Amino-benzosuberone: A novel warhead for selective inhibition of human aminopeptidase-N/CD13

Article abstract of DOI:10.1016/j.bmc.2011.01.008

This paper describes the design and synthesis of compounds belonging to a novel class of highly selective mammalian CD13 inhibitors. Racemic homologues of 3-amino-2-tetralone 1 were synthesised and evaluated for their ability to selectively inhibit the me

Full text of DOI:10.1016/j.bmc.2011.01.008

Bioorganic & Medicinal Chemistry 19 (2011) 1434–1449
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Amino-benzosuberone: A novel warhead for selective inhibition of human
aminopeptidase-N/CD13
Sébastien Albrecht a, Mira Al-Lakkis-Wehbe a, Alban Orsini a,b, Albert Defoin a, , Patrick Pale b,
⇑
b
Emmanuel Salomon a, Céline Tarnus a, , Jean-Marc Weibel
⇑
a Laboratoire de Chimie Organique et Bioorganique, FRE3252, ENSCMu, F-68093 Mulhouse Cedex, France
b Laboratoire de Synthèse et Réactivité Organiques, UMR 7509, Institut de Chimie, 4, rue Blaise Pascal, 67000 Strasbourg, France
a r t i c l e i n f o
a b s t r a c t
Article history:
This paper describes the design and synthesis of compounds belonging to a novel class of highly selective
mammalian CD13 inhibitors. Racemic homologues of 3-amino-2-tetralone 1 were synthesised and
evaluated for their ability to selectively inhibit the membrane-bound, zinc-dependent aminopeptidase-
N/CD13 (EC 3.4.11.2). Some of these novel non-peptidic compounds are potent, competitive inhibitors
of the mammalian enzyme, with Ki values in the low micromolar range in spite of their minimal size
(MW <200 Da). Moreover, they show an interesting selectivity profile against representative members
of the aminopeptidase family, that is leucine aminopeptidase (EC 3.4.11.1), Aeromonas proteolytica ami-
nopeptidase (EC 3.4.11.10) and the aminopeptidase activity of leukotriene A4 hydrolase (EC 3.3.2.6). The
amino-benzosuberone derivative 4 is the most promising compound in terms of potency, stability and
selectivity. A hypothetical binding mode of 4 to the catalytic zinc and several conserved active site res-
idues is proposed, based on the observed structure–activity relationships, structural insights from ami-
nopeptidase-N homologues of known three-dimensional structure.
Received 1 October 2010
Revised 23 December 2010
Accepted 5 January 2011
Available online 11 January 2011
Keywords:
Aminobenzoheptenone
Aminopeptidase-N inhibitor
APN/CD13
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
receptor, and virus binding does not appear to be affected by active
site directed APN inhibitors. Nevertheless, there seems to be an
Aminopeptidases constitute a large family of proteolytic en-
zymes that affect the maturation, degradation and regulation of
proteins and oligopeptides. Aminopeptidase-N (CD13/APN) is a
multifunctional ectoenzyme widely expressed in many cells and tis-
sues, suggesting a variety of biological functions depending on its
location.1 Among its well-established roles, CD13/APN modulates
the activity of numerous peptides that participate in important bio-
logical processes. For example, it regulates the metabolism of leu-
and met-enkephalins,2 angiotensins,3 kinins4,5 and a number of
cytokines or chemokines.6,7 Additionally, CD13/APN is involved in
signal transduction and cell motility, proliferation and differentia-
tion.8–12 Worth of note, APN expression is deregulated in inflamma-
tory diseases and in cancer.9–11 In view of the potential therapeutic
relevance of some of the CD13/APN functions, the rational design of
potent and selective CD13/APN inhibitors is of considerable interest
but remains a challenging endeavor.
interplay between the enzymatic activity-dependent and -inde-
pendent functions of CD13/APN.1 Unfortunately, the exact relation-
ship between the enzymatic and non enzymatic roles of CD13 was
so far obscured basically by the fact that, although many inhibitors
of aminopeptidases are available most of them are poorly selective.
Recent outstanding reviews summarized the main achievements in
this field.13 Among the most active compounds one can bring up
Gallic acid derivatives and pseudo peptides that used the concept
of transition state analogues, such as a-boronic acids, sulfonamide
and phosphonic surrogates of the scissile peptide bond. Natural
products such curcumin14 and psammaplin A15 or synthetic flavo-
noid16 derivatives were also worthy of note, as well as highly po-
tent inhibitors related in structure to hydroxamic acids
derivatives.17 However, the selectivity of this large diversity of
APN inhibitors towards other metallo-aminopeptidases has not al-
ways been assessed or proved to be modest.
CD13/APN belongs to the M1 family of zinc metallopeptidases
with one essential catalytic zinc ion. As an enzyme, APN removes
the aminoterminal amino acid from unsubstituted oligopeptides.
As a membrane-bound protein, CD13 is well-known as a viral
The rational design of truly selective APN/CD13 inhibitors is far
from obvious owing to the very high structural similarity of the
many zinc-dependent aminopeptidases. The problem of achieving
high selectivity is further compounded by the relatively broad sub-
strate specificity displayed by these enzymes.
We have already shown that 3-amino-2-tetralone 1 is an
interesting specific inhibitor of mammalian APN with a significant
selectivity towards the M1 subfamily of one-zinc aminopeptidases,
⇑
Corresponding authors. Tel.: +33 0 389336864 (A.D.).
E-mail addresses: Albert.Defoin@uha.fr (A. Defoin), Celine.Tarnus@uha.fr (C.
Tarnus).
0968-0896/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2011.01.008

S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
1435
as opposed to the M17 subfamily that require co-catalytic metal
2.1. Amino-indanone 2
ions for activity.18,19 Nevertheless, we have found that the stability
of this compound in aqueous solution at physiological pH is
limited, with an approximate half life of 2 h. We thus wondered
whether one could improve stability and potency with either more
rigid or more flexible analogues. We have shown in our previous
work,19 that the free amine in position 3 as well as a carbonyl
group in position 2 are essential features for the inhibitory activity,
presumably as surrogates for the free amino terminus and the
carbonyl group of the scissile bond, respectively, of peptide
substrates.
In the present work, we have studied the influence of the size of
cycle B of 1 on the stability, the inhibitory potency and the selec-
tivity against a panel of representative aminopeptidases.20 A com-
prehensive list of aminobenzocyclanones synthesised during the
course of this work is reported in Scheme 1, including the monocy-
clic aminocycloheptanone 5. All compounds were evaluated
against human, porcine and murine aminopeptidase-N/CD13 (EC
3.4.11.2), bovine lens leucine aminopeptidase (EC 3.4.11.1), Aero-
monas proteolytica aminopeptidase (EC 3.4.11.10) and the amino-
peptidase activity of human leukotriene A4 hydrolase (EC
3.3.2.6). The amino-benzocycloheptenone (amino-benzosuberone)
derivative 4 turned out to be the most promising analogue with
much improved stability and selectivity.
The three-dimensional structure of CD13/APN has not been elu-
cidated yet. However, in spite of a relatively low overall amino acid
sequence identity (between 20% and 30%), the mammalian enzyme
is expected to share substantial structural homology with the
known Escherichia coli21 or Neisseria meningitidis22 APNs, as well
as with the human leukotriene A4 hydrolase,23 most particularly
within the active site region. In support of this view, all these en-
zymes are inhibited to the same extent by the most widely used,
non-specific inhibitor and natural compound bestatin.13 Further-
more, these APs use a set of conserved residues for binding the free
N-terminal amino group of their substrate and the zinc ion essen-
tial for catalysis. This structural homology combined with the
shared catalytic mechanism, allows us to propose for the amino-
benzosuberone 4 a plausible binding mode to the catalytic zinc
of the mammalian APN.
1-Aminoindan-2-one 2 was synthesised from the commercially
available chiral cis amino-alcool (+)-7a in a three steps procedure
(Scheme 2). Selective N-protection was first achieved using tert-
butoxycarbonyl anhydride in methanol as for its known enantio-
mer.24 The obtained amido-alcohol (ꢀ)-7b was then smoothly oxi-
dized with Dess–Martin periodinane (DMP)25 into the N-protected
amino-indanone (ꢀ)-8 in good yield. The compound slowly race-
mises in solution (see below). Acidic deprotection with dry HCl
in ether provided the racemic aminoketone 2 as its crystalline
hydrochloride salt. This sequence afforded the desired five-mem-
bered aminoketone 2 in 47% yield from (+)-7a.
2.2. Benzosuberones 3 and 4
The simplest member in this series was obtained from the
known tetrahydrobenzocycloheptenone 926–28 through
a-nitrosa-
tion and reduction. Nitrosation adjacent to the keto group of 9 with
tert-butyl nitrite in methanol29 gave directly the ketal-oxime 10.
Reduction of the oxime function with Raney-nickel in the presence
of aqueous ammonia gave the corresponding amino-ketal 11 in
high yield. Hydrolysis of this crude amine with aqueous hydrochlo-
ric acid regenerated the keto group, yielding the amino-ketone 3 as
its hydrochloride salt. This three steps sequence provided the de-
sired 6-aminobenzosuberone 3 with a good overall yield (45%)
from the benzosuberone 9 (Scheme 2).
The ketal-oxime 10 could be a convenient entry for the prepa-
ration of the isomeric 7-aminobenzosuberone 4 and its oxime 14,
through reductive amination and eventually oxime cleavage.
Aqueous hydrolysis of the acetal group according to29 gave the
known keto-oxime 12. Reductive amination of the ketone by
imination with benzylamine in pyridine followed by reduction
with sodium borohydride led to the N-benzylated amino-oxime
13a in high yield. N-deprotection by hydrogenolysis over Pd–C in
the presence of hydrochloric acid led to the amino-oxime as its
hydrochloride salt 14 in high yield. However, all attempts to ap-
proach the target ketone 4 by hydrolyse or oxidise the oxime
group, either from the N-diprotected derivative 13b or from the
monoprotected 13a, yielded only unsatisfactory results.
Another route was thus planed from benzosuberone 9 through
-hydroxylation and amination (Scheme 2). a-Hydroxylation of a
2. Chemistry
a
ketone could be achieved by epoxidation of the corresponding silyl
enol ether. Thus, 9 was converted to its silyl enol ether 15 using tri-
methylsilyl chloride or triflate under basic conditions.30 Oxidation
The synthesis of the 3-aminotetralone 1 was already re-
ported.18,19 In contrast, 1-aminoindan-2-one 2 and the amin-
obenzosuberone derivatives 3–6 were prepared according to
different routes.
with m-CPBA31 gave the
a-siloxyketone 16 in quantitative yield.
Sensitive silylated compounds were not purified and the conver-
sion of carbonyl to amino group was achieved by reduction of its
oxime or by reductive amination. The first route started from the
ketoxime 17, easily obtained from the siloxyketone 16 under con-
ventional conditions. Reduction over Raney-nickel provided the
aminoalcohol 18, which was directly N-protected as tert-butyloxy-
carbonyl or benzyloxycarbonyl derivatives, 19a or 19b, respec-
tively. Both compounds were obtained as cis–trans mixtures in ca
35% overall yield from 9. On the other hand, reductive amination
of the siloxyketone 16 was readily performed upon treatment with
tetraisopropyl titanate and dry ammonia in methanol, with a sub-
sequent sodium borohydride reduction.32 This reaction directly
gave the amino-alcohol 18 in reasonable yields. N-protection gave
the carbamates 19a,b, again as cis–trans mixtures (ca 52% from 9).
The cis and trans isomers of the Boc-amide 19a can be separated by
chromatography. Their acidic deprotection was a good way to ob-
tain separately both isomers, cis-18ꢁHCl and trans-18ꢁHCl, of the
amino-alcohol. The oxidation of the alcohol function in 19a,b with
Dess–Martin periodinane25 afforded the N-protected aminoke-
tones 20a,b. Deprotection of 20a with dry hydrochloric acid in
3
1
O
2 O
2
B
A
NH2,HCl
3
1 NH2,HCl
1
2
5
NH2,HCl
O
5
6
6
7 O
NH2,HCl
7
1
3
4
6
O
O
NH2,HCl
NH2,HCl
5
Scheme 1.

1436
S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
4
3
c
b
OH
O
O
1 NHR
NHBoc
NH2,HCl
(-)-8
2
(+)-7a R=H
a
(-)-7b R = Boc
NOH
OMe
OMe
NH2
OMe
OMe
4
NH2,HCl
O
d
f
e
O
7
1
3
10
NOH
11
9
NOH
NHR
NOH
NBnBoc
g
h
j
O
4
10
X
12
13a R =Bn
14 R = H,HCl
13b
i
OSiMe3
OH
NOH
l
k
m
OSiMe3
O
9
15
16
17
o
t for 20a
u for 20b
OH
NHZ
O
O
s
n
NH2,HCl
NHZ
17
20a Z = Boc
b Z = CO2Bn
18 cis, trans Z = H
4
r
p
q
19a cis, trans Z = Boc
19b cis +trans Z = CO2Bn
Scheme 2. Reagents and conditions: (a) Boc2O, MeOH, 5.5 h, rt, quant.; (b) DMP, CH2Cl2, 7 h, rt, 69%; (c) dry HCl 2.2 M in Et2O, dioxane, rt, 72 h, 69%; (d) tBuONO, HCl, MeOH,
0 °C, 66%; (e) H2/Ra-Ni, concd NH4OH, EtOH, rt, 95%; (f) 1 N aq HCl, MeOH, rt, 90%; (g) aq HCl 6 N, Et2O, 15 min, 0 °C, 72%; (h) BnNH2, pyridine, 6 h, rt, then NaBH4, MeOH, 1 h,
rt, 93%; (i) H2/Pd–C, EtOH, aq HCl 1 N, rt, 75%; (j) ClCO2Bn, aq Na2CO3, THF, 24 h, rt, 64%; (k) Me3SiCl, DBU, CH2Cl2, quant.; or Me3SiOTf, NEt3, toluene, 85 °C, 2 h, quant.; (l) m-
CPBA, CH2Cl2, 0 °C, 2 h, quant.; (m) NH2OHꢁHCl, pyridine, rt, 3 h, 64%; (n) H2/Raney-Ni, EtOH, concd NH4OH, rt, 2.5 h; (o) Ti(OiPr)4, 2–3 M NH3 in MeOH, 6 h, then NaBH4, 2 h;
(p) Boc2O, Na2CO3, MeOH, 2 h, rt, 56% yield from 17, or Boc2O, MeOH, rt, 53% yield from 16; (q) ClCO2Bn, Et3N or Na2CO3, THF, rt, 52–54% yield from 16 or 17; (r) dry HCl 2 M in
Et2O, dioxane, rt, 48 h, 85% for cis-isomer, quant. for trans-isomer (as HCl salt); (s) DMP, CH2Cl2, 77% and 92% yield, respectively, from 19a or 19b; (t) dry HCl 2.2 M in Et2O,
dioxane, rt, 72 h, 85%; (u) H2/Pd–C, aq HCl, EtOH, rt, 60%.
ether or of 20b by hydrogenolysis in ethanolic hydrochloric acid
provided the desired aminoketone 4 as its hydrochloride salt with
good overall yield of 25% or 40%, respectively, from the ketone 9.
none38 or oxygen,39 palladium acetate catalysed dehydrosilylation,
nevertheless the enone yields proved non-reproducible (45–85%).
Thus, the
a-bromoketone 24 was quantitatively prepared either
from the silyl enol ether 15 with NBS,40 or directly from the ketone
9 with NBS in the presence of trimethylsilyl triflate.41 It was submit-
ted to DBU and HBr elimination gave the desired enone 25 in 80%
overall yield from 9 in a one pot procedure.
2.3. Monocyclic amino-suberone 5
The known azido-compound 2333 was prepared by
alisation of the suberone 21, successively by oxidation with NBS
a
-function-
To introduce the amine and ketone groups, we relied on the
same a-hydroxylation, reductive amination, oxidation sequence
into the
a
-bromoketone 2234 according to35 and, directly without
purification, by nucleophilic substitution with sodium azide36 in
DMF (Scheme 3). The reduction of the azide function of 23 by
hydrogenolysis over Pd/C in the presence of hydrochloric acid pro-
vided the amino-suberone 5 as hydrochloride with a 50% overall
yield from the ketone 21.
successfully applied to the synthesis of 4. The silyloxyenone 27
was obtained from the enone 25 upon silylation into the dienol
ether 26 and m-CPBA oxidation, as before. However, stability prob-
lems occurred with the trimethylsilyl ether and the tert-butyldi-
methylsilyl enol ether was preferred. The yield was nevertheless
lower than before in this case (70% vs quant.). In contrast, reductive
amination proved very efficient and provided the expected siloxy-
amine 28a which was directly N-protected into the O,N-diprotect-
ed aminoalcohol 28b as a cis–trans 80:20 mixture. Desilylation
under conventional conditions led to 28c, which was further oxi-
dised with Dess–Martin periodinane. This sequence provided the
N-protected unsaturated aminoketone 29 in 34% overall yield from
the enone 25.
2.4. Unsaturated benzocycloheptanone 6
The synthesis of the unsaturated analogue 6 of the aminobenzo-
suberone 4 was attempted from the ketone 9 through a similar route
using the known enone 2537 as intermediate (Scheme 3). Enones
could be obtained from the corresponding ketones either through
palladium catalysed dehydrosilylation of the corresponding silyl
enol ether or more classically through
tion. From the silyl enol ether 15 (cf above), the Pd-catalysed enone
formation was first explored. In the presence of para-benzoqui-
a
-bromination and elimina-
Unfortunately, this N-protected aminoketone 29 proved very
sensitive both to basic or acid conditions (Scheme 3). Minute
amounts of triethylamine in a CDCl3 solution of 29 promoted

