Syntheses of biliverdin derivatives sterically locked at the CD-ring components

Article abstract of DOI:10.1246/bcsj.79.1561

Total syntheses of biliverdin derivatives with a Z-syn, Z-anti, or E-syn CD-ring components were accomplished via new and efficient methods for the construction of sterically locked CD-ring components towards the elucidation of the stereochemistry of the chromophore in phytochromes.

Full text of DOI:10.1246/bcsj.79.1561

Ó 2006 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 79, No. 10, 1561–1572 (2006) 1561
Syntheses of Biliverdin Derivatives Sterically Locked
at the CD-Ring Components
Mostafa A. S. Hammam, Hiroshi Nakamura, Yukari Hirata, Htoi Khawn,
ꢀ
Yasue Murata, Hideki Kinoshita, and Katsuhiko Inomata
Division of Material Sciences, Graduate School of Natural Science and Technology,
Kanazawa University, Kakuma, Kanazawa 920-1192
Received March 22, 2006; E-mail: inomata@cacheibm.s.kanazawa-u.ac.jp
Total syntheses of biliverdin derivatives with a Z-syn, Z-anti, or E-syn CD-ring components were accomplished via
new and efficient methods for the construction of sterically locked CD-ring components towards the elucidation of the
stereochemistry of the chromophore in phytochromes.
Light is vital for photosynthesis, and it is also necessary for
directing plant growth and development. The sensing of light
in environmental conditions is essential for plants as vision
is for animals. To fine-tune their development according to
light intensity, direction, wavelength, and periodicity, they
possess multiple light sensors. There are several light-sensing
systems involved in these responses, such as the blue light
sensitive system with cryptochrome1a or phototropin1b and the
red light sensitive system with phytochrome.1c Phytochromes
are chromoproteins that have either phytochromobilin (PꢀB)
or phytocyanobilin (PCB) as a chromophore, which is cova-
lently bound to the protein by a thioether bond through an
A-ring ethylidene side chain and responds to red and far-red
light through a reversible interchange between Z- and E-forms
at the C15 position of the chromophores (Fig. 1).2 This
double-bond photoisomerization converts the physiologically
inactive red light absorbing Pr form into the active far-red light
absorbing Pfr form and vice versa. The interchange between
the Pr and Pfr forms is essential for light absorbing biological
processes in the phytochrome chromophore function. Some
bacterial phytochromes have biliverdin (BV) as a natural chro-
mophore, and we have recently determined that BV covalently
binds to the apoprotein of Agrobacterium phytochrome Agp1
via its A-ring vinyl side chain.3
During photoconversion, the chromophore also moves
around the exocyclic single bonds. In principle, each single
bond can adopt either a syn or anti conformation.4 Vibrational
spectroscopy provided indirect insight into the conformation of
Me
O
S
Protein
S
Protein
3
Me
R
Me
Me
5
O
A
18
3
A
HN
NH
Me
D
18
D
15
Za
15
O
5
Zs
O
R
N
N
Za
Ea
H
H
ca. 660 nm
ca. 730 nm
NH
10
NH HN
10
HN
Me
Me
C
B
B
C
Me
Me
Me
Zs
Zs
CO2
CO2
CO2
CO2
Pr
Pfr
Me
R
Me
Me
R
18
O
O
3
O
O
18
3
A
Me
D
HN
A
NH
NH
Me
D
HN
NH
5
15
5
15
N
NH
N
C
B
Me
Me
C
B
Me
Me
10
10
CO2H
CO2H
CO2H
CO2H
R = Vinyl, Phytochromobilin (PΦB)
R = Ethyl, Phycocyanobilin (PCB)
R = Vinyl, Biliverdin (BV)
Fig. 1. Photoreversibility of phytochromes between Pr and Pfr, and the structure of phytochrome chromophores.
Published on the web October 10, 2006; doi:10.1246/bcsj.79.1561

1562 Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006)
Syntheses of Locked Biliverdin Derivatives
the phytochrome chromophore in the Pr, Pfr, and intermediate
states, but the data were ambiguous and have been interpreted
in different ways.2,5–7 For example, it was proposed that the
formation of Pfr is accompanied by a syn/anti rotation around
the C14–C15 single bond.5 More recently, interpretation of
resonance Raman spectra by density functional theory calcula-
tions proposed that the C14–C15 single bond is in an anti con-
formation throughout the entire photocycle and that the C5–C6
single bond rotates from anti to syn upon conversion from Pr to
Pfr as shown in Fig. 1.2
coupled according to the original Wittig-type coupling reac-
tion8b in which tributylphosphine and 1,8-diazabicyclo[5.4.0]-
Me
Me
Me
A
Me
A
Me
A
O
O
O
O
O
Me
Me
Me
D
D
HN
N
Me
HN
HN
N
HN
D
N
Zs
Es
O
Za
NH
N
N
N
N
C
B
C
B
B
Me
C
Me
Me
Me
CO2R
CO2R
CO2R
CO2R
CO2R
CO2R
1a, R = H
1b, R = Allyl
2a, R = H
2b, R = Allyl
3a, R = H
3b, R = Allyl
Me
To analyze the structure and function of the chromophore in
phytochromes, we have studied on the total syntheses of natu-
ral and unnatural chromophores.8–11 In this paper, we describe
the syntheses of three different types of BV derivatives, in
which the stereochemistry between the rings C and D are
locked in Z-syn, Z-anti, and E-syn configuration and conforma-
tion,12 respectively, to determine the stereochemistry of the
chromophore at the C15 position of Pr and Pfr forms and the
function of the reconstituted Agp1. The retro-synthetic analy-
ses of the three chromophores are shown in Fig. 2.
