Design, Synthesis, and Evaluation of a Series of Novel Benzocyclobutene Derivatives as General Anesthetics

Article abstract of DOI:10.1021/acs.jmedchem.7b00253

In the present work, a series of structurally novel benzocyclobutene derivatives were identified as general anesthetics through the loss of righting reflex (LORR) experiment on mice. Our initial efforts found compound 1a with a fused four-membered ring on the 2,3-position of the phenol ring could significantly improve the safety profile. Further SAR study revealed that small hydrogen bond acceptor (HBA) groups are optimal for good ED₅₀ along with much broader therapeutic windows, such as compounds 16b and 17. Present work demonstrates the superiority of this novel benzocyclobutene scaffold.

Full text of DOI:10.1021/acs.jmedchem.7b00253

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Article
Design, synthesis and evaluation of a series of novel
benzocyclobutene derivatives as general anesthetics
Chen Zhang, Fangqiong Li, Yan Yu, Anbang Huang, Ping He, Ming Lei,
Jianmin Wang, Longbin Huang, Zhenhong Liu, Jianyu Liu, and Yonggang Wei
J. Med. Chem., Just Accepted Manuscript • Publication Date (Web): 21 Apr 2017
Downloaded from http://pubs.acs.org on April 22, 2017
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Design, synthesis and evaluation of a series of novel
benzocyclobutene derivatives as general anesthetics
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Chen Zhang*, Fangqiong Li, Yan Yu, Anbang Huang, Ping He, Ming Lei, Jianmin Wang,
Longbin Huang, Zhenhong Liu, Jianyu Liu, and Yonggang Wei
Haisco Pharmaceutical Group Co. Ltd., 136 Baili Road, Wenjiang district, Chengdu, 611130,
China
KEYWORDS general anesthetics, benzocyclobutene derivatives, hydrogen bond acceptor
substituent, GABA receptor
A
ABSTRACT In the present work, a series of structurally novel benzocyclobutene derivatives was
identified as general anesthetics through the loss of righting reflex (LORR) experiment on mice.
Our initial efforts found compound 1a with a fused fourꢀmembered ring on the 2,3ꢀposition of
the phenol ring could significantly improve the safety profile. Further SAR study revealed that
small hydrogen bond acceptor (HBA) groups are optimal for good ED50 along with much
broader therapeutic windows, such as compounds 16b and 17. Present work demonstrates the
superiority of this novel benzocyclobutene scaffold.
INTRODUCTION
Propofol (2,6ꢀdiisopropylphenol, compound 34), which was first discovered in 1977 by Kay
1
and Rolly, is now the most widely used intravenous general anesthetic in current clinical use. It
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2ꢀ3
is a shortꢀacting medication with rapid onset and offset effects, which can be clinically used
for induction and maintenance of general anesthesia, sedation for mechanically ventilated adults,
4
and procedural sedation. Therefore, it is on the WHO Model List of Essential Medicines.
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Despite being the most important medication needed in a health system, it is associated with side
effects including pain on injection, low blood pressure related to vasodilation, respiratory
5
ꢀ8
depression, and propofol infusion syndrome. Thus, the administration of compound 34 is
contraindicated in multiple clinical settings. Subsequently, many existing anesthetics have been
9ꢀ11
modified to improve the overall profile of compound 34.
Scheme 1. Design of novel anesthetics with a benzocyclobutene scaffold
We herein report our effort on the design, synthesis and evaluation of a series of novel
chemical scaffolds with improved potency and safety profiles as compared with compound 34. A
3,9
number of literature documents have reported on the structural modification of compound 34,
among which we noticed that the meta position of the phenol ring was a suitable position for
modification, for instance, methyl group substitution afforded a good therapeutic index along
3
with acceptable potency(Scheme 1). Reasonably, a novel benzocyclobutene scaffold was
designed by fusing the isopropyl to the meta position of the phenyl ring (Scheme 1). Many drug
molecule containing cyclobutane moiety such as ivabradine, sibutramine, butorphanol,
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carboplatin, and apalutamide etc. have been launched or in lateꢀstage clinical trial, which
indicates cyclobutane moiety possesses sufficient in vivo stability. This modification not only
reduced the molecule weight but also increased the rigidity as compared with the scaffold of
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compound 34. Such benzocyclobutene derivatives provided a chiral benzylic center for various
substituents. Through medicinal chemistry efforts, compounds 1a & 16b were identified as
optimal general anesthetics with much larger therapeutic windows than compound 34.
RESULTS AND DISCUSSION
Chemistry. The synthesis of benzocyclobutene derivatives is now becoming more attractive
1
3ꢀ14
for the synthetic community.
Drug candidates containing the benzocyclobutene scaffold have
1
5
14
emerged. Because benzocyclobutenone is an unique building block with rich reactivity, it was
chosen as an ideal intermediate for the quick assembly of various benzocyclobutene derivatives.
As shown in Scheme 2, orthoꢀsubstituted phenols were brominated using NBS and then
protected with a benzyl group to prepare compound 24. This was then reacted with NaNH and
2
1
,1ꢀdiethoxyethene 25 followed by treatment with acid to afford benzocyclobutenone
intermediate 26.
a
Scheme 2. Synthesis of key intermediate 26
a
Reagents and conditions: (a) NBS, (iꢀPr) NH, DCM; (b) BnBr, K CO , DMF; (c) NaNH ,
2
2
3
2
THF; (d) HCl, H O.
2
As shown in Scheme 3, Grignard reactions of ketone 26 led to benzocyclobutanols 27a-l.
Compounds 27aꢀl underwent acidꢀcatalyzed reactions with various reagents via the benzocyclic
cation intermediates to access different types of substituted benzocyclobutene derivatives
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(
Scheme 3). For example, tertiary benzocyclic cation intermediates derived from 27a-d can be
intercepted by triethylsilane to give compounds 28a-d. Similarly, compounds 27e-k reacted with
3
’
different alcohols R OH in the presence of TsOH to form compounds 28e-k. Compound 27l
.
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formed the corresponding tertiary benzocyclic cation in the presence of BF Et O, following by
3
2
the treatment of TMSCN to produce compound 28l. Debenzylation reactions of compounds 28a-
m provided compounds 1-3,6,8-16. Utilizing the tertiary benzocyclic cation intermediate again,
compound 8 was successfully transformed to compound 17 using NaN in the presence of
3
CF COOH.
3
a
Scheme 3. Synthesis of benzocyclobutene derivatives
a
2
3’
Reagents and conditions: (a)R MgBr, THF; (b)Et SiH, BF ,Et O, DCM; (c)TsOH, R OH;
3
3
2
(d)TMSCN, BF .Et O, DCM; (e)NaN , CF COOH; (f)H , 10% Pd/C, EtOH; (g)NaBH , MeOH;
3 2 3 3 2 4
4
(h)R MgBr, THF; (i)BnNMe Br , HCOOH; (j)CH MgBr, THF; (k)TsOH, MeOH; (l)BBr ,
3
3
3
3
DCM; (m)NBS, (iꢀPr) NH, DCM ; (n)NaN , CF COOH.
2
3
3
Debenzylation of intermediate 26 via Pd/C catalyzed hydrogenolysis provided ketone 5,
4
followed by reduction using NaBH to give compound 4 or Grignard reaction with R MgBr to
4
yield compound 7. Bromination of ketone 26 afforded compound 29 which was treated with
Grignard reagents to give tertiary alcohol 30. Tertiary alcohol 30 reacted with TsOH in methanol
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to furnish compound 31, followed by debenzylation using BBr in DCM to generate compound
3
1
5.