S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
1437
a
b
c
O
O
O
O
N3
NH2,HCl
Br
22
23
25
21
9
5
d
f
e
O
O
15
Br
24
OSiMe2tBu
OH
NHBoc
OSiMe2tBu
k
SiMe2tBu
l
g
NHZ
O
O
25
29
h
i
26
28a Z = H
28b Z = Boc
27
28c
j
193.3
O
OH
X
O
5
6
O
O
m
132.0
NH2,HCl
NHBoc
NHBoc
NHCO2Me
32o
n
8
153.7
6
30
29
31b X = NH
31a X = O
127.5
Scheme 3. Reagents and conditions: (a) NBS, cat. p-TsOH, rt, 2.5 h, quant.; (b) NaN3, DMF, rt, 30 min, quant.; (c) H2-Pd/C, rt, 16 h, 50% overall yield from 21; (d) Pd(OAc)2,
benzoquinone, MeCN, 3 d, rt, 45–75% or Pd(OAc)2, O2, DMSO, 16 h, rt, 45–85%; (e) cat. Me3SiOTf, NBS, MeCN, rt, quant.; (f) DBU, MeCN, rt, 80% over two steps; (g) Me2tBuSiCl,
DBU, CH2Cl2, 3 h, rt or Me2tBuSiOTf, NEt3, rt, 3 h; (h) m-CPBA, CH2Cl2, 0 °C, 16 h, 75–77% over two steps; (i) Ti(OiPr)4, NH3 in MeOH, 16 h, then NaBH4, 2 h, rt, quant.; (j) Boc2O,
Na2CO3, MeOH, 16 h, rt, quant.; (k) Bu4NF, THF, rt, quant.; (l) DMP, CH2Cl2, rt, 70–84%; (m) NEt3, CDCl3, rt; (n) aq 2 N HCl; (o) 13C NMR values.
immediately a double bond migration, isomerising 29 into the
a-
OR
OD
OD
OR
ND2
+
amino-enone 30. Its planar structure was clearly supported by
NMR data, with, for example, a singlet for the 5-methylene adja-
cent to the keto group, a triplet for the vinylic proton H-8 coupled
with a doublet for the 9-methylene. The 13C NMR values for C(6),
C(7) and C(8) (at d 190, 133 and 126 ppm) were consistent with
the corresponding data for the known cyclohexane analogue 3242
(Scheme 3).
Attempts to obtain the aminoketone 6 by deprotection of 29 in
aqueous 2 N hydrochloric acid gave an aromatised product, as-
sumed to be the benzotropolone imine 31b. This product proved
relatively unstable and had only been characterised in solution
by NMR (in H2O to avoid deuteration problems). In comparison
to the NMR data of the known benzotropolone 31a, which was syn-
thesised according to,43 the data of 31b were very similar, with
slightly different d-values and identical coupling values.
ROD
O
ND2
3
2a
2b
1 NH2
OD
OD
ND2
D2O
2
2c
Scheme 4. Addition reactions to the carbonyl function of amino indanone 2, in
deuterated solvents (CD3OD and D2O).
pound being the ketone. Interestingly, the hemiacetals were
already detectable after 10 min, revealing the sensitivity of the car-
bonyl group to nucleophilic addition. In deuterated water, the hy-
drate 2c was formed immediately and at equilibrium, a 60:40
mixture was observed with the hydrate form being the minor one.
For analogs 1 and 3 with extended six- and seven-membered
rings B, respectively, similar addition reactions were observed.
Nevertheless as expected, the equilibrium was clearly in favor of
the ketone form, with a ketone/hydrate ratio of 80:20, due to a less
constrained (rigid) cycle.
3. Reactivity of the carbonyl function in deuterated solvents
The reactivity of the carbonyl function of the tetralone 1, ami-
no-indanone 2, and benzosuberone 4 derivatives has been studied
in hydroxylated deuterated solvents by addition reaction, isotopic
exchange and self condensation.
3.1. Addition reactions
3.2. Keto-enol tautomerisation
The indanone derivative 2 slowly evolved in deuterated water
or methanol. It was converted to the corresponding hydrate and
hemiacetals (Scheme 4). In CD3OD 1H NMR spectra, the singlet at
This family of compounds was also slowly deuterated at adja-
cent positions to the carbonyl group (Scheme 5). Enolisation was
obviously responsible for this process. Monitoring the evolution
of these compounds 1, 2 and 4 as hydrochloride in D2O at pH 6
by 1H NMR allowed the estimation of enolisation rates through
deuteration.
Not so surprisingly, the deuteration rate proved different
depending on the proton position around the carbonyl function
and on the size of the saturated B cycle, it followed the general
rules for enolisation (Table 1).
5.06 ppm corresponding to the proton H-1 in
a-position of the
amino and the carbonyl groups decreased to the benefit of new
peaks at 4.53 and 4.39 ppm. Similarly, the AB system of the
CH2(3) group was replaced by new sets of shielded signals. These
shifts clearly indicated the disappearance of the carbonyl unit
and of its anisotropy. These new signal sets corresponded to the
isomeric hemiketals 2a and 2b. At equilibrium, the mixture con-
tained the three components in a 24:33:43 ratio, the minor com-

1438
S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
conformation. A spontaneous aromatisation transformed 33a to
D
O
O
the symmetrical pyrazine 34a (one night at room temperature in
solution). The 13C NMR showed two quaternary signals at ca
149 ppm, which corresponded to the mentioned structure, by com-
parison with the tetramethylpyrazine 35 (d ca 151 ppm44).
D2O
D2O
NH2,HCl
n
B
NH2,HCl
n
1,2,4
1,2,4-d
The dimerisation of
a-amino-ketones is an already known,
D
D
D D
common reaction.45 It was formerly described for the colchicine
analogues46 to lead to the hexamethoxy-derivative 33b, or more
probably the pyrimidine 34b. The first step, the imine formation,
is probably a reversible reaction. Worth of note, at the low con-
O
O
D
D2O
NH2,HCl
n
n
NH2,HCl
1,2,4-d3
1,2,4-d2
centrations used for the inhibition studies
(lM range), this
dimerisation did not occur to a significant extent, since, as we
will see below, the enzyme was inhibited by the amino-benzosu-
berone 4 for at least 10 h without any changes in inhibitory
potency.
Scheme 5. Proton exchanges at adjacent positions to the carbonyl group.
Another result illustrating our comments, dealt with the
synthetic pathway used to produce the amino-indanone 2. The
synthesis of this compound was carried out from the commercially
available chiral aminoalcool 7a (Scheme 2). The indanone keto-
amide intermediate 8, was still chiral, enolisation was then directly
observed in chloroform solution and led to a spontaneous racemi-
sation of position 1 bearing the amino group. As expected this
racemisation was slow, but significant and measured by the de-
4. Conformation analysis of the benzocycloheptane and amino-
ketones derivatives
4.1. Benzocycloheptane derivatives
The conformations of the seven-membered ring was already the-
oretically studied47–49 and the more stable one was determined to
be the chair conformation (see Fig. 1), with protons in axial or equa-
torial positions. A characteristic feature is that the dihedral angle be-
tween both equatorial H-8 and H-9 protons is nearly 15° and
between both axial ones nearly 195°.49 Consequently, the vicinal
coupling constant values between both equatorial protons, in one
hand, and between both axial protons, on the other hand, are impor-
tant: J(Heq-8,Heq-9) = 7–9 Hz, and J(Hax-8,Hax-9) = 9–12 Hz. An
example was set with the aminoalcohol 18 and its N-acylated deriv-
ative 19a. The NMR spectra of the trans isomers trans-18 and trans-
19a were fully resolved and the vicinal H–H couplings J(5a,6), J(6,7),
J(7,8b) and J(8b,9a) were large (9.7–12.2 Hz) corresponding to a
trans-diaxial relation between axial protons as depicted in Figure 1
for the aminoalcohol trans-18. The value of the trans equatorial-
equatorial coupling was likely large [J(8a,9b) = 7.2 Hz]. For the cis
isomers, their exact conformation was not studied, but the J(6,7) ax-
ial-equatorial value was smaller (ca 3 Hz).
crease of the [
4 days at 20 °C.
For the b-tetralone derivative 1, as expected, deuteriation of H-
3, position noted , to give 1-d3 is much slower since we do not
a] value. The half-time of this reaction was circa
D
c
form any conjugated system with the aromatic ring A. For com-
pounds 4, in water at pH 6 the stability is even better since we
had to increase the temperature up to 60 °C to observe any proton
exchange either for H-1 in a-position or H-7 in c-position. Not so
surprisingly, under physiological conditions at pH 7.5, we have
shown that deuteriation is much faster and occurs even at 20 °C.
3.3. Dimerisation at mM concentration
These stability experiments were only performed in the case of
the benzosuberone 4. We found that, in aqueous solution at pH 7.5,
it precipitated with a half-time of ca 1 h at a concentration of
2.5 mM. The 1H NMR spectrum in CDCl3 of this precipitate was
similar to the starting isomer 4 but with a clear loss of the coupling
J(7,NH). It was in agreement with the dimeric structure 33a
(Scheme 6). The axial position of the tertiary protons H-6a and
H-14a, characterised by a large coupling with one of the neigh-
bouring protons, corresponded rather to a trans-arrangement in
which the dihydropyridazine ring was in a more stable half-chair
4.2. Silyloxy-ketone 16 and bromo-ketone 24
For these 6-substituted compounds, the coupling values be-
tween H-6 and methylene H-5 protons gave the conformational
position of these substituents (Fig. 1).
Table 1
Hydration ratio and deuteration rates for amino-benzocyclanones (as hydrochlorides) at pH 6
Ring B
Compound
Ketone/hydrate ratio
Protons exchanged
Deuteration half-time
a
c
20 °C
60 °C
5
6
2
1
60/40
80/20
Ha-3
Hb-3
14 d
14 d
7 h
3 h
6 h
25 d
H H
α
β
O
H-1
H-3
γ
H
Hb-1
Ha-1
NH2
n
52 h
1 n = 1
2 n = 0
4 n = 2
7
7
4
80/20
ndb
Ha-5
Hb-5
31 h
44 h
12 d
H-7
H-7
4a (pH 7.5)
Ha-5
3 h
>10 hc
a
b
c
For compound 4 the deuteration rate was also determined at pH 7.5 in Hepes or Tris buffers.
nd: not determined.
Deuteration of H-7 for compound 4 is slower than the observed dimerisation (see next section). 10 h represents the duration of the experiment.

S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
1439
tion with equatorial substituents was ascertained by X-ray struc-
ture determination.
R
R
H
N
N
pH 7.5
H2O
R
In the case of the benzocycloheptenes 3 and 4, the large value
J(5b,6) = 10.0 Hz for 3 showed a clear trans–trans diaxial relation-
ship between these two protons. For 4 the large value of the pro-
ton–proton couplings between H-7, H-8 and H-9 protons
(J(7,8b) = 12.0 Hz, J(8b,9a) = 9.5 Hz) showed clearly a trans–trans
diaxial relation between H-7 and Hb-8 and between Hb-8 and
Ha-9. Thereof, the amino group of the amino-benzocycloheptenon-
es 3 and 4 was in equatorial position. In all the compounds, the
conformation was also directed by an hydrogen bond between
amine and ketone groups.
In the case of the hydrate forms of 1 and 4, the situation was not
so simple. For the amino-tetralone 1, the values of the corresponding
couplings J(3,4a) = 5.8 Hz, J(3,4b) = 8.2 Hz indicated here an
equilibrium between both the possible chair conformations. By
contrast, the similar values of the couplings between H-7 and
CH2(8) with those of the ketone form were in agreement with
the same conformation of the hydrate form for the amino-benzocy-
cloheptenone 4 and its ketone form.
4
R
H
R
R
33a R = H
b R =OMe
R
R
6
N
4
[O]
N
N
R
1
R
N
14
R
R
35
34a R = H
b R =OMe
Scheme 6.
O
Hb
2
NH2
3
4
H
1
5. Aminopeptidase inhibition and discussion
H
O
6
NH2
Hb
6
NH2
All compounds were evaluated as racemic mixtures. All active
compounds behaved as competitive inhibitors of the panel amino-
peptidases. The inhibition parameters (Ki or IC50) are reported in
Table 2.
The amino-tetralone 1 was previously described as a selective
competitive inhibitor of the ‘one zinc’ subfamily of M1 metallo-
aminopeptidases whereas bestatin is much more potent on the
‘two zincs’ M17 family of enzymes.18,19 These two compounds
were here used as reference inhibitors. Our strategy for the design
of novel amino-tetralone analogues focused on investigating more
constrained as well as more flexible derivatives, while also probing
the position and nature of the functional groups.
5 H
O
7
8
H
H
H
Hb
9
Ha
4
3
H
Br
6
6
OSiMe3
O
H
H
Hb
O
Ha
H
O
16
24
H
Hb
6
OH
7
NH2
5.1. Structural requirement
5
8
NHBoc
H
MeO2C
4
5.1.1. Modification of the tetralone scaffold
The five-membered ring amino-indanone 2 (Ki 20 lM), the most
conformationally-constrained analogue in our series of com-
5
Ha
Ha
9
H
36
trans-18
pounds, is 40 times less active against APN than the corresponding
Figure 1.
amino-tetralone 1 (Ki 0.5 l
M).18 Nevertheless 2 remained a highly
selective inhibitor of APN. Indeed we did not observe any inhibi-
tion of the mammalian ‘two zincs’ enzyme LAPc with up to
1 mM of compound 2. LTA4H, an enzyme with aminopeptidase
activity structurally related to APN, is not even inhibited by ami-
no-tetralone 1, suggesting that zinc-chelation is more difficult to
achieve for LTA4H than for APN, a more typical aminopeptidase,
presumably as a result of steric hindrance. In contrast, we observed
weak inhibition of the ‘two-zincs’ bacterial enzyme APaero (Ki
For the bromo-compound 24, the equatorial–equatorial relation
of H-6 and Hb-5 (J(5b,6) = 7.8 Hz) corresponded to the axial posi-
tion of the bromine atom. This was supported by the strong desh-
ielding of 0.5 ppm of the spatially near axial Ha-8, which was in
trans-diaxial relation with Hb-9 (J(8a,9b) = 11.0 Hz).
For the silyloxy-compound 16, by contrast, a trans-diaxial rela-
tion of H-6 and Ha-5 (J(5a,6) = 10.2 Hz) corresponded to the equa-
torial position of the silyloxy substituent.
150 lM).
The seven-membered aminobenzocycloheptenone 4, with a
higher conformational flexibility, appeared to be the most
interesting compound in our series. It was almost equipotent to
4.3. Conformation of the amino-ketones
the parent compound 1 (Ki 1 lM) on APN. Moreover we observed
The conformation of amino-ketones was determined by NMR in
the case of the aminotetralone 1 and aminobenzocycloheptenone 4
in D2O (Fig. 1) by a careful analysis of the proton–proton couplings
in 1H NMR spectra. In the first case, a clear trans-diaxial coupling
a remarkable selectivity against our panel of aminopeptidases,
since none of them was inhibited in presence of up to 1 mM con-
centration of 4.
(J(3,4b) = 13.2 Hz) for the H-3 proton in the a-position of the ami-
no group of 1 corresponded to a strictly equatorial position of this
amino group in a chair conformation, the coupling value with the
equatorial H-4 proton J(3,4a) being relatively large (6.4 Hz). Similar
coupling values (J(4,5trans) = 11.8 Hz, J(4,5cis) = 5.6 Hz) were
found for the amido-cyclohexanone 3650 whose chair conforma-
5.1.2. Key roles of the carbonyl and primary amine groups
Structural requirements for APN inhibition were previously
determined in the tetralone series.19 It was shown that the primary
amine and the carbonyl group were essential features for activity.
Here again, we confirm that these functional groups are key