O
A
HN
HN
4
4
4
B
Me
H
Me
CO2Allyl
Me
O
Me
O
Me
Me
Me
D
D
HN
D
N
N
O
Za
Zs
NH
Es
N
C
C
N
CHO
C
Me
CHO
CHO
CO2Allyl
CO2Allyl
CO2Allyl
Results and Discussion
5
6
7
Preparation of Allyl (Z)-3-(4-Methyl-5-{[4-methyl-5-oxo-
3-vinyl-1H-pyrrol-2(5H)-ylidene]methyl}-1H-pyrrol-3-yl)-
propanoate (4). The AB-ring component 4 is common for all
chromophores prepared herein. We previously reported that it
can be readily prepared by cleavage of BV diallyl ester with
thiobarbituric acid in methanol; however, unusable barbituric
acid adducts were produced at the same time.13c Therefore,
an alternative method was developed starting from 3-methyl-
4-[2-(p-tolylthio)ethyl]-5-tosyl-1,5-dihydro-2H-pyrrol-2-one8f
(11) as the A-ring precursor and t-butyl 3-(3-allyloxy-3-oxo-
propyl)-5-formyl-4-methyl-1H-pyrrole-2-carboxylate8c (10a),
the latter of which is a precursor common to the B- and C-rings
of BV, as shown in Scheme 1. Compounds 11 and 10a were
R1 = CH2CH2OMs
R2 = Me
nBu3P
Base
Br
R1, R2 = Me
R
1 = Me
Base
Base
R2 = CH2CH2Cl
Br
Me
D
Me
O
R1
O
NH
R1
D
9a, R1 = Me
9b, R1 = CH2CH2OMs
R1 = Me
2 = Me or CH2CH2Cl
NH
Ts
R
Z
+
OHC
R2
NH
R2
NH
C
C
CO2tBu
CO2tBu
CO2Allyl
(Z)-8a, R1 = R2 = Me
(Z)-8b, R1 = Me, R2 = CH2CH2Cl
CO2Allyl
10a, R2 = Me
10b, R2 = CH2CH2Cl
Fig. 2. Retrosynthetic analysis of the sterically locked
chromophores 1–3.
Me
Sp-Tol
Me
O
Sp-To l
A
O
nBu3P (2.2 equiv.)
HN
A
11
HN
mCPBA (1.0 equiv.)
CH2Cl2, 0 °C, 20 min
Ts
DBU (1.1 equiv.)
+
THF, 0 °C
overnight
rt
HN
CHO
Me
B
Me
HN
tBuO2C
B
tBuO2C
CO2Allyl
10a
CO2Allyl
12, 88%
Me
O
Me
O
H
Sp-Tol
O
H
A
A
HN
HN
HN
HN
HCO2H/TFA (2/1)
Pyridine (10.0 equiv.)
DMF, reflux, 2 h
5 °C, 1 h
B
Me
B
Me
CO2Allyl
CO2Allyl
13
4, 57% (in 3 steps)
Scheme 1.

M. A. S. Hammam et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006) 1563
Me
Me
Me
O
Me
O
D
O
NH
+
nBu3P (2.5 equiv.)
DBU (1.5 equiv.)
NaH (6.7 equiv.)
Me
Me
D
C
Me
Me
D
NH
Br
N
9a Ts
OHC
Me
Br
THF, rt, overnight
(Z)-8a
Zs
THF, 0 °C
rt
NH
N
overnight
C
NH
CO2tBu
C
R
CO2tBu
CO2Allyl
CO2Allyl
10a
CO2Allyl
8a, 87% (E/Z mixture)
(E)-8a
14, 84%
1) TFA
rt, 30 min
(R = CO2tBu)
I2 (0.3 equiv.)
2) (MeO)3CH
rt, 1 h
CH2Cl2, rt, 20 h
5, quant.
(R = CHO)
(Z)-8a, 95%
Scheme 2.
H
O
1)
17(1.0 equiv.)
1) Ac2O (1.1 equiv.)
DMAP (0.2 equiv.)
CO2Me, KOH (0.1 equiv.)
MeOH, 0 °C rt, overnight
NO2
NO2
NO2
Br
THF, 0 °C
rt, 2.5 h
OAc
+
2) NaNO2 (2.0 equiv.)
Phloroglucinol (1.1 equiv.)
DMF, rt, overnight
2) Ac2O (1.1 equiv.)
DMAP (0.2 equiv.)
AcO
AcO
AcO
HO
CO2Me
CO2Me
THF, 0 °C
rt, 4 h
15
16, 53%
(in two steps)
18, 66% (in two steps)
t
1) KOH (5.0 equiv.)
MeOH, 0 °C, 2 h
CNCH2CO2 Bu (1.0 equiv.)
DBU (2.2 equiv.)
NH
NH
CO2tBu
t
CO2 Bu
AcO
HO
2) AllylBr (1.1 equiv.)
DBU (1.0 equiv.)
THF/DMF, 0 °C
1.5 h
MeCN, -40 °C rt, 6 h
rt
CO2Me
CO2Allyl
20, 60% (in two steps)
19, 55%
OHC
1) POCl3 (2.5 equiv.)
NH
DMF, 80 °C, 2 h
C
CO2tBu
Cl
2) aq. 10% NaOAc
rt, 2 h
CO2Allyl
10b, 94%
Scheme 3.
undec-7-ene (DBU) are used in THF to afford a mixture of Z-
and E-isomers of the AB-ring precursor 12 bearing a p-tolyl-
thioethyl side chain in 88% yield. Compound 12 was convert-
ed to the corresponding sulfoxide with mCPBA in CH2Cl2, fol-
lowed by treatment with a mixture of formic acid and trifluoro-
acetic acid (TFA) at 5 ꢁC to afford the decarboxylated dipyr-
rin-1(10H)-one intermediate 13. The crude product 13 was
refluxed in DMF in the presence of pyridine to afford the de-
sired AB-ring component 4 as only Z-isomer in 57% yield in
three steps from compound 12.
Preparation of Allyl (Z)-3-(2-Ethyl-8-formyl-1,10-di-
methyl-3-oxo-5,6-dihydro-3H-dipyrrolo[1,2-d:20,10-g][1,4]-
diazepin-9-yl)propanoate (5). The sterically locked CD-ring
component 5 bearing Z-syn configuration and conformation
was prepared via our Wittig-type coupling reaction between
3-ethyl-4-methyl-5-tosyl-1,5-dihydro-2H-pyrrol-2-one8b (9a)
and formylpyrrole 10a in the presence of a mixture of tributyl-
phosphine and DBU in THF to afford a mixture of coupling
products (Z)- and (E)-8a in 87% yield (Scheme 2). The cou-
pling product (E)-8a was readily converted to the correspond-
ing isomer (Z)-8a by treatment with a catalytic amount of
iodine in CH2Cl2 in 95% yield. Compound (Z)-8a, thus ob-
tained, was then reacted with 1,2-dibromoethane in the pres-
ence of NaH in THF to afford the cyclized CD-ring component
14 in 84% yield. The t-butoxycarbonyl group of compound 14
was converted to a formyl group by treating with TFA fol-
lowed by addition of trimethyl orthoformate (MeO)3CH at
room temperature to give the formylated CD-ring component
5 in quantitative yield.