Another set of compounds featuring an indazoleꢀbased chemical structure were prepared
Scheme 4, compounds 18ꢀ20). 2ꢀIsopropylaniline 32 was treated with BCl , AlCl , and alkyl
1
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(
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nitriles to produce ketones 33. Ketone 33a reacted with hydroxylamine chloride and sodium
hydroxide, and then treated with Et3N and MsCl to generate compound 18. Compound 21 was
generated from compound 33b using concentrated hydrochloric acid, sodium nitrite and tin(II)
chloride dehydrate. Methylation of compound 18 provided compound 19 using NaH and CH3I.
Nitration reaction transformed compound 18 into compound 20 using concentrated sulphuric
acid and sodium nitrate.
a
Scheme 4. Synthesis of indazole derivatives
a
1
Reagents and conditions: (a) BCl , AlCl , R CN; (b) NH OHHCl, NaOH, CH SO Cl, Et N;
3
3
2
3
2
3
(
c) NaNO , conc. HCl, SnCl ; (d) NaH, CH I,THF; (e) H SO , NaNO .
2 2 3 2 4 3
Biological Evaluation. When the isopropyl group of compound 34 was fused to the phenyl
ring, benzocyclobutene compound 1 exhibited a 2ꢀfold broader therapeutic index with a
comparable ED to compound 34 through the loss of righting reflex experiment on mice (as
5
0
explained in the experimental section). Meanwhile, compound 1 took effect during the
injection (within 10s) with an anesthesia duration over 5mins. This finding encouraged us to
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explore more of the chemistry space around this benzocyclobutene scaffold, which led to the
discovery a series of novel compounds with fast onꢀset effect and moderate duration time (Table
1). Similarly, these benzocyclobutene derivatives may still associate with aforementioned side
effects of compound 34 such as low blood pressure related to vasodilation and respiratory
depression, which could be lethal in high dose.
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2
Initial efforts were focused on the modification of the R group in order to improve the
2
potency, while keeping a tertiary benzylic carbon center. However, changing R from methyl
group to ethyl, cyclopropyl, hydroxyl or oxo groups did not enhance potencies or increase
therapeutic index values (compound 2
the potency (compound 6).
ꢀ
5), and the orthoꢀbromo substitution significantly reduced
Table 1. In vivo study of benzocyclobutene derivatives
Onꢀset
Duration
ED50
(mg/kg)
16.3
a
1
2
3
4
b
Compound
R
R
R
R
TI
(Sec)
(Sec)
1
2
3
4
5
6
7
8
9
iꢀPr
iꢀPr
iꢀPr
iꢀPr
iꢀPr
Br
Me
Et
H
H
H
H
H
H
H
H
H
H
<10
319.7±158.4
744.3±389.3
126.6±84.4
212.3±113.7
5.2
2.4
3.6
ND
ND
ND
ND
3.8
3.7
H
20.2±7.0
14.9±4.8
<10
14.3
H
18.5
OH
=O
Me
Me
Me
Me
H
24.5
ꢀ
14.9±9.9
<10
105.6±119.02 36.9
H
124.4±51.3
401.2±315.3
324.8±140.7
367.4±123.6
39.0
27.5
5.8
iꢀPr
iꢀPr
iꢀPr
OH
OMe
OEt
<10
12.8±14.5
30.8±17.7
6.0
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c
c
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0
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iꢀPr
iꢀPr
iꢀPr
iꢀBu
Et
Me
Me
Et
OiꢀPr
H
H
H
H
H
Br
H
H
19.4±5.8
20.2±7.0
<10
ND
ND
ND
ND
ND
5.8
ND
>5
ND
OMe
OMe
OMe
OMe
CN
221.0±117.1
343.0±21.8
211.3±145.7
407.8±140.7
340.8±180.0
381.7±131.6
10.0
5.0
Me
Me
Me
Me
Me
<10
1
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<10
16.2
42.5
7.7
iꢀPr
iꢀPr
iꢀPr
11.6±2.9
<10
ND
7.4
5.9
N3
<10
9.4
compound 34: ED = 11.7mg/kg, TI = 2.7; ND: not determined;
5
0
a: racemic; b: TI(Therapeutic index)=LD /ED
50
5
0
c: unable to find a safe dosage from righting reflex experiment on mice
Next, benzocyclobutene derivatives with a quaternary benzylic carbon center were evaluated
1
3
3
with various R and R substituents (compound 7 17). Hydroxyl substitution at the R position
ꢀ
did not benefit the activity (compound 7), however, when the hydroxyl group was alkylated to
methoxyl or ethoxyl groups, these compounds showed both good potencies and TI values
3
(
compound 8, 9). Further, increasing the size of R to the even bulkier isopropoxy or methoxyꢀ
ethoxyl (compound 10, 11) significantly increase the toxicity, in which the safe and effective
dosage in mice could not be found. Compared to compound 8, compound 12 was less effective
2
1
when modifying R from methyl to ethyl. Substitution at R with isobutyl (compound 13) has
1
minor effects on potency, while an ethyl group as R greatly decreased potency (compound 14).
Furthermore, the para halogen substitution decreased the potency significantly (compound 15).
3
These results suggested that R may favor a small hydrogen bond acceptor (HBA) to maintain
3
a good overall profile. Subsequently, two other small HBA groups were built on the R position
1
while keeping R as isopropyl. Satisfactorily, compound 16, with a benzylic cyanide group on
3
R , demonstrated a much better therapeutic index (TI=7.4) as well as a strong potency
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(
7.7mg/kg). Similarly, the azido group at the R position (compound 17) also showed a good
potency (9.4mg/kg) and an improved TI value (TI=5.9). Herein, we have successfully discovered
3
a series of structurally unique benzocyclobutene derivatives, featuring small HBA group on R ,
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as potent and safe candidates of general anesthetics.
3
Furthermore, we suspected that a small HBA on R , like the cyano group, might have an
intramolecular hydrogen bond interaction with the phenolic hydroxyl group, which could benefit
both the higher potency and safety profiles (Scheme 4). Thus, compounds 18ꢀ20 featuring by an
indazoleꢀbased chemical structure were assessed, in which case an aniline group was utilized to
mimic the phenolic hydroxyl group. However, insufficient activities were detected in these cases,
which indicated the importance of a phenolic hydroxyl group to maintain a good activity.
Therefore the intramolecular interaction may not contribute to the better potency and safety
profile.
Table 2. Chiral resolution and evaluation of compounds 1 and 16
GABAA
Onꢀset
Sec)
Duration
(Sec)
ED50
receptor
binding assay
Compound
Propofol
TI
(
(mg/kg)
(% inh.)
16
34
<10
303.2±97.8
319.7±158.4
373.5±98.2
332.1±198.5
340.8±180.0
521.4±180.6
11.7
2.7
IC =10μM
5
0
Racemic <10
16.3±1.4
16.0±5.9
18.3±2.2
7.7±0.1
14.3±0.1
8.2±1.7
5.2±1.7
5.4±0.3
4.1±0.6
7.4±0.5
3.7±0.2
9.1±1.9
ꢀ
1
a (R)
b (S)
<10
<10
33 (10 μM)
19 (10 μM)
ꢀ
1
Racemic <10
16a (S)
<10
35 (10 μM)
19 (10 μM)
1
6b (R)
13.8±4.2 364.8±110.4
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To further investigate the lead Compounds 1 and 16, enantiopure compounds (Compounds 1a,
b, 16a, and 16b) were obtained through preparative chiral HPLC, and the absolute
1
configurations of compounds 1a and 16b were determined by the XꢀRay crystallography of their
ester derivatives of (1S,4R)ꢀcamphanic acid chloride. Table 2 are summarizes the ED , TI
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
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3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
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5
5
5
5
5
6
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values and GABA receptor binding assays of these compounds. Compound 1a was more active
A
than its enantiomer compound 1b along with a better TI value. The binding assay of compound
1
a was also stronger than compound 1b, which corresponds well with their efficacies.
