 (1.6; CH₂Cl₂); ¹H NMR (CD₂Cl₂):

d

[ppm] ¼ 3.18 (s, 3H, OCH₂OCH₃), 3.53 (dd, J ¼ 10.8/4.3 Hz, 1H,

OCHCH₂O), 3.62e3.70 (m, 3H, OCHCH₂O (1H), NCH₂CH₂O), 3.81 (dt,

J ¼ 14.1/5.4 Hz, 1H, NCH₂CH₂O), 3.90 (ddd, J ¼ 14.1/7.0/5.2 Hz, 1H,

NCH₂CH₂O), 4.45e4.49 (m, 2H, OCHCH₂O, OCH₂OCH₃(1H)), 4.50 (d,

J ¼ 6.5 Hz, 1H, OCH₂OCH₃), 7.22e7.26 (m, 2H, 2⁰-H_{4-(phenylethynyl)}

_phenyl, 6⁰-H_{4-(phenylethynyl)phenyl}), 7.33e7.41 (m, 5H, C-3⁰_{4-(phenylethynyl)}

_phenyl, C-5⁰_{4-(phenylethynyl)phenyl}, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl),

7.50e7.55 (m, 2H, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl), 7.72e7.76 (m, 2H, 5⁰⁰⁰-

H_isoindoline, 6⁰⁰⁰-H_isoindoline), 7.80e7.86 (m, 2H, 4⁰⁰⁰-H_isoindoline, 7⁰⁰⁰-

ethyl acetate ¼ 1:1); speciﬁc rotation: ½a _D²⁰

¼ þ91.2 (5.5; CH₂Cl₂);

ꢁ

¹H NMR (CD₂Cl₂):

d

[ppm] ¼ 2.40e2.48 (m,1H, OCHCH₂OH), 3.05 (s,

3H, OSO₂CH₃), 3.59e3.74 (m, 4H, OCH₂CH₂OS, OCHCH₂OH),

4.34e4.41 (m, 2H, OCH₂CH₂OS), 4.49 (dd, J ¼ 8.2/3.6 Hz, 1H, OCH-

CH₂O), 7.32e7.35 (m, 2H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_4-(phenyl-

_{ethynyl)phenyl}), 7.35e7.39 (m, 3H, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl),

H

_isoindoline); ¹³C NMR (CD₂Cl₂):

d

[ppm] ¼ 38.3 (1C, NCH₂CH₂O), 55.4

(1C, OCH₂OCH₃), 66.5 (1C, NCH₂CH₂O), 71.7 (1C, OCHCH₂O), 81.9

(1C, OCHCH₂O), 89.6 (1C, ₀C^C), 89.9 (1C, C^C), 97.1 (1C,

OCH₂OCH₃), 123.3 (1C, C-4 _{4-(phenylethynyl)phenyl}), 123.6 (2C, C-

4⁰⁰⁰_isoindoline, C-7⁰⁰⁰_isoindoline), 123.7 (1C, C-1⁰⁰_phenyl), 127.6 (2C, C-2⁰_4-

_{(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 128.9 (1C, C-4⁰⁰_phenyl),

7.52e7.56 (m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}

,

2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl); ¹³C NMR (CD₂Cl₂):

d

[ppm] ¼ 38.2 (1C,

OSO₂CH₃), 67.56 (1C, OCHCH₂O), 67.63 (1C, OCH₂CH₂OS), 69.7 (1C,

OCH₂CH₂OS), 84.2 (1C, OCHCH₂O), 89.4 (1C, C^C), 90.1 (1C, C^C),

123.6 (1C, C-1⁰⁰_phenyl), 123.7 (1C, C-4⁰_{4-(phenylethynyl)phenyl}), 127.6 (2C,

129.0 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 132.0 (2C, C-3⁰_{4-(phenylethynyl)phenyl}

,

C-5⁰_{4-(phenylethynyl)phenyl}), 132.1 (2C, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl), 132.7 (2C,

C-2⁰_{4-(phenylethynyl)phenyl}

,

C-6⁰_{4-(phenylethynyl)phenyl}), 129.0 (3C, C-

C₀-3a⁰⁰⁰

,

C-7a⁰⁰⁰_isoindoline), 134.5 (2C, C-5⁰_isoindoline

,

C-

isoindoline

3⁰⁰_phenyl, C-5⁰⁰_phenyl, C-4⁰⁰_phenyl), 132.1 (2C, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl),

132.3 (2C, C-3⁰_{4-(phenylethynyl)phenyl}, C-5⁰_{4-(phenylethynyl)phenyl}), 139.0

(1C, C-1⁰_{4-(phenylethynyl)phenyl}); IR (neat): ṽ [cm^ꢂ1] ¼ 3522, 2924,

1508, 1443, 1346, 1173, 1115, 1015, 972, 918, 833, 802, 756; LCMS (m/

6 _isoindoline), 140.2 (1C, C-1⁰_{4-(phenylethynyl)phenyl}), 168.6 (2C, C-

1⁰⁰⁰_isoindoline, C-3⁰⁰⁰_isoindoline); IR (neat): ṽ [cm^ꢂ1] ¼ 2882, 1775, 1709,

1393, 1107, 1030, 918, 837, 756, 718, 691; LCMS (m/z): [MþH]^þcalcd

for C₂₈H₂₆NO₅: 456.1805, found: 456.1784; HPLC (method 1):

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

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14

M. Galster et al. / Tetrahedron xxx (xxxx) xxx

(1C, C-4⁰⁰_phenyl), 129.6 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 132.5 (2C, C_arom.),

t_R¼ 24.8 min, purity 98.8%.

132.6 (2C, C_arom.), 141.1 (1C, C-1⁰_{4-(phenylethynyl)phenyl}); IR (neat): ṽ

[cm^ꢂ1] ¼ 3453, 3352, 3287, 3040, 2913, 2851, 1605, 1504, 1443,

1335, 1192, 1177, 1099, 1049, 1015, 964, 910, 887, 860, 829, 752, 687;

LC-MS (m/z): [MþH]^þcalcd for C₁₈H₂₀NO₂: 282.1489, found:

282.1514; HPLC (method 1): t_R¼ 17.2 min, purity 97.4%.

4.2.15. (S)-2-{2-(Methoxymethoxy)-1-[4-(phenylethynyl)phenyl]

ethoxy}ethan-1-amine (24)

An aqueous solution of methylamine (40 % wt., 0.89 mL,

10 mmol) was added to a solution of 23 (1.6 g, 3.4 mmol) in absolute

ethanol (60 mL). The mixture was heated to 70 ^ꢀC for 16 h. Then

water (60 mL) was added, the mixture was acidiﬁed (pH < 2) with a

1 N aqueous solution of sulfuric acid and extracted with ethyl ac-

etate. Afterwards, the water layer was basiﬁed (pH > 10) with a

0.5 M aqueous solution of sodium hydroxide and extracted with

ethyl acetate (3ꢃ). The combined organic layers were dried over

sodium sulfate, ﬁltered, and the solvent was removed in vacuo. The

residue was puriﬁed by ﬂash column chromatography (Ø ¼ 4 cm,

h ¼ 15 cm, dichloromethane/methanol ¼ 20:1 /5:1, V ¼ 30 mL) to

give 24 as yellowish solid (910 mg, 2.8 mmol, 82% yield). R_f(RP-

TLC) ¼ 0.33 (acetonitrile/water ¼ 2:1); melting point: 97 ^ꢀC; spe-

4.2.17. (S)-N-(2-{2-(Methoxymethoxy)-1-[4-(phenylethynyl)

phenyl]ethoxy}ethyl)-1H-pyrrole-2-carboxamide (26)

Under N₂atmosphere, triethylamine (0.13 mL, 93 mg,

0.92 mmol) and EDCI∙HCl (88 mg, 0.46 mmol) were added to a

suspension of pyrrole-2-carboxylic acid (26 mg, 0.23 mmol) and

HOBt (47 mg, 0.35 mmol) in dry dichloromethane (2 mL). After

stirring the reaction mixture for 1 h at ambient temperature, a so-

lution of 24 (150 mg, 0.46 mmol) in dry dichloromethane (1 mL)

was added at 0 ^ꢀC (ice bath). Afterwards, the ice bath was removed

and the mixture was stirred at ambient temperature overnight.

Then a saturated aqueous solution of ammonium chloride and

water were added and the mixture was extracted with dichloro-

methane (3ꢃ). The combined organic layers were dried over so-

dium sulfate, ﬁltered, and the solvent was removed in vacuo. The

residue was puriﬁed by ﬂash column chromatography (Ø ¼ 2 cm,

h ¼ 17 cm, cyclohexane/ethyl acetate ¼ 1:2, V ¼ 10 mL) to give 26 as

colorless oil (85 mg, 0.20 mmol, 87% yield). R_f¼ 0.28 (cyclohexane/

ciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ62.1 (3.3; CH₂Cl₂); ¹H NMR (CD₃OD):

d

[ppm] ¼ 3.06e3.14 (m, 1H, H₂NCH₂CH₂O), 3.14e3.21 (m, 1H,

H₂NCH₂CH₂O), 3.30 (s, 3H, OCH₂OCH₃), 3.59e3.66 (m, 2H,

H₂NCH₂CH₂O), 3.68 (dd, J ¼ 10.8/4.2 Hz, 1H, OCHCH₂O), 3.79 (dd,

J ¼ 10.8/7.4 Hz, 1H, OCHCH₂O), 4.63 (dd, J ¼ 7.4/4.2 Hz, 1H, OCH-

CH₂O), 4.65 (s, 2H, OCH₂OCH₃), 7.34e7.45 (m, 5H, 2⁰-H_4-(phenyl-

,

6⁰-H_{4-(phenylethynyl)phenyl}

H_phenyl), 7.48e7.57 (m, 4H, C-3⁰_{4-(phenylethynyl)phenyl}, C-5⁰_4-(phenyl-

2⁰⁰-H_phenyl6⁰⁰-H_phenyl); ¹³C NMR (CD₃OD):

[ppm] ¼ 40.8 (1C, H₂NCH₂CH₂O), 55.7 (1C, OCH₂OCH₃), 66.4 (1C,

, , ,

3⁰⁰-H_phenyl5⁰⁰-H_phenyl4⁰⁰-

ethynyl)phenyl

ethyl acetate ¼ 1:2); speciﬁc rotation: ½a _D²⁰

¼ þ35.3 (2.6; CH₂Cl₂);

ꢁ

¹H NMR (CDCl₃):

d

[ppm] ¼ 3.33 (s, 3H, OCH₂OCH₃), 3.50e3.61 (m,

,

ethynyl)phenyl

2H, HNCH₂CH₂O (1H), HNCH₂CH₂O (1H)), 3.62e3.72 (m, 3H,

HNCH₂CH₂O (1H), HNCH₂CH₂O (1H), OCHCH₂O (1H)), 3.75 (dd,

J ¼ 10.9/8.0 Hz, 1H, OCHCH₂O), 4.55 (dd, J ¼ 8.0/3.6 Hz, 1H, OCH-

CH₂O), 4.68 (d, J ¼ 6.9 Hz 1H, OCH₂OCH₃), 4.70 (d, J ¼ 6.9 Hz 1H,

OCH₂OCH₃), 6.23e6.27 (m, 1H, 4⁰-H_pyrrole), 6.53e6.66 (m, 2H, 3⁰-

H_pyrrole, CONH), 6.91e6.94 (m, 1H, 5⁰-H_pyrrole), 7.29e7.39 (m, 5H, 2⁰-

d

H₂NCH₂CH₂O), 72.6 (1C, OCHCH₂O), 82.8 (1C, OCHCH₂O), 89.7 (1C,

C^C), 90.6 (1C, C^C), 97.8 (1C, OCH₂OCH₃), 124.4 (1C, C-1⁰⁰_phenyl),

124.6 (1C, C-4⁰_{4-(phenylethynyl)phenyl}), 128.4 (2C, C-2⁰_{4-(phenylethynyl)}

_phenyl, C-6⁰_{4-(phenylethynyl)phenyl}), 129.6 (3C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl, C-

4⁰⁰_phenyl), 132.5 (2C, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl), 132.8 (2C, C-3⁰_4-(phenyl-

_{ethynyl)phenyl}, C-5⁰_{4-(phenylethynyl)phenyl}), 140.1 (1C, C-1⁰_{4-(phenylethynyl)}

_phenyl); IR (neat): ṽ [cm^ꢂ1] ¼ 2874, 1597, 1508, 1485, 1150, 1099,

1022, 914, 829, 752, 687; LCMS (m/z): [MþH]^þcalcd for C₂₀H₂₄NO₃:

326.1751, found: 326.1779; HPLC (method 2): t_R¼ 13.7 min, purity

97.6%.

H_{4-(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl

4⁰⁰-H_phenyl), 7.48e7.56 (m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_4-(phe-

_{nylethynyl)phenyl}, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl), 9.53 (s br, 1H, 1⁰-H_pyrrole); ¹³

NMR (CDCl₃):

,

C

d

[ppm] ¼ 39.3 (1C, HNCH₂CH₂O), 55.5 (1C,

OCH₂OCH₃), 68.4 (1C, HNCH₂CH₂O), 72.0 (1C, OCHCH₂O), 81.8 (1C,

OCHCH₂O), 89.1 (1C, C^C), 89.9 (1C, C^C), 96.9 (1C, OCH₂OCH₃),

109.1 (1C, 3⁰-C_pyrrole), 110.0 (1C, 4⁰-C_pyrrole), 121.5 (1C, 5⁰-C_pyrrole),

123.3 (1C, C_arom.), 123.4 (1C, C_arom.), 126.1 (1C, 2⁰-C_pyrrole), 126.9 (2C,

4.2.16. (S)-2-(2-Aminoethoxy)-2-[4-(phenylethynyl)phenyl]ethan-

1-ol (25)

C-2⁰_{4-(phenylethynyl)phenyl}

,

C-6⁰_{4-(phenylethynyl)phenyl}), 128.49 (1C, C-

24 (560 mg, 1.7 mmol) was dissolved in a mixture of HCl-

saturated ethanol (6 mL) and pure ethanol (9 mL). The reaction

mixture was stirred at ambient temperature for 16 h. After addition

of a saturated aqueous solution of sodium bicarbonate and water,

the mixture was extracted with ethyl acetate (3ꢃ). The combined

organic layers were dried over sodium sulfate, ﬁltered, and the

solvent was removed in vacuo. The residue was puriﬁed by ﬂash

column chromatography (Ø ¼ 3 cm, h ¼ 9 cm, dichloromethane/

methanol/triethylamine ¼ 9:1:0 / 5:1:0.05, V ¼ 5 mL) to give 25

as yellowish solid (200 mg, 0.70 mmol, 41% yield). R_f(RP-

TLC) ¼ 0.20 (acetonitrile/water ¼ 1:1); melting point: 72 ^ꢀC; spe-

4⁰⁰_phenyl), 128.50 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 131.8 (2C, C-2⁰⁰_phenyl, C-

6⁰⁰_phenyl), 132.0 (2C, C-3⁰_{4-(phenylethynyl)phenyl}

,

C-5⁰_{4-(phenylethynyl)}

_phenyl), 139.0 (1C, C-1⁰_{4-(phenylethynyl)phenyl}), 161.2 (1C, CONH); IR

(neat): ṽ [cm^ꢂ1] ¼ 3248, 2928, 1632, 1732, 1558, 1512, 1408, 1312,

1107, 1034, 833, 752, 691; LCMS (m/z): [MþH]^þcalcd for

C

₂₅H₂₇N₂O₄: 419.1965, found: 419.2006; HPLC (method 1):

t_R¼ 22.4 min, purity 99.3%.

4.2.18. (S)-N-(2-{2-Hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}

ethyl)-1H-pyrrole-2-carboxamide (27)

ciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ66.9 (1.5; CH₃OH); ¹H NMR: (CD₃OD):

p-Toluenesulfonic acid monohydrate (16 mg, 0.09 mmol) was

added to a solution of 26 (71 mg, 0.17 mmol) in methanol (2 mL)

and the mixture was stirred at ambient temperature overnight.