Preparation of t-Butyl 3-(3-Allyloxy-3-oxopropyl)-4-
(2-chloroethyl)-5-formyl-1H-pyrrole-2-carboxylate (10b).
The formylpyrrole derivative11 10b was prepared starting from
the commercially available 3-bromo-1-propanol (15) as shown
in Scheme 3. Alcohol 15 was first acetylated using acetic

1564 Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006)
Syntheses of Locked Biliverdin Derivatives
Me
O
Me
Me
Me
Me
D
O
NH
+
nBu3P (2.5 equiv.)
DBU (1.5 equiv.)
Me
D
D
NH
NH
Ts
DBU (3.0 equiv.)
9a
N
O
Za
NH
(Z)-8b
C
THF, 50 °C
overnight
THF, 0 °C
rt, 4 h
R
OHC
C
CO2tBu
NH
Cl
C
CO2tBu
CO2Allyl
Cl
CO2Allyl
10b
CO2Allyl
8b, 98% (E/Z mixture)
(E)-8b
21, 76% (R = CO2tBu)
6, quant. (R = CHO)
1) TFA, rt
30 min
2) (MeO)3CH
I2 (0.3 equiv.)
CH2Cl2, rt, 24 h
(Z)-8b, 80%
0 °C rt, 1 h
Scheme 4.
Me
(8.2 equiv.)
KOH (0.05 equiv.)
MeOH, 0 °C rt, 2 h
O N
Me
1)
2
AcOH (1.0 equiv.)
Zn(OAc)2•2H2O
(0.2 equiv.)
H
O
O2N
AcO
OAc
H
O
OAc
2) Ac2O (1.2 equiv.)
DMAP (0.1 equiv.)
neat, 40 °C, 3 h
22, 40%
(based on AcOH)
THF, 0 °C
rt, 2 h
(1.5 equiv.)
23, 85% (in 2 steps)
Me
Me
1) PhMe3N+Br3- (1.2 equiv.)
CH2Cl2, 0 °C, 1 h
CNCH2Ts (1 equiv.)
DBU (2.1 equiv.)
Br
HN
OAc
OH
HN
2) 1 M NaOH/H2O (5 equiv.)
MeCN, -40 °C rt
5 h
Ts
MeOH, 0 °C rt, 1 h
Ts
25, 72% (in 2 steps)
24, 59%
1) MsCl (1.2 equiv.)
Et3N (2.0 equiv.)
Me
O
OMs
THF, 0 °C
rt, 30 min
D
HN
2) TFA, DMSO (4.0 equiv.)
rt, overnight
Zn (2.0 equiv.)
rt, 1 h
Ts
9b, 55% (in 2 steps)
Scheme 5.
anhydride in the presence of catalytic amount of 4-(dimethyl-
amino)pyridine (DMAP) in THF, followed by nitration with
sodium nitrite in the presence of phloroglucinol in DMF to
give 3-nitropropyl acetate (16) in 53% yield in two steps.
Compound 16 was coupled with the oxo-ester 17 in a manner
similar to our previous preparation of the B- and C-rings,8c,g
followed by acetylation of the resulting nitro-alcohol to give
the nitro-acetate 18 which was contaminated with the corre-
sponding nitro-olefin. When compound 18 was treated with
t-butyl isocyanoacetate and DBU according to Barton’s meth-
od14 in acetonitrile, the pyrrole derivative 19 was obtained in
55% yield. Hydrolysis of compound 19 with KOH in MeOH,
followed by allylation with allyl bromide in the presence of
DBU in THF/DMF afforded the pyrrole 20 in 60% yield.
When compound 20 was formylated by Vilsmeier reaction to
give the formylated product in situ, chlorination of the hydroxy
group proceeded simultaneously to afford the formylpyrrole
10b bearing 2-chloroethyl group in 94% yield.
propanoate (6). As shown in Scheme 4, compounds 9a and
10b were coupled according to the Wittig-type reaction devel-
oped in our laboratory using tributylphosphine in the presence
of DBU in THF to afford the CD-ring precursor 8b as a mix-
ture of E- and Z-isomers in 98% yield. We found that com-
pound (E)-8b should be converted to the Z-isomer by treating
with a catalytic amount of iodine in CH2Cl2 prior to the
cyclization. Compound (Z)-8b was cyclized at 50 ꢁC in the
presence of DBU in THF affording the desired product 21
in 76% yield. Subsequent formylation was accomplished by
treating with (MeO)3CH in TFA to give the formylated CD-
ring component 6 in quantitative yield.
Preparation of 3-Ethyl-4-[2-(mesyloxy)ethyl]-5-tosyl-1,5-
dihydro-2H-pyrrol-2-one (9b). The 5-tosylpyrrolinone de-
rivative 9b was prepared starting from propenal as shown in
Scheme 5. Treatment of propenal with acetic acid in the pres-
ence of catalytic amount of zinc diacetate afforded 3-oxopro-
pyl acetate (22) in 40% yield.15 Compound 22 was then cou-
pled with 1-nitropropane according to Henry reaction in the
presence of catalytic amount of KOH in MeOH. The resulting
Preparation of Allyl (Z)-3-(8-Ethyl-2-formyl-9-methyl-7-
oxo-1,4,5,7-tetrahydrodipyrrolo[1,2-a:20,30-d]azepin-3-yl)-

M. A. S. Hammam et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006) 1565
Me
Me
O
Me
O
OMs
O
D
HN
9b
nBu3P (2.0 equiv.)
DBU (3.1 equiv.)