Remarkably, compound 16b possessed a fourꢀfold broader therapeutic window and was more
active than compound 34. However, compound 16a showed a better binding affinity than 16b,
which is contrary to their ED values. Although these compounds all exhibited binding affinity
5
0
17
to GABA , the mismatches of efficacies and binding assays in the case of compounds 16a vs.
A
1
6b or 16b vs. 34 suggested that these compounds might also interact with other effective
targets, which needs further exploration and mechanistic study.
The pharmacokinetic profiles of 1a and 1b were evaluated in rats owing to their good in vivo
profile. As shown in Table 3, compound 1a and 1b demonstrated similar halfꢀlives to compound
3
4, with t1/2 = 38 mins for 1a and t1/2 = 41 mins for 1b, respectively. Compared with compound
4, relatively low systemic clearances were observed, with Cl=77 mL/kg·min for 1a and Cl=67
3
mL/kg·min for 1b. However, the relatively low volume of distribution of each target compound
resulted in an overall halfꢀlife similar to compound 34, with Vdss = 2.14 L/kg for 1a and Vdss
=
2.53 L/kg for 1b, respectively. Both the AUC values of 1a and 1b are almost 3ꢀfold more than
compound 34, which suggests a lower dose for further clinical use.
Table 3. Pharmacokinetic Profiles of Compounds compound 34, 1a & 1b
ED50
TI
t1/2
Cl
Vdss
Cmax
AUC
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(
mL/kg)
(min) (mL/kg (L/kg)
(ng/mL) (ng·h/mL)
·min)
34
1a
1b
11.7
2.7
42±13 204±9
5.23±0.67 384±56
77±4
16.0±5.9
18.3±2.2
5.4±0.3 38±14 77±6
4.1±0.6 41±6 67±4
2.14±0.21 861±57
2.53±0.41 728±81
205±12
227±10
0
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CONCLUSION
We have developed a novel series of benzocyclobutene derivatives as general anesthetics, with
potent anesthetic effect and much better therapeutic index than compound 34, such as
compounds 1a and 16b. In addition to much better pharmacokinetic profiles, these candidates
predicted lower human dosage and broader therapeutic window. Subsequent results from our
laboratories will detail further mechanistic studies in this series that address enhancing potency
and safety window for general anesthesia.
EXPERIMENTAL SECTION
In vivo loss of righting reflex (LORR) assays on mice. The onꢀset and duration time of
anesthesia effect of benzocyclobutene derivatives was evaluated through the experiment of loss
1
8
of righting reflex (LORR) using a validated rodent model of general anesthesia. The tested
compounds were formulated with 5% of dimethyl sulfoxide, 5ꢀ10% of Solutol HSꢀ15 and 85ꢀ
9
0% of saline. The fasted ICR mice were randomly divided into 7ꢀ9 dosage groups, and each
dosage group has 10 ICR mice, then were administered a single intravenous bolus injection in
clear or emulsion solution in the lateral tail vein, which took approximately 10 seconds.
Anesthetic effects were assessed using: (1) onset of LORR, as measured by the time from dosing
to LORR, (2) LORR duration as measured by the time from dosing to recovery of fighting reflex.
Nonꢀlinear fitting using GraphPad Prism5 was applied to calculated ED50 and LD50 values.
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Therapeutic Index (TI) was calculated by LD divided by ED . A high TI is preferable to have
5
0
50
a favorable safety profile. The duration time of the tested compounds is corresponding to the
dosage which could produce 100% LORR of the mice.
1
1
1
1
1
1
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Binding assay A radioligand binding assay method was utilized to evaluate the GABAA
receptor binding ability of compounds 1a, 1b, 16a, and 16b. According to Maksay and
1
9
Simonyi , crude synaptosomal membranes of cerebral cortex of male Wistar rats were prepared
for this study, and then, membrane suspension in 20 mM TrisꢀHCl (pH 7.4) containing 200 mM
35
NaCl were preꢀincubated with 2.0 nM [ S]TBPS at 25℃. After 3 hours, the suspension was
filtered under reduced pressure and washed with iceꢀcold buffer (3 x 3 mL). The radioactivity of
the filters was measured in a scintillation counter. Nonspecific binding of the test compound was
measured with 200 µM picrotoxin. GABA receptor binding assays of the tested compounds
A
were obtained and expressed as the percent inhibition of control specific TBPS binding.
Animals Male and female ICR mice (18ꢀ22g) and Sprague–Dawley rats (180ꢀ220g) were
purchased from Vital River Laboratory Animal Technology Co., Ltd, Beijing, China. Male and
female beagle dogs (7ꢀ8kg) were supplied by Dossy Experimental Animals Co., Ltd, Chengdu,
China. The animals were groupꢀhoused and maintained in a controlled environment of constant
temperature of 24 ± 1 ℃ and 58% humidity with a 12 h lightꢀdark cycle and were allowed free
access to food and water. Food was withdrawn 12 h prior to study. Animal facilities, animal care
and study programs were in accordance with inꢀhouse guidelines of Institute of Laboratory
Animal Resources, Commission on Life Science, National Research Council (National Academy
Press, Washington, D.C., 2010).
General procedures All purchased starting materials were used without further purification.
1
H NMR spectra were acquired on a Bruker Avanceꢀ400 spectrometer (400 MHz) or a Bruker
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Avanceꢀ300 spectrometer (300 MHz), with tetramethylsilane (TMS) as an internal standard;
chemical shifts are expressed in parts per million (ppm, δunits). Data are reported as app =
apparent, s = singlet, d = doublet, t = triplet, q = quartet, hept = heptet, m = multiplet, br = broad,
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coupling constant(s) in Hz. Protonꢀdecoupled carbon nuclear magnetic resonance spectra ( Cꢀ
NMR) spectra were recorded on a Bruker Avanceꢀ400 spectrometer (400 MHz) or a Bruker
Avanceꢀ300 spectrometer (300 MHz), with tetramethylsilane (TMS) as an internal standard;
chemical shifts are expressed in parts per million (ppm, δunits). Melting points were recorded on
an OptiMelt automated melting point system and are uncorrected. Mass spectra were obtained on
a FinniganLCQAd instrument (ESI). Most masses were reported as those of the protonated
parent ions. Preparative column chromatography was performed using YantaiHuanghai 200ꢀ
3
00mesh silica. CLogP values of the title compounds were calculated by
Chemdraw/CLogP(Biobyte). Purities of title compounds were ≥95% by HPLC.
4-Isopropyl-7-methyl-bicyclo[4.2.0]octa-1,3,5-trien-5-ol (1). To a stirred solution of 6ꢀ
(benzyloxy)ꢀ5ꢀisopropylꢀ1ꢀmethylꢀ1,2ꢀdihydrocyclobutabenzene (28a, 1.80 g，6.75 mmol) in
1
00 mL of methanol was added Pd/C (0.14 g, 10wt%). The mixture was stirred under a hydrogen
atmosphere at room temperature for 4 hrs. The resulting solution was filtered. The solvent was
removed under reduced pressure. The residue was purified by flash column chromatography
(1:20 ethyl acetate/hexanes). The title compound was obtained as colorless oil (1.04 g) in 87.3%
1
yield. cLogPcompound1=3.675. R =0.20 (1:20 ethyl acetate/hexanes, TLC). H NMR (400 MHz,
f
CDCl ): δ 7.05 (d, J = 7.4 Hz, 1H), 6.65 (d, J = 7.4 Hz, 1H), 4.42 (br s, 1H), 3.65 – 3.47 (m, 1H),
3
3
.28 (dd, J = 13.8, 5.3 Hz, 1H), 3.18(hept, J = 6.9 Hz, 1H), 2.58 (dd, J = 13.7, 2.4 Hz, 1H), 1.41
1
3
(d, J = 7.0 Hz, 3H), 1.25 (d, J = 6.9 Hz, 3H), 1.23 (d, J = 6.9 Hz, 3H). C NMR (101 MHz,
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CDCl ) δ 145.18, 140.23, 132.03, 131.13, 123.87, 114.44, 35.33, 34.12, 25.29, 21.42, 21.26,