Then HCl-saturated methanol (0.5 mL) was added and the reaction

mixture was stirred until TLC control indicated completion of the

reaction. Then a saturated aqueous solution of sodium bicarbonate

and water were added and the mixture was extracted with ethyl

acetate (3ꢃ). The combined organic layers were dried over sodium

sulfate, ﬁltered, and the solvent was removed in vacuo. The residue

was puriﬁed by ﬂash column chromatography (Ø ¼ 2 cm, h ¼ 15 cm,

ethyl acetate ¼ 100%, V ¼ 10 mL) to give 27 as colorless solid (52 mg,

0.14 mmol, 82% yield). R_f¼ 0.25 (ethyl acetate); melting point:

d

[ppm] ¼ 2.80 (ddd, J ¼ 13.2/6.9/4.0 Hz, 1H, H₂NCH₂CH₂O), 2.85

(ddd, J ¼ 13.2/6.0/3.9 Hz, 1H, H₂NCH₂CH₂O), 3.41 (ddd, J ¼ 9.8/6.9/

3.9 Hz, 1H, H₂NCH₂CH₂O), 3.48 (ddd, J ¼ 9.8/6.0/4.0 Hz, 1H,

H₂NCH₂CH₂O), 3.59 (dd, J ¼ 11.8/3.7 Hz, 1H, OCHCH₂OH), 3.67 (dd,

J ¼ 11.8/7.9 Hz, 1H, OCHCH₂OH), 4.42 (dd, J ¼ 7.9/3.7 Hz, 1H, OCH-

CH₂OH), 7.33 ꢂ 7.39 (m, 5H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_4-(phenyl-

_{ethynyl)phenyl}, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.48 ꢂ 7.54 (m, 4H,

2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)}

_phenyl); ¹³C NMR (CD₃OD):

d

[ppm] ¼ 42.3 (1C, H₂NCH₂CH₂O), 67.7

(1C, OCHCH₂OH), 71.4 (1C, H₂NCH₂CH₂O), 84.6 (1C, OCHCH₂OH),

89.9 (1C, C^C), 90.3 (1C, C^C), 124.2 (1C, C_arom.), 124.5 (1C, C_arom.),

128.2 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 129.5

124 ^ꢀC; speciﬁc rotation: ½a ²_D⁰

ꢁ

¼ þ48.9 (3.0; CH₂Cl₂); ¹H NMR:

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

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M. Galster et al. / Tetrahedron xxx (xxxx) xxx

15

(CDCl₃):

d

[ppm] ¼ 3.48e3.60 (m, 2H, HNCH₂CH₂O (1H),

ﬁltered, and the solvent was removed in vacuo. The residue was

puriﬁed by ﬂash column chromatography (Ø ¼ 1 cm, h ¼ 15 cm,

cyclohexane/ethyl acetate ¼ 2:1 /0:1, V ¼ 5 mL) to give 29 as

colorless oil (39 mg, 0.11 mmol, 85% yield). R_f¼ 0.35 (dichloro-

HNCH₂CH₂O (1H)), 3.60e3.78 (m, 4H, HNCH₂CH₂O (1H),

HNCH₂CH₂O (1H), OCHCH₂OH), 4.48 (dd, J ¼ 8.2/3.7 Hz, 1H, OCH-

CH₂OH), 6.21e6.27 (m, 1H, 4⁰⁰⁰-H_pyrrole), 6.55e6.72 (m, 2H, CONH,

3⁰⁰⁰-H_pyrrole), 6.90e6.96 (m,1H, 5⁰⁰⁰-H_pyrrole), 7.25e7.31 (m, 2H, 2⁰-H_4-

_{(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}), 7.31e7.40 (m, 3H, 3⁰⁰-

H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.46e7.57 (m, 4H, 2⁰⁰-H_phenyl, 6⁰⁰-

H_phenyl, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}), 9.70 (s,

methane/methanol ¼ 20:1); speciﬁc rotation: ½a _D²⁰

¼ þ51.8 (7.0;

ꢁ

CH₂Cl₂); ¹H NMR (CD₃OD):

d

[ppm] ¼ 2.97 (s, 3H, SO₂CH₃),

3.23e3.32 (m, 2H, HNCH₂CH₂O), 3.47 (ddd, J ¼ 10.0/6.7/4.2 Hz, 1H,

HNCH₂CH₂O), 3.53 (ddd, J ¼ 10.0/5.9/4.4 Hz, 1H, HNCH₂CH₂O), 3.60

(dd, J ¼ 11.8/3.8 Hz, 1H, OCHCH₂O), 3.67 (dd, J ¼ 11.8/7.9 Hz, 1H,

OCHCH₂O), 4.45 (dd, J ¼ 7.9/3.8 Hz, 1H, OCHCH₂O), 7.33e7.40 (m,

5H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}, 3⁰⁰-H_phenyl, 5⁰⁰-

H_phenyl, 4⁰⁰-H_phenyl), 7.48e7.54 (m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-

H_{4-(phenylethynyl)phenyl}, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl); ¹³C NMR (CD₃OD):

1H, 1⁰⁰⁰-H_pyrrole); ¹³C NMR (CDCl₃):

d

[ppm] ¼ 39.5 (1C,

HNCH₂CH₂O), 67.3 (1C, OCHCH₂OH), 68.6 (1C, HNCH₂CH₂O), 83.5

(1C, OCHCH₂OH), 89.0 (1C, C^C), 90.0 (1C, C^C), 109.7 (1C, 3⁰⁰⁰-

C_pyrrole), 110.1 (1C, 4⁰⁰⁰-C_pyrrole), 121.9 (1C, 5⁰⁰⁰-C_pyrrole), 123.3 (1C, C-

1⁰⁰_phenyl), 123.5 (1C, C-4⁰_{4-(phenylethynyl)phenyl}), 125.8 (1C, 2⁰⁰⁰-C_pyrrole),

126.9 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 128.5

(3C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl, C-4⁰⁰_phenyl), 131.8 (2C, C-2⁰⁰_phenyl, C-

d

[ppm] ¼ 40.2 (1C, SO₂CH₃), 44.2 (1C, HNCH₂CH₂O), 67.6 (1C,

OCHCH₂O), 69.5 (1C, HNCH₂CH₂O), 84.7 (1C, OCHCH₂O), 89.9 (1C,

C^C), 90.3 (1C, C^C), 124.3 (1C, C_arom.), 124.5 (1C, C_arom.), 128.3 (2C,

6⁰⁰_phenyl), 132.0 (2C, C-3⁰_{4-(phenylethynyl)phenyl}

,

C-5⁰_{4-(phenylethynyl)}

_phenyl), 138.6 (1C, C-1⁰_{4-(phenylethynyl)phenyl}), 161.6 (1C, CONH); IR

(neat): ṽ [cm^ꢂ1] ¼ 3657, 3291, 2978, 2886, 1620, 1562, 1516, 1393,

1319, 1250, 1099, 1069, 953, 833, 752, 691; LCMS (m/z): [MþH]^þ

calcd for C₂₃H₂₃N₂O₃: 375.1703, found: 375.1697; HPLC (method 2):

t_R¼ 17.2 min, purity 99.5%.

C-2⁰_{4-(phenylethynyl)phenyl}

,

C-6⁰_{4-(phenylethynyl)phenyl}), 129.5 (1C, C-

4⁰⁰_phenyl), 129.6 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 132.5 (2C, C_arom.), 132.7

(2C, C_arom.), 140.7 (1C, C-1⁰_{4-(phenylethynyl)phenyl}); IR (neat):

ṽ

[cm^ꢂ1] ¼ 3480, 3287, 2928, 2870, 1732, 1508, 1439, 1408, 1312, 1150,

1103, 1065, 980, 833, 756, 691; LCMS (m/z): [MþH]^þcalcd for

C

₁₉H₂₂NO₄S: 360.1264, found: 360.1268; HPLC (method 1):

t_R¼ 19.9 min, purity 99.4%.

4.2.19. (S)-N-(2-{2-(Methoxymethoxy)-1-[4-(phenylethynyl)

phenyl]ethoxy}ethyl)methanesulfonamide (28)

Under N₂atmosphere, triethylamine (40

mL, 28 mg, 0.28 mmol)

4.2.21. (S)-1,1,1-Triﬂuoro-N-(2-{2-(methoxymethoxy)-1-[4-

(phenylethynyl)phenyl]ethoxy}ethyl)methanesulfonamide (30)

and methanesulfonyl chloride (20 L, 32 mg, 0.28 mmol) were

m

added to a solution of 24 (45 mg, 0.14 mmol) in dry dichloro-

methane (3 mL). After stirring the reaction mixture at ambient

temperature for 16 h, water was added and the mixture was

extracted with ethyl acetate (3ꢃ). The combined organic layers

were dried over sodium sulfate, ﬁltered, and the solvent was

removed in vacuo. The residue was puriﬁed by ﬂash column chro-

matography (Ø ¼ 1 cm, h ¼ 20 cm, dichloromethane/meth-

anol ¼ 98:2, V ¼ 2.5 mL) to give 28 as colorless oil (44 mg,

0.11 mmol, 79% yield). R_f¼ 0.24 (dichloromethane/meth-

Under N₂atmosphere, triethylamine (60

and triﬂuoromethanesulfonyl chloride (46

m

L, 44 mg, 0.43 mmol)

mL, 73 mg, 0.43 mmol)

were added to a solution of 24 (70 mg, 0.22 mmol) in dry

dichloromethane (7 mL). After stirring the reaction mixture at

ambient temperature for 16 h, the solvent was removed in vacuo.

Then water was added and the mixture was extracted with ethyl

acetate (3ꢃ). The combined organic layers were dried over sodium

sulfate, ﬁltered, and the solvent was removed in vacuo. The residue

was puriﬁed by ﬂash column chromatography (Ø ¼ 1 cm,

h ¼ 20 cm, dichloromethane/methanol ¼ 98:2, V ¼ 2.5 mL) to give

30 as colorless oil (44 mg, 0.10 mmol, 45% yield). R_f¼ 0.30 (cyclo-

anol ¼ 99:1); speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ40.0 (4.5; CH₂Cl₂); ¹H NMR

(CDCl₃):

d

[ppm] ¼ 2.97 (s, 3H, SO₂CH₃), 3.26e3.39 (m, 2H,

HNCH₂CH₂O), 3.35 (s, 3H, OCH₂OCH₃), 3.52 (ddd, J ¼ 10.2/7.1/3.5 Hz,

1H, HNCH₂CH₂O), 3.62e3.68 (m, 2H, HNCH₂CH₂O (1H), OCHCH₂O

(1H)), 3.72 (dd, J ¼ 11.0/8.0 Hz, 1H, OCHCH₂O), 4.53 (dd, J ¼ 8.0/

3.6 Hz, 1H, OCHCH₂O), 4.67 (s, 2H, OCH₂OCH₃), 7.28e7.33 (m, 2H,

2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}), 7.33e7.38 (m, 3H,

3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.50e7.56 (m, 4H, 3⁰-H_4-(phenyl-

_{ethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl); ¹³C

hexane/ethyl acetate ¼ 3:1); speciﬁc rotation: ½a _D²⁰

¼ þ53.8 (3.5;

ꢁ

CH₂Cl₂); ¹H NMR (CDCl₃):

d

[ppm] ¼ 3.41 (s, 3H, OCH₂OCH₃),

3.44e3.54 (m, 3H, HNCH₂CH₂O, HNCH₂CH₂O (1H)), 3.65e3.81 (m,

3H, OCHCH₂O, HNCH₂CH₂O (1H)), 4.55 (dd, J ¼ 7.8/4.0 Hz, 1H,

OCHCH₂O), 4.70 (d, J ¼ 6.6 Hz, 1H, OCH₂OCH₃), 4.73 (d, J ¼ 6.6 Hz,

1H, OCH₂OCH₃), 6.90 (s br, 1H, SO₂NH), 7.27e7.32 (m, 2H, 2⁰-H_4-

_{(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}), 7.32e7.39 (m, 3H, 3⁰⁰-

H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.50e7.57 (m, 4H, 2⁰⁰-H_phenyl, 6⁰⁰-

H_phenyl, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}); ¹³C NMR

NMR (CDCl₃):

d

[ppm] ¼ 40.5 (1C, SO₂CH₃), 43.3 (1C, HNCH₂CH₂O),

55.6 (1C, OCH₂OCH₃), 68.3 (1C, HNCH₂CH₂O), 72.1 (1C, OCHCH₂O),

82.0 (1C, OCHCH₂O), 89.0 (1C, C^C), 90.0 (1C, C^C), 96.9 (1C,

OCH₂OCH₃), 123.2 (1C, C-1⁰⁰_phenyl), 123.5 (1C, C-4⁰_{4-(phenylethynyl)}

_phenyl), 126.9 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}),

128.51 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 128.53 (1C, C-4⁰⁰_phenyl), 131.8 (2C,

C-2⁰⁰_phenyl, C-6⁰⁰_phenyl), 132.0 (2C, C-3⁰_{4-(phenylethynyl)phenyl}, C-5⁰_4-(phe-

_{nylethynyl)phenyl}), 138.6 (1C, C-1⁰_{4-(phenylethynyl)phenyl}); IR (neat): ṽ

[cm^ꢂ1] ¼ 3283, 2978, 2882, 1508, 1439, 1404, 1315, 1150, 1107, 1072,

1030, 976, 837, 756, 691; LCMS (m/z): [MþH]^þcalcd for

(CDCl₃):

d

[ppm] ¼ 44.4 (1C, HNCH₂CH₂O), 55.8 (1C, OCH₂OCH₃),

68.6 (1C, HNCH₂CH₂O), 73.0 (1C, OCHCH₂O), 82.8 (1C, OCHCH₂O),

88.9 (1C, C^C), 90.1 (1C, C^C), 97.3 (1C, OCH₂OCH₃), 120.0 (q,

J ¼ 321 Hz, 1C, CF₃), 123.2 (1C, C-1⁰⁰_phenyl), 123.7 (1C, C-4⁰_4-(phenyl-

_{ethynyl)phenyl}), 126.7 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)}

_phenyl), 128.5 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 128.6 (1C, C-4⁰⁰_phenyl), 131.8

(2C, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl), 132.1 (2C, C-3⁰_{4-(phenylethynyl)phenyl}, C-5⁰_4-

_{(phenylethynyl)phenyl}), 138.1 (1C, C-1⁰_{4-(phenylethynyl)phenyl}); IR (neat): ṽ

[cm^ꢂ1] ¼ 3144, 2978, 2886, 1508, 1443, 1373, 1231, 1188, 1150, 1107,

1030, 968, 833, 756, 691; LCMS (m/z): [M þ NH₄]^þcalcd for

C

₂₁H₂₆NO₅S: 404.1526, found: 404.1524; HPLC (method 1):

t_R¼ 21.7 min, purity 99.2%.

C₂₁H₂₆F₃N₂O₅S: 475.1509, found: 475.1513; HPLC (method 1):

t_R¼ 25.0 min, purity 94.7%.

4.2.20. (S)-N-(2-{2-Hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}

ethyl)methanesulfonamide (29)

28 (52 mg, 0.13 mmol) was dissolved in HCl-saturated methanol

(5 mL). The reaction was stirred at ambient temperature for 16 h.

After addition of a saturated aqueous solution of sodium bicar-

bonate and water, the mixture was extracted with ethyl acetate

(3ꢃ). The combined organic layers were dried over sodium sulfate,

4.2.22. (S)-1,1,1-Triﬂuoro-N-(2-{2-hydroxy-1-[4-(phenylethynyl)

phenyl]ethoxy}ethyl)methanesulfonamide (31)

30 (58 mg, 0.13 mmol) was dissolved in a mixture of HCl-

saturated methanol (0.5 mL) and pure methanol (1.5 mL). The re-

action mixture was stirred at ambient temperature for 16 h. After

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

https://doi.org/10.1016/j.tet.2018.12.011

16

M. Galster et al. / Tetrahedron xxx (xxxx) xxx

addition of a saturated aqueous solution of sodium bicarbonate and

water, the mixture was extracted with ethyl acetate (3ꢃ). The

combined organic layers were dried over sodium sulfate, ﬁltered,

and the solvent was removed in vacuo. The residue was puriﬁed by

ﬂash column chromatography (Ø ¼ 1 cm, h ¼ 21 cm, cyclohexane/

ethyl acetate ¼ 2:1, V ¼ 5 mL) to give 31 as colorless oil (33 mg,

0.08 mmol, 63% yield). R_f¼ 0.22 (cyclohexane/ethyl acetate ¼ 2:1);

2878, 1597, 1508, 1443, 1404, 1327, 1153, 1092, 1030, 961, 814, 756,

691, 660; LCMS (m/z): [MþH]^þcalcd for C₂₇H₃₀NO₅S: 480.1839,

found: 480.1846; HPLC (method 1): t_R¼ 24.4 min, purity 96.3%.