D
D
HN
HN
Ts
1) TFA, rt, 30 min
2) (MeO)3CH, rt, 1 h
Es
Es
+
N
C
N
C
THF, 0 °C
rt
OHC
Me
Me
overnight
CO2tBu
NH
CHO
C
Me
CO2tBu
CO2Allyl
CO2Allyl
10a
CO2Allyl
26, 65%
7, 85%
Scheme 6.
catalyzed reaction using sodium p-toluenesulfinate (NaTs) as a
nucleophile in THF/MeOH to give the desired chromophores
1a, 2a, and 3a in 80, 90, and 42% yields, respectively, in free
acid forms.
Table 1. Construction of the Biliverdin Derivatives with the
Sterically Locked CD-Ring Components
4, H2SO4 (2.0 equiv.)
CD-Ring Component
Sterically Locked BV
Diallyl Ester
Chromophores 1a, 2a, and 3a were attached to the Agp1 apo-
protein to determine the stereochemistry of CD-ring component
of BV in Agp1. It was found that compound 2a, which is a BV
derivative having 15Za configuration and conformation, forms
a covalent bond with Agp1 apoprotein, and the absorption spec-
trum corresponding to Pr form was observed. Furthermore, size
exclusion chromatograph of Agp1-M15 (the N-terminal 504
amino acids of Agp1) apoprotein adduct with compound 2a and
the autophosphorylation of the Agp1 adduct with compound 2a
showed that the stereochemistry of CD-ring moiety of Pr form
of natural Agp1 is 15Za.16 Recently, we also prepared another
derivative of the chromophore in which the stereochemistry of
the CD-ring moiety is fixed to 15Ea.17 This 15Ea chromophore
was also attached to the Agp1 apoprotein, and the adduct was
found to be the Pfr form of Agp1.16 From these results, sterical-
ly locked chromophores will open new avenues of investigation
concerning the stereochemistry and function of phytochrome
chromophores both in vitro and in vivo.
MeOH, rt, 1 h
[Pd(PPh3)4] (0.2 equiv.)
NaTs (2.0 equiv.)
Sterically Locked BV
THF/MeOH, rt, 10 min
CD-ring
component
Sterically locked
BV diallyl ester/%
Sterically locked
BV/%
5
6
7
1b, 69
2b, 87
3b, 45
1a, 80
2a, 90
3a, 42
nitro-alcohol was then acetylated using acetic anhydride in the
presence of catalytic amount of DMAP in THF to give the
nitro-diacetate 23 in 85% yield in two steps. Compound 23
was reacted under Barton’s method conditions, i.e., tosylmeth-
yl isocyanide (TosMIC) in the presence of DBU, to afford
tosylpyrrole derivative 24 in 59% yield. Compound 24 was
then brominated with trimethylphenylammonium tribromide
(PhMe3NþBr3ꢂ) in CH2Cl2, followed by hydrolysis of the
acetoxy group with 1 M (¼ 1 mol dmꢂ1) aq NaOH in MeOH
to give compound 25 in 72% yield in two steps. Mesylation
and subsequent redox-type reaction8a,i using DMSO and zinc
in TFA afforded the 5-tosylpyrrolinone derivative 9b in 55%
yield in two steps.
Preparation of Allyl (E)-3-(3-Ethyl-7-formyl-9-methyl-2-
oxo-1,2,4,5-tetrahydrodipyrrolo[1,2-a:20,30-d]azepin-8-yl)-
propanoate (7). As shown in Scheme 6, compounds 9b and
10a were coupled by a Wittig-type reaction with tributylphos-
phine in the presence of DBU in THF to afford directly the
cyclized CD-ring component 26 as E-syn isomer in 65% yield.
Formylation reaction was carried out by treating with TFA and
subsequent addition of (MeO)3CH to give the formylated CD-
ring component 7 in 85% yield.
Experimental
1H NMR spectra were recorded on JEOL JNM-GX Lambda
400 and 300 NMR spectrometers. Chemical shifts are reported
in ꢀ-scale relative to TMS (ꢀ ¼ 0) as an internal standard. The
IR spectra were measured on a JASCO FT/IR-230 spectrometer,
and the MS spectra were recorded by using Hitachi M-80 and
JEOL SX-102A mass spectrometers. All solvents were distilled
and stored over drying agents. THF was freshly distilled from
sodium diphenylketyl. Thin-layer chromatography (TLC) and
flash column chromatography were performed using Merck’s
silica gel 60 PF254 (Art. 7749) and Cica-Merck’s silica gel 60
(No. 9385-5B), respectively. Commercially available reagents
were used without further purification, unless otherwise noted.
t-Butyl 3-(3-Allyloxy-3-oxopropyl)-4-methyl-5-({4-methyl-5-
oxo-3-[2-(p-tolylthio)ethyl]-1H-pyrrol-2(5H)-ylidene}methyl)-
1H-pyrrole-2-carboxylate (12). To a mixed solution of 5-tosyl-
pyrrolinone8e 11 (2.0 g, 5 mmol) and formylpyrrole8b 10a (1.6 g,
5 mmol) in THF (30 mL) was added nBu3P (2.7 mL, 11 mmol)
dropwise at 0 ꢁC under N2, followed by dropwise addition of
DBU (0.82 g, 5.5 mmol) in THF (2 mL). The reaction mixture
was allowed to stir at room temperature overnight. The solvent
was removed under reduced pressure, and the residue was parti-
tioned between EtOAc and water. The organic layer was washed
with both a saturated aqueous solution of NH4Cl and brine, and
Construction of the Biliverdin Derivatives as 15Z-syn,
15Z-anti, and 15E-syn Chromophores in Free Acid Forms.
Coupling reactions between the CD-ring components 5, 6,
and 7, prepared above, with the AB-ring component 4 were
carried out in methanol under acidic conditions to afford the
sterically locked BV diallyl ester derivatives 1b, 2b, and 3b
in 69, 87, and 45% yields, respectively (Table 1).