3
+
1
7.45. MS m/z (ESI): Calcd. for C H O [M+H] 177.1. Found: 177.1.
1
2
17
7-Ethyl-4-isopropyl-bicyclo[4.2.0]octa-1,3,5-trien-5-ol (2). Yellow oil; yield 67.0% (1.50 g,
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
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7
8
9
0
1
2
3
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5
6
7
8
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0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
7
.9 mmol), cLogPcompound2=4.204. R =0.21 (1:30 ethyl acetate/hexanes, TLC). H NMR (400
f
MHz, CDCl ): δ7.07 (d, J = 7.4 Hz, 1H), 6.68 (d, J = 7.4 Hz, 1H), 4.58 (br s, 1H), 3.52 – 3.35
3
(m, 1H), 3.33 – 3.12 (m, 2H), 2.72 – 2.60 (m, 1H), 1.90 – 1.81 (m, 1H), 1.77ꢀ1.68 (m, 1H), 1.25
ꢀ
(
app, t, J = 6.9 Hz, 6H), 1.09 (t, J = 7.3 Hz, 3H). MS m/z (ESI): Calcd. for C H O [MꢀH]
1
3
17
1
89.1. Found: 189.1.
-Cyclopropyl-3-isopropylbicyclo[4.2.0]octa-1,3,5-trien-2-ol (3). Yellow solid; yield 85%
8
(265 mg, 1.31 mmol), cLogPcompound3=4.029. R =0.22 (1:60 ethyl acetate/hexanes, TLC). mp:
f
1
4
4–46℃; H NMR (400 MHz, CDCl ) δ7.08 (d, J = 7.4 Hz, 1H), 6.67 (d, J = 7.4 Hz, 1H), 4.52
3
(s, 1H), 3.28ꢀ3.16 (m, 2H), 2.97 – 2.90 (m, 1H), 2.84 (dd, J = 13.8, 2.5 Hz, 1H), 1.25 (d, J = 6.9
Hz, 3H), 1.23 (d, J = 6.9 Hz, 3H), 1.12 – 1.01 (m, 1H), 0.62 – 0.54 (m, 2H), 0.40 – 0.34 (m, 1H),
13
0
.28 – 0.21 (m, 1H). C NMR (101 MHz, CDCl ) δ 147.08, 142.22, 132.79, 131.58, 125.93,
3
1
16.09, 45.86, 35.32, 27.14, 23.09, 22.85, 14.20, 4.42, 3.61. MS m/z (ESI): Calcd. for C H O
14 17
ꢀ
[
MꢀH] 201.1. Found: 201.0.
5
-Isopropyl-1,2-dihydrocyclobutabenzene-1,6-diol (4). To a stirred solution of 5ꢀhydroxyꢀ4ꢀ
isopropylꢀbicyclo[4.2.0]octaꢀ1,3,5ꢀtrienꢀ7ꢀone (5, 0.58 g, 3.29 mmol) in 15 mL of methanol was
added sodium borohydride (0.25 g, 6.41 mmol). The mixture was stirred at room temperature for
0
.5 hr. The reaction mixture was quenched with a saturated solution of ammonium chloride (4.0
mL), extracted with dichloromethane (50 mL×2), and dried with sodium sulfate. The solvent was
removed under reduced pressure. The residue was purified by flash column chromatography
(1:15 ethyl acetate/hexanes). The title compound was obtained as white solid (350 mg) in 59.7%
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5
5
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6
1
yield. cLogPcompound4=1.669. R =0.18 (1:15 ethyl acetate/hexanes, TLC). H NMR (400 MHz,
f
DMSOꢀd ): δ 9.22(s, 1H), 7.02 (d, J = 7.3 Hz, 1H), 6.55 (d, J = 7.3 Hz, 1H), 5.31 (d, J = 6.5 Hz,
6
1H), 5.08 (ddd, J = 6.5, 4.5, 1.8 Hz, 1H), 3.28 (dd, J = 13.6, 4.5 Hz, 1H), 3.17 (hept, J = 7.0 Hz,
1
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0
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0
1
H), 2.72 (dd, J = 13.6, 1.8 Hz, 1H), 1.12 (d, J = 7.0 Hz, 6H). C NMR (101 MHz, CDCl ) δ
3
1
47.60, 139.94, 134.38, 130.35, 128.66, 115.76, 69.53, 41.22, 26.84, 22.95, 22.92. MS m/z (ESI):
ꢀ
Calcd. for C H O [MꢀH] 177.1. Found: 177.0.
11 13
2
5
-Hydroxy-4-isopropyl-bicyclo[4.2.0]octa-1,3,5-trien-7-one (5). To a stirred solution of 5ꢀ
benzyloxyꢀ4ꢀisopropylꢀbicyclo[4.2.0]octaꢀ1,3,5ꢀtrienꢀ7ꢀone (26a, 3.50g, 13.14 mmol) in 70 mL
of methanol was added Pd/C (2.1 g, 10wt%). The mixture was stirred under a hydrogen
atmosphere at room temperature for 1.5 hrs. The resulting solution was filtered. The solvent was
removed under reduced pressure. The residue was purified by flash column chromatography
(
1:15 ethyl acetate/hexanes). The title compound was obtained as white solid (1.23 g) in 53.1%
1
yield. mp: 45–46℃, cLogPcompound5=2.918. R =0.25 (1:15 ethyl acetate/hexanes, TLC). H NMR
f
(
300 MHz, CDCl ): δ 7.77 (s, 1H), 7.42 (d, J = 7.3 Hz, 1H), 7.00 (d, J = 7.3 Hz, 1H), 3.87 (s,
3
2
H), 3.31 (hept, J = 6.9 Hz, 1H), 1.23 (d, J = 6.9 Hz, 6H). MS m/z (ESI): Calcd. for C H O2
11 11
ꢀ
[
MꢀH] 175.1. Found: 175.0.
4
-Bromo-7-methyl-bicyclo[4.2.0]octa-1,3,5-trien-5-ol (6). White solid; yield 63% (1.6 g, 7.5
1
mmol). mp: 58–62℃, cLogPcompound6=3.328. R =0.63 (40:1 hexanes/ethyl acetate, TLC). H
f
NMR (400 MHz, CDCl ): δ7.37ꢀ7.27 (m, 1H), 6.66 ꢀ6.44(m, 1H), 5.44 (s, 1H), 3.75ꢀ3.50 (m,
3
1
H), 3.35 ꢀ3.15(m, 1H), 2.60 (d, J = 13.9 Hz, 1H), 1.50ꢀ1.35 (m, 3H). MS m/z (ESI): Calcd. for
+
C H BrO [M+H] 213.0. Found: 212.9.