4.2.24. (S)-N-(2-{2-Hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}

ethyl)-4-methylbenzenesulfonamide (33)

32 (42 mg, 0.09 mmol) was dissolved in HCl-saturated methanol

(4 mL). The reaction was stirred at ambient temperature for 16 h.

After addition of a saturated aqueous solution of sodium bicar-

bonate and water, the mixture was extracted with ethyl acetate

(3ꢃ). The combined organic layers were dried over sodium sulfate,

ﬁltered, and the solvent was removed in vacuo. The residue was

puriﬁed by ﬂash column chromatography (Ø ¼ 2 cm, h ¼ 10.5 cm,

cyclohexane/ethyl acetate ¼ 2:1 /1:1, V ¼ 10 mL) to give 33 as

colorless oil (34 mg, 0.08 mmol, 89% yield). R_f¼ 0.17 (cyclohexane/

speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ44.0 (1.4; CH₂Cl₂); ¹H NMR (CDCl₃):

d

[ppm] ¼ 3.40e3.57 (m, 3H, HNCH₂CH₂O, HNCH₂CH₂O (1H)),

3.59e3.68 (m, 1H, HNCH₂CH₂O), 3.72 (dd, J ¼ 11.8/4.0 Hz, 1H,

OCHCH₂OH), 3.77 (dd, J ¼ 11.8/7.8 Hz, 1H, OCHCH₂OH), 4.51 (dd,

J ¼ 7.8/4.0 Hz, 1H, OCHCH₂OH), 6.86e6.97 (m, 1H, SO₂NH),

7.26e7.31 (m, 2H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}),

7.32e7.39 (m, 3H, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.50e7.58 (m,

4H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}, 2⁰⁰-H_phenyl, 6⁰⁰-

_phenyl); ¹³C NMR (CDCl₃):

d

[ppm] ¼ 44.4 (1C, HNCH₂CH₂O), 67.3

ethyl acetate ¼ 2:1); speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ52.1 (1.5; CH₂Cl₂);

H

¹H NMR (CD₂Cl₂):

d

[ppm] ¼ 2.26e2.31 (m, 1H, OCHCH₂OH), 2.44 (s,

(1C, OCHCH₂OH), 68.1 (1C, HNCH₂CH₂O), 83.4 (1C, OCHCH₂OH),

88.9 (1C, C^C), 90.2 (1C, C^C), 119.9 (q, J ¼ 321 Hz, 1C, CF₃), 123.2

(1C, C-1⁰⁰_phenyl), 123.9 (1C, C-4⁰_{4-(phenylethynyl)phenyl}), 126.9 (2C, C-2⁰_4-

_{(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 128.5 (2C, C-3⁰⁰_phenyl, C-

5⁰⁰_phenyl), 128.6 (1C, C-4⁰⁰_phenyl), 131.8 (2C, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl),

132.2 (2C, C-3⁰_{4-(phenylethynyl)phenyl}, C-5⁰_{4-(phenylethynyl)phenyl}), 137.6

(1C, C-1⁰_{4-(phenylethynyl)phenyl}); IR (neat): ṽ [cm^ꢂ1] ¼ 3661, 3314, 2978,

2886, 1508, 1443, 1373, 1227, 1184, 1150, 1111, 1065, 976, 833, 756,

691; LCMS (m/z): [MþH]^þcalcd for C₁₉H₁₉F₃NO₄S: 414.0981, found:

414.0975; HPLC (method 2): t_R¼ 18.3 min, purity 99.7%.

3H, SO₂PhCH₃), 3.07e3.13 (m, 1H, HNCH₂CH₂O), 3.17 (dtd, J ¼ 13.4/

6.3/3.6 Hz, 1H, HNCH₂CH₂O), 3.39 (ddd, J ¼ 10.2/6.8/3.6 Hz, 1H,

HNCH₂CH₂O), 3.44 (ddd, J ¼ 10.1/6.3/3.8 Hz, 1H, HNCH₂CH₂O),

3.56e3.65 (m, 2H, OCHCH₂OH), 4.35 (dd, J ¼ 7.9/3.9 Hz, 1H, OCH-

CH₂OH), 5.13 (t, J ¼ 6.1 Hz, 1H, SO₂NH), 7.21e7.25 (m, 2H, 2⁰-H_4-

_{(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}), 7.32e7.35 (m, 2H, 3⁰⁰⁰-

H_{4-methylbenzenesulfonamide}, 5⁰⁰⁰-H_{4-methylbenzenesulfonamide}), 7.35e7.40

(m, 3H, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.49e7.52 (m, 2H, 3⁰-H_4-

_{(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}), 7.52e7.56 (m, 2H, 2⁰⁰-

H_phenyl, 6⁰⁰-H_phenyl), 7.70e7.73 (m, 2H, 2⁰⁰⁰-H_{4-methylbenzenesulfonamide}

,

4.2.23. (S)-N-(2-{2-[Methoxymethoxy]-1-[4-(phenylethynyl)

phenyl]ethoxy}ethyl)-4-methylbenzenesulfonamide (32)

6⁰⁰⁰-H_{4-methylbenzenesulfonamide}); ¹³C NMR (CD₂Cl₂):

d

[ppm] ¼ 21.8 (1C

SO₂PhCH₃), 43.8 (1C, HNCH₂CH₂O), 67.5 (1C, OCHCH₂OH), 68.2 (1C,

HNCH₂CH₂O), 83.8 (1C, OCHCH₂O), 89.4 (1C, C^C), 90.2 (1C, C^C),

123.6 (1C, C-1⁰⁰_phenyl),123.7 (1C, C-4⁰_{4-(phenylethynyl)phenyl}),127.47 (2C,

Under N₂atmosphere, triethylamine (40 mL, 26 mg, 0.26 mmol)

and p-toluenesulfonyl chloride (50 mg, 0.26 mmol) were added to a

solution of 24 (43 mg, 0.13 mmol) in dry dichloromethane (5 mL).

After stirring the reaction mixture at ambient temperature for 16 h,

water was added and the mixture was extracted with dichloro-

methane (3ꢃ). The combined organic layers were dried over so-

dium sulfate, ﬁltered, and the solvent was removed in vacuo. The

residue was puriﬁed by ﬂash column chromatography (Ø ¼ 1 cm,

C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 127.53 (2C, C-2⁰⁰⁰

4-

_{methylbenzenesulfonamide}, C-6⁰⁰⁰_{4-methylbenzenesulfonamide}), 129.0 (3C, C-

3⁰⁰

,

C-5⁰⁰

,

C-4⁰⁰_phenyl),

130.3

(2C,

C-3⁰⁰⁰

phenyl

4-

_{methylbenzenesulfonamide}, C-5⁰⁰⁰_{4-methylbenzenesulfonamide}), 132.1 (2C, C-

2⁰⁰_phenyl, C-6⁰⁰_phenyl), 132.3 (2C, C-3⁰_{4-(phenylethynyl)phenyl}, C-5⁰_4-(phenyl-

_{ethynyl)phenyl}), 137.6 (1C, C-1⁰⁰⁰_{4-methylbenzenesulfonamide}), 139.2 (1C, C-

1⁰_{4-(phenylethynyl)phenyl}), 144.3 (1C, C-4⁰⁰⁰_{4-methylbenzenesulfonamide}); IR

(neat): ṽ [cm^ꢂ1] ¼ 3487, 3287, 2924, 2870, 1597, 1504, 1443, 1400,

1323, 1157, 1092, 961, 814, 756, 691, 660; LCMS (m/z): [MþH]^þcalcd

for C₂₅H₂₆NO₄S: 436.1577, found: 436.1572; HPLC (method 1):

t_R¼ 22.8 min, purity 98.3%.

h ¼ 15 cm,

dichloromethane/methanol ¼ 100:0 / 98:2,

V ¼ 2.5 mL) to give 32 as colorless oil (53 mg, 0.11 mmol, 85% yield).

R_f¼ 0.28 (dichloromethane/methanol ¼ 98:2); speciﬁc rotation:

½

a ²_D⁰

ꢁ

¼ þ22.3 (1.7; CH₂Cl₂); ¹H NMR (CD₂Cl₂):

[ppm] ¼ 2.44 (s, 3H,

d

SO₂PhCH₃), 3.02e3.11 (m, 1H, HNCH₂CH₂O), 3.11e3.20 (m, 1H,

HNCH₂CH₂O), 3.31 (s, 3H, OCH₂OCH₃), 3.37 (ddd, J ¼ 10.2/7.3/3.6 Hz,

1H, HNCH₂CH₂O), 3.49 (ddd, J ¼ 10.2/5.9/3.8 Hz, 1H, HNCH₂CH₂O),

3.58 (dd, J ¼ 10.9/3.9 Hz, 1H, OCHCH₂O), 3.65 (dd, J ¼ 10.9/7.8 Hz,

1H, OCHCH₂O), 4.40 (dd, J ¼ 7.8/3.9 Hz, 1H, OCHCH₂O), 4.63 (s, 2H,

OCH₂OCH₃), 5.36 (t, J ¼ 5.9 Hz, 1H, SO₂NH), 7.22e7.28 (m, 2H, 2⁰-H_4-

_{(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}), 7.31e7.41 (m, 5H, 3⁰⁰-

H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl, 3⁰⁰⁰-H_{4-methylbenzenesulfonamide}, 5⁰⁰⁰-H_4-

_{methylbenzenesulfonamide}), 7.48e7.57 (m, 4H, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl, 3⁰-

H_{4-(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}), 7.68e7.74 (m, 2H,

4.2.25. (S)-1-[1-(Allyloxy)-2-(methoxymethoxy)ethyl]-4-

bromobenzene (35)

Under N₂atmosphere, a 1 M solution of LiHMDS in THF (4.8 mL,

4.8 mmol) and tetrabutylammonium iodide (150 mg, 0.40 mmol)

were added to a solution of 34 (1.0 g, 4.0 mmol) in THF (50 mL).

Then allyl bromide (0.69 mL, 960 mg, 8.0 mmol) was added and the

mixture was heated to reﬂux for 16 h. After cooling the mixture to

ambient temperature, water was added and the mixture was

extracted with ethyl acetate (3ꢃ). The combined organic layers

were dried over sodium sulfate, ﬁltered, and the solvent was

removed in vacuo. The residue was puriﬁed by ﬂash column chro-

matography (Ø ¼ 4 cm, h ¼ 15 cm, cyclohexane/ethyl acetate ¼ 8:2,

V ¼ 30 mL) to give 35 as colorless oil (760 g, 2.5 mmol, 64% yield).

R_f¼ 0.17 (cyclohexane/ethyl acetate ¼ 20:1); speciﬁc rotation:

2⁰⁰⁰-H_{4-methylbenzenesulfonamide}

NMR (CD₂Cl₂):

,

6⁰⁰⁰-H_{4-methylbenzenesulfonamide}); ¹³C

d

[ppm] ¼ 21.8 (1C SO₂PhCH₃), 43.8 (1C,

HNCH₂CH₂O), 55.8 (1C, OCH₂OCH₃), 68.2 (1C, HNCH₂CH₂O), 72.4

(1C, OCHCH₂O), 82.2 (1C, OCHCH₂O), 89.4 (1C, C^C), 90.1 (1C,

C^C), 97.3 (1C, OCH₂OCH₃), 123.6 (1C, C-4⁰_{4-(phenylethynyl)phenyl}),

123.7 (1C, C-1⁰⁰_phenyl), 127.4 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_4-(phe-

_{nylethynyl)phenyl}), 127.5 (2C, C-2⁰⁰⁰

,

C-6⁰⁰⁰

½

a ²_D⁰

ꢁ

¼ þ58.9 (2.0; CH₂Cl₂); ¹H NMR (CDCl₃):

[ppm] ¼ 3.29 (s, 3H,

d

4-methylbenzenesulfonamide

4-

_{methylbenzenesulfonamide}), 128.99 (1C, C-4⁰⁰_phenyl), 129.00 (2C, C-

OCH₂OCH₃), 3.60 (dd, J ¼ 10.8/4.3 Hz, 1H, OCHCH₂O), 3.73 (dd,

J ¼ 10.8/7.3 Hz, 1H, OCHCH₂O), 3.87 (ddt, J ¼ 12.8/6.0/1.3 Hz, 1H,

OCH₂CH]CH₂), 3.98 (ddt, J ¼ 12.8/5.2/1.5 Hz, 1H, OCH₂CH]CH₂),

4.51 (dd, J ¼ 7.3/4.3 Hz, 1H, OCHCH₂O), 4.61 (d, J ¼ 6.6 Hz, 1H,

OCH₂OCH₃), 4.64 (d, J ¼ 6.6 Hz, 1H, OCH₂OCH₃), 5.16 (dq, J ¼ 10.4/

1.4 Hz, 1H, OCH₂CH]CH₂), 5.24 (dq, J ¼ 17.2/1.6 Hz, 1H, OCH₂CH]

3⁰⁰_phenyl, C-5⁰⁰_phenyl), 130.3 (2C, C-3⁰⁰⁰_{4-methylbenzenesulfonamide}, C-5⁰⁰⁰

4-

_{methylbenzenesulfonamide}), 132.1 (2C, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl), 132.2 (2C,

C-3⁰_{4-(phenylethynyl)phenyl}, C-5⁰_{4-(phenylethynyl)phenyl}), 137.7 (1C, C-1⁰⁰⁰

4-

_{methylbenzenesulfonamide}), 139.6 (1C, C-1⁰_{4-(phenylethynyl)phenyl}), 144.1

(1C, C-4⁰⁰⁰_{4-methylbenzenesulfonamide}); IR (neat): ṽ [cm^ꢂ1] ¼ 3256, 2928,

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

https://doi.org/10.1016/j.tet.2018.12.011

M. Galster et al. / Tetrahedron xxx (xxxx) xxx

17

CH₂), 5.86e5.93 (m, 1H, OCH₂CH]CH₂), 7.21e7.25 (m, 2H, 2⁰-H_4-

_bromophenyl, 6⁰-H_{4-bromophenyl}), 7.46e7.50 (m, 2H, 3⁰-H_{4-bromophenyl}

5⁰-H_{4-bromophenyl}); ¹³C NMR (CDCl₃):

OCHCH₂OH), 5.19e5.21 (m, 1H, OCH₂CH]CH₂), 5.25e5.29 (m, 1H,

OCH₂CH]CH₂), 5.89e5.96 (m, 1H, OCH₂CH]CH₂), 7.29e7.33 (m,

2H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}), 7.33e7.38 (m,

3H, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.51e7.56 (m, 4H, 3⁰-H_4-(phe-

_{nylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl); ¹³C

,

d

[ppm] ¼ 55.4 (1C,

OCH₂OCH₃), 70.1 (1C, OCH₂CH]CH₂), 71.6 (1C, OCHCH₂O), 79.9 (1C,

OCHCH₂O), 96.8 (1C, OCH₂OCH₃), 117.3 (1C, OCH₂CH]CH₂), 122.0

(1C, C-4⁰_{4-bromophenyl}), 128.9 (2C, C-2⁰_{4-bromophenyl}, C-6⁰_{4-bromophenyl}),

131.7 (2C, C-3⁰_{4-bromophenyl}, C-5⁰_{4-bromophenyl}), 134.6 (1C, OCH₂CH]

CH₂), 138.5 (1C, C-1⁰_{4-bromophenyl}); IR (neat): ṽ [cm^ꢂ1] ¼ 2928, 2882,

NMR (CDCl₃):

d

[ppm] ¼ 67.3 (1C, OCHCH₂OH), 70.1 (1C, OCH₂CH]

CH₂), 82.0 (1C, OCHCH₂OH), 89.1 (1C, C^C), 89.8 (1C, C^C), 117.6

(1C, OCH₂CH]CH₂), 123.29 (1C, C_arom.), 123.30 (1C, C_arom.), 127.1

(2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 128.48 (1C, C-

4⁰⁰_phenyl), 128.50 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 131.8 (2C, C-2⁰⁰_phenyl, C-

1593, 1485, 1404, 1339, 1211, 1150, 1107, 1069, 1038, 1011, 918, 822;

79

LCMS (m/z): [MþH]^þcalcd for C₁₃

H BrO₃: 301.0434, found:

18

301.0412; HPLC (method 1): t_R¼ 20.2 min, purity 99.5%.