1440
S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
Table 2
Inhibition data of aminopeptidase activity by the synthesised amino-ketones 1-5, oxime 14 and amino-alcohols cis-18 and trans-18a
Compound
APN (EC 3.4.11.2)
LAPc (EC 3.4.11.1)
LTA4H (EC 3.3.2.6)
APaero (EC 3.4.11.10)
Bestatin
1
2
3
4
5
14
3.5
0.0005
120
>1000
>1000
>1000
>100
>1000
nd
>1000
0.5
0.0016
130
150
>1000
900
350
15
nd
>1000
0.5b
20b
>1000
1b
>1000
>1000
>1000
>1000
nd
>1000
nd
nd
310
110
300
60b
trans-18ꢁHCl
cis-18ꢁHClc
All substances were evaluated as racemic mixtures. IC50
enzyme (see Section 7). Inactive compounds were tested up to their solubility limit under the assay conditions that is, 1 mM. Ki values (
(
l
M) values were determined from Dixon plots at a substrate concentration set to the Km value for the corresponding
M) were determined from Dixon
l
plots. LAPc: cytosolic leucine aminopeptidase from bovine lens (EC 3.4.11.1), APN: human aminopeptidase-N (EC 3.4.11.2); APaero: Aeromonas proteolytica aminopeptidase
(EC 3.4.11.10) and LTA4H: human leukotriene A4 hydrolase (EC 3.3.2.6).
a
IC50
(
l
M), nd: not determinated.
M).
Containing 10% of trans-isomer.
b
c
Ki (l
pharmacophores, and, in addition, show that their positioning is
also crucial. The three derivatives 1, 2 and 4 bearing the ketone
and the primary amine in positions b and c, respectively, of the benzo
group, are specific inhibitors of APN with potencies in the low
micromolar range, irrespective of the size of the B cycle. In sharp
contrast, when the positions of these functional groups were
swapped, like in compound 3 of the seven-membered ring series,
the inhibitory potency was totally lost. Our data also further
emphasise the requirement for a ketone functional group. When
this latter was replaced by an oxime moiety or an alcohol function,
a dramatic drop in potency was observed (compound 14 (Ki
110
lM), compound cis-18 (Ki 60
lM) or trans-18 (Ki 300 lM) ver-
sus compound 4 (Ki 1
l
M)). This result suggests that the ketone
moiety plays an important role, most likely in coordinating the ac-
tive site zinc, and that this role is only poorly fulfilled by the oxime
or alcohol functions. As discussed before, compound 4 is readily
hydrated in solution and, therefore, the higher potency afforded
by the ketone functionality could originate from the binding of
the hydrated form. This latter has the potential to be a close mimic
of the transition state formed during the nucleophilic attack of the
scissile bond carbonyl by the zinc-activated water/hydroxide ion.
Figure 2. Enzyme assays were run at 25 °C in 20 mM Tris–HCl buffer pH 7.5, with
leucine-para-nitroanilide (0.2 mM) as substrate, in a total reaction volume of 1 ml.
The formation of para-nitroaniline was followed at 405 nm
(ꢀ = 10,800
molꢀ1 L cmꢀ1). The reaction was started by addition of 3 milliunits of porcine
kidney AP-N. Under these experimental conditions linear kinetics were observed for
at least 10 h. Dotted line A corresponds to control (no inhibitor; Vo = 6.8 nmol hꢀ1).
In experiments B and C 2 lM of 1 and 2 lM of 4, respectively, were used. In
experiment B, 60% of inhibition (Vi = 3.1 nmol hꢀ1) was observed during the first
hour. After 8 h, the enzyme activity was back to control (Vi = Vo = 6.5 nmol hꢀ1). In
contrast, 60% inhibition (Vi = 3.1 nmol hꢀ1) was observed throughout experiment C.
5.1.3. Monocyclic amino-suberone 5
The loss of the aromatic A cycle led to a dramatic decrease in the
inhibitory potency (Table 1). This effect confirmed the importance
of this aromatic part in the recognition of the inhibitors by the
enzyme.
members of the M1 family of peptidases have already been
solved.21–23,51–54 All these enzymes are dependent on a single zinc
ion for their activity and remove the amino terminal residue of
polypeptides. The structural data show that their active site is re-
lated to the metallo-endoproteinase thermolysin,54 including in
particular the consensus zinc binding motif (HEXXH-(X18)-E),
but with an additional recognition motif, the exopeptidase motif
(GXMEN), for binding the free primary amino group of the N-ter-
minal residue of their peptidic substrates. An example is given in
5.2. Stablity of the amino-benzosuberone 4 under enzyme assay
conditions
We showed here above that the amino-benzocycloheptenone 4
was less prone to proton exchange in position
a
to the carbonyl
Figure 3 with a partial sequence alignment of the human
group, in comparison to the five- and six-membered ring deriva-
tives 1 and 2. We have further investigated the stability of this
scaffold under our enzyme assay conditions. We observed that
inhibition was maintained during at least 10 h while the inhibition
by the amino-tetralone derivative 1 levelled off after about 2 h, as
already reported19 (Fig. 2). This result was in agreement with the
stability observed through previously deuteration experiments.
We have already noted that the dimerisation of 4 clearly did not
occur at the micromolar concentrations used in the enzyme assay.
(P15144) and E. coli (P04835) APNs.
Although the one-zinc aminopeptidases of known three-dimen-
sional structure share little overall amino acid sequence similarity,
they display remarkable structural conservation, including a com-
mon fold and a highly conserved active site. Interestingly, the
three-dimensional fold of aminopeptidases with a binuclear metal
centre, such as LAPc, is totally different56,57 (pdb entries 1BPN,
2EWB). This structural segregation rules out the possibility of a
common ancestor for the super-family of zinc-dependent
aminopeptidases.
5.3. Potential binding mode
The structural homology of the mammalian APN to the micro-
bial enzymes of known 3D structure, inferred from the presence
of characteristic sequence motifs, is confirmed by HHPRED58 anal-
ysis, one of the most powerful structure prediction algorithm
To date, no three dimensional structure is available for a
mammalian APN. Nevertheless the crystal structures of several

S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
1441
Figure 3. Partial sequence alignment of the human (P15144, black) and the E. coli (P04835, blue) APNs around the active site region. The alignment was produced with the
55
program LALIGN
.
currently available. The remote homology to thermolysin from Bacillus
thermoproteolyticus around the active site (amino acids 310–530) is
detected by HHPRED, and, more interestingly, structural homology
spanning over 800 amino acids is detected at the 100% confidence
level with four PDB entries (release January 2010): 1Z5H (Tricorn
interacting factor F3 from Thermoplasma acidophilum), 3EBH (Plas-
modium falciparum M1 neutral aminopeptidase), 3B34 (E. coli ami-
nopeptidase-N), 2gtq (Neisseria meningitidis aminopeptidase-N)
(Fig. 4). The structural homology to human LTA4 (3B7S, amino
acids 70–770) is also detected at the highest confidence level,
underscoring the relevance of this enzyme for the assessment of
the selectivity of our novel inhibitors.
Based on the predicted structural similarity, we have derived a
working model of the binding of the amino-benzosuberone 4, in its
hydrated and non-hydrated forms, to the human APN active site
zinc. To this end, we used the X-ray structure of the E. coli APN,
ePepN,21 in complex with bestatin, and focused on the conserved
residues involved in substrate recognition, zinc binding and
catalysis. Although we do not know which enantiomer is the active
species, we assumed that the amino group was in equatorial posi-
tion, in order to best match the binding mode observed with best-
atin. We then superimposed the primary amino groups of 4 and
bestatin, and either the ketone or the cis-hydroxyl group of the hy-
drate form of 4 with the hydroxyl functionality of bestatin (Fig. 5).
Both proposed binding modes account for the observation that the
positions of the primary amine and carbonyl pharmacophores are
crucial for inhibitory activity and cannot be interchanged. The pri-
mary amine of 4 is engaged in strong electrostatic interactions
with the side-chain carboxylate of Glu121 and Glu264 (ePepN
numbering scheme), fully conserved in the one-zinc family of ami-
nopeptidases and responsible for the recognition and binding of
the free amino terminus of peptidic substrates. In the case of the
non-hydrated form of the ketone, the ketone oxygen binds to the
zinc ion in a way similar to that proposed for the scissile amide car-
bonyl of a peptide substrate. In the case of the hydrated form, both
hydroxyl groups contribute binding interactions. The cis-hydroxyl
one is part of the zinc coordination sphere, and can be viewed as
a mimic of the nucleophilic zinc-bound water involved in catalysis.
The trans-hydroxyl group occupies the position of the substrate
amide carbonyl oxygen following the formation of the tetrahedral
transition state. This hydroxyl makes a hydrogen-bonded interac-
tion to the side-chain of Glu298 (ePepN numbering scheme).
Indeed, we observed a reduced potency of the trans-isomer versus
the cis-isomer, and a synergistic effect with the hydrated ketone.
Figure 4. The human APN sequence (966 residues) was used as template (black bar). Reported here are only the top scoring hits identified by HHPRED in the January 8, 2010
release of the PDB (probability of structural homology: red, 100%; orange, 94–95%). PDB entries: 1Z5H (Tricorn interacting factor F3 from Thermoplasma acidophilum), 3EBH
(Plasmodium falciparum M1 neutral aminopeptidase), 3B34 (E. coli aminopeptidase-N), 2GTQ (Neisseria meningitidis aminopeptidase-N), 3B7S (Human leukotriene A4
hydrolase), 3CIA (Cold-active aminopeptidase from Colwellia psychrerythraea), 2TMN (Bacillus thermoproteolyticus thermolysin).
Figure 5. Schematic model of the binding interactions of amino-benzosuberone 4 to the catalytic zinc. Note: one enantiomer of 4 was arbitrarily chosen. (A) overlay with
bestatin bound to the E. coli APN (pdb entry 2HPT, Web LaB viewer Pro, Accelrys). The primary amino groups of both inhibitors and the carbonyl and hydroxyl groups of 4 and
bestatin, respectively, were used as anchoring points. (B) Schematic model showing the key interactions of the hydrated form of 4, which mimics the transition state
intermediate formed during peptide bond hydrolysis.