9
10
4
-Isopropyl-7-methyl-bicyclo[4.2.0]octa-1,3,5-triene-5,7-diol (7). To a stirred solution of 5ꢀ
hydroxyꢀ4ꢀisopropylꢀbicyclo[4.2.0]octaꢀ1,3,5ꢀtrienꢀ7ꢀone (Compound 5, 0.27 g, 1.40 mmol) in
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0 mL of dry THF was added dropwise methylmagnesium bromide (3.0 M, 4.66 mL, 13.98
mmol) under nitrogen at ꢀ78℃. Subsequent to the addition, the reaction mixture was allowed to
warm to room temperature and stirred for 10 hrs. The reaction mixture was quenched with a
saturated solution of ammonium chloride (10 mL), extracted with ethyl acetate (10 mL×2), and
dried with sodium sulfate. The solvent was removed under reduced pressure. The residue was
purified by flash column chromatography (1:15 ethyl acetate/hexanes). The title compound was
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
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3
3
3
3
3
3
3
4
4
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4
4
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4
4
4
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5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
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5
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9
0
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0
obtained as yellow solid (130 mg) in 48% yield. cLogPcompound7=2.188. R =0.19 (1:15 ethyl
f
1
acetate/hexanes, TLC). H NMR (400 MHz, DMSOꢀd ) δ 8.95 (s, 1H), 6.99 (d, J = 7.3 Hz, 1H),
6
6.56 (d, J = 7.3 Hz, 1H), 5.39 (s, 1H), 3.19 (hept, J = 6.9 Hz, 1H), 3.01ꢀ2.91 (m, 2H), 1.57 (s,
1
3
3
1
H), 1.13 (d, J = 6.9 Hz, 3H), 1.12(d, J = 6.9 Hz, 3H). C NMR (100 MHz, DMSOꢀd ) δ 147.4,
6
39.2, 135.9, 133.5, 126.7, 115.1, 76.5, 46.6, 26.8,26.7, 23.5, 23.2. MS m/z (ESI): Calcd. for
ꢀ
C H O [MꢀH] 191.1. Found: 190.9.
12
15
2
4
-Isopropyl-7-methoxy-7-methyl-bicyclo[4.2.0]octa-1,3,5-trien-5-ol (8). White solid; yield
4
1.1% (0.6 g, 3 mmol). cLogPcompound8=3.024. mp: 125–128 ℃ , R =0.20 (1:20 ethyl
f
1
acetate/hexanes, TLC). H NMR (400 MHz, CDCl ): δ 7.14 (d, J = 7.4 Hz, 1H), 6.71 (d, J = 7.4
3
Hz, 1H), 5.14 (s, 1H), 3.36 (d, J = 14.0 Hz, 1H), 3.33 (s, 3H), 3.23 (hept, J = 6.9 Hz, 1H), 2.95
1
3
(d, J = 14.0 Hz, 1H), 1.70 (s, 3H), 1.25 (d, J = 6.9 Hz, 3H), 1.23 (d, J = 6.9 Hz, 3H). C NMR
(101 MHz, CDCl ) δ 147.35, 139.03, 133.79, 131.44, 127.89, 116.01, 82.68, 52.17, 40.68, 26.82,
3
ꢀ
2
4.24, 23.03, 22.96. MS m/z (ESI): Calcd. for C H O [MꢀH] 205.1. Found: 205.1.
1
3
17
2
8
-Ethoxy-3-isopropyl-8-methylbicyclo[4.2.0]octa-1,3,5-trien-2-ol (9). Yellow solid; yield
54% (0.44 g, 2 mmol). cLogPcompound9=3.413. mp: 80–84℃, R =0.25 (1:15 ethyl acetate/hexanes,
f
1
TLC). H NMR (400 MHz, CDCl ) δ 7.15 (d, J = 7.4 Hz, 1H), 6.71 (d, J = 7.4 Hz, 1H), 5.70 (s,
3
1
H), 3.63 – 3.52 (dq, J = 9.1, 7.0 Hz,1H), 3.51 – 3.41 (dq, J = 9.1, 7.0 Hz, 1H), 3.34 (d, J = 14.0
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Hz, 1H), 3.23 (hept, J = 6.9 Hz, 1H), 2.98 (d, J = 14.0 Hz, 1H), 1.71 (s, 3H), 1.27 – 1.19 (m, 9H).
1
3
C NMR (101 MHz, CDCl ) δ 147.19, 138.91, 133.55, 132.26, 127.70, 115.97, 81.81, 60.09,
3
ꢀ
41.65, 26.82, 24.55, 22.96, 22.94, 15.75. MS m/z (ESI): Calcd. for C H O [MꢀH] 219.1.
1
4
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6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Found: 219.2.
-Isopropoxy-3-isopropyl-8-methylbicyclo[4.2.0]octa-1,3,5-trien-2-ol (10). Yellow oil;
8
yield 75% (0.21 g, 0.9 mmol), cLogPcompound10=3.722. R =0.21 (1:30 ethyl acetate/hexanes, TLC).
f
1
H NMR (400 MHz, CDCl ) δ 7.14 (d, J = 7.4 Hz, 1H), 6.70 (d, J = 7.4 Hz, 1H), 5.28 (s, 1H),
3
3
1
.77 (hept, J = 6.2 Hz,1H), 3.28 (d, J = 14.0 Hz, 1H), 3.21 (hept, J = 6.9 Hz, 1H), 3.01 (d, J =
4.0 Hz, 1H), 1.68 (s, 3H), 1.26ꢀ1.21 (m, 6H), 1.19 (d, J = 6.2 Hz,3H), 1.13 (d, J = 6.2 Hz,3H).
ꢀ
MS m/z (ESI): Calcd. for C H O [MꢀH] 233.2. Found: 233.3.
15
21
2
3
-Isopropyl-8-(2-methoxyethoxy)-8-methylbicyclo[4.2.0]octa-1,3,5-trien-2-ol (11). Yellow
oil; yield 65% (0.25 g, 1 mmol), cLogPcompound11=2.779. R =0.22 (1:100 ethyl acetate/hexanes,
f
1
TLC). H NMR (400 MHz, CDCl ) δ 7.28 (s, 1H), 7.15 (d, J = 7.4 Hz, 1H), 6.69 (d, J = 7.4 Hz,
3
1
H), 3.74 – 3.62 (m, 3H), 3.53 – 3.47 (m, 1H), 3.45 (s, 3H), 3.30 (hept, J = 6.9 Hz,1H), 3.22 (d, J
13.6 Hz, 1H), 2.99 (d, J = 13.6 Hz,1H), 1.68 (s, 3H), 1.228 (d, J = 6.9 Hz, 3H), 1,225 (d, J =
=
1
3
6
8
.9 Hz, 3H). C NMR (101 MHz, CDCl ) δ 147.98, 138.72, 134.36, 131.96, 127.83, 115.63,
3
3.03, 73.27, 64.54, 58.96, 43.12, 26.75, 25.31, 23.01, 22.98. MS m/z (ESI): Calcd. for C H O
3
1
5
21
ꢀ
[
MꢀH] 249.1. Found: 249.3.
-Ethyl-3-isopropyl-8-methoxybicyclo[4.2.0]octa-1,3,5-trien-2-ol (12). Yellow solid; yield
8
4
1% (0.42 g, 0.9 mmol). cLogPcompound12=3.553. mp: 62–66 ℃ , R =0.23 (1:60 ethyl
f
1
acetate/hexanes, TLC). H NMR (400 MHz, CDCl ) δ 7.14 (d, J = 7.4 Hz, 1H), 6.71 (d, J = 7.4
3
Hz, 1H), 5.34 (s, 1H), 3.32 (s, 3H), 3.27 (d, J = 14.1 Hz, 1H), 3.24ꢀ3.17 (m, 1H), 2.95 (d, J =
1
4.1 Hz, 1H), 1.99 (q, J = 7.3 Hz, 2H), 1.240 (d, J = 6.9 Hz, 3H), 1,233 (d, J = 6.9 Hz, 3H), 1.06
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8
9
13
–
1
1.01 (t, J = 7.4 Hz, 3H). C NMR (101 MHz, CDCl ) δ 147.50, 139.55, 133.39, 130.95,
3
27.72, 115.96, 86.19, 52.10, 38.52, 30.66, 26.86, 22.97, 22.90, 9.51. MS m/z (ESI): Calcd. for
ꢀ
C H O [MꢀH] 219.1. Found: 219.0.