6⁰⁰_phenyl), 132.0 (2C, C-3⁰_{4-(phenylethynyl)phenyl}C-5⁰_{4-(phenylethynyl)}

,

_phenyl), 134.5 (1C, OCH₂CH]CH₂), 138.9 (1C, C-1⁰_{4-(phenylethynyl)}

_phenyl); IR (neat): ṽ [cm^ꢂ1] ¼ 3426, 2866, 1597, 1508, 1408, 1339,

1219, 1096, 1042, 922, 833, 756, 691; HPLC (method 1):

t_R¼ 22.7 min, purity 97.9%.

4.2.26. (S)-1-[1-(Allyloxy)-2-(methoxymethoxy)ethyl]-4-

(phenylethynyl)benzene (36)

Under N₂atmosphere, copper(I) iodide (67 mg, 0.35 mmol),

tetrakis(triphenylphosphine)palladium(0) (280 mg, 0.24 mmol)

and phenylacetylene (0.36 mL, 340 mg, 3.3 mmol) were added to a

solution of 35 (710 mg, 2.4 mmol) in triethylamine (15 mL). The

mixture was heated to reﬂux and additional phenylacetylene

(0.36 mL, 340 mg, 3.3 mmol) was added. After heating the reaction

mixture to reﬂux for 16 h, the solvent was evaporated and the

residue was puriﬁed twice by ﬂash column chromatography (1.

Ø ¼ 6 cm, h ¼ 15 cm, cyclohexane/ethyl acetate ¼ 20:1, V ¼ 30 mL,

2. Ø ¼ 5 cm, h ¼ 15 cm, cyclohexane/ethyl acetate ¼ 100:0 / 20:1,

V ¼ 30 mL) to give 36 as yellowish oil (650 mg, 2.0 mmol, 86%

yield). R_f¼ 0.16 (cyclohexane/ethyl acetate ¼ 20:1); speciﬁc rota-

4.2.28. (R)-3-{(S)-2-Hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}

propane-1,2-diol (38)

AD-mix-a (410 mg) was added to a mixture of tert-butyl alcohol

(1.5 mL) and water (1.5 mL). The mixture was cooled to 0 ^ꢀC, a so-

lution of 37 (82 mg, 0.29 mmol) in a mixture of tert-butyl alcohol

(1 mL) and water (1 mL) was added and the reaction mixture was

stirred at 0 ^ꢀC for 16 h. Then sodium sulﬁte (440 mg) was added, the

mixture was warmed to ambient temperature and stirred for 1 h.

Then ethyl acetate was added to the reaction mixture and after

separation of the layers, the aqueous phase was again extracted

with ethyl acetate (3ꢃ). The combined organic layers were dried

over sodium sulfate, ﬁltered, and the solvent was removed in vacuo.

The crude product was puriﬁed by ﬂash column chromatography

(Ø ¼ 2 cm, h ¼ 10 cm, ethyl acetate/methanol ¼ 10:1, V ¼ 10 mL) to

give an inseparable mixture of diastereomers 38 and 39 (8:2) as

colorless solid (84 mg, 0.27 mmol, 93% yield). R_f¼ 0.36 (ethyl ace-

tate/methanol ¼ 10:1); melting point: 111 ^ꢀC; speciﬁc rotation:

tion: ½a ²_D⁰

ꢁ

¼ þ52.8 (1.6; CH₂Cl₂); ¹H NMR (CDCl₃):

[ppm] ¼ 3.29 (s,

d

3H, OCH₂OCH₃), 3.64 (dd, J ¼ 10.8/4.2 Hz, 1H, OCHCH₂O), 3.76 (dd,

J ¼ 10.8/7.3 Hz, 1H, OCHCH₂O), 3.89 (ddt, J ¼ 12.8/6.0/1.3 Hz, 1H,

OCH₂CH]CH₂), 4.01 (ddt, J ¼ 12.8/5.1/1.5 Hz, 1H, OCH₂CH]CH₂),

4.57 (dd, J ¼ 7.3/4.2 Hz, 1H, OCHCH₂O), 4.63 (d, J ¼ 6.6 Hz, 1H,

OCH₂OCH₃), 4.66 (d, J ¼ 6.6 Hz, 1H, OCH₂OCH₃), 5.17 (dq, J ¼ 10.4/

1.5 Hz, 1H, OCH₂CH]CH₂), 5.26 (dq, J ¼ 17.2/1.7 Hz, 1H, OCH₂CH]

CH₂), 5.87e5.97 (m, 1H, OCH₂CH]CH₂), 7.32e7.44 (m, 5H, 2⁰-H_4-

½

a ²_D⁰

ꢁ

¼ þ89.6 (2.6; CH₃OH); ¹H NMR (CD₃OD):

d

[ppm] ¼ 3.35 (dd,

_{(phenylethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl

4⁰⁰-H_phenyl), 7.50e7.57 (m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_4-(phe-

2⁰⁰-H_phenyl6⁰⁰-H_phenyl); ¹³C NMR (CDCl₃):

[ppm] ¼ 55.4 (1C, OCH₂OCH₃), 70.1 (1C, OCH₂CH]CH₂), 71.7 (1C,

,

J ¼ 9.8/6.8 Hz, 0.8H, OCH₂CHCH₂OH³⁸), 3.44e3.46 (m, 0.4H,

OCH₂CHCH₂OH³⁹), 3.49e3.53 (m, 1.6H, OCH₂CHCH₂OH³⁸(0.8H),

OCH₂CHCH₂OH³⁸(0.8H)), 3.56e3.60 (m, 2.2H, OCH₂CHCH₂OH³⁸

(0.8H), OCHCH₂OH³⁸(0.8H), OCHCH₂OH³⁹(0.2H), OCH₂CH-

CH₂OH³⁹), 3.66 (dd, J ¼ 11.7/7.9 Hz, 0.2H, OCHCH₂OH³⁹), 3.67 (dd,

J ¼ 11.7/8.0 Hz, 0.8H, OCHCH₂OH³⁸), 3.77e3.84 (m, 1H, OCH₂CH-

CH₂OH), 4.44 (dd, J ¼ 7.9/3.7 Hz, 1H, OCHCH₂OH), 7.34e7.39 (m, 5H,

,

nylethynyl)phenyl

d

OCHCH₂O), 80.3 (1C, OCHCH₂O), 89.3 (1C, C^C), 89.7 (1C, C^C),

96.8 (1C, OCH₂OCH₃), 117.2 (1C, OCH₂CH]CH₂), 123.1 (1C, C_arom.),

123.4 (1C, C_arom.), 127.3 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_4-(phenyl-

_{ethynyl)phenyl}), 128.4 (1C, C-4⁰⁰_phenyl), 128.5 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl),

131.76 (2C, C_arom.), 131.82 (2C, C_arom.), 134.8 (1C, OCH₂CH]CH₂),

139.7 (1C, C-1⁰_{4-(phenylethynyl)phenyl}); IR (neat): ṽ [cm^ꢂ1] ¼ 2924,

2882, 1597, 1508, 1485, 1439, 1339, 1211, 1150, 1111, 1038, 918, 833,

756, 691; LCMS (m/z): [MþH]^þcalcd for C₂₁H₂₃O₃: 323.1642, found:

323.1613; HPLC (method 1): t_R¼ 25.2 min, purity 71.9%.

2⁰-H_{4-(phenylethynyl)phenyl}

, , ,

6⁰-H_{4-(phenylethynyl)phenyl}3⁰⁰-H_phenyl5⁰⁰-

H_phenyl, 4⁰⁰-H_phenyl), 7.49e7.53 (m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-

H_{4-(phenylethynyl)phenyl}, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl); ratio of the daister-

eomers: 38: 39 ¼ 8: 2; ¹³C NMR (CD₃OD):

d

[ppm] ¼ 64.3 (0.8C,

OCH₂CHCH₂OH³⁸), 64.4 (0.2C, OCH₂CHOHCH₂OH³⁹), 67.7 (1C,

OCHCH₂OH), 71.7 (0.2C, OCH₂CHCH₂OH³⁹), 72.1 (0.8C, OCH₂CH-

CH₂OH³⁸), 72.3 (0.2C, OCH₂CHCH₂OH³⁹), 72.6 (0.8C, OCH₂CH-

CH₂OH³⁸), 84.8 (0.2C, OCHCH₂OH³⁹), 85.1 (0.8C, OCHCH₂OH³⁸),

4.2.27. (S)-2-(Allyloxy)-2-[4-(phenylethynyl)phenyl]ethan-1-ol

(37)

89.9 (1C, C^C), 90.2 (1C, C^C), 124.1 (0.2C, C³_ar⁹_om.), 124.2 (0.8C,

38

C

), 124.5 (1C, C_arom.), 128.3 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_4-

36 (620 mg, 1.9 mmol) was suspended in a mixture of HCl-

saturated methanol (4 mL) and pure methanol (6 mL). The reac-

tion mixture was stirred at ambient temperature for 16 h. After

addition of a saturated aqueous solution of sodium bicarbonate and

water, the mixture was extracted with ethyl acetate (3ꢃ). The

combined organic layers were dried over sodium sulfate, ﬁltered,

and the solvent was removed in vacuo. The residue was puriﬁed by

ﬂash column chromatography (Ø ¼ 3 cm, h ¼ 15 cm, cyclohexane/

ethyl acetate ¼ 8:2, V ¼ 20 mL) to give 37 as yellow oil (490 mg,

1.8 mmol, 91% yield). R_f¼ 0.25 (cyclohexane/ethyl acetate ¼ 8:2);

arom.

_{(phenylethynyl)phenyl}), 129.5 (1C, C-4⁰⁰_phenyl), 129.6 (2C, C-3⁰⁰_phenyl, C-

5⁰⁰_phenyl), 132.5 (2C, C_arom.), 132.6 (2C, C_arom.), 140.9 (0.8C, C-1⁰_4-

³⁸), 141.0 (0.2C, C-1⁰₄³_-⁹_{(phenylethynyl)phenyl}); ratio of

(phenylethynyl)phenyl

the daistereomers: 38: 39 ¼ 8: 2; IR (neat): ṽ [cm^ꢂ1] ¼ 3456, 3271,

2905, 2862, 1504, 1443, 1404, 1296, 1219, 1107, 1038, 1022, 930, 829,

752, 691; HRMS (m/z): [MþH]^þcalcd for C₁₉H₂₁O₄: 313.1434, found:

313.1399; HPLC (method 2): t_R¼ 15.2 min, purity 97.8%.

4.2.29. (S)-3-{(S)-2-Hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}

propane-1,2-diol (39)

speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ102.7 (2.7; CH₂Cl₂); ¹H NMR (CDCl₃):

d

[ppm] ¼ 3.64 (dd, J ¼ 11.7/3.8 Hz, 1H, OCHCH₂OH), 3.70 (dd,

AD-mix-b (410 mg) was added to a mixture of tert-butyl alcohol

J ¼ 11.7/8.4 Hz, 1H, OCHCH₂OH), 3.85e3.90 (m, 1H, OCH₂CH]CH₂),

4.00e4.05 (m, 1H, OCH₂CH]CH₂), 4.50 (dd, J ¼ 8.4/3.8 Hz, 1H,

(1.5 mL) and water (1.5 mL). The mixture was cooled to 0 ^ꢀC, a so-

lution of 37 (82 mg, 0.29 mmol) in a mixture of tert-butyl alcohol

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

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18

M. Galster et al. / Tetrahedron xxx (xxxx) xxx

5⁰-H_{4-bromophenyl}); ¹³C NMR (CDCl₃):

CH₂OH), 55.5 (1C, OCH₂OCH₃), 62.2 (1C, OCH₂CH₂CH₂OH), 68.9 (1C,

OCH₂CH₂CH₂OH), 71.7 (1C, OCHCH₂O), 81.3 (1C, OCHCH₂O), 96.8

(1C, OCH₂OCH₃), 122.2 (1C, C-4‘_{4-bromophenyl}), 128.8 (2C, C-2⁰_4-

d

[ppm] ¼ 32.1 (1C, OCH₂CH₂

(1 mL) and water (1 mL) was added and the reaction mixture was

stirred at 0 ^ꢀC for 16 h. Then sodium sulﬁte (440 mg) was added, the

mixture was warmed to ambient temperature and stirred for 1 h.

Then ethyl acetate was added to the reaction mixture and after

separation of the layers, the aqueous phase was again extracted

with ethyl acetate (3ꢃ). The combined organic layers were dried

over sodium sulfate, ﬁltered, and the solvent was removed in vacuo.

The crude product was puriﬁed by ﬂash column chromatography

(Ø ¼ 2 cm, h ¼ 10 cm, ethyl acetate/methanol ¼ 10:1, V ¼ 10 mL) to

give an inseparable mixture of diastereomers 39 and 38 (6:4) as

colorless solid (81 mg, 0.26 mmol, 90% yield). R_f¼ 0.35 (ethyl ace-

tate/methanol ¼ 10:1); melting point: 106 ^ꢀC; speciﬁc rotation:

-

C-6⁰_{4-bromophenyl}), 131.8 (2C, C-3⁰_{4-bromophenyl,}C-5⁰_4-

bromophenyl,

_bromophenyl), 138.1 (1C, C-1⁰_{4-bromophenyl}); IR (neat):

ṽ

[cm^ꢂ1] ¼ 3433, 2924, 2874, 1589, 1485, 1404, 1339, 1300, 1211, 1150,

1107, 1069, 1034, 1011, 964, 918, 822; HRMS (m/z): [MþH]^þcalc for

79

C

H BrO₄: 319.0562, found: 319.0539; HPLC (method 1):

13 20

t_R¼ 16.6 min, purity 99.5%.

4.2.31. (S)-3-{2-(Methoxymethoxy)-1-[4-(phenylethynyl)phenyl]

ethoxy}propan-1-ol (41)

½

a ²_D⁰

ꢁ

¼ þ83.1 (3.8; CH₃OH); ¹H NMR (CD₃OD):

d

[ppm] ¼ 3.35 (dd,

J ¼ 9.8/6.8 Hz, 0.4H, OCH₂CHCH₂OH³⁸), 3.43e3.47 (m, 1.2H,

OCH₂CHCH₂OH³⁹), 3.49e3.53 (m, 0.8H, OCH₂CHCH₂OH³⁸(0.4H),

OCH₂CHCH₂OH³⁸(0.4H)), 3.56e3.62 (m, 2.6H, OCH₂CHCH₂OH³⁸

(0.4H), OCHCH₂OH³⁸(0.4H), OCHCH₂OH³⁹(0.6H), OCH₂CH-

CH₂OH³⁹), 3.66 (dd, J ¼ 11.7/7.9 Hz, 0.6H, OCHCH₂OH³⁹), 3.67 (dd,

J ¼ 11.7/8.0 Hz, 0.4H, OCHCH₂OH³⁸), 3.79 (qi, J ¼ 5.3 Hz, 0.6H,

OCH₂CHCH₂OH³⁹), 3.79e3.84 (m, 0.4H, OCH₂CHCH₂OH³⁸), 4.44 (dd,

J ¼ 7.9/3.7 Hz, 1H, OCHCH₂OH), 7.34e7.39 (m, 5H, 2⁰-H_{4-(phenylethynyl)}

_phenyl, 6⁰-H_{4-(phenylethynyl)phenyl}, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl),

Under N₂atmosphere, copper(I) iodide (240 mg, 1.3 mmol),

tetrakis(triphenylphosphine)palladium(0) (420 mg, 0.4 mmol) and

phenylacetylene (0.8 mL, 740 mg, 7.2 mmol) were added to a solu-

tion of 40 (1.1 g, 3.6 mmol) in triethylamine (50 mL). The mixture

was heated to reﬂux and another portion of phenylacetylene

(0.8 mL, 740 mg, 7.2 mmol) was added. After heating the mixture to

reﬂux for 16 h, the solvent was evaporated and the residue was

puriﬁed twice by ﬂash column chromatography (1. Ø ¼ 4 cm,

h ¼ 15 cm, dichloromethane/methanol 98/2 / 90/10, V ¼ 20 mL, 2.