Finally, the carboxylate groups were deprotected via a Pd0-

1566 Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006)
Syntheses of Locked Biliverdin Derivatives
then dried over MgSO4. The solvent was evaporated, and the
product was separated by flash column chromatography (SiO2,
hexane/EtOAc = 4/1, v/v) to give compound 12 (2.42 g, 88%)
as a yellow solid of the mixture of (Z)- (60%) and (E)-isomers
(28%). Mp 177.5–178.0 ꢁC (from EtOAc/hexane). IR (KBr) 3330,
3122, 2974, 1735, 1695, 1656, 1450, 1365, 1273, 1157, 1132, 987,
1.4 mmol) in THF (2.0 mL). The reaction mixture was allowed to
stir at room temperature overnight. The solvent was removed
under reduced pressure, and the residue was partitioned between
EtOAc and water. The organic layer was washed with a saturated
aqueous solution of NH4Cl and with brine, and dried over MgSO4.
The solvent was evaporated, and the residue was separated by
flash column chromatography (SiO2, hexane/EtOAc = 4/1, v/v)
to afford compound 8a (349 mg, 87%) as a yellow solid [a mixture
of (Z)- (27%) and (E)-isomers (60%)]. IR (KBr) 3329, 3130, 2969,
2927, 2871, 1739, 1696, 1657, 1453, 1368, 1275, 1265, 1136, 779,
720 cmꢂ1. The (Z)- and (E)-isomers were further separated by
repeating the flash column chromatography with a longer column
under the same conditions. 1H NMR (CDCl3, 300 MHz) (Z)-8a: ꢀ
1.09 (t, J ¼ 7:5 Hz, 3H), 1.56 (s, 9H), 2.08 (s, 3H), 2.10 (s, 3H),
2.42 (q, J ¼ 7:4 Hz, 2H), 2.54 (t, J ¼ 8:1 Hz, 2H), 3.02 (t, J ¼ 8:1
Hz, 2H), 4.59 (d, J ¼ 5:9 Hz, 2H), 5.23 (d, J ¼ 10:5 Hz, 1H), 5.30
(d, J ¼ 17:2 Hz, 1H), 5.91 (ddt, J ¼ 17:2, 10.5, 5.9 Hz, 1H), 5.93
(s, 1H), 8.95 (s, 1H), 9.40 (s, 1H); (E)-8a: ꢀ 1.08 (t, J ¼ 7:5 Hz,
3H), 1.56 (s, 9H), 1.87 (s, 3H), 1.99 (s, 3H), 2.35 (q, J ¼ 7:5 Hz,
2H), 2.56 (t, J ¼ 7:9 Hz, 2H), 3.02 (t, J ¼ 8:0 Hz, 2H), 4.58 (d,
J ¼ 5:7 Hz, 2H), 5.23 (d, J ¼ 10:5 Hz, 1H), 5.31 (d, J ¼ 17:2 Hz,
1H), 5.91 (ddt, J ¼ 17:2, 10.5, 5.7 Hz, 1H), 6.17 (s, 1H), 8.63 (s,
1H), 9.05 (s, 1H). (E)-8a (210 mg, 0.5 mmol) was treated with a
catalytic amount of iodine (41 mg, 0.16 mmol) in CH2Cl2 (10 mL)
for 20 h at room temperature. The solvent was evaporated, and the
residue was partitioned between EtOAc and water. The organic
layer was successively washed with a saturated aqueous solution
of NaHSO3, a solution of NaHCO3, and brine, and then dried over
MgSO4. The solvent was evaporated, and the residue was separat-
ed by flash column chromatography (SO2, hexane/EtOAc = 4/1,
v/v) to give (Z)-8a (200 mg) in 95% yield. Mp 164–166 ꢁC (from
EtOAc/hexane). Found: C, 67.16; H, 7.49; N, 6.48%. Calcd for
C24H32N2O5: C, 67.27; H, 7.53; N, 6.54%.
847, 810, 760 cmꢂ1 1H NMR (CDCl3, 300 MHz) (Z)-isomer: ꢀ
;
1.56 (s, 9H), 1.93 (s, 3H), 2.00 (s, 3H), 2.34 (s, 3H), 2.54 (t, J ¼
8:1 Hz, 2H), 2.79 (t, J ¼ 7:9 Hz, 2H), 2.82 (t, J ¼ 8:3 Hz, 2H),
3.08 (t, J ¼ 8:3 Hz, 2H), 4.59 (d, J ¼ 5:7 Hz, 2H), 5.23 (dd, J ¼
10:4, 1.3 Hz, 1H), 5.31 (dd, J ¼ 17:2, 1.3 Hz, 1H), 5.79 (s, 1H),
5.92 (ddt, J ¼ 17:2, 10.4, 5.7 Hz, 1H), 7.13 (d, J ¼ 8:1 Hz, 2H),
7.32 (d, J ¼ 8:1 Hz, 2H), 9.48 (brs, 1H), 9.52 (brs, 1H); (E)-iso-
mer: ꢀ 1.57 (s, 9H), 1.82 (s, 3H), 1.96 (s, 3H), 2.29 (s, 3H), 2.55
(t, J ¼ 8:0 Hz, 2H), 2.55–2.65 (m, 4H), 3.00 (t, J ¼ 8:0 Hz, 2H),
4.59 (d, J ¼ 5:7 Hz, 2H), 5.23 (d, J ¼ 10:5 Hz, 1H), 5.31 (dd, J ¼
17:2, 1.3 Hz, 1H), 5.92 (ddt, J ¼ 17:2, 10.4, 5.7 Hz, 1H), 6.11 (s,
1H), 7.03 (d, J ¼ 8:2 Hz, 2H), 7.09 (d, J ¼ 8:2 Hz, 2H), 8.20 (brs,
1H), 8.98 (brs, 1H). Found: C, 67.62; H, 6.93; N, 4.82%. Calcd for
C31H38N2O5S: C, 67.61; H, 6.95; N, 5.09%.
Allyl (Z)-3-{4-Methyl-5-[(4-methyl-5-oxo-3-vinyl-1H-pyr-
rol-2(5H)-ylidene)methyl]-1H-pyrrol-3-yl}propanoate (4). To
a solution of compound 12 (2.42 g, 4.4 mmol) in CH2Cl2 (20 mL),
a solution of mCPBA (70% purity, 1.085 g, 4.4 mmol) in CH2Cl2
(5 mL) was added dropwise at 0 ꢁC, and the mixture was allowed
to stir for 20 min. The reaction mixture was quenched by the ad-
dition of a saturated aqueous solution of NaHSO3, and then, the
organic solvent was removed under reduced pressure. The residue
was partitioned between EtOAc and water. The organic layer was
washed with a saturated aqueous solution of NaHCO3 and with
brine, and dried over MgSO4. The solvent was evaporated, and
the solid residue was dissolved in a mixture of formic acid and
TFA (2/1, v/v, 9 mL/mmol) and allowed to stir at 5 ꢁC for 1 h.