14
19
2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
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4
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7
8
9
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2
3
4
5
6
7
8
9
0
3
-(Sec-butyl)-8-methoxy-8-methylbicyclo[4.2.0]octa-1,3,5-trien-2-ol (13). Yellow oil; yield
3
9.4% (0.28 g, 1.3 mmol), cLogPcompound13=3.553. R =0.18 (1:40 ethyl acetate/Petroleum ether,
f
1
TLC). H NMR (400 MHz, CDCl ): δ 7.10 (app dd, J = 7.4, 2.1 Hz, 1H), 6.71 (app dd, J = 7.4,
3
2
1
.3 Hz,1H), 5.38 (s, 1H), 3.36 (d, J = 14.0 Hz, 1H), 3.32 (s, 3H), 3.02ꢀ2.91 (m, 2H), 1.70 (s, 3H),
.68ꢀ1.54 (m, 2H), 1.22 (app dd, J = 7.0, 1.6 Hz,3H), 0.86 (app td, J = 7.4, 5.0 Hz, 3H) MS m/z
ꢀ
(
ESI): Calcd. for C H O [MꢀH] 219.1. Found: 218.9.
1
4
19
2
3-Ethyl-8-methoxy-8-methylbicyclo[4.2.0]octa-1,3,5-trien-2-ol (14). White solid; yield 77%
(
0.97 g, 5 mmol). cLogPcompound14=2.775. mp: 77–83℃, R =0.25 (1:20 ethyl acetate/hexanes,
f
1
TLC) H NMR (400 MHz, CDCl ): δ 7.09 (d, J = 7.2 Hz, 1H), 6.69 (d, J = 7.2 Hz, 1H), 5.75ꢀ
3
5
.45 (br, 1H), 3.38 (d, J = 14.0 Hz, 1H), 3.34 (s, 3H), 2.95 (d, J = 14.0 Hz, 1H), 2.62 (q, J = 7.6
13
Hz, 2H), 1.70 (s, 3H), 1.22 (t, J = 7.6 Hz, 3H). C NMR (101 MHz, CDCl ) δ 148.01, 139.25,
3
1
31.34, 130.90, 129.16, 115.86, 82.42, 52.13, 40.75, 24.17, 23.17, 14.53. MS m/z (ESI): Calcd.
ꢀ
for C H O [MꢀH] 191.1. Found: 191.0.
1
2
15
2
5
-Bromo-3-isopropyl-8-methoxy-8-methylbicyclo[4.2.0]octa-1,3,5-trien-2-ol (15). To a
stirred solution of 2ꢀ(benzyloxy)ꢀ5ꢀbromoꢀ3ꢀisopropylꢀ8ꢀmethoxyꢀ8ꢀmethylbicyclo [4.2.0]octaꢀ
1,3,5ꢀtriene (31, 0.55 g, 1.44 mmol) in 15 mL of dichloromethane was added dropwise a solution
of boron tribromide (0.3 mL, 2.93 mmol) in 3 mL of dichloromethane at ꢀ15℃. Subsequent to
the addition, the reaction mixture was allowed to warm to 0℃and stirred for 0.5 hr. The reaction
mixture was quenched with methane (3 mL), extracted with dichloromethane (15 mL×3), and
dried with sodium sulfate. The solvent was removed under reduced pressure. The residue was
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2
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purified by flash column chromatography (1:20 ethyl acetate/hexanes, TLC). The title compound
was obtained as yellow solid (0.22 g) in 53.6% yield. cLogPcompound15=4.184. mp: 118–126℃; Rf
1
=
0.23 (1:20 ethyl acetate/hexanes). H NMR (400 MHz, DMSOꢀd ) δ 9.47 (s, 1H), 7.11 (s, 1H),
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
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5
6
7
8
9
0
3
6
.24ꢀ3.11 (m, 5H), 2.78 (d, J = 13.9 Hz, 1H), 1.61 (s, 3H), 1.130 (d, J = 6.9 Hz, 3H), 1.126(d, J =
ꢀ
.9 Hz, 3H). MS m/z (ESI): Calcd. for C H BrO [MꢀH] 285.0. Found: 284.8.
13 16
2
5
-Hydroxy-4-isopropyl-7-methyl-bicyclo[4.2.0]octa-1,3,5-triene-7-carbonitrile (16). White
solid; yield 56% (0.36g, 1.8 mmol). cLogPcompound16=2.648. mp: 125–128 ℃, R =0.24 (1:40
f
1
ethyl acetate/hexanes, TLC). H NMR (400 MHz, CDCl ) δ 7.17 (d, J = 7.5 Hz, 1H), 6.69 (d, J =
3
7
.5 Hz, 1H), 6.14 (br s, 1H), 3.69 (d, J = 13.7 Hz, 1H), 3.22 (hept, J = 6.9 Hz, 1H), 3.15 (d, J =
1
3
1
3.7 Hz, 1H), 1.85 (s, 3H), 1.227 (d, J = 6.9 Hz, 3H), 1.221 (d, J = 6.9 Hz, 3H). C NMR (101
MHz, DMSOꢀd ) δ 147.93, 139.57, 134.82, 127.93, 127.92, 123.46, 115.23, 43.61, 36.91, 26.81,
6
+
2
3.30, 23.28, 22.92. MS m/z (ESI): Calcd. for C H NO [M+H] 202.1. Found: 202.1.
1
3
16
8
-Azido-3-isopropyl-8-methylbicyclo[4.2.0]octa-1,3,5-trien-2-ol (17). To a stirred solution
of 4ꢀisopropylꢀ7ꢀmethoxyꢀ7ꢀmethylꢀbicyclo[4.2.0]octaꢀ1,3,5ꢀtrienꢀ5ꢀol (8, 1.5 g, 7.27 mmol) and
sodium amide (1.6 g, 23.27 mmol) in 180 mL of dichloromethane was added
dropwisetrifluoroacetic acid (3.6 mL, 46 mmol) under nitrogen at 0℃. Subsequent to the
addition, the reaction mixture was allowed to warm to room temperature and stirred overnight.
The reaction was quenched with a saturated solution of sodium bicarbonate (80 mL), extracted
with dichloromethane (80 mL×2), and dried with sodium sulfate. The solvent was removed
under reduced pressure. The residue was purified by flash column chromatography (1:100 ethyl
acetate/hexanes). The title compound was obtained as a yellow solid (1.33 g) in 84.0% yield.
1
cLogPcompound17=4.348. R =0.30 (1:100 ethyl acetate/hexanes, TLC). H NMR (400 MHz,
f
CDCl ) δ 7.17 (d, J = 7.7 Hz, 1H), 6.73 (d, J = 7.7 Hz, 1H), 5.70 (br s, 1H), 3.36 (d, J = 14.0 Hz,
3
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1
H), 3.25 – 3.11 (m, 2H), 1.73 (s, 3H), 1.25 (d, J = 6.8 Hz, 6H). C NMR (101 MHz, DMSOꢀd )
6
δ 148.27, 139.03, 134.50, 130.43, 128.21, 115.15, 67.26, 44.67, 26.66, 23.65, 23.35, 23.30. MS
+
m/z (ESI): Calcd. for C H O [MꢀN ] 175.1. Found: 175.1.
1
2
15
3
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
7
-Isopropyl-3-methyl-1H-indazole (18). To
isopropylphenyl) ethanone (33a 20.0 g, 0.11 mol) and hydroxylamine hydrochloride (23.4 g,
.34 mol) in distilled water (17.0 mL) and ethanol (93.0 mL) was added sodium hydroxide (35.2
a
stirred solution of 1ꢀ(2ꢀaminoꢀ3ꢀ
0
g, 0.88 mol) under nitrogen at 0℃. Subsequent to the addition, the mixture was refluxed at 80℃
for 1 hr. The mixture was transferred to a 1ꢀL, singleꢀnecked roundꢀbottomed flask and
concentrated. The solid residue was dissolved in distilled water (140 mL) and extracted with
ethyl acetate (200 mL×2), dried over anhydrous MgSO , and concentrated in vacuo .The residue
4
was dissolved in dichloromethane 100 ml. Triethylamine (22.0 g, 0.23 mol) was added via
syringe, and the reaction mixture was stirred for 15 min at ambient temperature before being
cooled to 0–5℃ in an ice/water bath. Methanesulfonyl chloride (15.5 g, 0.14 mol) was added to
300 mL dichloromethane, and the resulting solution was cooled to 0–5℃ in an ice/water bath.