1442
S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
The seven-membered ring of compound 4 adopts chair confor-
Reagents and solvents. Raney-nickel, aqueous suspension and 5%
Pd/C were obtained from Fluka, other reactants were purchased
from usual furnisher. Dess–Martin periodinane (DMP) was pre-
pared according to25 or obtained in CH2Cl2 solution, and titrated
by oxidation of benzyl alcohol with NMR monitoring. tert-Butyl ni-
trite was prepared according to lit.60 Usual solvents were freshly
distilled, dry EtOH and MeOH distilled over Mg/MgI2, dry THF over
Na and benzophenone, dry Et2O was distilled and stored over Na,
CH2Cl2 was distilled over P2O5 and kept over Na2CO3. NEt3 and Si-
Me3Cl were distilled before use.
mation49 but the twisted conformation is of similar energy (within
1 kcal/mol). While the relative conformational versatility of this
scaffold may contribute to a more optimal fit of the inhibitor to
the enzyme active site and is therefore of advantage, it is difficult
to predict which is the biologically active absolute configuration
and associated conformation of this new class of APN inhibitors.
Furthermore, the observation that the phenylalanine side-chain
of bestatin has the configuration of
substrates have the L-configuration, indicates that amino-pepti-
dases do not strongly discriminate diastereoisomers at the C- po-
a-D-amino acid, while peptide
a
sition of the amino terminal residue. Therefore, the development of
a more refined model for the binding of 4 to the APN active site
must await the provision of detailed structural information on a
mammalian APN.
7.1. Indanone series
7.1.1. (1R,2S)-1-(tertio-Butyloxycarbonylamino)indan-2-ol ((ꢀ)-
7b)
To a solution of (+)-7a (400 mg, 2.68 mmol) in MeOH (10 mL)
was added Boc2O (662 mg, 3.0 mmol, 1.1 equiv). After 3–5 h stir-
ring at room temperature, the solvent was evaporated and the res-
idue (0.9 g) recrystallised in cyclohexane to give pure (ꢀ)-7b
(634 mg, 98%) as colorless crystals, mp = 77–79 °C [lit.24 for the
6. Conclusion
Mammalian APN appears to be involved in numerous and
complex biological functions, but it has not been possible up to
now to fully clarify which of its functions depend on its enzymatic
activity and which do not. The development of highly specific and
potent human APN inhibitors would greatly help shed light on the
exact involvement of APN in a number of physiological and path-
ological processes, with potential pharmaceutical applications,
notably in oncology and other, angiogenesis-dependent patholo-
gies.9–12 The main interest of 3-amino-2-tetralone was its high
selectivity for the ‘one zinc enzymes’ and particularly APN
whereas bestatin remained the best inhibitors to date for the
‘two zincs’ aminopeptidase sub-family.18,19 We successfully iden-
tified in this work the amino-benzosuberone scaffold as an ami-
no-tetralone analogue exhibiting greatly improved stability as
well as promising potency and a remarkable selectivity profile.
This compound is readily hydrated in aqueous solution. The ob-
served SAR strongly suggests that the active species is the hy-
drated form, which shares many structural features with the
transition state formed during the hydrolysis of a peptidic sub-
strate. In view of its minimal size, this compound displays an
excellent ligand efficiency (0.63 according to the definition by
Hopkins et al.59) and has therefore strong potential for further po-
tency and selectivity improvements through continued chemical
elaboration and derivatisation. The working model presented here
provides a basic understanding of how this class of compound
may bind to the catalytic zinc of APN, and may thus provide guid-
ance for further medicinal chemistry efforts.
(1S,2R)-enantiomer, mp 76.1–76.8 °C], ½a D20
ꢂ
= ꢀ13 (c 1, CHCl3). 1H
and 13C NMR (CDCl3) data were identical with those reported in
the lit.24
7.1.2. (1R)-(tertio-Butyloxycarbonylamino)-indan-2-one ((ꢀ)-8)
To a solution of (ꢀ)-7b (320 mg, 1.34 mmol) in CH2Cl2 (7 mL) at
0 °C was added DMP (0.46 M in CH2Cl2, 4.2 mL, 1.93 mmol,
1.4 equiv). After 2 h stirring at 0 °C, AcOEt (20 ml) and an aqueous
solution of 0.5 N sodium thiosulfate in 1 N NaHCO3 (20 mL) were
added to the reaction mixture. After 1 h stirring at rt, the organic
layer was successively washed with aqueous 1 N NaHCO3
(10 mL) and with brine (10 mL), dried (MgSO4) and evaporated.
Purification of the residue by flash chromatography (Cyclohex-
ane/AcOEt 8:2) gave (ꢀ)-8 (227 mg, 69%) as a colorless resin,
½
a 2D0
ꢂ
= ꢀ15 (c 1.1, CHCl3). IR (KBr): 3372, 2974, 1768, 1698, 1508,
1366, 1322, 1253, 1169, 1152, 1049, 1027, 904, 757, 747,
738 cmꢀ1 1H NMR (CDCl3): 1.48 (s, 9H, tBu); 3.54 and 3.66 (2 d,
.
2H, J = 21.6 Hz, H-3); 5.08 (br d, 1H, J = 8.0 Hz, H-1); 5.22 (br d,
1H, J = 8.0 Hz, NH); 7.32 (m, 3Har); 7.42 (m, 1Har). 13C NMR
(CDCl3): 28.4 (CMe3); 41.6 (C(3)); 59.8 (C(1)); 80.6 (CMe3); 124.7,
125.1, 128.1, 128.7 (4Car); 136.0, 139.2 (C(3a),C(7a)); 156.1
(NCO2); 212.4 (C(2)). Anal. Calcd for C14H17NO3 (247.30): C,
68.00; H, 6.93; N, 5.66. Found: C, 67.8; H, 7.1; N, 5.5.
7.1.3. 1-Aminoindan-2-one, hydrochloride (2)
A solution of 8 (158 mg, 0.64 mmol) in a mixture of 2.2 N HCl in
dry Et2O (1.2 mL) and dry dioxane (1.2 mL) was stirred for 3 days at
rt. The precipitate was isolated by filtration or centrifugation,
washed with dry Et2O, and recrystallised in iPrOH/Et2O to give 2
(80 mg, 69%) as ochre crystals, mp 198–201 °C. IR (KBr): 3421,
7. Experimental part
General. Flash chromatography (FC): silica gel (Merck 60, 230–
400 mesh). TLC: Al-roll silica gel (Merck 60, F254). Mp: Kofler hot
2975–2863, 1774, 1759, 1599, 1498, 1478, 1085, 743 cmꢀ1 1H
.
bench, corrected. IR spectra (m a]D: Per-
in cmꢀ1): Nicolet 405 FT-IR. [
NMR (D2O, 60:40 mixture of ketone and hydrate). Ketone: 3.92
and 3.70 (2 d, 2H, J = 22.9 Hz, H-3); 5.18 (s, 1H, H-1); 7.30–7.60
(m, 4Har). Hydrate: 3.29 and 3.38 (2 d, 2H, J = 16.9 Hz, H-3); 4.52
(s, 1H, H-1); 7.30–7.60 (m, 4Har); 1H NMR (CD3OD, 27:35:38 mix-
ture of ketone and 2 hemiacetals). Ketone: 3.87 and 3.60 (2 d, 2H,
J = 22.2 Hz, H-3); 5.06 (s, 1H, H-1); 7.3–7.6 (m, 4Har). Hemiacetal
1: 3.17 and 3.38 (2 d, 2H, J = 16.1 Hz, H-3); 4.39 (s, 1H, H-1);
7.3–7.6 (m, 4Har). Hemiacetal 2: 3.31 (s, 2H, H-3); 4.54 (s, 1H, H-
1); 7.3–7.6 (m, 4Har). 13C NMR (CD3OD), ketone: 42.3 (C(3)); 58.1
(C(1)); 131.3, 129.3, 128.6, 125.7 (4CHar)); 139.0, 135.4
(C(3a),C(7a)); 209.3 (CO(6). 2Hemiacetals: 43.3, 41.6 (2 C(3));
63.6, 61.5, (2 C(1)); 106.0, 105.4 (2 C(2)); 131.28, 130.9, 128.5,
126.9, 126.8, 126.7, 126.6, 126.1, (8CHar)); 142.8, 142.1, 137.3,
137.1 (4Car). HR-MS (TOF ESI), calcd for C9H10ON [M+H]+:
148.0762. Found: 148.0764.
kin–Elmer 341 LC polarimeter. 1H and 13C NMR (400 and
100.6 MHz resp.) spectra: Bruker Avance 400 at 295 K unless other-
wise noted, tetramethylsilane (TMS), or natrium (D4)-trimethyl-
silyl-propionate (D4-TSP) in D2O (1H NMR) and CDCl3, or MeOD-
D4 [d(CDCl3) = 77.0, d(CD3OD) = 35.0 with respect to TMS] (13
C
NMR) as internal standard; d in ppm and J in Hz. 1H NMR spectra
in 2 N HCl in H2O were recorded with external deuteriated lock
and irradiation of the H2O peak, acetone at d 2.22 ppm as internal
standard. High resolution MS were measured on a Bruker MicrOTof
spectrometer in Institut de Chimie, UMR 7177 CNRS, ULP, Stras-
bourg, or Agilent Technologies 6510 (QTof) spectrometer in FRE
3252 CNRS, UHA, Mulhouse, France, or in Basilea Pharmaceutical
Ltd, CH-Basel. Microanalyses were carried out by the Service Central
de Microanalyses du CNRS, F–69390 Vernaison, France.

S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
1443
7.2. Tetralone series
J(8b,9a) = 13.0, J(9a,9b) = 14.2 Hz. 13C NMR (CDCl3): 28.6, 29.0
(C(5),C(9)); 35.0 (C(8)); 47.3, 48.0 (2 OMe); 50.1 (C(5)); 104.0
(C(7)); 126.3, 127.0, 128.4, 131.5 (4CHar); 136.2, 142.1 (2Car).
HR-MS (ESI+) Calcd for C12H16NO [MꢀOMe]+: 190.1226; found:
7.2.1. 3-Amino-3,4-dihydro-1H-naphtalen-2-one, hydrochloride
(1)
Preparation of 1 was achieved from 1,4-dihydronaphtalene
according to the literature.18b,19 Colorless crystals, mp 180–
200 °C (dec.). 1H NMR (D2O, 80:20 mixture of ketone and hydrate).
Ketone: 3.30 (dd, 1H, J = 13.2, 15.0 Hz, Hb-4); 3.47 (dd, 1H, J = 6.4,
15.0 Hz, Ha-4); 3.89 and 3.98 (2 d, 2H, J = 21.9 Hz, H-1); 4.40 (dd,
1H, J = 6.4, 13.2 Hz, H-3); 7.18–7.26 (m, 2Har); 7.33 (m, 3Har); Hy-
drate: 3.06 (dd, 1H, J = 8.2, 16.8 Hz, Hb-4); 3.35 (dd, 1H, J = 5.8,
16.8 Hz, Ha-4); 3.19 and 3.23 (2 d, 2H, J = 18.4 Hz, H-1); 3.67 (dd,
1H, J = 5.8, 8.2 Hz, H-3); 7.18–7.26 (m, 2Har); 7.33 (m, 2Har). 1H
NMR (CD3OD): 3.22 (t, Hb-4); 3.40 (dd, Ha-4); 3.81 (d, 1H, Hb-1);
3.94 (d, 1H, Ha-1); 4.28 (dd, 1H, H-3); 7.23 (m, 1Har); 7.28 (m,
190.1227. Calcd for
222.1484.
C
13H20NO2 [M+H]+: 222.1489; found:
Compound 3: colorless crystals, mp 210–220 °C (dec). IR (KBr):
3367, 2970, 2719, 2624, 1720, 1600, 1486, 1448, 1154, 1055, 772,
761, 754, 718, 476 cmꢀ1 1H NMR (D2O): 2.69 (dt, 1H, J = 3.3,
.
12.4 Hz, Hb-8); 2.90 (m, 2H, Ha-8, Hb-9); 3.08 (ddd, 1H, J = 3.3,
7.0, 15.4 Hz, Ha-9); 3.21 (m, 2H, CH2(5)); 4.24 (dd, 1H, J = 4.5,
9.8 Hz, H-6); 7.28 (m, 1Har); 7.37 (m, 3Har). 13C NMR (D2O):
29.7 (C(9)); 35.0 (C5)); 42.8 (C(8)); 59.6 (C(6)); 128.3, 129.1,
130.0, 130.7 (4CHar); 135.3, 141.3 (2Car); 207.8 (CO(7)). HR-MS
(TOF ESI) calcd for [M+H]+ (C11H14NO): 176.1075; found: 176.1072.
3Har);
J(1a,1b) = 21.4,
J(3,4a) = 6.4,
J(3,4b) = 13.1,
J(4a,4b) = 14.9 Hz.
7.3.4. 6-Hydroxyimino-8,9-dihydro-5H-benzocyclohepten-7-
one (12)
7.3. Benzosuberone series
A biphasic solution of 10 (0.30 g, 1.27 mmol) in Et2O (5 ml) and
aqueous 6 N HCl (5 ml) was stirred at 0 °C for 15 min and poured in
aqueous N NaHCO3 (30 ml) and ice. The mixture was extracted
with Et2O, the organic phase washed with aq N NaHCO3, dried
(SO4Mg) and evaporated. Pure 12 (173 mg, 72%) was obtained by
flash chromatography (Cyclohexane/AcOEt 8:2), yellow crystals,
mp 153–154 °C (iPrOH) [lit.29 151–153 °C (benzene)]. IR (KBr):
3282, 2954, 1683, 1583, 1460, 1427, 1411, 1395, 1266, 1095,
7.3.1. 5,6,8,9-Tetrahydrobenzocycloheptene-7-one (9)
Preparation of 9 was achieved from a,a’-dibromoxylene accord-
ing to26–28 overall yield 81%. Colorless crystals, mp 40 °C (pentane)
(lit.27 41–42 °C, lit.26 43–43.8 °C). IR (CHCl3): 2950, 1690, 1450,
1090 cmꢀ1 1H NMR (CDCl3): 2.62 (m, 4H, CH2(6), CH2(8)); 2.91
.
(m, 4H, CH2(5), CH2(9)); 7.23 (s, 4Har). 13C NMR (CDCl3): 30.5
(C(5),C(9)); 44.6 (C(6),C(8)); 127.1 (C(2), C(3)); 129.1 (C(1),C(4));
140.5 (C(4a),C(9a)); 211.3 (C(7)).
979, 956, 938, 917, 889, 865, 770, 713 cmꢀ1 1H NMR (CDCl3):
.
2.87 (m, 2H, CH2(8)); 3.10 (m, 2H, CH2(9)); 4.03 (s, 2H, CH2(5));
7.23 (m, 4Har); 8.50 (br s, NOH). 13C NMR (CDCl3): 28.6 (C(5));
31.0 (C(9)); 43.7 (C(8)); 127.5, 128.0, 128.6, 130.2 (C(1), C(2),C(3),
C(4)); 133.2 (C(4a)); 139.9 (C(9a)); 156.8 (C(6)); 199.0 (C(7)).
7.3.2. 8,9-Dihydro-6-hydroxyimino-5H-benzocycloheptene-7-
one, 7-dimethylacetal (10)
Preparation according to29: To a stirred solution of 9 (1.0 g
6.24 mmol) in 2 M HCl in MeOH (13 ml) was added dropwise at
0 °C in ice bath tBuONO (1.1 m, 9.3 mmol, 1.5 equiv). After 1 hour,
the solution was poured in aqueous N NaHCO3 (30 ml) and ice. The
precipitate was isolated by filtration, washed with water and dried
on P2O5 under vacuum or washed with iPrOH, to give 10 (0.90 g,
61%). A second crop (70 mg, 5%) was obtained by extraction with
AcOEt of the aqueous phase. Colorless crystals, mp 194–198 °C
then 202–4 °C (MeOH) (lit.29 195–7 °C). IR (KBr): 3213, 2952,
2829, 1737, 1698, 1489, 1455, 1423, 1235, 1155, 1135, 1099,
7.3.5. 7-Benzylamino-5,7,8,9-tetrahydrobenzocyclohepten-6-one,
oxime (13a)
To a solution of 12 (2.32 g, 12.3 mmol) in pyridine (7 ml) at 0 °C
was added benzylamine (1.35 ml, 12.4 mmol, 1 equiv) and the red
solution stirred at rt for 6 h. Anhydrous MeOH (7 ml) was then
added, then NaBH4 (0.55 g, 14.5 mmol, 1.2 equiv) and the mixture
was vigorously stirred for 1 h. It was then poured in aqueous N
NaHCO3 (45 ml) filtered and the precipitate washed with water
and dried under vacuum, to give 13a (3.18 g, 93%), cream crystals,
mp 144–146 °C (EtOH). IR (KBr): 3145, 3027, 2842, 1640, 1490,
1090, 1058, 1041, 989, 951, 938, 925, 888, 781, 753, 728 cmꢀ1
.
1H NMR (CDCl3): 2.07 (m, 2H, CH2(8)); 2.91 (m, 2H, CH2(9)); 3.30
(s, 6H, 2 OMe); 3.73 (s, 2H, CH2(5)); 7.10–7.13 (m, 3Har); 7.32 (d,
1Har); 7.46 (br s, NOH). 13C NMR (CDCl3): 29.3, 29.6 (C(5),C(9));
36.5 (C(8)); 49.0 (2 OMe); 101.7 (C(7)); 126.6 (C(2),C(3)); 128.9,
129.8 (C(1),C(4)); 135.2 (C(4a)); 141.0 (C(9a)); 155.4 (C(6)). Anal.
Calcd for C13H17NO3 (235.29): C, 66.36; H, 7.28; N, 5.95. Found:
C, 66.3; H, 7.5; N, 5.9.
1475, 1455, 1374, 1116, 965, 870, 852, 763, 747, 724, 699 cmꢀ1
.
1H NMR (CDCl3): 1.85 (dddd, Hb-8); 2.07 (dddd, Ha-8); 2.65
(ddd, Hb-9); 3.14 (ddd, Ha-9); 3.50 (dd, H-7); 3.67 (d, J = 12.9 Hz,
CHa(Bn)); 3.72 (d, Hb-5); 3.81 (d, J = 12.9 Hz, CHb(Bn)); 3.95 (d,
Ha-5); 7.14 (m, 3Har); 7.32 (m, 6Har); J(5a,5b) = 14.3,
J(7,8a) = 4.8,
J(7,8b) = 6.4,
J(8a,8b) = 13.6,
J(8a,9a) = 10.8,
J(8b,9a) = 2.6, J(8a,9b) = 2.9, J(8b,9b) = 7.2, J(9a,9b) = 14.4 Hz. 13C
NMR (CDCl3): 30.1, 30.9 (C(5), C(9)); 35.2 (C(8)); 51.7 (NCH2);
60.1 (C(7)); 126.6, 126.8, 126.9 (Car-p,C(2),C(3)); 128.2, 128.3
(Car-o, Car-m); 129.0, 129.7 (C(1),C(4)); 133.2 (C(4a)); 140.2,
141.3 (C(9a), Car-s); 159.1 (C(6)). Anal. Calcd for C18H20N2O
(280.37): C, 77.11; H, 7.19; N, 9.99. Found: C, 77.3; H, 7.4; N, 10.0.
7.3.3. 6-Amino-5,6,8,9-tetrahydrobenzocycloheptene-7-one, 7-
dimethylacetal (11) and 6-amino-5,6,8,9-
tetrahydrobenzocycloheptene-7-one, hydrochloride (3)
Acetal 10 (40 mg, 0.17 mmol) was hydrogenolysed in EtOH
(1.7 ml) with concentrated aqueous NH4OH (0.12 ml, 1.7 mmol)
over wet Raney-Nickel (400 mg) for 6 h at rt. The catalyst was dis-
carded by filtration on celite or by centrifugation and the solution
evaporated to give 11 (36 mg, 95%). Crude amine 11 was hydroly-
sed by stirring in aqueous N HCl (1.8 ml) and EtOH (0.7 ml) for 6 h.
Evaporation of the solvents and washing with dry Et2O gave crys-
talline 3 (30 mg, 90%).
7.3.6. 7-Amino-5,7,8,9-tetrahydrobenzocyclohepten-6-one, 6-
oxime hydrochloride (14)
Compound 13a (100 mg, 0.36 mmol) was hydrogenolysed at rt
in EtOH (3 mL) and 1 N aqueous HCl (0.36 ml) over 5% Pd/C
(7 mg) for 13 h. The catalyst was discarded by centrifugation and
the solvent evaporated. The crude product was recrystallised in
iPrOH/Et2O to give pure 14 (60 mg, 75%). Colorless crystals, mp
270–280 °C (iPrOH/Et2O). IR (KBr): 3297, 3016, 2946, 2451, 1581,
1554, 1491, 1448, 1427, 1046, 977, 936, 925, 763, 755, 720,
Compound 11, colorless resin. 1H NMR (CDCl3): 1.54 (dd, 1H,
Hb-8); 2.05 (dd, 1H, Ha-8); 2.55 (dd, 1H, Hb-9); 2.81 (dd, 1H, Ha-
9); 2.87 (dd, 1H, Hb-5); 3.23 (s, 3H, OMe); 3.28 (d, 1H, Ha-5);
3.34 (d, 1H, H-6); 3.30 (s, 3H, OMe); 7.10–7.18 (m, 4Har);
450 cmꢀ1
.
1H NMR (CD3OD): 1.66 (dddd, 1H, Hb-8); 2.41 (dddd,
J(5a,5b) = 14.4,
J(5b,6) = 6.8,
J(8a,8b) = 14.8,
J(8a,9b) = 7.2,
1H, Ha-8); 2.93 (ddd, 1H, Hb-9; 3.04 (ddd, 1H, Ha-9); 3.42 (d, 1H,