The reaction mixture was treated with solid Na2CO3 and was par-
titioned between EtOAc and water. The organic layer was washed
with a saturated aqueous solution of NaHCO3 and brine, and dried
over Na2SO4. The solvent was evaporated, and the residual mix-
ture was dissolved in DMF (20 mL) under N2. After addition of
pyridine (3 mL, 44 mmol), the mixture was refluxed for 2 h with
stirring. The reaction mixture was partitioned between EtOAc/
Et2O and water, and the organic layer was successively washed
with 1 M HCl, a saturated aqueous solution of NaHCO3 and brine,
and then dried over MgSO4. The solvent was evaporated, and the
residue was separated by flash column chromatography (SiO2,
hexane/EtOAc = 3/1, v/v) to afford compound 4 as a yellow sol-
id (850 mg) in 57% yield in three steps. Mp 151–153 ꢁC (from
EtOAc/hexane). IR (KBr) 3336, 3154, 2920, 1738, 1657, 1638,
t-Butyl (Z)-9-(3-Allyloxy-3-oxopropyl)-2-ethyl-1,10-dimethyl-
3-oxo-5,6-dihydro-3H-dipyrrolo[1,2-d:20,10-g][1,4]diazepine-8-
carboxylate (14). To a suspension of NaH (34 mg, 60% in min-
eral oil, 0.8 mmol) in THF (1 mL) was added a catalytic amount of
18-crown-6 (32 mg, 0.12 mmol), suspended in THF (1 mL), and a
solution of compound (Z)-8a (52 mg, 0.12 mmol) in THF (2 mL),
followed by the addition of 1,2-dibromoethane (3 mL). The mix-
ture was stirred at room temperature overnight. The solvent was
removed under reduced pressure, and the residue was partitioned
between EtOAc and water. The organic layer was washed with
brine and dried over MgSO4. The solvent was evaporated, and
the residue was purified by flash column chromatography (SiO2,
hexane/EtOAc = 3/1, v/v) to afford compound 14 (46 mg, 84%)
as a yellow solid. Mp 70–71 ꢁC (from EtOAc/hexane). IR (neat)
2976, 2933, 1738, 1691, 1458, 1425, 1396, 1370, 1345, 1294,
1442, 1418, 1377, 1339, 1262, 1171, 984, 926, 808, 756 cmꢂ1
;
1H NMR (CDCl3, 400 MHz) ꢀ 1.95 (s, 3H), 2.09 (s, 3H), 2.59 (t,
J ¼ 7:7 Hz, 2H), 2.76 (t, J ¼ 7:6 Hz, 2H), 4.60, (d, J ¼ 5:6 Hz,
2H), 5.23 (d, J ¼ 10:5 Hz, 1H), 5.31 (d, J ¼ 17:1 Hz, 1H), 5.56 (d,
J ¼ 17:5 Hz, 1H), 5.58 (d, J ¼ 11:5 Hz, 1H), 5.92 (ddt, J ¼ 17:1,
10.5, 5.6 Hz, 1H), 6.18 (s, 1H), 6.59 (dd, J ¼ 17:6, 11.7 Hz, 1H),
6.77 (brd, J ¼ 1:7 Hz, 1H), 10.53 (s, 1H), 11.34 (s, 1H). Found: C,
69.90; H, 6.71; N, 8.56%. Calcd for C19H22N2O3: C, 69.92; H,
6.79; N, 8.58%.
1243, 1167, 1128, 1047, 1002, 959, 849, 773 cmꢂ1 1H NMR
;
(CDCl3, 400 MHz) ꢀ 1.12 (t, J ¼ 7:6 Hz, 3H), 1.58 (s, 9H), 2.09
(s, 3H), 2.13 (s, 3H), 2.39 (q, J ¼ 7:6 Hz, 2H), 2.53 (t, J ¼ 8:1 Hz,
2H), 3.00 (t, J ¼ 8:1 Hz, 2H), 4.59 (d, J ¼ 5:9 Hz, 2H), 5.23 (dd,
J ¼ 10:2, 1.7 Hz, 1H), 5.30 (dd, J ¼ 17:3, 1.7 Hz, 1H), 5.93 (ddt,
J ¼ 17:3, 10.2, 5.9 Hz, 1H), 5.99 (s, 1H). The protons of the ethyl-
ene bridge were not observed clearly. Found: C, 68.58; H, 7.47; N,
6.08%. Calcd for C26H34N2O5: C, 68.70; H, 7.54; N, 6.16%.
Allyl (Z)-3-(2-Ethyl-8-formyl-1,10-dimethyl-3-oxo-5,6-di-
hydro-3H-dipyrrolo[1,2-d:20,10-g][1,4]diazepin-9-yl)propanoate
(5). A solution of compound 14 (46 mg, 0.1 mmol) in TFA
(1 mL) was allowed to stir for 30 min at room temperature under
N2. Then, (CH3O)3CH (0.5 mL) was added dropwise. After stir-
ring for 1 h at room temperature, the reaction mixture was
t-Butyl 3-(3-Allyloxy-3-oxopropyl)-5-[(4-ethyl-3-methyl-5-
oxo-1H-pyrrol-2(5H)-ylidene)methyl]-4-methyl-1H-pyrrole-2-
carboxylate (8a). To a mixed solution of 5-tosylpyrrolinone 9a8b
(313 mg, 1.1 mmol) and formylpyrrole 10a8a (300 mg, 0.9 mmol)
in THF (18 mL) was added nBu3P (0.6 mL, 2.3 mmol) dropwise
at 0 ꢁC under N2, followed by dropwise addition of DBU (213 mg,

M. A. S. Hammam et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006) 1567
quenched by adding water and extracted with EtOAc, and then,
the organic layer was washed with a saturated aqueous solution
of NaHCO3 and with brine, and dried over MgSO4. The solvent
was evaporated, and the residue was separated by flash column
chromatography (SiO2, hexane/EtOAc = 3/1, v/v) to give com-
pound 5 as a yellow solid in quantitative yield (38 mg). Mp 88–
89 ꢁC (from EtOAc/hexane). IR (KBr) 2970, 2932, 2874, 1735,
1689, 1639, 1427, 1369, 1339, 1285, 1242, 1161, 1062, 840, 774,
722 cmꢂ1; 1H NMR (CDCl3, 300 MHz) ꢀ 1.12 (t, J ¼ 7:7 Hz, 3H),
2.11 (s, 3H), 2.14 (s, 3H), 2.40 (q, J ¼ 7:5 Hz, 2H), 2.58 (t, J ¼
7:6 Hz, 2H), 3.03 (t, J ¼ 7:6 Hz, 2H), 4.02 (br, 2H), 4.58 (d, J ¼
5:7 Hz, 2H), 5.23 (d, J ¼ 10:5 Hz, 1H), 5.29 (d, J ¼ 17:2 Hz, 1H),
5.91 (ddt, J ¼ 17:2, 10.5, 5.7 Hz, 1H), 5.98 (s, 1H), 9.70 (s, 1H).