Ø ¼ 4 cm, h ¼ 15 cm, cyclohexane/ethyl acetate 8/2 / 1/2,

V ¼ 20 mL) to give 41 as yellowish oil (950 mg, 2.8 mmol, 78%

yield). R_f¼ 0.49 (cyclohexane/ethyl acetate ¼ 1:1); speciﬁc rota-

7.49e7.53 (m, 4H, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}

,

2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl); ratio of the daistereomers: 39: 38 ¼ 6: 4; ¹³

C

NMR (CD₃OD):

d

[ppm] ¼ 64.3 (0.4C, OCH₂CHCH₂OH³⁸), 64.4 (0.6C,

OCH₂CHOHCH₂OH³⁹), 67.7 (1C, OCHCH₂OH), 71.7 (0.6C, OCH₂CH-

CH₂OH³⁹), 72.1 (0.4C, OCH₂CHCH₂OH³⁸), 72.3 (0.6C, OCH₂CH-

CH₂OH³⁹), 72.6 (0.4C, OCH₂CHCH₂OH³⁸), 84.8 (0.6C, OCHCH₂OH³⁹),

85.1 (0.4C, OCHCH₂OH³⁸), 89.9 (1C, C^C), 90.2 (1C, C^C), 124.1

tion: ½a ²_D⁰

ꢁ

¼ þ57.2 (3.0; CH₂Cl₂); ¹H NMR: (CDCl₃):

d

[ppm] ¼ 1.83

(quin, J ¼ 5.6 Hz, 2H, OCH₂CH₂CH₂OH), 3.33 (s, 3H, OCH₂OCH₃),

3.51e3.68 (m, 3H, OCH₂CH₂CH₂OH, OCHCH₂O (1H)), 3.70 (dd,

J ¼ 10.8/8.1 Hz, 1H, OCHCH₂O), 3.77e3.85 (m, 2H, OCH₂CH₂CH₂OH),

4.53 (dd, J ¼ 8.0/3.8 Hz, 1H, OCHCH₂O), 4.65 (s, 2H, OCH₂OCH₃),

7.29e7.38 (m, 5H, H_arom.), 7.51e7.55 (m, 4H, H_arom.); ¹³C NMR

39

38

(0.6C, C

), 124.2 (0.4C, C

), 124.5 (1C, C_arom.), 128.3 (2C, C-2⁰_4-

arom.

_{(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 129.5 (1C, C-4⁰⁰_phenyl),

129.6 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 132.5 (2C, C_arom.), 132.6 (2C, C_arom.),

140.9 (0.4C, C-1⁰₄³_-⁸_{(phenylethynyl)phenyl}), 141.0 (0.6C, C-1⁰_{4-(phenylethynyl)}

(CDCl₃):

d

[ppm] ¼ 32.1 (1C, OCH₂CH₂CH₂OH), 55.5 (1C,

OCH₂OCH₃), 62.3 (1C, OCH₂CH₂CH₂OH), 69.0 (1C, OCH₂CH₂CH₂OH),

71.8 (1C, OCHCH₂O), 81.6 (1C, OCHCH₂O), 89.1 (1C, C^C), 89.8 (1C,

C^C), 96.8 (1C, OCH₂OCH₃), 123.27 (1C, C_arom.), 123.28 (1C, C_arom.),

127.1 (2C, C_arom.), 128.48 (1C, C_arom.), 128.50 (2C, C_arom.), 131.8 (2C,

³⁹); ratio of the daistereomers: 39: 38 ¼ 6: 4; IR (neat): ṽ

phenyl

[cm^ꢂ1] ¼ 3653, 3318, 2978, 2866, 1597, 1443, 1393, 1238, 1111, 1038,

833, 752, 687; HRMS (m/z): [MþH]^þcalcd for C₁₉H₂₁O₄: 313.1434,

found: 313.1415; HPLC (method 2): t_R¼ 15.2 min, purity 96.9%.

C

_arom.), 131.9 (2C, C_arom.), 139.2 (1C, C_arom.); IR (neat): ṽ

[cm^ꢂ1] ¼ 3441, 2928, 2882, 1597, 1508, 1443, 1400, 1342, 1211, 1150,

1107, 1034, 964, 918, 833, 756, 691; HRMS (m/z): [MþH]^þcalc for

4.2.30. (S)-3-[1-(4-Bromophenyl)-2-(methoxymethoxy)ethoxy]

propan-1-ol (40)

C₂₁H₂₅O₄: 341.1747, found: 341.1742; HPLC (method 1):

t_R¼ 20.0 min, purity 94.6%.

Under N₂atmosphere, a 0.5 M solution of 9-borabicyclo[3.3.1]

nonane (9-BBN) in THF (13.2 mL, 6.6 mmol) was added to a solution

of 35 (1.0 g, 3.3 mmol) in THF (50 mL) and the mixture was stirred at

ambient temperature overnight. Then again a 0.5 M solution of 9-

BBN in THF (6.6 mL, 3.3 mmol) was added. After 1.5 h, the reac-

tion mixture was cooled to ꢂ25 ^ꢀC and methanol (1 mL) was added.

After 15 min, 1 M NaOH (13.2 mL, 13.2 mmol) was added, where-

upon after 15 min H₂O₂(30% in H₂O) (3.3 mL, ~33 mmol) was

added. Then the mixture was stirred for 1 h at ꢂ25 ^ꢀC, 1 h at

ambient temperature and ﬁnally heated to 40 ^ꢀC. After the gas

formation had ﬁnished, the mixture was cooled to ambient tem-

perature, water was added, and the mixture was extracted with

dichloromethane (3ꢃ). The combined organic layers were dried

over sodium sulfate, ﬁltered, and the solvent was removed in vacuo.

The residue was puriﬁed by ﬂash column chromatography

(Ø ¼ 4 cm, h ¼ 15 cm, cyclohexane/ethyl acetate 8/2 / 1/2,

V ¼ 20 mL) to give 40 as colorless oil (1.1 g, 3.3 mmol, 99% yield).

R_f¼ 0.49 (cyclohexane/ethyl acetate ¼ 1:1); speciﬁc rotation:

4.2.32. (S)-2-{2-(Methoxymethoxy)-1-[4-(phenylethynyl)phenyl]

ethoxy}ethyl 4-methylbenzenesulfonate (42)

Under N₂atmosphere, triethylamine (0.65 mL, 0.48 g, 4.7 mmol)

and 4-dimethylaminopyridine (60 mg, 0.50 mmol) were added to a

solution of 17 (770 mg, 2.3 mmol) in dry DCM (50 mL). Then 4-

toluenesulfonyl chloride (900 mg, 4.7 mmol) was added and the

reaction was stirred for 24 h at room temperature. Afterwards, the

mixture was extracted with EtOAc (3ꢃ), the organic phase dried

over sodium sulfate, ﬁltered, and concentrated in vacuo. The res-

idue was puriﬁed by ﬂash column chromatography (Ø ¼ 4 cm,

h ¼ 15 cm, cyclohexane/ethyl acetate 8/2 / 1/2, V ¼ 10 mL) to give

42 as colorless oil (970 mg, 2.0 mmol, 86% yield). R_f¼ 0.76 (cyclo-

hexane/ethyl acetate ¼ 2:1); speciﬁc rotation: ½a _D²⁰

¼ þ15.3 (3.2;

ꢁ

CH₂Cl₂); ¹H NMR (CDCl₃):

(s, 3H, OCH₂OCH₃), 3.55e3.65 (m, 3H, OCH₂CH₂OS, OCHCH₂O (1H)),

d

[ppm] ¼ 2.45 (s, 3H, SO₃C₆H₄CH₃), 3.27

3.67 (dd, J ¼ 10.8/7.5 Hz, 1H, OCHCH₂O), 4.13e4.21 (m, 2H, OCH₂

-

½

a ²_D⁰

ꢁ

¼ þ37.7 (3.6; CH₂Cl₂); ¹H NMR (CDCl₃):

d

[ppm] ¼ 1.83 (quin,

CH₂OS), 4.47 (dd, J ¼ 7.4/4.1 Hz, 1H, OCHCH₂O), 4.58 (d, J ¼ 6.6 Hz,

1H, OCH₂OCH₃), 4.61 (d, J ¼ 6.6 Hz, 1H, OCH₂OCH₃), 7.23e7.26 (m,

2H, H_arom.), 7.31e7.38 (m, 5H, H_arom.), 7.47e7.50 (m, 2H, H_arom.),

7.52e7.55 (m, 2H, H_arom.), 7.75e7.79 (m, 2H, H_arom.); ¹³C NMR

J ¼ 5.6 Hz, 2H, OCH₂CH₂CH₂OH), 3.32 (s, 3H, OCH₂OCH₃), 3.49e3.64

(m, 3H, OCH₂CH₂CH₂OH, OCHCH₂O (1H)), 3.67 (dd, J ¼ 10.7/8.1 Hz

1H, OCHCH₂O), 3.79 (m, 2H, OCH₂CH₂CH₂OH), 4.47 (dd, J ¼ 7.9/

3.9 Hz,1H, OCHCH₂O), 4.63 (s, 2H, OCH₂OCH₃), 7.19e7.24 (m, 2H, 2⁰-

H_{4-bromophenyl,}6⁰-H_{4-bromophenyl}), 7.47e7.51 (m, 2H, 3⁰-H_{4-bromophenyl,}

(CDCl₃):

d

[ppm] ¼ 21.8 (1C, SO₃C₆H₄CH₃), 55.4 (1C, OCH₂OCH₃),

66.8 (1C, OCH₂CH₂OS), 69.3 (1C, OCH₂CH₂OS), 71.5 (1C, OCHCH₂O),

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

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M. Galster et al. / Tetrahedron xxx (xxxx) xxx

19

81.8 (1C, OCHCH₂O), 89.1 (1C, C^C), 89.9 (1C, C^C), 96.7 (1C,

OCH₂OCH₃), 123.27 (1C, C_arom.), 123.28 (1C, C_arom.), 127.1 (2C, C_arom.),

128.1 (2C, C_arom.), 128.49 (1C, C_arom.), 128.51 (2C, C_arom.), 129.9 (2C,

C_arom.), 128.50 (2C, C_arom.), 131.8 (2C, C_arom.), 131.9 (2C, C_arom.), 139.1

(1C, C_arom.); IR (neat): ṽ [cm^ꢂ1] ¼ 2928, 2882, 2102,1597,1508,1443,

1342, 1285, 1211, 1150, 1107, 1034, 964, 918, 833, 756, 691; HRMS

(m/z): [MþH]^þcalc for C₂₀H₂₂N₃O₃: 352.1656, found: 352.1656;

HPLC (method 1): t_R¼ 22.3 min, purity 97.8%.

C

_arom.), 131.8 (2C, C_arom.), 131.9 (2C, C_arom.), 133.2 (1C, C_arom.), 138.9

(1C, C_arom.), 144.9 (1C, C_arom.); IR (neat): ṽ [cm^ꢂ1] ¼ 2924, 2882,

1597, 1508, 1443, 1400, 1358, 1177, 1107, 1018, 918, 814, 756, 691,

664; HRMS (m/z): [MþH]^þcalc for C₂₇H₂₉O₆S: 481.1679, found:

481.1646; HPLC (method 1): t_R¼ 23.0 min, purity 98.2%.

4.2.35. (S)-1-[1-(3-Azidopropoxy)-2-(methoxymethoxy)ethyl]-4-

(phenylethynyl)benzene (45)

Sodium azide (800 mg, 12 mmol) was added to a solution of 43

(1.1 g, 2.2 mmol) in DMSO (80 mL). The mixture was heated to

reﬂux for 16 h. After cooling the mixture to ambient temperature,

water was added and the mixture was extracted with ethyl acetate

(3ꢃ). The combined organic layers were dried (Na₂SO₄), ﬁltered,

and the solvent was removed in vacuo. The residue was puriﬁed by

ﬂash column chromatography (Ø ¼ 4 cm, h ¼ 15 cm, cyclohexane/

ethyl acetate 8/2 / 1/2, V ¼ 20 mL) to give 45 as yellowish oil

(730 mg, 2.0 mmol, 90% yield). R_f¼ 0.66 (cyclohexane/ethyl ace-

4.2.33. (S)-3-{2-(Methoxymethoxy)-1-[4-(phenylethynyl)phenyl]

ethoxy}propyl 4-methylbenzenesulfonate (43)

Under N₂atmosphere, triethylamine (0.75 mL, 0.55 g, 5.4 mmol)

and 4-dimethylaminopyridine (66 mg, 0.54 mmol) were added to a

solution of 41 (920 mg, 2.7 mmol) in dry DCM (50 mL). Then 4-

toluenesulfonyl chloride (1.0 g, 5.4 mmol) was added and the re-

action was stirred for 16 h at room temperature. Afterwards, the

mixture was extracted with EtOAc (3ꢃ), the organic phase dried

over sodium sulfate, ﬁltered, and concentrated in vacuo. The res-

idue was puriﬁed by ﬂash column chromatography (Ø ¼ 4 cm,

h ¼ 15 cm, cyclohexane/ethyl acetate 8/2 / 1/2, V ¼ 10 mL) to give

43 as yellowish oil (1.1 g, 2.2 mmol, 82% yield). R_f¼ 0.62 (cyclo-

tate ¼ 8:2); speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ38.6 (1.9; CH₂Cl₂); ¹H NMR

(CDCl₃):

d

[ppm] ¼ 1.77e1.94 (m, 2H, OCH₂CH₂CH₂N₃), 3.30 (s, 3H,

OCH₂OCH₃), 3.35e3.48 (m, 2H, OCH₂CH₂CH₂N₃), 3.47 (t, J ¼ 6.1 Hz,

2H, OCH₂CH₂CH₂N₃), 3.62 (dd, J ¼ 10.8/4.1 Hz, 1H, OCHCH₂O), 3.74

(dd, J ¼ 10.8/7.4 Hz, 1H, OCHCH₂O), 4.48 (dd, J ¼ 7.5/4.1 Hz, 1H,

OCHCH₂O), 4.62 (d, J ¼ 6.5 Hz, 1H, OCH₂OCH₃), 4.65 (d, J ¼ 6.5 Hz,

1H, OCH₂OCH₃), 7.29e7.38 (m, 5H, H_arom.), 7.50e7.56 (m, 4H,

hexane/ethyl acetate ¼ 2:1); speciﬁc rotation: ½a _D²⁰

¼ þ26.0 (2.2;

ꢁ

CH₂Cl₂); ¹H NMR (CDCl₃):

d

[ppm] ¼ 1.87e1.98 (m, 2H, OCH₂CH₂

-

CH₂O), 2.45 (s, 3H, SO₃C₆H₄CH₃), 3.26 (s, 3H, OCH₂OCH₃), 3.42 (t,

J ¼ 6.0 Hz, 2H, OCH₂CH₂CH₂O), 3.57 (dd, 1H, J ¼ 10.8/4.2 Hz, OCH-

CH₂O), 3.66 (dd, J ¼ 10.8/7.3 Hz, 1H, OCHCH₂O), 4.12e4.22 (m, 2H,

OCH₂CH₂CH₂O), 4.40 (dd, J ¼ 7.3/4.2 Hz, 1H, OCHCH₂O), 4.58 (d,

J ¼ 6.6 Hz, 1H, OCH₂OCH₃), 4.60 (d, J ¼ 6.6 Hz, 1H, OCH₂OCH₃),

7.24e7.27 (m, 2H, H_arom.), 7.32e7.38 (m, 5H, H_arom.), 7.48e7.51 (m,

H

_arom.); ¹³C NMR (CDCl₃):

d

[ppm] ¼ 29.4 (1C, OCH₂CH₂CH₂N₃), 48.6

(1C, OCH₂CH₂CH₂N₃), 55.4 (1C, OCH₂OCH₃), 66.1 (1C,

OCH₂CH₂CH₂N₃), 71.7 (1C, OCHCH₂O), 81.6 (1C, OCHCH₂O), 89.2

(1C, C^C), 89.7 (1C, C^C), 96.7 (1C, OCH₂OCH₃), 123.1 (1C, C_arom.),

123.3 (1C, C_arom.), 127.1 (2C, C_arom.), 128.4 (1C, C_arom.), 128.5 (2C,

2H, H_arom.), 7.52e7.55 (m, 2H, H_arom.), 7.75e7.78 (m, 2H, H_arom.); ¹³

NMR (CDCl₃):