The cold solution of methanesulfonyl chloride was added via cannula to the colorless oxime
mixture over 30 min. The resulting yellow solution was stirred at 0–5℃for 1.5 h. Silica gel was
added, and the green/brown solution was concentrated by rotary evaporation. The residue was
purified by flash column chromatography (1:4 ethyl acetate/hexanes) to give the title compound
18 (6.3 g, 36 %) as white solid. cLogPcompound18=3.321. mp: 114–116℃; R =0.30 (1:40 ethyl
f
1
acetate/hexanes, TLC). H NMR (400 MHz, DMSOꢀd ) δ 12.64 (s, 1H), 7.49 (d, J = 7.9 Hz, 1H),
6
7
.15 (d, J = 7.0 Hz,1H), 7.02 (m, 1H), 3.34 (hept, J = 6.8 Hz, 1H), 2.47 (s, 3H), 1.30 (d, J = 6.8
+
Hz, 6H). MS m/z (ESI): Calcd. for C H N [M+H] 175.1. Found: 175.3.
1
1
15
2
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-Isopropyl-1,3-dimethyl-1H-indazole (19). To a stirred solution of 7ꢀisopropylꢀ3ꢀmethylꢀ1H
ꢀ
indazole (18, 3.6 g, 20.70 mmol) in 250 mL of THF was added sodium hydride (1.65 g, 41.38
mmol) under nitrogen. The reaction mixture was stirred for 15 min at 0–5℃in an ice/water bath,
then methyl iodide (3.87 ml, 62.07 mmol) was added. The mixture was stirred at 30℃ for 3 h.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
The reaction mixture was poured into iceꢀwater (100 mL), extracted with ethyl acetate (200
mL×2), and dried with sodium sulfate. The solvent was removed under reduced pressure. The
residue was purified by flash column chromatography (1:5 ethyl acetate/hexanes)to give the title
compound 19 (1.1 g, 28 %) as light yellow solid. cLogPcompound19=3.337. mp: 55–58℃; R =0.40
f
1
(
1:5 ethyl acetate/hexanes, TLC). H NMR (400 MHz, DMSOꢀd ) δ 7.49 (d, J = 8.0 Hz,1H), 7.24
6
(d, J = 7.2 Hz,1H), 7.04 (t, J = 7.6 Hz,1H), 4.16 (s, 3H), 3.73 (hept, J = 6.8 Hz, 1H), 2.42 (s, 3H),
+
1
.31 (d, J = 6.8 Hz, 6H). MS m/z (ESI): Calcd. for C H N [M+H] 189.1. Found: 189.2.
12
17
2
7
-Isopropyl-3-methyl-5-nitro-1H-indazole (20). To a stirred solution of 7ꢀisopropylꢀ3ꢀ
methylꢀ1H ꢀindazole (18, 1.5 g, 8.60 mmol) in 10 mL of concentrated sulfuric acid was added
sodium nitrate (806 mg, 9.48 mmol) under nitrogen. The reaction mixture was stirred for 4 hrs at
ambient temperature. The reaction mixture was poured into iceꢀwater (100 mL), extracted with
ethyl acetate (200 mL×2), and dried with sodium sulfate. The solvent was removed under
reduced pressure. The residue was purified by flash column chromatography (1:4 ethyl
acetate/hexanes) to give the title compound 20 (1.5 g, 80 %) as light yellow solid.
1
cLogPcompound20=3.424. R =0.40 (1:4 ethyl acetate/hexanes, TLC). H NMR (400 MHz, DMSOꢀ
f
d6) δ 13.42 (s, 1H), 8.62 (d, J = 2.0 Hz,1H), 7.98 (d, J = 2.0 Hz,1H), 3.42 (hept, J = 6.9 Hz, 1H),
+
2
.58 (s, 3H), 1.35 (d, J = 6.9 Hz, 6H). MS m/z (ESI): Calcd. for C H N O [M+H] 220.1.
1
1
14
3
2
Found: 220.1.
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-Cyclopropyl-7-isopropyl-1H-indazole (21).To a stirred solution of (2ꢀaminoꢀ3ꢀ
isopropylphenyl)(cyclopropyl)methanone (33b, 400 mg, 1.97 mmol) in concentrated
hydrochloric acid (2 ml) was added dropwise a solution of sodium nitrite (273 mg, 3.94 mmol) in
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
3
ml of water with stirring at 0℃, and the mixed solution was further stirred at 0℃for 1h. To the
reaction solution was added dropwise tin (II) chloride dihydrate (823 mg, 4.33 mmol) dissolved
in concentrated hydrochloric acid (2 ml), and the solution was stirred at 0℃ for 2 hours. The
reaction solution was extracted with dichloromethane, the organic layer was washed with brine,
dried over sodium sulfate and filtered, and the filtrate was concentrated under reduced pressure.
The residue was purified by silicaꢀgel chromatography (developing solvent: hexane / ethyl
acetate = 2:1) to give the title compound 21 (280 mg, 71%) as a white solid.
1
cLogPcompound21=3.765. R =0.30 (1:2 ethyl acetate/hexanes, TLC). H NMR (400 MHz, DMSOꢀ
f
d6) δ 12.56 (s, 1H), 7.56 (d, J = 8.0 Hz,1H), 7.14 (d, J = 7.0 Hz, 1H), 7.01 (dd, J = 8.0, 7.0 Hz,
1
H), 3.38ꢀ3.26 (m, 1H), 2.28ꢀ2.20 (m, 1H), 1.30 (d, J = 6.9 Hz, 6H), 0.98ꢀ0.92 (m, 4H). MS m/z
+
(
ESI): Calcd. for C H N [M+H] 201.1. Found: 201.2.
13 17
2
ASSOCIATED CONTENT
Supporting Information Available: Characterization data for compounds 1-21. This material
is available free of charge via the internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*
Eꢀmail: zhangc@haisco.com. Phone: (+86)02867258864. Fax:(+86)02867250548.
ACKNOWLEDGMENTS
We thank Mr. Wei Zheng from Haisco Pharmaceutical Group Co. Ltd., for continuous support.
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ABBREVIATIONS USED
DMF, N,Nꢀdimethylformamide; NBS, Nꢀbromosuccinimide; DCM, dichloromethane; BCl3,
boron trichloride; BBr , boron tribromide; AlCl , aluminium chloride; NaH, sodium hydride;
3
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
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5
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9
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1
2
3
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5
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9
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1
2
3
4
5
6
7
8
9
0
NaNH , sodium amide; BnBr, benzyl bromide; Et SiH, triethylsilane; CH I, iodomethane; THF,
2
3
3
tetrahydrofuran; TMSCN, cyanotrimethylsilane; MeOH, methanol; EtOH, ethanol; DMSO,
dimethyl sulfoxide; Et N, triethylamine; pꢀTsOH, tolueneꢀpꢀsulfonic acid; K CO , potassium
3
2
3
carbonate.
REFERENCES
(
1) Kay, B.; Rolly, G. I.C.I. 35868, a new intravenous induction agent. Acta Anaesthesiol.
Belg. 1977, 28, 303–316.
2) Trapani, G.; Altomare, C.; Sanna, E.; Biggio, G.; Liso G. Propofol in anesthesia.
(
Mechanism of action, structureꢀactivity relationships, and drug delivery. Curr. Med. Chem. 2000,
7, 249–271.
(3) James, R.; Glen, J. B. Synthesis, biological evaluation, and preliminary structureꢀactivity
considerations of a series of alkylphenols as intravenous anesthetic agents. J. Med. Chem. 1980,
2
3, 1350–1357.