1444
S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
Hb-5); 4.01 (dd, 1H, H-7); 4.23 (d, 1H, Ha-5); 7.18 (m, 3Har); 7.26
(m, 1Har); J(5a,5b) = 15.2, J(7,8a) = 5.4, J(7,8b) = 11.6, J(8a,8b) =
12.6, J(8a,9a) = 3.4, J(8a,9b) = 8.6, J(8b,9a) = 9.0, J(8b,9b) = 3.4,
J(9a,9b) = 14.6 Hz. 13C NMR ((CD3OD): 31.3, 32.7 (C(5),C(9)); 35.8
(C(8)); 55.2 (C(7)); 128.0, 128.2 (C(2),C(3)); 130.0, 130.8
(C(1),C(4)); 136.1 (C(4a)); 141.5 (C(9a)); 155.6 (C(6)). HR-MS
(FAB+) calcd for [M+H]+ (C11H15N2O): 191.1184. Found 191.1186.
42.2 (C(5), C(8)); 77.9 C(6); 127.4, 127.6 (C(2), C(3)) 129.1, 130.8
(C(1), C(4)); 136.2, 140.9 (C(4a), C(9a)); 209.5 (CO(7)).
7.3.9. 6-Hydroxy-5,6,8,9- tetrahydro-benzocyclohepten-7-one,
oxime (17)
A suspension of crude 16 (from 9 (3.98 g, 24.8 mmol)) and
NH2OHꢁHCl (2.09 g, 30 mmol, 1.2 equiv) in pyridine (40 ml) was
stirred at rt under Ar for 3.5 h. The solvent was evaporated, the res-
idue dissolved in AcOEt and the organic solution washed with 2 M
aqueous NH4Cl and with brine, dried (MgSO4) and evaporated to
give crystallised 17 (3.04 g, 64%) after washing with toluene. Crys-
tallised major oxime: Colorless crystals, mp 122–124 °C (PhMe). IR
(KBr): 706, 753, 836, 915, 949, 1009, 1045, 1058, 1455, 1492, 1654,
7.3.7. 7-[Benzyl(benzyloxycarbonyl)amino]-8,9-dihydro-5H-
benzocyclohepten-6-one, 6-oxime (13b)
To a biphasic solution of 13a (0.25 g, 0.90 mmol) in THF (1.4 ml)
and H2O (0.6 ml), was added Na2CO3 (0.38 g, 3.6 mmol, 4 equiv)
and at 0 °C dropwise in two times ClCO2Bn (126
ll, 0.89 mmol,
1 equiv, and after 4 h, 63 l, 0.45 mmol, 0.5 equiv). The reaction
l
2919, 3256, 3489 cmꢀ1 1H NMR (CDCl3): 2.31 (m, 1H, Hb-8); 2.83
.
was stirred for 24 h, then diluted with H2O and extracted with
AcOEt. After evaporation of the solvent, purification by FC (Cyclo-
hexane/AcOEt 9:1) gave pure 13b (237 mg, 64%), colorless resin.
IR (CHCl3): 3583, 3327, 3014, 2952, 1694, 1497, 1453, 1416,
(m, 2H, CH2(9)); 3.06 (dd, 1H, J = 9.6, 14.2 Hz, Ha-5); 3.16 (dd, 1H,
J = 2.8, 14.2 Hz, Hb-5); 3.22 (m, Ha-9); 4.32 (dd, 1H, J = 2.8, 9.6 Hz,
H-6)); 7.20 (m, 3Har); 7.26 (m, 1Har). 13C NMR (1:1, CD3OD/
CDCl3): 23.2 (C(9)); 31.7 (C(5)); 41.8 (C(8)); 70.8 (C(6)); 126.7,
127.1 (C(2), C(3)); 128.9, 130.9 (C(1), C(4)); 135.7 (C(4a)); 141.4
(C(9a)); 161.5, (C(7)). Anal. Calcd for C11H13NO2 (191.23): C,
69.08; H, 6.85; N, 7.32. Found: C, 69.2; H, 7.0; N, 7.2.
1364, 1263, 1120, 963, 909 cmꢀ1 1H NMR (CDCl3): 1.79 (m, 1H,
.
Hb-8); 2.02 (m, 1H, Ha-8); 2.77 (ddd, 1H, J(9a,9b) = 14.1 Hz,
J(8,9b) = 3.5, 9.0 Hz, Hb-9); 2.85 (m, 1H, Ha-9); 3.32, 4.21 (2 d,
2H, J = 15.1 Hz, NCH2Ph); 4.21, 4.92, (2 d, 2H, J = 17.1 Hz, CH2(5));
ca 5.0 (br s, 1H, H-7); 5.08, 5.19 (2 d, 2H, J = 12.6 Hz, OCH2Ph);
7.09 (m, 1Har); 7.15–7.28 (m, 13Har). 13C NMR (CDCl3): 31.5,
32.2, 32.6 (C(5),C(8),C(9)); 49.2 (NCH2Ph); 60.2 (C(7)); 67.4
(OCH2Ph); 126.3, 126.5, 127.1, 127.2, 126.7, 127.4 (Cp(NBn),
Cp(OBn), C(2),C(3), Co(OBn), Co(NBn)); 128.3 (Cm(NBn), Cm(OBn);
128.8, 129.8 (C(1), C(4)); 134.6 (C(4a)); 136.5 (Cs(NBn)); 139.8,
140.1 (C(9a), Cs(OBn)); 156.8, 156.9 (C(6), NCO2). Anal. Calcd for
Minor oxime, colorless resin, 1H NMR (CDCl3): 2.52 (m, 1H, Hb-
8); 2.82 (m, 2H, CH2(9)); 3.02 (m, 1H, Ha-8); 3.08 (dd, 1H, Hb-5);
3.13 (dd, 1H, Ha-5); 4.37 (dd, 1H, H-6); 7.16–7.25 (m, 4Har);
J(5a,6) = 3.0, J(5b,6) = 5.3, J(5a,5b) = 14.1 Hz.
7.3.10. 7-(tertio-Butyloxycarbonylamino)-6,7,8,9-tetrahydro-
5H-benzocyclohepten-6-ol (19a)
a. From oxime 17. A solution of 17 (0.80 g, 4.18 mmol) in EtOH
(20 ml) and aqueous concd NH4OH (3 ml) was hydrogenolysed
over wet Raney-Ni (2 g) at rt for 15 h. The catalyst was discarded
by centrifugation or filtration on celite and the solvent evaporated
to give 18. A solution of crude 18 (4.18 mmol) in MeOH (20 ml) and
(Boc)2O (1.36 g, 7.84 mmol, 1.5 equiv) was stirred under Ar for 15 h
at rt, then evaporated. The obtained crystals were washed with
iPr2O to give 19a (0.65 g, 56%) as 1:1 cis–trans mixture.
b. From silyloxyketone 16. A solution of 16 (from 1.07 g of 8,
6.68 mmol) and Ti(OiPr)4 (4.0 mL, 13.3 mmol, 2.0 equiv) in a 2–
3 M solution of dry NH3 in EtOH (20 mL) was stirred at rt for 6 h.
NaBH4 (380 mg, 10 mmol, 1.5 equiv) was then added and the solu-
tion was stirred for further 2 h. The mixture was evaporated, the
residue dissolved in AcOEt and stirred with 1 N aqueous NH4OH
(10 ml). The precipitate was filtrated off, washed with AcOEt/1 N
aqueous NH4OH and the filtrate extracted with AcOEt. The organic
phases were then dried (MgSO4) and evaporated to give crude 18. A
solution of crude 18 (6.68 mmol), Na2CO3 (780 mg, 7.34 mmol,
1.1 equiv) and Boc2O (3.2 g, 14.6 mmol, 2.2 equiv) in MeOH
(10 mL) was stirred at rt for 2 h under Ar. Precipitation with H2O
(20 ml), filtration, washing with H2O and iPr2O and drying led to
19a (985 mg, 53%) as crystalline mixture of 50:50 cis and trans iso-
mers which can be separated by flash chromatography (AcOEt/
cyclohexane 1:1).
C
26H26N2O3 (414.51): C, 75.34; H, 6.32; N, 6.76. Found: C, 74.9;
H, 6.6; N, 6.5.
7.3.8. 7-(Trimethylsilyloxy)-6,9-dihydro-5H-benzocycloheptene
(15) and 6-(trimethylsilyloxy)-5,6,8,9-tetrahydro-
benzocyclohepten-7-one (16)
Silyl ether 15 from ClSiMe3 and DBU: To a stirred solution of 9
(0.40 g, 2.50 mmol) in dry CH2Cl2 (2.5 mL) were successively added
under Ar at rt DBU (0.94 mL, 6.24 mmol, 2.5 equiv) and SiMe3Cl
(0.64 mL, 5.0 mmol, 2 equiv). After 1–3 h stirring, H2O (10 mL)
was added and the mixture extracted with cyclohexane (100 mL).
The organic phase was dried (Na2SO4) and evaporated to give crude
15 as a brownish resin (0.60 g, quant.).
Silyl ether 15 from SiMe3OTf and NEt3: To a solution of 9 (3.98 g,
24.8 mmol) and Et3N (4.8 ml, 34.8 mmol, 1.4 equiv) in dry toluene
(40 mL), was added dropwise SiMe3OTf (5.4 ml, 29.8 mmol,
1.2 equiv) at rt under Ar. The mixture was stirred at 85 °C for 2 h,
then cooled at 0 °C, diluted with cyclohexane (100 ml), washed
successively with 2 M aq NH4Cl and brine and dried (MgSO4).
Evaporation of the solvent gave the crude 15 (ca 6 g, quant.).
Silyloxyketone 16: Crude 15 (ca 6 g, 24.8 mmol) was dissolved in
CH2Cl2 (40 ml) at 0 °C, m-CPBA (5.13 g, 29.7 mmol, 1.2 equiv) was
then added portionwise (or in CH2Cl2 solution) and the solution
stirred at 0 °C for 2 h. The solid was filtered off and the solvent
evaporated. Cyclohexane (100 mL) was added, the insoluble fil-
trated off, and the filtrate evaporated to give crude 16 (ca 4.8 g,
quant.) which was used without further purification.
trans-19a: colorless crystals, mp 174–175 °C (iPrOH). IR (KBr):
756, 882, 1003, 1034, 1172, 1246, 1321, 1370, 1453, 1526, 1683,
2933, 2979, 3370 cmꢀ1 1H NMR (CDCl3): 1.36 (m, 1H, Hb-8);
.
1.47 (s, 9H, CMe3); 2.19 (dddd, 1H, Ha-8); 2.73 (ddd, 1H, Hb-9);
2.83 (ddd, 1H, Ha-9); 2.99 (dd, 1H, Hb-5); 3.02 (dd, 1H, Ha-5);
3.36 (ddd, 1H, H-6); 3.70 (br ddt, 1H, H-7); 4.54 (br s, 1H, NH-7);
7.05–7.20 (m, 4Har); J(5a,5b) = 14.0, J(5a,6) = 8.8, J(5b,6) = 3.6,
Compound 15, Rf = 0.56 (AcOEt/cyclohexane 5:5), only charac-
terised by NMR. 1H NMR (CDCl3): 0.12 (s, 9H, (CH3)3Si)); 2.31 (m,
2H, CH2(6)); 2.92 (m, 2H, CH2(5)); 3.29 (dt, 2H, CH2(9)); 5.08 (tt,
1H, H-8); 7.06–7.26 (m, 4Har); J(6,8) = 1.4, J(6,9) = 2.1,
J(8,9) = 6.2 Hz.
J(6,7) = 9.2, J(7,8a) = 4.1,
J
(7,8b) = 11.5, J(NH,7) = ca 9;
J(8a,9b) = 7.5, J(8b,9a) = 11.2,
Compound 16, only characterised by NMR. 1H NMR (CDCl3):
0.15 (s, 9H, SiMe3); 2.43 (m, 1H, Hb-8); 2.84 (m, 3H, Ha-8,
CH2(9)); 2.95 (dd, 1H, Hb-5); 3.11 (dd, 1H, Ha-5); 4.26 (ddd, 1H,
H-6); 7.21–7.28 (4Har); J(5a,5b) = 14.3, J(5a,6) = 10.2, J(5b,6) = 3.0,
4J(6,8b) = 1.0 Hz. 13C RMN (CDCl3): 0.22 (SiMe3); 31.1 (C(9)); 41.4,
J(8a,8b) = 13.6, J(8a,9a) = 1.8,
J(8b,9b) = 2.0, J(9a,9b) = 14.8 Hz. 13C NMR (CDCl3): 28.3 (CMe3);
31.8 (C(9)); 32.7 (C(8)); 41.6 (C(5)); 60.0 (C(7)); 74.4 (C(6)); 80.2
(CMe3); 126.7, 127.0, 128.6, 130.2 (4CHar); 136.5, 142.0 (C(4a),
C(9a)); 156.8 (CO).