C

_arom.), 131.7 (2C, C_arom.), 131.8 (2C, C_arom.), 139.6 (1C, C_arom.); IR

(neat): ṽ [cm^ꢂ1] ¼ 2928, 2874, 2095, 1597, 1508, 1443, 1400, 1342,

1300, 1261, 1211, 1150, 1107, 1034, 972, 918, 837, 756, 691; HRMS (m/

z): [MþH]^þcalc for C₂₁H₂₄N₃O₃: 366.1812, found: 366.1819; HPLC

(method 1): t_R¼ 25.1 min, purity 97.3%.

d

[ppm] ¼ 21.8 (1C, SO₃C₆H₄CH₃), 29.6 (1C,

OCH₂CH₂CH₂O), 55.4 (1C, OCH₂OCH₃), 64.9 (1C, OCH₂CH₂CH₂O),

67.7 (1C, OCH₂CH₂CH₂O), 71.5 (1C, OCHCH₂O), 81.5 (1C, OCHCH₂O),

89.2 (1C, C^C), 89.8 (1C, C^C), 96.7 (1C, OCH₂OCH₃), 123.1 (1C,

C

_arom.), 123.3 (1C, C_arom.), 127.0 (2C, C_arom.), 128.0 (2C, C_arom.), 128.46

(1C, C_arom.), 128.50 (2C, C_arom.), 130.0 (2C, C_arom.), 131.7 (2C, C_arom.),

131.8 (2C, C_arom.), 133.3 (1C, C_arom.), 139.5 (1C, C_arom.), 144.8 (1C,

4.2.36. 3-(Benzyloxy)-2-methyl-4H-pyran-4-one (47)

47 was synthesized according to the literature [65]:

C

_arom.); IR (neat): ṽ [cm^ꢂ1] ¼ 2924, 2878, 1597, 1508, 1443, 1358,

Potassium carbonate (4.8 g, 35 mmol) and benzyl bromide

(1.3 mL, 1.9 g, 11 mmol) were added to a solution of 3-hydroxy-2-

methyl-4H-pyran-4-one (1.1 g, 8.7 mmol) in dry acetonitrile

(50 mL). After heating the mixture to reﬂux for 16 h, water was

added and the mixture was extracted with ethyl acetate (3ꢃ). The

combined organic layers were dried over sodium sulfate, ﬁltered,

and the solvent was removed in vacuo. The residue was puriﬁed by

ﬂash column chromatography (Ø ¼ 4 cm, h ¼ 15 cm, cyclohexane/

ethyl acetate ¼ 8:2 / 2:1, V ¼ 30 mL) to give 47 as yellowish oil

(1.8 g, 8.3 mmol, 95% yield). R_f¼ 0.49 (cyclohexane/ethyl ace-

1177, 1107, 1034, 941, 833, 814, 756, 691, 664; HRMS (m/z): [MþH]^þ

calc for C₂₈H₃₁O₆S: 495.1836, found: 495.1891; HPLC (method 1):

t_R¼ 25.7 min, purity 92.8%.

4.2.34. (S)-1-[1-(2-Azidoethoxy)-2-(methoxymethoxy)ethyl]-4-

(phenylethynyl)benzene (44)

Sodium azide (880 mg, 14 mmol) was added to a solution of 42

(1.1 g, 2.4 mmol) in DMSO (80 mL). The mixture was heated to

reﬂux for 16 h. After cooling the mixture to ambient temperature,

water was added and the mixture was extracted with ethyl acetate

(3ꢃ). The combined organic layers were dried (Na₂SO₄), ﬁltered,

and the solvent was removed in vacuo. The residue was puriﬁed by

ﬂash column chromatography (Ø ¼ 4 cm, h ¼ 15 cm, cyclohexane/

ethyl acetate 8/2 / 1/2, V ¼ 20 mL) to give 44 as yellowish oil

(770 mg, 2.2 mmol, 92% yield). R_f¼ 0.77 (cyclohexane/ethyl ace-

tate ¼ 1:1); ¹H NMR (CDCl₃):

[ppm] ¼ 2.11 (s, 3H, CH₃), 5.16 (s, 2H,

d

OCH₂Ph), 6.50 (d, J ¼ 5.6 Hz, 1H, OCH]CHCO), 7.30e7.36 (m, 3H, 3⁰-

H_phenyl, 4⁰-H_phenyl, 5⁰-H_phenyl), 7.37e7.40 (m, 2H, 2⁰-H_phenyl, 6⁰-

H

_phenyl), 7.64 (d, J ¼ 5.6 Hz, 1H, OCH]CHCO); ¹³C NMR (CDCl₃)

d

[ppm] ¼ 15.0 (1C, CH₃), 73.8 (1C, OCH₂Ph),117.0 (1C, OCH]CHCO),

128.5 (1C, C-4⁰_phenyl), 128.6 (2C, C-3⁰_phenyl, C-5⁰_phenyl), 129.2 (2C, C-

2⁰_phenyl, C-6⁰_phenyl), 136.9 (1C, C-1⁰_phenyl), 143.8 (1C, OC]CCH₃),

153.8 (1C, OCH]CHCO), 160.6 (1C, OC]CCH₃) 175.3 (1C, OCH]

CHCO); IR (neat): ṽ [cm^ꢂ1] ¼ 3063, 3028, 2959, 2882, 1643, 1574,

1497, 1427, 1389, 1354, 1250, 1173, 1080, 1026, 972, 914, 829, 748,

702; LCMS (m/z): [MþH]^þcalcd for C₁₃H₁₃O₃: 217.0859, found:

217.0875; HPLC (method 1): t_R¼ 17.2 min, purity 97.9%.

tate ¼ 2:1); speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ1.9 (2.5; CH₂Cl₂); ¹H NMR

(CDCl₃):

d

[ppm] ¼ 3.30 (s, 3H, OCH₂OCH₃), 3.36 (dt, J ¼ 13.2/5.1 Hz,

1H, OCH₂CH₂N₃), 3.42 (dt, J ¼ 13.2/5.1 Hz, 1H, OCH₂CH₂N₃), 3.59 (t,

J ¼ 5.1 Hz, 2H, OCH₂CH₂N₃), 3.65 (dd, J ¼ 10.8/4.2 Hz,1H, OCHCH₂O),

3.78 (dd, J ¼ 10.8/7.4 Hz, 1H, OCHCH₂O), 4.54 (dd, J ¼ 7.4/4.2 Hz, 1H,

OCHCH₂O), 4.63 (d, J ¼ 6.6 Hz, 1H, OCH₂OCH₃), 4.66 (d, J ¼ 6.6 Hz,

1H, OCH₂OCH₃), 7.32e7.37 (m, 5H, H_arom.), 7.51e7.56 (m, 4H,

H

_arom.); ¹³C NMR (CDCl₃):

d

[ppm] ¼ 51.0 (1C, OCH₂CH₂N₃), 55.4 (1C,

4.2.37. (S)-3-(Benzyloxy)-1-(2-{2-(methoxymethoxy)-1-[4-

(phenylethynyl)phenyl]ethoxy}ethyl)-2-methylpyridin-4(1H)-one

(48)

OCH₂OCH₃), 68.3 (1C, OCH₂CH₂N₃), 71.7 (1C, OCHCH₂O), 81.9 (1C,

OCHCH₂O), 89.2 (1C, C^C), 89.8 (1C, C^C), 96.8 (1C, OCH₂OCH₃),

123.30 (1C, C_arom.), 123.32 (1C, C_arom.), 127.2 (2C, C_arom.), 128.48 (1C,

Under N₂atmosphere, polymer-bound triphenylphosphine

Please cite this article as: M. Galster et al., Phenylethylene glycol-derived LpxC inhibitors with diverse Zn^2þ-binding groups, Tetrahedron,

https://doi.org/10.1016/j.tet.2018.12.011

20

M. Galster et al. / Tetrahedron xxx (xxxx) xxx

(1.6 mmol/g, 2.0 g, 3.2 mmol) was added to a solution of 44

(570 mg, 1.6 mmol) in dry THF (50 mL) and the reaction was stirred

for 72 h at room temperature. Then water (0.5 mL) was added and

the mixture was ﬁltered through Celite via a Nutsch-type ﬁlter. The

organic solvent was dried over Na₂SO₄, ﬁltered, and concentrated in

vacuo (obtained crude product: 407 mg). A portion of the crude

product (180 mg) was dissolved in water (50 mL) and 47 (130 mg,

0.58 mmol) was added. The reaction mixture was stirred for 7 d at

140 ^ꢀC and then quenched with a saturated aqueous solution of

NH₄Cl. After cooling the mixture to ambient temperature, it was

extracted with ethyl acetate (3ꢃ). The combined organic layers

were dried (Na₂SO₄), ﬁltered, and the solvent was removed in

vacuo. The residue was puriﬁed by ﬂash column chromatography

(Ø ¼ 1 cm, h ¼ 15 cm, dichloromethane/methanol 98/2 / 90/10,

V ¼ 5 mL) to give 48 as brown solid (71 mg, 0.14 mmol, 19% yield).

R_f¼ 0.67 (dichloromethane/methanol ¼ 9:1); melting point:

J ¼ 10.7/8.1 Hz, 1H, OCHCH₂O), 3.94e4.15 (m, 2H, OCH₂CH₂CH₂N),

4.42 (dd, J ¼ 8.1/3.6 Hz, 1H, OCHCH₂O), 4.64 (d, J ¼ 6.3 Hz, 1H,

OCH₂OCH₃), 4.66 (d, J ¼ 6.3 Hz, 1H, OCH₂OCH₃), 5.24 (s, 2H,

OCH₂C₆H₅), 6.81e7.00 (m, 1H, NCH]CHCO), 7.26e7.41 (m, 11H,

NCH]CHCO, H_arom.), 7.49e7.58 (m, 4H, H_arom.); ¹³C NMR (CDCl₃):

d

[ppm] ¼ 12.7 (1C, OC]CCH₃), 30.4 (1C, OCH₂CH₂CH₂N), 51.3 (1C,

OCH₂CH₂CH₂N), 55.6 (1C, OCH₂OCH₃), 64.3 (1C, OCH₂CH₂CH₂N),

71.7 (1C, OCHCH₂O), 73.6 (1C, OCH₂C₆H₅), 81.8 (1C, OCHCH₂O), 88.9

(1C, C^C), 90.1 (1C, C^C), 96.8 (1C, OCH₂OCH₃), 116.5 (1C, NCH]

CHCO), 123.2 (1C, C_arom.), 123.6 (1C, C_arom.), 127.0 (2C, C_arom.), 128.4

(1C, C_arom.), 128.48 (2C, C_arom.), 128.53 (2C, C_arom.), 128.6 (1C, C_arom.),

129.3 (2C, C_arom.), 131.8 (2C, C_arom.), 132.0 (2C, C_arom.), 138.7 (1C,

C_arom.), 139.6 (1C, NCH]CHCO); the signals for 1C_arom., OC]CCH₃,

OC]CCH₃, NCH]CHCO could not be observed in the spectrum; IR

(neat): ṽ [cm^ꢂ1] ¼ 2928, 2882, 1624, 1566, 1497, 1250, 1215, 1150,

1107, 1034, 972, 918, 833, 756, 694; HRMS (m/z): [MþH]^þcalc for

127 ^ꢀC; speciﬁc rotation: ½a ²_D⁰

ꢁ

¼ þ2.8 (c ¼ 1.5; CH₂Cl₂); ¹H NMR

C₃₄H₃₆NO₅: 538.2588, found: 538.2627; HPLC (method 2):

t_R¼ 18.9 min, purity 96.4%.

(CDCl₃):

d

[ppm] ¼ 2.12 (s, 3H, OC]CCH₃), 3.28 (s, 3H, OCH₂OCH₃),

3.50e3.55 (m, 2H, OCHCH₂O (1H), OCH₂CH₂N (1H)), 3.60e3.67 (m,

2H, OCHCH₂O (1H), OCH₂CH₂N (1H)), 3.93e4.00 (m, 1H,

OCH₂CH₂N), 4.06 (ddd, J ¼ 14.9/7.6/3.8 Hz, 1H, OCH₂CH₂N), 4.42

(dd, J ¼ 7.8/3.9 Hz, 1H, OCHCH₂O), 4.58 (d, J ¼ 6.6 Hz, 1H,

OCH₂OCH₃), 4.59 (d, J ¼ 6.6 Hz, 1H, OCH₂OCH₃), 5.17 (d, J ¼ 11.4 Hz,

1H, OCH₂C₆H₅), 5.29 (d, J ¼ 11.4 Hz, 1H, OCH₂C₆H₅), 6.58e6.66 (m,

1H, NCH]CHCO), 7.06e7.09 (m, 2H, H_arom.), 7.26e7.31 (m, 3H,

4.2.39. (S)-3-Hydroxy-1-{2-[2-hydroxy-1-(4-phenethylphenyl)

ethoxy]ethyl}-2-methylpyridin-4(1H)-one (50)

48 (60 mg, 0.11 mmol) was dissolved in dry methanol (5 mL) and

a saturated solution of hydrochloric acid in methanol (1 mL) was

added. After stirring the mixture at room temperature overnight,

the mixture was extracted with EtOAc (3ꢃ), the combined organic

layers were dried over Na₂SO₄, ﬁltered, and concentrated in vacuo.

The crude product was dissolved in dry methanol (10 mL) and Pd/C

(10%, 10 mg) was added. The mixture was stirred under H₂atmo-

sphere (4 bar) at room temperature for 16 h. The catalyst was

ﬁltered off (Celite) and the solvent was removed in vacuo. The

residue was puriﬁed by ﬂash column chromatography (Ø ¼ 1 cm,

h ¼ 15 cm, dichloromethane/methanol 98/2 / 90/10, V ¼ 5 mL) to

give 50 as red solid (12 mg, 0.03 mmol, 27% yield). R_f¼ 0.47

H

_arom.), 7.32e7.37 (m, 4H, NCH]CHCO, H_arom.), 7.40e7.43 (m, 2H,

_arom.), 7.46e7.48 (m, 2H, H_arom.), 7.49e7.52 (m, 2H, H_arom.); ¹³C

NMR (CDCl₃):

d

[ppm] ¼ 12.9 (1C, OC]CCH₃), 53.5 (1C, OCH₂CH₂N),

55.4 (1C, OCH₂OCH₃), 67.7 (1C, OCH₂CH₂N), 71.6 (1C, OCHCH₂O),

73.4 (1C, OCH₂C₆H₅), 82.0 (1C, OCHCH₂O), 88.9 (1C, C^C), 90.2 (1C,

C^C), 96.8 (1C, OCH₂OCH₃), 116.9 (1C, NCH]CHCO), 123.1 (1C,

C

_arom.), 123.7 (1C, C_arom.), 126.9 (2C, C_arom.), 128.2 (1C, C_arom.), 128.4

(2C, C_arom.), 128.5 (2C, C_arom.), 128.6 (1C, C_arom.), 129.2 (2C, C_arom.),

131.8 (2C, C_arom.), 132.1 (2C, C_arom.), 137.6 (1C, C_arom.), 138.1 (1C,

(dichloromethane/methanol ¼ 9:1);

melting

¼ þ0.5 (1.2; CH₂Cl₂); ¹H

point:

255 ^ꢀC

C

_arom.), 139.3 (1C, NCH]CHCO), 141.9 (1C, OC]CCH₃), 145.9 (1C,

(decomposition); speciﬁc rotation: ½a _D²⁰

ꢁ

OC]CCH₃), 172.9 (1C, NCH]CHCO); IR (neat): ṽ [cm^ꢂ1] ¼ 2928,

2882, 1624, 1566, 1508, 1443, 1250, 1215, 1150, 1107, 1030, 968, 918,

833, 756, 691; HRMS (m/z): [MþH]^þcalc for C₃₃H₃₄NO₅: 524.2431,

found: 524.2455; HPLC (method 2): t_R¼ 18.5 min, purity 96.5%.