The protons of the ethylene bridge were not observed clearly.
Found: C, 68.97; H, 6.73; N, 7.27%. Calcd for C22H26N2O4: C,
69.09; H, 6.85; N, 7.32%.
J ¼ 7:3 Hz, 2H), 3.24 (t, J ¼ 7:3 Hz, 2H), 3.34 (t, J ¼ 7:3 Hz,
2H), 4.52 (br, 2H), 4.84 (br, 2H), 5.56 (d, J ¼ 11:7 Hz, 1H),
5.63 (d, J ¼ 17:8 Hz, 1H), 5.99 (s, 1H), 6.26 (s, 1H), 6.68 (dd,
J ¼ 17:8, 11.5 Hz, 1H), 7.62 (s, 1H). Protons of CO2H and NH
were not observed clearly. UV–vis (MeOH) ꢁmax 383 (" ¼
39850), 639 (" ¼ 18650) nm. HRMS (FAB) (Mþ þ 1), Found:
m=z 611.2876. Calcd for C35H39N4O6: 611.2869.
3-Nitropropyl Acetate (16). To a mixed solution of DMAP
(1.952 g, 16 mmol) and 3-bromopropan-1-ol 15 (11.12 g, 80 mmol)
in THF (40 mL) was added Ac2O (9.7 mL, 88 mmol) dropwise
under N2 at 0 ꢁC. After stirring for 30 min at 0 ꢁC and 2.5 h at
room temperature, the solvent was removed under reduced pres-
sure, and the residue was partitioned between EtOAc and water.
The organic extract was washed with a saturated aqueous solution
of NaHCO3 and with brine, and dried over MgSO4. The solvent
was evaporated to give the acetylated product (12.742 g, 88%)
as a colorless oil, which was used for the next reaction without
further purification. IR (neat) 2966, 2902, 1741, 1439, 1387, 1366,
Allyl 3-{(Z)-2-{[(Z)-2-(3-Allyloxy-3-oxopropyl)-9-ethyl-1,10-
dimethyl-8-oxo-5,6-dihydro-8H-dipyrrolo[1,2-d:20,10-g][1,4]di-
azepin-3-yl]methylene}-4-methyl-5-[(Z)-(4-methyl-5-oxo-3-vinyl-
1H-pyrrol-2(5H)-ylidene)methyl]-2H-pyrrol-3-yl}propanoate
(1b). To a mixed solution of compounds 5 (38 mg, 0.1 mmol) and
4 (33 mg, 0.1 mmol) in MeOH (4 mL), a solution of H2SO4
(20 mg, 0.2 mmol) in MeOH (1 mL) was added dropwise at room
temperature under N2, and the mixture was allowed to stir for 1 h.
The reaction mixture was quenched by addition of a buffer solu-
tion (pH 7.0) and partitioned between EtOAc and water. The or-
ganic layer was washed with brine and dried over Na2SO4. The
solvent was evaporated, and the blue residue was separated by thin
layer chromatography (SiO2, hexane/CHCl3/MeOH = 7/4/0.5,
v/v/v) to afford compound 1b as a blue solid (47 mg, 69%).
Mp 63–65 ꢁC (from EtOAc/hexane). IR (KBr) 3536, 2965, 1733,
1698, 1675, 1589, 1456, 1414, 1357, 1317, 1269, 1201, 1160,
1238, 1037 cmꢂ1 1H NMR (CDCl3, 300 MHz) ꢀ 2.06 (s, 3H),
;
2.18 (quint, J ¼ 6:2 Hz, 2H), 3.47 (t, J ¼ 6:5 Hz, 2H), 4.20 (t, J ¼
6:1 Hz, 2H) ppm. The resulting 3-bromopropyl acetate (12.62 g,
70 mmol) was treated with NaNO2 (9.62 g, 140 mmol) and phloro-
glucinol (12.472 g, 77 mmol) under N2 in DMF (100 mL), and the
mixture was allowed to stir overnight at room temperature. The
mixture was then partitioned between EtOAc/Et2O and water,
and the organic extract was washed with brine and dried over
MgSO4. The solvent was evaporated, and the product was purified
by flash column chromatography (SiO2, hexane/EtOAc = 2/1,
v/v) to give compound 16 as an oil in 60% yield (6.174 g); IR
(neat) 2253, 1740, 1556, 1363, 1223 cmꢂ1; 1H NMR (CDCl3, 300
MHz) ꢀ 2.07 (s, 3H), 2.36 (quint, J ¼ 6:6 Hz, 2H), 4.19 (t, J ¼
6:1 Hz, 2H), 4.50 (t, J ¼ 6:8 Hz, 2H). HRMS (TOF) (Mþ þ 1),
Found: m=z 148.0641. Calcd for C5H10NO4: 148.0610.