S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
1445
cis-19a: colorless crystals, mp 180–181 °C (iPrOH). IR (KBr):
cis); 2.23 (m, 1H, Ha-8 trans); 2.7–2.9 (m, 2H cis + trans); 3.0–3.2
(m, 2H cis + trans); 3.41 (t, J = 9 Hz, 1H, H-6 trans); 3.79 (q,
J = 8 Hz, 1H, H-7 trans); 3.88 (s, 1H, H-7 cis); 4.13 (s, 1H, H-6 cis);
4.77 (s, 1H, NH-7 trans); 5.11 (m, 2H, CH2(Bn) cis + trans); 5.39
(d, J = 8 Hz, 1H, NH-7 cis); 7.1–7.4 (m, 9Har cis + trans). 13C NMR
(CDCl3): 28.8 (C(8) cis); 31.8 (C(9) trans); 32.3 (C(9) cis); 32.8
(C(8) trans); 39.2 (C(5) cis); 41.6 (C(5) trans); 57.6 (C(7) cis); 60.6
(C(7) trans); 66.8, 67.3 (CH2Ph cis + trans); 69.3 (C(6) cis); 74.2
(C(6) trans); 126.6, 126.89, 126.91, 127.2, 127.9, 128.26, 128.37,
128.41, 128.66, 128.72, 128.75, 129.1 (12CHar); 130.4 (CHar trans);
132.0 (CHar cis); 133.9 (C(4a) cis); 136.3, 136.4, 136.6 (Cs(Ph) cis +
trans, C(4a) trans); 142.2 (C(9a) trans); 142.7 (C(9a) cis); 155.8
(NCO cis); 157.1 (NCO trans). Anal. Calcd for C19H21NO3 (311.37):
C, 73.29; H, 6.80; N, 4.50. Found: C, 73.5; H, 6.9; N, 4.4.
751, 867, 957, 1013, 1045, 1081, 1166, 1250, 1372, 1393, 1453,
1528, 1664, 2936, 2982, 3005, 3377, 3472 cmꢀ1 1H NMR (CDCl3):
.
1.46 (s, 10H, Hb-8, CMe3); 2.00 (dq, 1H, J = 13.2, 4.4, Ha-8); 2.75
(m, 2H, CH2(9)); 3.05 (dd, 1H, Hb-5); 3.08 (dd, 1H, Ha-5); 3.82
(dddd, 1H, H-7); 4.11 (br dddd, 1H, H-6); 5.06 br d, 1H, NH-7);
7.11–7.20 (m, 4Har); J(5a,5b) = 14.6, J(5a,6) = 1.6, J(5b,6) = 7.2,
J(6,7) = 2.2, J(6,OH) = 7.8, J(7,NH) = 9.6, J(7,8a) = 4.4, J(7,8b) =
11.2 Hz. 13C NMR (CDCl3): 28.4 (CMe3); 28.8 (C(8)); 32.3 (C(9));
39,2 (C(5)); 56.9 (C(7)); 69,3 (C(6)); 79,4 (CMe3); 126.7, 127.6,
128.9, 131.8 (4Car); 133.8, 142.6 (C(4a), C(9a)); 155.3 (CO). Anal.
Calcd for C16H23NO3 (277.37) for the cis–trans mixture: C, 69.29;
H, 8.36; N, 5.05. Found: C, 69.3; H, 8.4; N, 4.9.
7.3.11. cis and trans-7-amino-6,7,8,9-tetrahydro-5H-benzocy-
clohepten-6-ol (cis-18 and trans-18)
7.3.13. 7-(tertio-Butyloxycarbonylamino)-5,7,8,9-tetrahydro-
benzocyclohepten-6-one (20a)
trans-18: to a solution of trans-19a (8 mg, 0.035 mmol) in dioxane
(0.3 ml) was added 5 N HCl in dry Et2O (0.2 ml, 1 mmol). After
2 d at rt, the precipitate of trans-18 (6 mg, 97%) was isolated by
centrifugation, washed with dry Et2O (0.5 ml) and dried as color-
less crystals, mp >250 °C. IR (KBr): 751, 762, 1041, 1092, 1449,
1494, 1586, 1613, 2927, 3440 cmꢀ1. 1H NMR (CD3OD): 1.46 (dddd,
1H, Hb-8); 2.26 (dddd, 1H, Ha-8); 2.82 (ddd, 1H, Hb-9); 2.90 (ddd,
1H, Ha-9); 2.93 (dd, 1H, Hb-5); 3.11 (dd, 1H, Ha-5); 3.24 (ddd, 1H,
H-7); 3.38 (ddd, 1H, H-6); 7.13–7.23 (m, 4Har); J(5a,5b) = 14.0,
J(5a,6) = 10.5, J(5b,6) = 2.1, J(6,7) = 9.7, J(7,8a) = 4.0, J (7,8b) = 12.2,
To a solution of 19a (1.0 g, 3.6 mmol) in CH2Cl2 (20 ml) was
added at rt DMP (2.3 g, 5 mmol, 1.5 equiv) portionwise or dissolved
in CH2Cl2. The mixture was stirred for 3 h at rt, and reduced by stir-
ring with a solution of sodium thiosulfate (4 g, 7 equiv) in aqueous
N NaHCO3 (20 mL) for 1 h. The mixture was extracted with AcOEt
(100 mL) and the organic phase washed with aqueous N NaHCO3
(20 mL) and brine (20 mL), dried (MgSO4) and evaporated. Purifica-
tion by flash chromatography (AcOEt/Cyclohexane 1:9) and wash-
ing with Et2O gave pure 20a (765 mg, 77%), colorless crystals, mp
150–152 °C (iPrOH). IR (KBr): 750, 759, 1007, 1050, 1156, 1169,
1250, 1296, 1365, 1451, 1491, 1522, 1688, 1723, 2933, 2976,
J(8a,8b) = 13.4,
J(8a,9a) = 1.6,
J(8a,9b) = 7.2,
J(8b,9a) = 11.6,
J(8b,9b) = 1.9, J(9a,9b) = 14.8 Hz. 13C NMR (CD3OD): 31.5 (C(8));
32.0 (C(9)); 43.3 (C(5)); 61.2 (C(7)); 72.3 (C(6)); 128.2, 128.4,
130.0, 131.0 (4Car); 137.4, 142.6 (C(4a), C(9a)). HR-MS calcd for
3004, 3380 cmꢀ1 1H NMR (CDCl3): 1.43 (s, 9H, CMe3); 1.46 (m,
.
1H, Hb-8); 2.63 (dddd, 1H, Ha-8); 2.89 (ddd, 1H, Hb-9); 3.03
(ddd, 1H, Ha-9); 3.60 (d, 1H, Hb-5); 3.95 (d, 1H, Ha-5); 4.55 (dt,
1H, H-7); 5.43 (d, 1H, NH); 7.18 (m, 4Har); J(5a,5b) = 14.6,
J(7,NH) = 7.0, J(7,8a) = 7.0, J(7,8b) = 11.3, J(8a,8b) = 12.8, J(8a,9a) =
3.4, J(8a,9b) = 9.0, J(8b,9a) = 8.7, J(8b,9b) = 3.4, J(9a,9b) = 14.6 Hz.
13C NMR (CDCl3): 28.4 (CMe3); 31.1 (C(9)); 34.8 (C(8)); 48.2
(C(5)); 60.9 (C(7)); 79.8 (CMe3); 127.6, 128.0 (C(2), C(3)); 129.3,
129.8 (C(1), C(4)); 132.3 (C(4a)); 140.3 (C(9a)); 155.1 (NCO);
204.9 (C(6)). Anal. Calcd for C16H21NO3 (275.34): C, 69.79; H,
7.69; N, 5.09. Found: C, 69.7; H, 7.8; N, 4.9.
C
11H16N [M+H]+: 178.1232; found: 178.1226.
cis-18: same procedure with cis-19a (22 mg, 0.08 mmol, con-
taining 10% of trans-isomer) in dioxane (0.6 ml) and 5 N HCl in
dry Et2O (0.4 ml, 2 mmol) to give cis-18 (14 mg, 82%, containing
10% of trans-isomer) as colorless crystals, mp >250 °C. IR (KBr):
689, 747, 757, 979, 1029, 1185, 1240, 1454, 1495, 1511, 2920,
3020, 3596 cmꢀ1
.
1H NMR (CD3OD): 1.83 (br dt, 1H,
J(7,8b) = 11.2, J(8a,8b) = 14 Hz, Hb-8); 1.93 (m, 1H, Ha-8), 2.78–
2.92 (m, 2H, CH2(9)); 3.08 br m, 2H, CH2(5)); 3.48 (ddd, 1H,
J(6,7) = 2.8, J(7,8a) = 4.0, J (7,8b) = 11.2 Hz, H-7); 4.16 (br s, 1H, H-
6); 7.13–7.23 (m, 4Har). 13C NMR (CD3OD): 27.4 (C(8)); 32.0
(C(9)); 39,8 (C(5)); 58.4 (C(7)); 67.4 (C(6)); 127.7, 128.1, 129.7,
132.4 (4Car); 136.7, 142.4 (C(4a), C(9a)). HR-MS calcd for
7.3.14. 7-(Benzyloxycarbonylamino)-6,7,8,9-tetrahydro-
benzocyclohepten-6-one (20b)
Same procedure as for 20a with 19b (2.71 g, 8.7 mmol), DMP
(5.2 g, 12 mmol, 1.4 equiv) in CH2Cl2 (40 ml) to obtain 20b
(2.48 g, 92%) as colorless crystals, mp 119–121 °C (iPrOH). IR
(KBr): 697, 737, 751, 1015, 1238, 1247, 1531, 1685, 1718, 2938,
C
11H16N [M+H]+: 178.1232; found: 178.1226.
7.3.12. 7-(Benzyloxycarbonylamino)-6,7,8,9-tetrahydro-5H-
benzocyclohepten-6-ol (19b)
3338 cmꢀ1 1H NMR (CDCl3): 1.50 (dddd, 1H, Hb-8); 2.68 (m, 1H,
.
a. From oxime 17. Compound 19b was obtained with the same
procedure as above from 17 (2.47 g, 12.9 mmol) and Raney-Ni
(wet 6.2 g) in EtOH (25 ml) and concd NH4OH (7.5 ml). Crude 18
was N-protected in THF (40 ml) with stirring under Ar at 0 °C with
NEt3 (5 ml) and ClCO2Bn (2.6 ml, 18.1 mmol, 1.4 equiv). The solu-
tion was stirred at rt for 10 h, then hydrolysed with 2 M aqueous
NH4Cl (20 mL), extracted with AcOEt (100 mL) and the organic
solution was washed with brine (20 mL), dried (MgSO4) and evap-
orated. The obtained crystals were washed with iPr2O to give pure
19b (2.17 g, 54%).
Ha-8); 2.90 (ddd, 1H, Hb-9); 3.06 (ddd, 1H, Ha-9); 3.60 (d, 1H,
Hb-5); 3.97 (d, 1H, Ha-5); 4.61 (dt, 1H, H-7); 5.09 (s, 2H, CH2Ph);
5.71 (d, 1H, NH); 7.20 (m, 4Har); 7.34 (m, 5Har); J(5a,5b) = 14.2,
J(7,NH) = 7.5,
J(7,8a) = 6.5,
J(7,8b) = 11.2,
J(8a,8b) = 12.7,
J(8a,9a) = 3.2, J(8a,9b) = 9.0, J(8b,9a) = 9.0, J(8b,9b) = 3.2, J(9a,9b) =
14.6 Hz. 13C NMR (CDCl3): 31.0 (C(9)); 34.7 (C(8)); 48.1 (C(5));
61.4 (C(7)); 66.9 (CH2Ph); 127.6, 128.1, 128.2, 128.3; 128.6
(5Car); 129. 4, 129.8 (C(1), C(4)); 132.1 (C(4a)); 136.4 (Car-s);
140.3 (C(9a)); 155.5 (NCO2); 204.3 (CO(6)). Anal. Calcd for
C19H19NO3 (309.37): C, 73.77; H, 6.19; N, 4.53. Found: C, 73.5; H,
b. From silyloxyketone 16. Compound 19b was obtained with the
same procedure as above from 16 (3.0 g, 18.7 mmol). A solution of
crude 18 in THF (40 ml) was stirred with Na2CO3 (5.6 g, 52.4 mmol,
2.8 equiv) and ClCO2Bn (2.6 ml, 18.1 mmol, 1.4 equiv) at rt for 16 h.
Work up as for a) gave pure 19b (3.0 g, 52%). Colorless crystals,
70:30 isomeric cis/trans mixture, mp 148–150 °C (toluene). IR
(KBr): 697, 751, 1017, 1039, 1085, 1130, 1249, 1315, 1453, 1534,
6.2; N, 4.4.
7.3.15. 7-Amino-5,7,8,9-tetrahydro-benzocyclohepten-6-one,
hydrochloride (4)
From 20a. A solution of 20a (765 mg, 2.78 mmol) was stirred in
dioxane (5 mL) and HCl 2.2 N in Et2O (5 mL) at rt under Ar for 72 h.
The precipitate was isolated by filtration and recrystallised in
iPrOH/Et2O to give pure 4 (500 mg, 85%).
.
1673, 1685, 2942, 3318, 3401 cmꢀ1 1H NMR (CDCl3, 70:30 cis
and trans isomers): 1.3–1.5 (m, 1H cis + trans); 2.04 (m, 1H, Ha-8