(
4) WHO Model List of Essential Medicines. 19th List (April 2015) World Health
Organization. URL: http://www.who.int/medicines/publications/essentialmedicines/en/ (April 9,
017)
2
(5) Matta, J. A.; Cornett, P. M.; Miyares, R. L.; Abe, K.; Sahibzada, N.; Ahern, G. P. General
anesthetics activate a nociceptive ion channel to enhance pain and inflammation. Proc. Natl.
Acad. Sci. U. S. A. 2008, 105, 8784–8789.
ACS Paragon Plus Environment

Page 23 of 26
Journal of Medicinal Chemistry
1
2
3
4
5
6
7
8
9
(
6) Robinson, B. J.; Ebert, T. J.; O’Brein, T. J.; Colinco, M. D.; Cerny, R. L.; Muzi, M.
Mechanisms whereby propofol mediates peripheral vasodilation in humans. Anesthesiology
1997, 86, 64–72.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
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0
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6
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0
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1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(7) Muir, W. W.; Gadawski, J. E. Respiratory depression and apnea induced by propofol in
dogs. Am. J. Vet. Res. 1998, 59, 157–161.
(8) (a)Diedrich, D. A.; Brown, D. R. Analytic reviews: propofol infusion syndrome in the ICU.
J. Intensive Care Med. 2011, 26, 59–72. (b)Vasile, B.; Rasulo, F.; Candiani, A.; Latronico, N.
The pathophysiology of propofol infusion syndrome: a simple name for a complex syndrome.
Intensive Care Med. 2003, 29, 1417–1425.
(9) Krasowski, M. D.; Hong, X.; Hopfinger, A. J.; Harrison, N. L. 4DꢀQSAR analysis of a set
of propofol analogues: mapping binding sites for an anesthetic phenol on the GABA receptor. J.
A
Med. Chem. 2002, 45, 3210–3221.
(10) (a)Sneyd, J. R.; RigbyꢀJones, A. E. New drugs and technologies, intravenous anaesthesia
in on the move (again). Br. J. Anaesth. 2010, 105, 246–254. (b)Jenkins, T. E. Therapeutic
compounds. WO2008141097A2, 2008.
(11) Banaszczyk, M. G.; Carlo, A. T.; Millan, V.; Lindsey, A.; Moss, R.; Carlo, D. J.; Hendler,
S. S. Propofol phosphate, a waterꢀsoluble propofol prodrug: in vivo evaluation. Anesth. Analg.
(
Philadelphia, PA, U. S.) 2002, 95, 1285–1292.
(12) Zhang, C.; Li, F.; Huang, A.; Lei, M.; Wang, J.; He, P.; Wei, Y.; Tang, P. C. Phenol
derivative, method of preparing same, and pharmaceutical application of same.
WO2014180327A1, 2014.
ACS Paragon Plus Environment

Journal of Medicinal Chemistry
Page 24 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
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1
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4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
13) (a)Klundt, I. L. Benzocyclobutene and its derivatives. Chem. Rev. 1970, 70, 471–487.
(
b)Kefalidis, C. E.; Davi, M.; Holstein, P. M.; Clot, E.; Baudoin, O. Mechanistic study of the
selectivity of olefin versus cyclobutene formation by palladium(0)ꢀcatalyzed intramolecular
3
0
1
2
3
4
5
6
7
8
9
0
1
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9
0
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4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
C(sp )ꢀH Activation J. Org. Chem. 2014, 79, 11903–11910. (c)Hayes, C. O.; Chen, P.ꢀH.;
Thedford, R. P.; Ellison, C. J.; Dong, G.; Willson, C. G. Effect of ring functionalization on the
reaction temperature of benzocyclobutene thermoset polymers. Macromolecules 2016, 49, 3706–
3
715.
(14) (a)FloresꢀGaspar, A.; Martin, R. Recent advances in the synthesis and application of
benzocyclobutenones and related compounds. Synthesis 2013, 45, 563–580. (b)Kobayashi, K.;
Kanno, Y.; Seko, S.; Suginome, H. Photoinduced molecular transformations. Part 135. New
synthesis of taiwanin C and justicidin E based on a radical cascade process involving βꢀscission
of alkoxyl radicals generated from 3ꢀ and 8ꢀarylꢀ1ꢀethylꢀ1,2ꢀdihydrocyclobuta[b]naphthaleneꢀ1ꢀ
ols prepared by thermolysis of (Z)ꢀtertꢀbutyl 3ꢀaminoꢀ3ꢀ(bicycle[4.2.0]octaꢀ1,3,5ꢀtrienꢀ7ꢀ
yl)propenoates. J. Chem. Soc. Perkin Trans.1 1992, 22, 3111–3117. (c)Matsuya, Y.; Ohsawa, N.;
Nemoto, H. Facile transformation of benzocyclobutenones into 2,3ꢀbenzodiazepines via 4πꢀ8π
tandem electrocyclic reactions involving net insertion of diazomethylene compounds. J. Am.
Chem. Soc. 2006, 128, 13072–13073. (d)Deng, L.; Xu, T.; Li, H.; Dong, G. Enantioselective Rhꢀ
catalyzed carboacylation of C=N bonds via CꢀC activation of benzocyclobutenones. J. Am.
Chem. Soc. 2016, 138, 369–374.
(15) (a)Fox, K.; Ford, I.; Steg, P. G.; Tardif, J.ꢀC.; Tendera, M.; Ferrari, R. Ivabradine in stable
coronary artery disease without clinical heart failure. N. Engl. J. Med. 2014, 371, 1091–1099.
(
b)JeanꢀLouis Peglion, L. V.; Joel Vian, C.; JeanꢀPaul Vilaine, C. M.; Nicole Villeneuve, R. M.;
ACS Paragon Plus Environment

Page 25 of 26
Journal of Medicinal Chemistry
1
2
3
4
5
6
7
8
9
Philip Janiak, C.; JeanꢀPierre Bidouard, C. M. (Benzocycloalkyl)alkylamines. US5296482A,
1
994.
(16) (a)Franks, N.P.; Lieb, W. R. Molecular and cellular mechanisms of general anaesthesia.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
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2
3
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7
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9
0
1
2
3
4
5
6
7
8
9
0
Nature 1994, 367, 607–614. (b)CampagnaꢀSlater, V.; Weaver, D. F. Anaesthetic binding sites for
etomidate and propofol on a GABA receptor model. Neurosci. Lett. 2007, 418, 28–33.
A
(17) (a)Lingamaneni, R.; Hemmings Jr., H. C. Differential interaction of anaesthetics and
+
2+
antiepileptic drugs with neuronal Na channels, Ca channels, and GABA receptors. Br. J.
A
Anaesth. 2003, 90, 199–211. (b)Jayakar, S. S.; Zhou, X.; Chiara, D. C.; Dostalova, Z.;
Savechenkov, P. Y.; Bruzik, K. S.; Dailey, W. P.; Miller, K. W.; Eckenhoff, R. G.; Cohen, J. B.
Multiple propofolꢀbinding sites in a γ–aminobutyric acid type A receptor(GABA R) identified
A
using a photoreactive propofol analog. J. Biol. Chem. 2014, 289, 27456–27468
(18) HillꢀVenning, C.; Peters, J. A.; Callachan, H.; Lambert, J. J.; Gemmell, D. K.; Anderson,
A.; Byford, A.; Hamilton, N.; Hill, D. R. The anesthetic action and modulation of GABAA
receptor activity by the novel waterꢀsoluble aminosteroid Org 20599. Neuropharmacology 1996,
3
5, 1209–1222.
35
(
19) Maksay, G.; Simonyi, M. Nonequilibrium modulation of SꢀTBPS binding by
Benzodiazepine agonists and antagonists. Biochem. Pharmacol. 1988, 37, 2195–2200.
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