NMR (CD₃OD):

d

[ppm] ¼ 2.34 (s, 3H, HOC]CCH₃), 2.83e2.89 (m,

4H, PhCH₂CH₂Ph), 3.40e3.65 (m, 3H, OCHCH₂O, OCH₂CH₂N (1H)),

3.68e3.74 (m, 1H, OCH₂CH₂N), 4.14e4.34 (m, 3H, OCHCH₂O,

OCH₂CH₂N), 6.36e6.41 (m, 1H, NCH]CHCO), 6.89e6.94 (m, 2H,

H

_arom.), 7.03e7.07 (m, 2H, H_arom.), 7.11e7.17 (m, 3H, H_arom.),

7.19e7.25 (m, 2H, H_arom.), 7.56e7.64 (m, 1H, NCH]CHCO); ¹³C NMR

(CD₃OD):

39.0 (1C, PhCH₂CH₂Ph), 54.8 (1C, OCH₂CH₂N), 67.6 (1C, OCH-

CH₂OH), 68.4 (1C, OCH₂CH₂N), 84.8 (1C, OCHCH₂O), 112.3 (1C,

NCH]CHCO), 126.9 (1C, C_arom.), 127.9 (2C, C_arom.), 129.3 (2C, C_arom.),

129.5 (2C, C_arom.), 129.7 (2C, C_arom.), 133.3 (1C, HOC]CCH₃), 137.3

(1C, C_arom.), 139.9 (1C, NCH]CHCO), 142.9 (1C, C_arom.), 143.2 (1C,

4.2.38. (S)-3-(Benzyloxy)-1-(3-{2-(methoxymethoxy)-1-[4-

(phenylethynyl)phenyl]ethoxy}propyl)-2-methylpyridin-4(1H)-one

(49)

d

[ppm] ¼ 12.2 (1C, HOC]CCH₃), 38.7 (1C, PhCH₂CH₂Ph),

Under N₂atmosphere, polymer-bound triphenylphosphine

(1.6 mmol/g, 2.2 g, 3.6 mmol) was added to a solution of 45

(650 mg, 1.8 mmol) in dry THF (50 mL) and the reaction was stirred

for 72 h at room temperature. Then water (0.5 mL) was added and

the mixture was ﬁltered through Celite via a Nutsch-type ﬁlter. The

organic solvent was dried over Na₂SO₄, ﬁltered, and concentrated in

vacuo (obtained crude product: 330 mg). A portion of the crude

product (180 mg) was dissolved in water (50 mL) and 47 (120 mg,

0.53 mmol) was added. The reaction mixture was stirred for 7 d at

140 ^ꢀC. Then a saturated aqueous solution of NH₄Cl was added.

After cooling the mixture to ambient temperature, it was extracted

with ethyl acetate (3ꢃ). The combined organic layers were dried

(Na₂SO₄), ﬁltered, and the solvent was removed in vacuo. The res-

idue was puriﬁed by ﬂash column chromatography (Ø ¼ 1 cm,

h ¼ 15 cm, dichloromethane/methanol 98/2 / 90/10, V ¼ 5 mL) to

give 49 as yellowish oil (71 mg, 0.13 mmol, 14% yield). R_f¼ 0.69

C

_arom.), 147.0 (1C, HOC]CCH₃), 170.8 (1C, NCH]CHCO); IR (neat): ṽ

[cm^ꢂ1] ¼ 3267, 2978, 2920, 1624, 1562, 1504, 1454, 1346, 1250, 1107,

1072, 822, 748, 698; HRMS (m/z): [MþH]^þcalc for C₂₄H₂₈NO₄:

394.2013, found: 394.2073; HPLC (method 2): t_R¼ 15.5 min, purity

98.0%.

4.2.40. (S)-3-Hydroxy-1-{3-[2-hydroxy-1-(4-phenethylphenyl)

ethoxy]propyl}-2-methylpyridin-4(1H)-one (51)

49 (60 mg, 0.11 mmol) was dissolved in dry methanol (5 mL) and

a saturated solution of hydrochloric acid in methanol (1 mL) was

added. After stirring the mixture at room temperature overnight,

the mixture was extracted with EtOAc (3ꢃ). The combined organic

layers were dried over Na₂SO₄, ﬁltered, and concentrated in vacuo.

The crude product was dissolved in dry methanol (10 mL) and Pd/C

(10%, 10 mg) was added. The mixture was stirred under H₂atmo-

sphere (4 bar) at room temperature for 16 h. The catalyst was

ﬁltered off (Celite) and the solvent was removed in vacuo. The

(dichloromethane/methanol ¼ 9:1); speciﬁc rotation: ½a _D²⁰

¼ þ17.0

ꢁ

(1.6; CH₂Cl₂); ¹H NMR (CDCl₃):

d

[ppm] ¼ 1.81e1.96 (m, 2H,

OCH₂CH₂CH₂N), 2.17 (s, 3H, OC]CCH₃), 3.17e3.26 (m, 1H,

OCH₂CH₂CH₂N), 3.33 (s, 3H, OCH₂OCH₃), 3.35e3.43 (m, 1H,

OCH₂CH₂CH₂N), 3.61 (dd, J ¼ 10.7/3.6 Hz, 1H, OCHCH₂O), 3.72 (dd,

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21

residue was puriﬁed by ﬂash column chromatography (Ø ¼ 1 cm,

h ¼ 15 cm, dichloromethane/methanol 98/2 / 90/10, V ¼ 5 mL) to

give 51 as red solid (12 mg, 0.03 mmol, 26% yield). R_f¼ 0.49

were dried over sodium sulfate, ﬁltered, and the solvent was

removed in vacuo. The residue was puriﬁed by ﬂash column chro-

matography

(Ø ¼ 3 cm,

h ¼ 15 cm,

dichloromethane/meth-

(dichloromethane/methanol ¼ 9:1); speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ29.3

anol ¼ 97:3, V ¼ 20 mL) to give 55 as brownish oil (250 mg,

(1.8; CH₂Cl₂); ¹H NMR (CD₃OD):

d

[ppm] ¼ 1.90e2.06 (m, 2H,

0.62 mmol, 60% yield). R_f

¼

0.29 (dichloromethane/meth-

[ppm] ¼ 2.03 (s, 3H, OC]CCH₃),

anol ¼ 10:1); ¹H NMR (CDCl₃):

d

OCH₂CH₂CH₂N), 2.43 (s, 3H, HOC]CCH₃), 2.84e2.94 (m, 4H,

PhCH₂CH₂Ph), 3.32e3.35 (m, 1H, OCH₂CH₂CH₂N), 3.36e3.41 (m, 1H,

OCH₂CH₂CH₂N), 3.56 (dd, J ¼ 11.7/3.5 Hz, 1H, OCHCH₂OH), 3.69 (dd,

J ¼ 11.7/8.2 Hz, 1H, OCHCH₂OH), 4.12e4.25 (m, 2H, OCH₂CH₂CH₂N),

4.31 (dd, J ¼ 8.2/3.5 Hz, 1H, OCHCH₂OH), 6.34 (d, J ¼ 7.0 Hz, 1H,

NCH]CHCO), 7.12e7.20 (m, 5H, H_arom.), 7.20e7.24 (m, 4H, H_arom.),

7.59 (d, J ¼ 7.0 Hz, 1H, NCH]CHCO); ¹³C NMR (CD₃OD):

2.84 (t, J ¼ 6.8 Hz, 2H, NCH₂CH₂Ph), 3.95 (t, J ¼ 6.8 Hz, 2H,

NCH₂CH₂Ph), 5.22 (s, 2H, OCH₂Ph), 6.34 (d, J ¼ 7.3 Hz, 1H, NCH]

CHCO), 6.80e6.85 (m, 2H, 2⁰-H_{4-bromophenyl}, 6⁰-H_{4-bromophenyl}), 6.90

(d, J ¼ 7.3 Hz, 1H, NCH]CHCO), 7.28e7.35 (m, 3H, 3⁰⁰-H_benzyloxy, 4⁰⁰-

H_benzyloxy, 5⁰⁰-H_benzyloxy), 7.37e7.42 (m, 4H, 2⁰⁰-H_benzyloxy, 6⁰⁰-H_ben-

,

3⁰-H_{4-bromophenyl,}5⁰-H_{4-bromophenyl}); ¹³C NMR (CDCl₃):

zyloxy

d

[ppm] ¼ 12.6 (1C, OC]CCH₃), 36.6 (1C, NCH₂CH₂Ph), 54.9 (1C,

NCH₂CH₂Ph), 73.1 (1C, OCH₂Ph), 117.3 (1C, NCH]CHCO), 121.5 (1C,

C-4⁰_{4-bromophenyl}), 128.2 (1C, C-4⁰⁰_benzyloxy), 128.4 (2C, C-3⁰⁰

d

[ppm] ¼ 11.9 (1C, HOC]CCH₃), 31.6 (1C, OCH₂CH₂CH₂N), 38.8 (1C,

PhCH₂CH₂Ph), 39.0 (1C, PhCH₂CH₂Ph), 52.3 (1C, OCH₂CH₂CH₂N),

65.9 (1C, OCH₂CH₂CH₂N), 67.7 (1C, OCHCH₂OH), 84.9 (1C, OCH-

CH₂OH), 112.5 (1C, NCH]CHCO), 126.9 (1C, C_arom.), 128.1 (2C,

,

benzyloxy

C-5⁰⁰_benzyloxy), 129.4 (2C, C-2⁰⁰_benzyloxy, C-6⁰⁰_benzyloxy), 130.6 (2C, C-2⁰_4-

_bromophenyl, C-6⁰_{4-bromophenyl}), 132.3 (2C, C-3⁰_{4-bromophenyl}, C-5⁰_4-

_bromophenyl), 135.3 (1C, C-1⁰_{4-bromophenyl}), 137.6 (1C, C-1⁰⁰_benzyloxy),

138.3 (1C, NCH]CHCO), 140.6 (1C, OC]CCH₃), 146.2 (1C, OC]

CCH₃), 173.5 (1C, NCH]CHCO); IR (neat): ṽ [cm^ꢂ1] ¼ 2978, 1701,

1624, 1566, 1524, 1489, 1454, 1400, 1362, 1246, 1215, 1150, 1069,

C

_arom.), 129.3 (2C, C_arom.), 129.5 (2C, C_arom.), 129.8 (2C, C_arom.), 132.9

(1C, OC]CCH₃), 137.9 (1C, C_arom.), 139.2 (1C, NCH]CHCO), 143.0

(1C, C_arom.), 143.1 (1C, C_arom.), 147.3 (1C, HOC]CCH₃), 170.5 (1C,

NCH]CHCO); IR (neat): ṽ [cm^ꢂ1] ¼ 3275, 2924, 2859, 1624, 1562,

1508, 1346, 1246, 1103, 1038, 822, 748, 698; HRMS (m/z): [MþH]^þ

calc for C₂₅H₃₀NO₄: 408.2169, found: 408.2268; HPLC (method 2):

t_R¼ 16.0 min, purity 97.8%.

1011, 972, 818, 737, 702; HRMS (m/z): [MþH]^þcalcd for

79

C

H BrNO₂: 398.0750, found: 398.0761; HPLC (method 1):

21 21

t_R¼ 20.3 min, purity 97.4%.

4.2.41. (S)-N-Hydroxy-2-[2-hydroxy-1-(4-phenethylphenyl)ethoxy]

acetamide (53)

4.2.43. 3-(Benzyloxy)-2-methyl-1-[4-(phenylethynyl)phenethyl]

pyridin-4(1H)-one (56)

Under N₂atmosphere, copper(I) iodide (10 mg, 0.05 mmol),

tetrakis(triphenylphosphine)palladium(0) (46 mg, 0.04 mmol) and

phenylacetylene (54 mL, 50 mg, 0.49 mmol) were added to a solu-

tion of 55 (140 mg, 0.35 mmol) in a mixture of triethylamine (5 mL)

and acetonitrile (2 mL). The mixture was heated to reﬂux and

52 (53 mg, 0.19 mmol) was dissolved in dry methanol (10 mL)

and Pd/C (10%, 10 mg) was added. The mixture was stirred under H₂

atmosphere (balloon) at ambient temperature for 16 h. Then, the

catalyst was ﬁltered off (Celite) and the solvent was removed in

vacuo. The crude product (50 mg) was dissolved in dry methanol

(5 mL) and hydroxylamine hydrochloride (38 mg, 0.54 mmol) and a

5.4 M solution of sodium methoxide in methanol (0.1 mL,

0.54 mmol) were added. The reaction mixture was stirred at

ambient temperature for 16 h until TLC showed complete conver-

sion. Then the reaction mixture was acidiﬁed with 1.0 M HCl and

the mixture was extracted with ethyl acetate (3ꢃ). The combined

organic layers were dried (Na₂SO₄), ﬁltered, and the solvent was

removed in vacuo. The residue was puriﬁed by ﬂash column chro-

additional phenylacetylene (54 mL, 50 mg, 0.49 mmol) was added.

After stirring the mixture under reﬂux conditions for 16 h, the

solvent was evaporated and the residue was puriﬁed by ﬂash col-

umn chromatography (Ø ¼ 3 cm, h ¼ 15 cm, ethyl acetate/meth-

anol ¼ 10:1, V ¼ 20 mL) to give 56 as brown oil (99 mg, 0.24 mmol,

67% yield). R_f¼ 0.29 (dichloromethane/methanol ¼ 10:1); ¹H NMR

(CDCl₃):

d

[ppm] ¼ 2.04 (s, 3H, OC]CCH₃), 2.90 (t, J ¼ 7.0 Hz, 2H,

NCH₂CH₂Ph), 3.98 (t, J ¼ 7.0 Hz, 2H, NCH₂CH₂Ph), 5.24 (s, 2H,

OCH₂Ph), 6.37 (d, J ¼ 7.5 Hz,1H, NCH]CHCO), 6.92 (d, J ¼ 7.5 Hz,1H,

NCH]CHCO), 6.93e6.96 (m, 2H, 2⁰-H_{4-(phenylethynyl)phenyl}, 6⁰-H_4-

_{(phenylethynyl)phenyl}), 7.28e7.38 (m, 6H, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-

H_phenyl, 3⁰⁰⁰-H_benzyloxy, 5⁰⁰⁰-H_benzyloxy, 4⁰⁰⁰-H_benzyloxy), 7.40e7.46 (m,

4H, 2⁰⁰⁰-H_benzyloxy, 6⁰⁰⁰-H_benzyloxy, 3⁰-H_{4-(phenylethynyl)phenyl}, 5⁰-H_4-(phe-

_{nylethynyl)phenyl}), 7.50e7.55 (m, 2H, 2⁰⁰-H_phenyl, 6⁰⁰-H_phenyl); ¹³C NMR

matography

(Ø ¼ 1 cm,

h ¼ 15 cm,

dichloromethane/meth-

anol ¼ 98/2 / 90/10, V ¼ 5 mL) to give 53 as brown oil (33 mg,

0.10 mmol, 55% yield). R_f¼ 0.61 (dichloromethane/meth-

anol ¼ 9:1); speciﬁc rotation: ½a _D²⁰

ꢁ

¼ þ66.4 (3.0; CH₂Cl₂); ¹H NMR

(CD₃OD):

d

[ppm] ¼ 2.84e2.95 (m, 4H, PhCH₂CH₂Ph), 3.58 (dd,

J ¼ 11.9/3.2 Hz, 1H, OCHCH₂OH), 3.69 (dd, J ¼ 11.9/8.4 Hz, 1H, OCH-

CH₂OH), 3.84 (d, J ¼ 14.9 Hz,1H, OCH₂CONHOH), 3.92 (d, J ¼ 14.9 Hz,

1H, OCH₂CONHOH), 4.41 (dd, J ¼ 8.4/3.2 Hz, 1H, OCHCH₂OH),

(CDCl₃):

d

[ppm] ¼ 12.6 (1C, OC]CCH₃), 37.1 (1C, NCH₂CH₂Ph), 55.0

7.11e7.25 (m, 9H, H_arom.); ¹³C NMR (CD₃OD):

d

[ppm] ¼ 38.7 (1C,

(1C, NCH₂CH₂Ph), 73.2 (1C, OCH₂Ph), 88.8 (1C, C]C), 90.2 (1C, C]

C),117.3 (1C, NCH]CHCO),122.6 (1C, C-4⁰_{4-(phenylethynyl)phenyl}),123.2

(1C, C-1⁰⁰_phenyl), 128.2 (1C, C-4⁰⁰⁰_benzyloxy), 128.4 (2C, C-3⁰⁰⁰_benzyloxy, C-

5⁰⁰⁰_benzyloxy), 128.5 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl), 128.6 (1C, C-4⁰⁰_phenyl),

129.0 (2C, C-2⁰_{4-(phenylethynyl)phenyl}, C-6⁰_{4-(phenylethynyl)phenyl}), 129.4

(2C, C-2⁰⁰⁰_benzyloxy, C-6⁰⁰⁰_benzyloxy), 131.7 (2C, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl),

132.3 (2C, C-3⁰_{4-(phenylethynyl)phenyl}, C-5⁰_{4-(phenylethynyl)phenyl}), 136.5

(1C, C-1⁰_{4-(phenylethynyl)phenyl}), 137.6 (1C, C-1⁰⁰⁰_benzyloxy), 138.4 (1C,

NCH]CHCO), 140.7 (1C, OC]CCH₃), 146.2 (1C, OC]CCH₃), 173.5

(1C, NCH]CHCO); IR (neat): ṽ [cm^ꢂ1] ¼ 2978, 2886, 1732, 1624,

1562, 1508, 1497, 1454, 1369, 1242, 1215, 1153, 1069, 968, 826, 752,

691; HRMS (m/z): [MþH]^þcalcd for C₂₉H₂₆NO₂: 420.1958, found:

420.1961; HPLC (method 1): t_R¼ 22.8 min, purity 97.9%.