1446
S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
From 20b. A solution of 20b (200 mg, 0.65 mmol) in EtOH
evaporated. The resulted solid was washed with hot AcOEt to give
(10 ml) and aqueous 1 N HCl (0,8 ml) was hydrogenolysed over
5% Pd/C (20 mg) at rt for 1 h. The catalyst was discarded by cen-
trifugation or filtration on celite, the solution evaporated and the
product recrystallised in iPrOH/Et2O to give pure 4 (120 mg, 60%).
Colorless crystals, mp 230–240 °C (dec.) (iPrOH/Et2O). IR (KBr):
448, 762, 1042, 1050, 1146, 1226, 1278, 1446, 1454, 1489,
5 (241 mg, 50%) as colorless solid, mp 208–211 °C. IR (KBr): 938,
1143, 1176, 1226, 1475, 1710, 2936 cmꢀ1 1H NMR (D2O): 1.38
.
(m, 1H); 1.66–1.97 (m, 6H); 2.12 (m, 1H); 2.56 (ddd, 1H, J = 4.0,
11.0, 18.0 Hz, Hb-7); 2.77 (ddd, 1H, J = 3.6, 6.0, 18.0 Hz, Ha-7);
4.41 (dd, J = 3.2, 10.0 Hz, H-2). 13C NMR (D2O): 22.9, 27.3, 28.8,
29.6 (C(5), C(4), C(6), (C(3)); 41.4 (C(7)); 60.1 (C(2)); 211.5 (C(1)).
HR-MS (QTof), calcd for C7H14NO [M+H]+: 128.1075; found:
128.1070.
1597, 1723, 2625, 2904, 2970, 3425 cmꢀ1 1H NMR (D2O) 80:20
.
ketone–hydrate mixture). Ketone: 1.69 (q, 1H, Hb-8); 2.61 (m,
1H, Ha-8); 3.06 (ddd, 1H, Hb-9); 3.21 (ddd, 1H, Ha-9); 3.72 (d,
1H, Hb-5); 4.23 (d, 1H, Ha-5); 4.50 (dd, 1H, H-7); 7.24–7.32 (m,
4Har); J(5a,5b)) = 14.4, J(7,8a) = 7.0, J(7,8b) = 12.0, J(8a,8b) = 13.0,
7.5. Insaturated benzosuberone series
J(8a,9a) = 3.2,
J(8a,9b) = 8.5,
J(8b,9a) = 9.5,
J(8b,9b) = 3.2,
7.5.1. 6-Bromo-5,6,8,9-tetrahydrobenzocyclohepten-7-one (24)
and 5,6-dihydrobenzocyclohepten-7-one (25)
J(9a,9b) = 15.0 Hz. Hydrate: 1.46 (m, 1H, Hb-8); 2.28 (m, 1H, Ha-
8); 2.88 (m, 2H, CH2(9)); 3.10, 3.40 (2d, 2H, J = 14.5 Hz, CH2(5));
3.54 (dd, 1H, J = 4.2, 12.7 Hz, H-7); 7.32 (s, 4Har). 1H NMR
(CD3OD): 1.68 (dddd, 1H, Hb-8); 2.53 (m, 1H, Ha-8); 3.03 (ddd,
1H, Hb-9); 3.25 (ddd, 1H, Ha-9); 3.62 (d, 1H, Hb-5); 4.21(d, 1H,
Ha-5); 4.38 (dd, 1H, H-7); 7.19–7.26 (m, 4Har); J(5a,5b) = 13.8,
1. Oxidation of 15 with p-benzoquinone: To a solution of 15
(0.725 g, 3.12 mmol) in CH3CN (10 mL) were added Pd(OAc)2
(0.35 g, 1.56 mmol, 0.5 equiv) and p-benzoquinone (0.17 g,
1.56 mmol, 0.5 equiv). The reaction mixture was stirred at room
temperature for 3 days, then filtrated through a pad of celite which
was washed with CH2Cl2 (3 ꢃ 20 ml). The organic layer was
washed with H2O (10 mL), dried over Na2SO4 and evaporated.
The residue was purified by flash chromatography (AcOEt/cyclo-
hexane, 1:9) to afford 25 (0.367 g, 75%) as a colorless oil. The yields
varied between 45% and 75%.
J(7,8a) = 6.8,
J(7,8b) = 12.1,
J(8a,8b) = 12.8,
J(8a,9a) = 2.8,
J(8a9b) = 8.2, J(8b9a) = 10.0, J(8b,9b) = 3.0, J(9a,9b) = 14.8 Hz. 13C
NMR (CD3OD), ketone: 31.0 (C(9)); 33.3 (C(8)); 48.0 (C(5)); 61.2
(C(7)); 128.9, 129.2 (C(2), C(3)); 130.4, 130.7 (C(1), C(4)); 133.0
(C(4a)); 141.3 (C(9a)); 202.4 (CO(6)). HR-MS (FAB+), calcd for
C
10H14NO [M+H]+: 176.1076; found: 176.1067.
2. Oxidation of 15 with O2: A solution of 15 (4.5 g, 19 mmol) and
Pd(OAc)2 (0.43 g, 1.9 mmol, 0.1 equiv) in DMSO (25 mL) was stir-
red under an oxygen atmosphere. After 16 h stirring at rt, water
(10 mL) was added and the mixture extracted with Et2O
(3 ꢃ 20 mL). The organic layer was dried (MgSO4), and evaporated.
The residue was purified by distillation to afford 25 (2.59 g, 85%,
Bp0.5 Torr 85–90 °C, the yields varied between 50% and 85%).
3. Directly from ketone 9 and bromoketone 24: To a solution of 9
(0.5 g, 3.12 mmol) in MeCN (12 mL) were successively added Si-
Me3OTf (0.045 mL, 0.25 mmol, 0.08 equiv) and NBS (0.61 g,
3.5 mmol, 1.1 equiv). The solution was stirred at rt for 4.5 h (TLC
monitoring. Treatment of the solution allowed isolating the rather
unstable 24). DBU (1.03 mL, 7.0 mmol, 2.2 equiv) was added drop-
wise to the solution of crude 24 and the solution was stirred for
further 30 minutes, then diluted with Et2O or AcOEt (100 mL)
and washed with brine (2 ꢃ 20 mL). The organic layer was dried
over MgSO4 and evaporated. Purification by flash chromatography
(AcOEt/cyclohexane 2:8) gave 25 (0.42 g, 80%) as a brownish oil,
and by further elution, the benzocycloheptene-3-one (40–70 mg,
7.4. Heptanone series
7.4.1. 2-Bromocycloheptanone (22)
Compound 21 (0.5 mL, 4.5 mmol) was added dropwise to a
stirred mixture of NBS (0.8 g, 4.5 mmol, 1 equiv) and p-toluene-
sulfonic acid (77 mg, 0.45 mmol). The mixture became warm
and liquid. After 2 h 30 stirring, water (20 mL) was added and
the solution was extracted with CH2Cl2 (3 ꢃ 20 mL), the organic
phases washed with H2O, dried over MgSO4 and evaporated to
give 22 as colorless oil (0.9 g, quant.). For analytical purpose, a
sample was purified by chromatography (cyclohexane/AcOEt
70:30). IR (KBr): 1453, 1711, 2857, 2933 cmꢀ1 1H NMR (CDCl3):
.
1.38 (m, 1H, Hb-4); 1.55–1.59 (m, 1H, Hb-5, Hb-6); 1.77 (m, 1H,
Ha-6); 1.78–2.04 (m, 1H, Ha-4, Ha-5); 2.02 (dtd, 1H, J = 1.8, 9.6,
14.4 Hz, Hb-3); 2.37 (dddd, 1H, J = 1.8, 5.0, 8.8, 14.4 Hz, Ha-3);
2.50 (ddd, 1H, J = 2.8, 7.6, 13.2 Hz, Hb-7); 2.86 (ddd, 1H, J = 3.4,
10.4, 13.2 Hz, Ha-7); 4.38 (dd, 1H, J = 5.0, 9.6 Hz, H-2). 13C NMR
(CDCl3) values are identical as in lit.34,61 IR and 1H NMR values
are in accordance with the lit.34,35
ca 10%, resulting from the elimination of
compound).
a 6,8-dibromo-
Compound 24: colorless resin; Rf = 0.64 (AcOEt/cyclohexane
7.4.2. 2-Azidocycloheptanone (23)
5:5). IR (KBr): 752, 773, 1090, 1188, 1456, 1493, 1703, 2854,
3024 cmꢀ1 1H NMR (CDCl3): 2.63 (dddd, 1H, J = 1.6, 3.0, 7.8,
;
A solution of 22 (614 mg, 3.2 mmol) in DMF (20 mL) was stirred
with NaN3 (312 mg, 4.8 mmol, 1.5 equiv) for 30 min. Brine (10 mL)
was added and the solution extracted with AcOEt (3 ꢃ 20 ml). The
reunified organic phases were dried (MgSO4) and evaporated to
give 23 as colorless oil (490 mg, quant.). For analytical purpose, a
sample was purified by chromatography (cyclohexane/AcOEt
13.5 Hz, Hb-8); 2.87 (ddd, 1H, J = 3.0, 11.0, 14.8 Hz, Hb-9); 2.97
(ddd, 1H, J = 3.6, 7.8, 14.8 Hz, Ha-9); 3.17 (ddd, 1H, J = 3.6, 11.0,
13.5 Hz, Ha-8); 3.25 (dd, 1H, J = 7.8, 15.0 Hz, Hb-5); 3.44 (dd,
J = 2.8, 15.0 Hz, Ha-5); 4.57 (ddd, J = 1.6, 2.8, 7.8 Hz, H-6); 7.20
(m, 4Har). 13C NMR (CDCl3): 30.4 (C(9)); 39.1 (C(5)); 39.5
(C(8)); 53.5 (C(6)); 127.2, 128.5, 132.1, 135.8 (4Car); 136.4,
140.0 (C(4a)), C(9a)); 203.8 (C(7)). Too unstable for MS
measurement.
70:30). IR (KBr): 1143, 1264, 1455, 1712, 2106, 2862, 2937 cmꢀ1
.
1H NMR (CDCl3): 1.45 (m, 1H); 1.62–1.82 (m, 6H); 2.02 (m, 1H,
Ha-3); 2.53 (ddd, 1H, J = 4.2, 10.0, 16.0 Hz, Hb-7); 2.61 (ddd, 1H,
J = 4.2, 6.8, 16.0 Hz, Ha-7); 4.08 (dd, 1H, J = 3.6, 9.2 Hz, H-2). 13C
NMR (CDCl3): 23.5, 26.5, 28.8 (C(5), C(4), C(6)); 30.7 (C(3)); 41.3
(C(7)); 67.7 (C(2)); 208.6 (C(1)). IR and 1H NMR values are in accor-
dance with the lit.33
Compound 25: colorless oil, Rf = 0.57 (AcOEt/cyclohexane 5:5).
IR (KBr): 3022, 2953, 1662, 1612, 1275, 1202, 1101, 815, 751,
543, 443 cmꢀ1 1H NMR (CDCl3): 2.76 (m, 2H, H-6); 3.01 (m, 2H,
.
H-5); 6.18 (d, 1H, J = 12.6 Hz, H-8); 7.13 (d, 1H, J = 12.6 Hz, H-9);
7.22–7.37 (m, 4Har). 13C NMR (CDCl3): 29.3 (C(5)); 42.2 (C(6));
132.6, 130.1, 129.1, 129.0, 127.1 (4CHar, C(8)); 134.2 (C(9a));
141.7 (C(4a)); 142.8 (C(9)); 201.3 (CO(7)). 1H NMR data are in
agreement with those of the lit.37 HR-MS (ESI+) calcd for
7.4.3. 2-aminocycloheptanone (5)
Compound 23 (480 mg, 3.13 mmol) was hydrogenolysed on 5%
Pd/C (63 mg) in EtOH (116 mL) and 1 N aqueous HCl (3.1 mL,
3.1 mmol) for 16 h. The catalyst was centrifuged off and the solvent
C
11H10NaO [M+Na]+: 181.0629; found: 181.0668.

S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
1447
7.5.2. 7-tert-Butyldimethylsilyloxy-5H-benzocycloheptene (26)
and 6-(tert-butyl-dimethylsilyl)oxy-5,6-
dihydrobenzocyclohepten-7-one (27)
1.5 equiv). After 16 h stirring, the reaction mixture was diluted
with ether (50 mL), washed with brine (10 mL), dried over MgSO4
and evaporated. Purification by flash chromatography (AcOEt/
cyclohexane 1:9) gave pure 28b (1.48 g, 74%) as a 80:20 diastereo-
isomeric mixture.
1. With Me2tBuSiOTf-NEt3. To a stirred solution of 25 (3.13 g,
19.8 mmol) in dry CH2Cl2 (55 mL) were added under Ar at rt
Me2tBuSiOTf (10.0 mL, 44 mmol, 2.2 equiv) and NEt3 (6.68 g,
48 mmol, 2.4 equiv). The solution was stirred for another 3 h, then
H2O (50 mL) was added and the mixture extracted with cyclohex-
ane (3 ꢃ 100 mL). The combined organic phases were dried
(MgSO4) and evaporated to give crude dienol ether 26 (5 g, 92%).
For analytical purpose, a sample was purified by chromatography
(eluent: AcOEt/cyclohexane 9:1). To the solution of the crude 26
(5 g, 18.3 mmol) in CH2Cl2 (53 mL) was added portionwise m-CPBA
(3.8 g, 22 mmol, 1.2 equiv) at 0 °C under Ar and the mixture stirred
for 16 h. The reaction mixture was diluted with AcOEt (200 mL),
washed successively with aqueous Na2SO3 solution, aqueous 1 M
NaHCO3 (50 mL) and with H2O (2 ꢃ 50 mL), dried (MgSO4) and
evaporated. Purification by flash chromatography (AcOEt/n-hep-
tane, 1:9 or cyclohexane/CH2Cl2 7:3) gave 27 (3.82 g, 77%).
2. With Me2tBuSiCl-DBU. To a stirred solution of 25 (0.1 g
0.62 mmol) in dry CH2Cl2 (1 mL) at rt were added DBU (0.22 mL,
1.58 mmol, 2.5 equiv) and ClSiMe2tBu (0.19 g, 1.26 mmol, 2 equiv).
After 3 h stirring, same work-up as above gave 26 (0.18 g, quant.).
The oxidation in CH2Cl2 (2 mL) with m-CPBA (0.13 g, 0.76 mmol,
1.2 equiv, then 0.05 g, 0.5 equiv) at 0 °C gave 27 (136 mg, 75%) after
same work-up as above. Compound 26 yellowish oil, Rf (AcOEt/
cyclohexane 5:5) = 0.75. IR (KBr): 796, 839, 896, 1169, 1231,
1256, 1636, 1741, 2853, 2929, 2956 cmꢀ1.1H NMR (CDCl3,
400 MHz): 0.07 (s, 6H, SiMe2); 0.89 (s, 9H, CMe3); 2.94 (d, 2H,
J = 7.2 Hz, H-5); 5.06 (dt, 2H, J = 1.7, 7.2 Hz, H-6); 6.25 (dd, 1H,
J = 1.7, 11.9 Hz, H-8); 6.99 (d, J = 11.9 Hz, H-9); 7.14 (d, 1Har,
J = 7.5 Hz); 7.20 (ddd, 1Har, J = 1.5, 7.1, 7.8 Hz); 7.28 (m, 2Har).
13C NMR (CDCl3): ꢀ4.5 (SiMe2); 18.0 (SiCMe3); 25.6 (CMe3); 31.2
(C(5)); 106.7 (C(6)); 125.5, 127.2, 128.0, 128.5 (4CHar); 128.7
(C(8)); 133.3 (C(9)); 135.5, 138.5 (C(4a), C(9a)); 149.5 (C(7)). HR-
MS (ESI+) calcd for C13H17OSi [Mꢀ(C4H8)+H]+: 217.1043; found:
217.1043; calcd for C17H25OSi [M+H]+: 273.1669; found: 273.1665.
Compound 27: colorless resin, Rf = 0.77 (AcOEt/cyclohexane
5:5). IR (KBr): 837, 1119, 1254, 1679, 1725, 2855, 2929,
Compound 28a, only characterised by NMR. 1H NMR (CDCl3,
300 MHz), major diastereoisomer: 0.06, 0.08 (2s, 6H, SiMe2); 0.88
(s, 9H, CMe3); 2.67 (ddd, 1H, J = 1.5, 2.0, 14.3 Hz, Hb-5); 3.04 (dd,
1H, J = 10.0, 14.3 Hz, Ha-5); 3.49 (tdd, 1H, J = 1.5, 4.2, 4.8, H-7);
3.99 (ddd, 1H, J = 2.0, 4.2, 10.0 Hz, H-6); 5.42 (br s, 2H, NH2);
5.81 (dd, 1H, J = 4.8, 12.2 Hz, H-8); 6.44 (dd, 1H, J = 1.5, 12.2, H-
9); 7.17 (m, 4Har); minor diastereoisomer, partial data: 0.15, 0.08
(2s, 6H, SiMe2); 0.92 (s, 9H, CMe3); 2.99 (dd, 1H, J = 7.2, 10.4 Hz,
Ha-5); 5.78 (dd, 1H, J = 4.0, 10.0 Hz, H-8).
Compound 28b: yellowish resin. IR (KBr): 1074, 1169, 1254,
1494, 1717, 2857, 2930, 2955, 2978, 3454 cmꢀ1 1H NMR (CDCl3,
.
300 MHz) major diastereoisomer: 0.05, 0.08 (2s, 6H, SiMe2); 0.82
(s, 9H, SiCMe3); 1.43 (s, 9H, CMe3); 2.76 (dd, 1H, J = 9.0, 13.5 Hz,
Hb-5); 2.93 (dd, 1H, J = 4.0, 13.5 Hz, Ha-5); 4.23 (br dddd, 1H,
J = 2.2, 4.2, 4.5, 9.0H-7); 4.37 (dddd, 1H, J = 1.0, 4.0, 4.5, 9.0, H-6);
5.00 (br d, 1H, J = 9.0 Hz, NH); 5.73 (ddd, 1H, J = 1.0, 4.2, 11.5 Hz,
H-8); 6.55 (dd, 1H, J = 2.2, 11.5 Hz, H-9); 7.13 (m, 4Har); minor dia-
stereoisomer, partial data: 0.07 (s, 6H, SiMe2); 0.83 (s, 9H, SiCMe3);
1.43 (s, 9H, CMe3); 2.85 (dd, 1H, J = 2.0, 14.6 Hz, Hb-5); 2.98 (dd,
1H, J = 6.8, 14.6 Hz, Ha-5); 4.04 (m, 2H, H-6 and H-7); 5.78 (m,
1H, H-8); 6.45 (dd, 1H, J = 2.0, 12.2 Hz, H-9). 13C NMR (CDCl3,
100 MHz): Major diastereoisomer: ꢀ4.5, ꢀ5.0 (SiMe2); 18.0
(SiCMe3); 25.7 (SiCMe3); 28.4 (OCMe3); 41.1 (C(5)); 54.1 (C(7));
76.6 (C(6)); 79.3 (OCMe3); 126.5, 127.2, 129.4, 130.0 (4CHar);
130.3 C(9)); 131.5 (C(8)); 136.2, 136.8 (C(4a), C(9a)); 155.2
(NCO). HR-MS (ESI+): calcd for C22H35NNaO3Si [M+Na]+:
412.2284; found: 412.2271.
7.5.4. 7-(tert-Butyloxycarbonyl)amino-6,7-dihydro-5H-
benzocyclohepten-6-ol (28c), 7-(tert-butyloxycarbonyl)amino-
5,7-dihydro-benzocyclohepten-6-one (29)
To a solution of 28b (414 mg, 1.06 mmol) in Et2O (5 mL) was
added Bu4NFꢁ3H2O (0.5 g, 1.58 mmol, 1.5 equiv). After 16 h stirring
at rt under Argon, the solution was diluted with Et2O (50 mL),
2954 cmꢀ1
.
1H NMR (CDCl3, 400 MHz): 0.02, 0.14 (2 s, 6H, SiMe2);
washed successively with a 20% aqueous NH4Cl solution
0.87 (s, 9H, CMe3); 2.98 (dd, 1H, J = 1.6, 15.0 Hz, Hb-5); 3.39 (dd,
1H, J = 12.0, 15.0 Hz, Ha-5); 4.29 (dd, 1H, J = 1.6, 12.0 Hz, H-6);
6.09 (d, 1H, J = 12.8 Hz, H-8); 7.09 (d, 1H, J = 12.8 Hz, H-9); 7.33
(m, 4Har). 13C NMR (CDCl3, 100 MHz): ꢀ5.5, ꢀ4.5 (SiMe2); 18.5
(SiCMe3); 25.8 (SiCMe3); 40.0 (C(5)); 75.9 (C(6)); 125.9 (C(8));
127.4, 130.2, 130.4, 132.7 (4CHar); 134.1 (C(9a)); 137.5 (C(4a));
142.5 (C(9)); 199.1 (CO(7)). HR-MS (ESI+): calcd for C17H24O2Si
[M+H]+: 289.1618; found: 289.1602; calcd for [M+Na]+:
311.1438; found: 311.1433.
(2 ꢃ 10 mL) and then with brine (10 mL), dried over Na2SO4 and
evaporated. 28c (207 mg, 70%) was crystallised in iPr2O as a
80:20 diastereoisomeric mixture.
To a solution of 28c (43 mg, 0.16 mmol) in dry CH2Cl2 (10 mL)
was added DMP (0.121 g, 0.29 mmol, 1.5 equiv). After 1 h stirring
at rt, AcOEt (25 mL) and H2O (10 mL) were then added to the reac-
tion mixture that was stirred for 2 h further. The organic layer was
separated, washed successively with aqueous 1 N NaHCO3 (10 mL),
aqueous Na2SO3 (10 mL), and brine (10 mL), dried over Na2SO4 and
concentrated to give 29 (42 mg, quant.)
7.5.3. 6-(tert-Butyldimethylsilyl)oxy-6,7-dihydro-5H-
benzocyclohepten-7-amine (28a), tert-butyl 6-(tert-
butyldimethylsilyl)oxy-6,7-dihydro-5H-benzocyclohepten-7-
carbamate (28b)
Compound 28c: Major diastereoisomer, isolated by crystallisa-
tion in iPr2O. Colorless crystals, mp 121–123 °C (iPr2O). IR (KBr):
1164, 1325, 1389, 1529, 1667, 2875, 2954, 2975, 2988, 3360,
3501 cmꢀ1.1H NMR (CDCl3, 300 MHz): 1.45 (s, 9H, CMe3); 1.85 (s,
1H, OH); 2.95 (dd, 1H, Hb-5); 3.06 (dd, 1H, Ha-5); 4.26 (ddd, 1H,
H-6); 4.42 (br dddd, 1H, H-7); 5.18 (br d, 1H, NH); 5.70 (dd, 1H,
H-8); 6.51 (dd, 1H, H-9); 7.19 (m, 4Har); J(5a,5b) = 14.4;
J(5a,6) = 2.8 Hz; J(5b,6) = 9.2; J(6,7) = 4.2; J(7,8) = 4.4; J(7,9) = 2.0;
J(7,NH) = 8.4; J(8,9) = 12.0 Hz. 13C NMR (CDCl3, 100 MHz): 28.4
(CMe3); 40.0 (C(5)); 55.0 (C(7)); 73.1 (C(6)); 80.0 (CMe3); 127.0,
128.0, 130.8, 130.9 (4 CH-ar); 128.9 (C(8)); 130.9 (C(9)); 135.0,
135.4 (C-(4a), C-(9a)); 156.1 (NCO). HR-MS (ESI+) calcd for
To a solution of 27 (1.80 g, 6.64 mmol) in 2–3 M NH3 in dry
EtOH (40 mL) was added Ti(OiPr)4 (3.9 mL, 13.2 mmol, 2 equiv).
After 16 h stirring at rt, NaBH4 (0.3 g, 9 mmol, 1.5 equiv) was added
and the mixture stirred for 2 h further. After evaporation of the sol-
vent, the residue was dissolved in AcOEt (50 mL) and stirred with
aqueous 1 N NH4OH (10 mL) for 16 h. The precipitate was filtered
off and washed with AcOEt/1 N aqueous NH4OH (5 ꢃ 20 mL). The
organic layer was separated, washed with aqueous N NH4OH
(20 mL), dried over MgSO4 and evaporated to give the crude amine
28a (as a 80:20 diastereoisomeric mixture). To a solution of the
crude 28a (6.64 mmol) in MeOH (20 mL) were added at rt NaHCO3
(0.462 g, 5.49 mmol, 1 equiv) and Boc2O (1.8 g, 8.24 mmol,
C
16H21NO3 [M+Na]+: 298.1414; found: 298.1410.
Minor diastereoisomer, only characterised by 1H NMR (CDCl3,
300 MHz), partial data: 1.45 (s, 9H, CMe3); 2.92 (dd, 1H, J = 2.5,
14.4 Hz, Hb-5); 3.05 (dd, 1H, J = 7.6, 14.4 Hz, Ha-5); 4.01 (dt, 1H,