PhCH₂CH₂Ph), 39.0 (1C, PhCH₂CH₂Ph), 67.5 (1C, OCHCH₂OH), 68.3

(1C, OCH₂CONHOH), 85.6 (1C, OCHCH₂OH), 126.9 (1C, C_arom.), 128.0

(2C, C_arom.), 129.3 (2C, C_arom.), 129.5 (2C, C_arom.), 129.9 (2C, C_arom.),

136.4 (1C, C_arom.), 142.9 (1C, C_arom.), 143.5 (1C, C_arom.), 169.1 (1C,

OCH₂CONHOH); IR (neat): ṽ [cm^ꢂ1] ¼ 2978, 1728, 1670, 1431, 1192,

1130, 1053, 1030, 818, 721, 698; HRMS (m/z): [MþH]^þcalc for

C

₁₈H₂₂NO₄: 316.1543, found: 316.1548; HPLC (method 2):

t_R¼ 15.8 min, purity 96.3%.

4.2.42. 3-(Benzyloxy)-1-(4-bromophenethyl)-2-methylpyridin-

4(1H)-one (55)

2-(4-Bromophenyl)ethylamine (210 mg, 1.0 mmol) was added to

an emulsion of 47 (230 mg, 1.0 mmol) in water (5 mL). The reaction

mixture was stirred at 140 ^ꢀC for 10 d. Afterwards, ethyl acetate was

added and after separation of the layers, the aqueous phase was

extracted with ethyl acetate (2ꢃ). The combined organic layers

4.2.44. 3-Hydroxy-2-methyl-1-[4-(phenylethynyl)phenethyl]

pyridin-4(1H)-one (57)

An emulsion of 56 (87 mg, 0.21 mmol) in a 6 M aqueous solution

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22

M. Galster et al. / Tetrahedron xxx (xxxx) xxx

of hydrochloric acid (7.5 mL) and methanol (2 mL) was heated to

reﬂux for 4 h. Then the reaction mixture was cooled to ambient

temperature, a saturated aqueous solution of potassium carbonate

was added, and the mixture was extracted with ethyl acetate (3ꢃ).

The combined organic layers were washed with a saturated

aqueous solution of NaHCO₃and brine, dried over sodium sulfate,

ﬁltered, and the solvent was removed in vacuo. The residue was

puriﬁed by ﬂash column chromatography (Ø ¼ 1 cm, h ¼ 15 cm,

resulting suspension centrifuged for 20 min at 4 ^ꢀC at 9000 g. The

supernatant was centrifuged at 45,000 g for 90 min. The resulting

microsome pellet was resolved in sodium phosphate buffer (pH 7.4,

0.1 M). Aliquots were stored at ꢂ80 ^ꢀC prior to use.

4.3.2.3. Determination of protein concentration [69]

4.3.2.3.1. Bradford solution. 5 mg Coomassie^®Brilliant Blue G

250 was dissolved in 2.5 mL abs ethanol. 10 mL dist. water and 5 mL

of phosphoric acid were added. The solution was diluted with dist.

water to 50 mL. The resulting solution was stored in the dark and at

4 ^ꢀC overnight. Before the experiment, the solution was ﬁltered

twice through paper ﬁlters.

cyclohexane/ethyl acetate

¼

1:2 / 0:1 / ethyl acetate/

methanol ¼ 10:1 /10:1 þ 0.1% triethylamine, V ¼ 5 mL) to give 57

as yellowish solid (43 mg, 0.13 mmol, 60% yield). R_f¼ 0.21 (ethyl

acetate/methanol ¼ 10:1); melting point ¼ 212 ^ꢀC (decomposition);

¹H NMR (DMSO‑d₆):

d

[ppm] ¼ 2.27 (s, 3H, OC]CCH₃), 3.00 (t,

A stock solution of BSA in dist. water (1.25 mg/mL) was pre-

J ¼ 7.3 Hz, 2H, NCH₂CH₂Ph), 4.17 (t, J ¼ 7.3 Hz, 2H, NCH₂CH₂Ph), 6.04

(d, J ¼ 7.3 Hz, 1H, NCH]CHCO), 7.24e7.29 (m, 2H, 2⁰-H_4-(phenyl-

_{ethynyl)phenyl}, 6⁰-H_{4-(phenylethynyl)phenyl}), 7.40e7.45 (m, 4H, NCH]

CHCO, 3⁰⁰-H_phenyl, 5⁰⁰-H_phenyl, 4⁰⁰-H_phenyl), 7.46e7.51 (m, 2H, 3⁰-H_4-

_{(phenylethynyl)phenyl}, 5⁰-H_{4-(phenylethynyl)phenyl}), 7.52e7.57 (m, 2H, 2⁰⁰-

pared. A multi-point calibration curve (19.5

312 g, 615 g, 1000 g all of them per mL) was created by dilution

of the stock solution with dist. water. The samples where diluted

20-fold (50 L microsome solution, 200 L 1 M NaOH, 750 L dist.

water) and 50-fold (20 L microsome solution, 200 L 1 M NaOH,

780 L dist. water). The measurements were performed in a 96-

well plate. To 10 L of a diluted sample and each of the calibra-

tion solutions, 190 L Bradford solution were added, respectively.

mg, 39 mg, 78 mg, 156 mg,

m

H_phenyl, 6⁰⁰-H_phenyl); ¹³C NMR (DMSO‑d₆):

d

[ppm] ¼ 11.3 (1C, OC]

m

CCH₃), 36.1 (1C, NCH₂CH₂Ph), 53.5 (1C, NCH₂CH₂Ph), 89.2 (2C, C]

C), 110.4 (1C, NCH]CHCO), 120.5 (1C, C-4⁰_{4-(phenylethynyl)phenyl}),

122.3 (1C, C-1⁰⁰_phenyl), 128.4 (1C, OC]CCH₃), 128.71 (1C, C-4⁰⁰_phenyl),

128.73 (2C, C-3⁰⁰_phenyl, C-5⁰⁰_phenyl),129.5 (2C, C-2⁰_{4-(phenylethynyl)phenyl}

m

The plate was shaken for 5 min and the absorption at 595 nm was

recorded. Samples and calibration were prepared in triplicate.

,

C-6⁰_{4-(phenylethynyl)phenyl}) 131.3 (2C, C-2⁰⁰_phenyl, C-6⁰⁰_phenyl), 131.4 (2C,

C-3⁰_{4-(phenylethynyl)phenyl}, C-5⁰_{4-(phenylethynyl)phenyl}), 137.5 (1C, NCH]

CHCO), 138.4 (1C, C-1⁰_{4-(phenylethynyl)phenyl}), 145.4 (1C, HOC]CCH₃),

168.9 (1C, NCH]CHCO); IR (neat): ṽ [cm^ꢂ1] ¼ 3653, 3136, 2978,

2889, 1624, 1574, 1531, 1508, 1443, 1381, 1346, 1265, 1223, 1184,

1157, 1061, 1042, 953, 818, 756, 691; HRMS (m/z): [MþH]^þcalcd for

4.3.2.4. Incubation of 3 with rat liver microsomes and cofactors.

A stock solution of hydroxamic acid 3 in DMSO (1.0

added to a solution that contained PBS (pH 7.4, 23

solution (50 L, 50 mM), NADPH solution (50 L, 2 mg/mL in PBS),

UDPGA solution (50 L, 2 mg/mL in PBS), and rat liver microsome

suspension (26 L, 7.8 mg protein/mL). The experiments were per-

formed in duplicate. In case of the incubation without UDPGA or

NADPH, 50 L PBS was added instead of the solution of the

mL, 10 mM) was

mL, 0.1 M), MgCl₂

m

C

₂₂H₂₀NO₂: 330.1489, found: 330.1502; HPLC (method 1):

t_R¼ 27.0 min, purity 99.5% (tailing).

m

respective cofactor. The resulting suspensions were mixed vigor-

ously and shaken for 120 min at 37 ^ꢀC (900 rpm). The incubation

was stopped by the addition of ice-cold acetonitrile/methanol (1:1,

4.3. Metabolism studies

4.3.1. In silico prediction of metabolism

400 m

L). The Eppendorf cups were cooled to 0 ^ꢀC for 10 min using a

Sites of metabolism were predicted with FAME 2⁴⁶with default

settings. SyGMa was executed via a KNIME [66] node available

within the 3D-e-Chem virtual machine [67,68]. The number of

phase 1 and phase 2 cycles were each set to “1”.

water/ice bath. The precipitated proteins were separated via

centrifugation (15 min, 16,000 rpm, 4 ^ꢀC) and the supernatant was

analyzed by the LC-MS method described below in positive and

negative ion polarity. With the same procedure, the empty value

(without stock solution), the blank value (without cofactors) were

prepared. To detect possible impurities in the stock solution, a

4.3.2. In vitro metabolism studies with rat liver microsome

suspensions

positive control (599 mL solvent and 1 mL DMSO stock solution) was

4.3.2.1. Chemicals and materials. Double distilled water for HPLC

and for the preparation of buffer solutions was generated by a Milli-

Q Advantage Ultrapure Water System, Millipore (Billerica, MA,

USA). Magnesium chloride hexahydrate was purchased from Hon-

prepared and analyzed by the LC-MS method immediately.

4.3.2.5. HPLC-ESI-MS with micrOTOF-Q II (HPLC method 3).

For the determination of exact masses, an Ultimate 3000 RS LC

system from Dionex (Dionex Softron, Bremen, Germany) was

coupled with a microOTOF-Q II (Bruker Daltonics, Bremen, Ger-

many). The MS was operated with the standard ESI-source. The LC

system consisted of a solvent rack (SRD 3600), a pump (DGP-

3600RS), an autosampler (WPS-3000RS), a column oven (TCC-

3000RS) and a DAD-detector (DAD-3000RS) operating at 230 and

250 nm. Control of the system and data handling were carried out

using the software Hystar and DataAnalysis from Bruker Daltonics

(Bremen, Germany). The calibration of the TOF spectra was ach-

ieved by injection of 10 mM lithium formiate (isopropyl alcohol/

€

eywell Riedel-de Haen (Seelze, Germany). Acetonitrile in LC-MS

grade was obtained from Thermo Fischer Scientiﬁc (Schwerte,

Germany). NADPH tetra sodium salt was purchased from Carl Roth

(Karlsruhe, Germany). Formic acid p.a. was obtained from Acros

Organics (Thermo Fischer Scientiﬁc). Phosphate buffer saline tab-

lets, uridine 5⁰-diphospoglucoronic acid trisodium salt (UDGPA),

Coomassive Brilliant Blue G^®and methanol in LC-MS grade were

purchased from Sigma-Aldrich (Munich, Germany).

4.3.2.2. Preparation of rat liver microsomes. Deep frozen livers of

rats were obtained from the working group of Prof. Dr. M. Düfer,

Institute of Pharmaceutical and Medicinal Chemistry, Münster,

Germany.

Livers (20 g) were thawed in 1.15% (m/V) potassium chloride

solution at 4 ^ꢀC. Livers were cut in slices and homogenized in an

Elvehjem-Potter (10 strokes, 3 s) with 20 mL of cold phosphate

buffer (pH 7.4, 0.1 M) containing sodium EDTA (0.5 mM). 60 mL of

cold sodium phosphate buffer (pH 7.4, 0.1 M) was added and the

bidist. water ¼ 1:1) via a 20

1 min. Precolumn: Security GuardTM Cartridge C18 (4.0 ꢃ 2.0 mm,

m particle size); main column: Phenomenex Synergi Hydro RP

m particle size); solvents: A: bidist. water/

mL sample loop within each LC run at

4

m

(50 ꢃ 2.10 mm, 2.6

m

acetonitrile ¼ 90:10 with 0.1% formic acid (V/V), B: bidist. water/

acetonitrile ¼ 10:90 with 0.1% formic acid (V/V); gradient elution:

(A %): 0e5 min: gradient from 100% to 0%, 5e6.5 min: 0%,

6.5e7 min: gradient from 0% to 100%, 7e10 min: 100%; ﬂow:

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M. Galster et al. / Tetrahedron xxx (xxxx) xxx

23

0.4 mL; temperature: 25 ^ꢀC.

were then converted into K_ivalues using the Cheng-Prusoff equa-

tion. The K_iand IC₅₀values are given as mean value SD from three

independent experiments. The K_Mvalue was calculated from the

Lineweaver-Burk plot.

4.3.2.6. Metabolite identiﬁcation. 3: HRMS (m/z): [MþNa]^þcalc for

C

₁₈H₁₇NO₄Na: 334.1050, found: 334.1023; [M ꢂ H]^-calc for

₁₈H₁₆NO₄: 310.1085, found: 310.1091; HPLC (method 3):

t_R¼ 5.6 min.

Acknowledgements

3

þ

Glu: HRMS (m/z): [MþNa]^þcalc for C₂₄H₂₅NO₁₀Na:

519.1371, found: 510.1331; [M ꢂ H]^-calc for C₂₄H₂₄NO₁₀: 486.1406,

found: 486.1414; HPLC (method 3): t_R¼ 5.4 min.

Magdalena Galster received generous funding from the Apoth-

ekerstiftung Westfalen-Lippe. Johannes Kirchmair is supported by

the Deutsche Forschungsgemeinschaft (KI 2085/1-1) and the Ber-

gen Research Foundation (BFS) (BFS2017TMT01), Ralph Holl is

supported by the DZIF (German Center for Infection Research) and

the Deutsche Forschungsgemeinschaft (HO 5220/2-1), which is

gratefully acknowledged.

3-NH: HRMS (m/z): [MþNa]^þcalc for C₁₈H₁₆O₄Na: 319.0941,

found: 319.0905; [M ꢂ H]^-calc for C₁₈H₁₅NO₄: 295.0976, found:

295.0991; HPLC (method 3): t_R¼ 6.1 min.

4.4. Biological evaluation

4.4.1. Agar diffusion clearance assay

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