1448
S. Albrecht et al. / Bioorg. Med. Chem. 19 (2011) 1434–1449
J = 2.5, 7.6 Hz, H-6); 4.42 (m, 1H, J = 2.2, 4.4, 7.6, H-7); 5.68 (dd, 1H,
J = 4.4, 12.0 Hz, H-8); 6.50 (dd, 1H, J = 2.2, 12.0 Hz, H-9).
7.6.4. Dimerisation of 4: 5,6a,7,8,13,14a,15,16-octahydro-
dibenzo[d,d0]pyrazino[2,3-a;5,6-a0]dicycloheptene (33a) and
5,7,8,13,15,16-hexahydro-dibenzo[d,d0]pyrazino[2,3-a;5,6-
a0]dicycloheptene (34a)
Compound 29: colorless crystals, mp 155–157 °C. IR (KBr):
3355, 2969, 2931, 1732, 1688, 1521, 1390, 1152, 1051,
1023 cmꢀ1
.
1H NMR (CDCl3, 300 MHz): 1.43 (s, 9H, CMe3); 3.65
Compound 4 (5 mg, 0.025 mmol) was stirred in 20 mM Hepes
buffer (2 ml) at pH 7.5 at rt. A precipitate appeared immediately
and was isolated after 16 h by centrifugation, washing with H2O
and drying under vacuum to give a 75:25 mixture of 33a and
34a (ca 3 mg, 60%). In CDCl3 solution, this mixture was quantita-
tively transformed into 34a at rt after 16 h and isolated after evap-
oration of the solvent and washing with Et2O (0.5 mL) to give 34a
(3 mg, quant.).
(d, 1H, J = 17.7 Hz, Hb-5); 3.76 (d, 1H, J = 17.7 Hz, Ha-5); 4.66 (br
dd, 1H, J = 2.5, 4.3 Hz, H-7); 5.72 (br s, 1H, NH); 5.82 (dd, 1H,
J = 4.3, 10.6 Hz, H-8); 6.87 (dd, 1H, J = 2.5, 10.6 Hz, H-9); 7.25 (m,
4Har). 13C NMR (CDCl3, 75 MHz): 28.9 (OCMe3); 47.7 (C(5)); 60.8
(C(7)); 80.2 (OCMe3); 127.2, 128.1, 129.2, 130.1, 130.4, 130.7
(4CHar, C(8), C(9)); 132.4, 136.6 (C(4a), C(9a)); 155.8 (NCO);
207.6 (C(6)). HR-MS (ESI+) calcd for C16H19NNaO3 [M+Na]+:
296.1263; found: 296.1268.
Compound 33a, only characterised by 1H NMR (CDCl3): 1.42
(ddt, 2H, Hb-7, Hb-15); 2.62 (dddd, 2H, Ha-7, Ha-15); 2.93 (ddd,
2H, Hb-8, Hb-16); 3.07 (ddd, 2H, Ha-8, Ha-16); 3.45 (d, 2H, Hb-5,
Hb-13); 3.73 (d, 2H, Ha-5, Ha-13); 4.01 (m, 2H, H-6a, H-14a);
7.10–7.25 (m, 4Har). J(5a,5b) = 13.2, J(6a,7a) = 5.0, J(6a,7b) = 11.0,
7.6. Transformations of 29
7.6.1. 7-tert-Butoxycarbonylamino-5,9-dihydrobenzocyclo-
hepten-6-one (30)
To a solution of 29 (2 mg) in CDCl3 (0.7 ml), was added NEt3
(5 ll). The isomerisation was achieved after 2 h at rt (NMR moni-
J(7a,7b) = 13.8,
J(7b,8b) = 2.2, J(8a,8b) = 13.8 Hz.
Compound 34a: yellowish crystals, mp 234–236 °C. IR (KBr):
J(7a,8a) = 2.1,
J(7a,8b) = 7.7,
J(7b,8a) = 11.0,
3023, 2926, 2901, 1488, 1456, 1436, 1428, 1394, 755, 721 cmꢀ1
.
toring). After addition of some silicagel and centrifugation, a solu-
tion of 30 in CDCl3 was obtained. 1H NMR (CDCl3): 1.44 (s, 9H,
CMe3); 3.74 (d, 2H, J = 7.0 Hz, CH2(9)); 3.98 (s, 2H, CH2(5)); 7.19
(m, 4Har); 7.74 (t, 1H, J = 7.0 Hz, H-8). 13C NMR (CDCl3 75 MHz):
28.3 (CMe3); 33.7 (C(9)); 50.0 (C(5)); 80.3 (CMe3); 126.1 (C(8));
127.2, 127.3, 127.9, 129.2 (4CHar); 132.0, 134.0 (C(4a), C(7));
140.0 (C(9a)); 153.1 (NHCO2); 190.4 (CO(6)). HR-MS (ESI+): calcd
1H NMR (CDCl3): 3.20 (m, 4H); 3.24 (m, 4H); 4.25 (s, 4H, CH2(5),
CH2(13)); 7.10–7.25 (m, 8Har). 13C NMR (CDCl3): 30.6, 35.4
(C(7),C(8), C(15),C(16)); 41.8 C(5),C(13)); 126.7, 127.4, 128.5,
128.8 (8CHar); 137.7 (C(4a),C(12a)); 140.0 (C(8a),C(16a)); 149.3,
149.7 (C(5a),C(6a), C(13a),C(14a)). HR-MS (FAB+) calcd for
C
10H14NO [M+H]+: 313.1699; found 313.1705.
for
272.1276.
C
16H18NO3 [MꢀH]+ (aromatisation): 272.1287; found:
Acknowledgements
The support of the Centre National de la Recherche Scientifique
(FRE 3253), the École Nationale de Chimie de Mulhouse and the Uni-
versité de Haute-Alsace is gratefully acknowledged. We also wish to
thank the Ville de Mulhouse and the Fondation de l’ENSCMu for a Ph.
D. grant to S. Albrecht and the Ligue contre le Cancer (INCa) for
financial support. We thank also Dr Didier LeNouën for the NMR
explanations, Dr Cécile Joyeux for the HR-MS measurements as
well as Dr Mathias Wind from Basilea Pharmaceutical Ldt in CH-
Basel, and the students Héloise Raynard, Bertrand Honnert, Yves
Muller, Faïma Asreg and Lionel Roux for their participation to this
work.
7.6.2. 6-Hydroxybenzocyclohepten-7-imine (31a)
A solution of 29 (2 mg) in aqueous 2 N HCl in H2O (0.7 mL) was
studied in 1H NMR. The signals of 31a were only observed, 1H NMR
(2 N HCl in H2O): 7.50 (d, 1H, H-8); 7.81 (dd, 1H, H-2); 7.89 (dd, 1H,
H-3);7.99 (s, 1H, H-5) 7.99 (d, 1H, H-4); 8.06 (d, 1H, H-1); 8.32 (d,
1H, H-9). J(1,2) = 7.9, J(2,3) = 7.1, J(3,4) = 7.4, J(8,9) = 12.3 Hz.
7.6.3. 6-Methoxybenzocyclohepten-7-one and 6-
hydroxybenzocyclohepten-7-one (benzotropolone 31b)
The methoxybenzotropolone was prepared according to43
:
brownish crystals, mp 85–87 °C (lit.42 89–90 °C), yield 87% after
purification by flash chromatography (AcOEt/cyclohexane (1:9).
1H NMR (CDCl3): 3.99 (s, 3H, OMe); 7.01 (d, 1H, J = 12.8 Hz, H-8);
7.43 (s, 1H, H-5); 7.61, 7.70 (2ddd, 2H, J = 7.9 Hz, 8.3, 1.3 Hz, H-2,
H-3); 7.85 (d, 1H, J = 12.8 Hz, H-9); 7.87, 7.94 (2 d, 2H, J = 7.9 Hz,
H-1, H-4).
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Benzotropolone 31a was prepared according to43 by hydrolysis
of the methoxy-benzotropolone: yellow needles, mp 158–160 °C
(EtOH) (lit.43 159.5–160.5 °C (EtOH)), yield 58% after recrystallisa-
tion in EtOH. IR (KBr): 1223, 1249, 1303, 1352, 1426, 1459, 1535,
1570, 1614, 1625 cmꢀ1 1H NMR (CDCl3): 7.19 (d, 1H, H-8); 7.55
.
(ddd, 1H, H-2); 7.59 (s, 1H, H-5); 7.65 (ddd, 1H, H-3); 7.74 (dm,
1H, H-4); 7.79 (dm, 1H, H-1); 7.84 (d, 1H, H-9); J(1,2) = 8.0,
J(1,3) = 1.5, J(2,3) = 7.3, J(2,4) = 1.5, J(3,4) = 7.8, J(8,9) = 12.5 Hz. 1H
NMR (D2O): 7.22 (d, 1H, H-8); 7.66 (dd, 1H, H-2); 7.77 (dd, 1H,
H-3); 7.76 (s, 1H, H-5); 7.90 (d, 1H, H-4); 7.97 (d, 1H, H-1); 8.09
(d, 1H, H-9); J(1,2) = 8.0, J(2,3) = 7.3, J(3,4) = 7.9, J(8,9) = 12.5 Hz.
Data in 2 N HCl in D2O: 7.25 (d, 1H, H-8); 7.71 (t, 1H, H-2); 7.80
(t, 1H, H-3); 7.84 (s, 1H, H-5); 7.94 (d, 1H, H-4); 8.01 (d, 1H, H-
1); 8.15 (d, 1H, H-9); same J values as in D2O. 13C NMR (CDCl3):
118.6 (C(5)); 127.9 (C(2)); 128.3(C(8)); 131.1 (C(3)); 132.3 (C(4));
132.9 (C(4a)); 134.3 (C(1)); 135.7 (C(9a)); 144.1 (C(9)); 154.8
(C(6)); 180.8 (CO(7).

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