1104, 986, 961, 932 cmꢂ1 1H NMR (CDCl3, 400 MHz) ꢀ 1.11
;
(t, J ¼ 7:3 Hz, 3H), 2.05 (s, 3H), 2.09 (s, 3H), 2.14 (s, 3H), 2.18
(s, 3H), 2.39 (q, J ¼ 7:6 Hz, 2H), 2.53 (t, J ¼ 8:1 Hz, 2H), 2.59 (t,
J ¼ 7:6 Hz, 2H), 2.96 (t, J ¼ 7:6 Hz, 2H), 2.99 (t, J ¼ 7:6 Hz,
2H), 3.79–4.24 (br, 2H), 4.52 (d, J ¼ 5:6 Hz, 2H), 4.57 (d, J ¼
5:6 Hz, 2H), 5.18 (dd, J ¼ 10:3, 1.2 Hz, 1H), 5.20 (dd, J ¼ 10:2,
1.5 Hz, 1H), 5.23 (dd, J ¼ 16:8, 1.4 Hz, 1H), 5.27 (dd, J ¼ 17:3,
1.5 Hz, 1H), 5.66 (d, J ¼ 11:5 Hz, 1H), 5.70 (d, J ¼ 18:8 Hz, 1H),
5.85 (ddt, J ¼ 16:7, 10.8, 5.6 Hz, 1H), 5.88 (ddt, J ¼ 16:1, 11.0,
5.6 Hz, 1H), 6.03 (s, 2H), 6.62 (dd, J ¼ 17:9, 11.5 Hz, 1H), 6.94
(s, 1H), 10.49 (brs, 1H). The protons of the ethylene bridge were
not observed clearly. Found: C, 71.24; H, 6.68; N, 8.08%. Calcd
for C41H46N4O6: C, 71.28; H, 6.71; N, 8.11%.
t-Butyl 4-(2-Acetoxyethyl)-3-(3-methoxy-3-oxopropyl)-1H-
pyrrole-2-carboxylate (19). To a mixture of methyl 4-oxobutan-
oate 17 (2.32 g, 20 mmol) and compound 16 (2.94 g, 20 mmol), a
solution of KOH (131 mg, 2 mmol) in MeOH (3 mL) was added
dropwise at 0 ꢁC, and the mixture was allowed to stir overnight
at room temperature. After evaporation of the solvent, the residue
was partitioned between EtOAc and water. The organic layer was
washed with a saturated aqueous solution of NaHCO3 and with
brine, and dried over MgSO4. The solvent was evaporated to give
the nitro-alcohol as a crude product. This product was mixed with
DMAP (488 mg, 4 mmol) in THF (15 mL) at 0 ꢁC, and Ac2O
(2.1 mL, 22 mmol) was added dropwise with stirring at room tem-
perature. After stirring for 4 h, the mixture was quenched by
MeOH (2 mL) for 15 min. The solvent was removed under re-
duced pressure and the residue was partitioned between EtOAc
and water. The organic extract was washed with both a saturated
aqueous solution of NaHCO3 and brine, and dried over MgSO4.
The solvent was evaporated, and the product was isolated by flash
column chromatography (SiO2, hexane/EtOAc = 3/1, v/v) to
give a mixture of diastereomers of compound 18 (4.03 g, ca. 66%
yield) contaminated with the corresponding nitro-olefin as an oil.
To a solution of t-butyl isocyanoacetate (1.27 g, 9 mmol) in
MeCN (10 mL) at ꢂ40 ꢁC under N2, DBU (2.95 mL, 19.8 mmol)
was added, followed by dropwise addition of compound 18
(2.748 g, 9 mmol) in MeCN (5 mL). After stirring for 6 h at room
temperature, the solvent was removed under reduced pressure, and
the residue was partitioned between EtOAc and water. The extract
was successively washed with a saturated aqueous solution of
NaHSO3, a solution of NaHCO3, and brine, and then dried over
3-{(Z)-2-{[(Z)-2-(2-Carboxyethyl)-9-ethyl-1,10-dimethyl-8-
oxo-5,6-dihydro-8H-dipyrrolo[1,2-d:20,10-g][1,4]diazepin-3-yl]-
methylene}-4-methyl-5-[(Z)-(4-methyl-5-oxo-3-vinyl-1H-pyrrol-
2(5H)-ylidene)methyl]-2H-pyrrol-3-yl}propanoic Acid (1a).
To a mixed solution of 1b (38 mg, 0.05 mmol) and [Pd(PPh3)4]
(13 mg, 0.011 mmol) in THF (1.4 mL), a solution of NaTs (20 mg,
0.11 mmol) in MeOH (1.4 mL) was added at room temperature un-
der N2. After stirring for 10 min, the solvent was evaporated, and
the residue was separated by flash column chromatography (SiO2,
CHCl3/MeOH/AcOH = 200/15/1, v/v/v). The solvent of the
blue fraction was evaporated, and the resulting solid residue was
recrystallized from CHCl3/hexane to afford compound 1a as a
blue solid (24 mg, 80%). Decomposed above 270 ꢁC. IR (KBr)
3537, 3265, 3022, 2944, 2293, 2253, 1931, 1443, 1375, 1230,
1038, 919, 759, 668 cmꢂ1 1H NMR (C5D5N, 400 MHz) ꢀ 1.03
;
(t, J ¼ 7:6 Hz, 3H), 1.90 (s, 3H), 1.98 (s, 3H), 2.11 (s, 3H), 2.16
(s, 3H), 2.33 (q, J ¼ 7:6 Hz, 2H), 2.85 (t, J ¼ 7:3 Hz, 2H), 2.91 (t,

1568 Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006)
Syntheses of Locked Biliverdin Derivatives
MgSO4. The solvent was evaporated, and the residue was separat-
ed by flash column chromatography (SiO2, hexane/EtOAc = 4/1,
v/v) to give compound 19 (1.69 g, 55%) as an oil. IR (neat) 3320,
2977, 2936, 1737, 1720, 1684, 1455, 1408, 1368, 1243, 1135,
1050, 933 cmꢂ1; 1H NMR (CDCl3, 400 MHz) ꢀ 1.57 (s, 9H), 2.05
(s, 3H), 2.53 (t, J ¼ 8:2 Hz, 2H), 2.78 (t, J ¼ 7:1 Hz, 2H), 3.01 (t,
J ¼ 8:1 Hz, 2H), 3.67 (s, 3H), 4.18 (t, J ¼ 7:1 Hz, 2H), 6.71 (d,
J ¼ 2:9 Hz, 1H), 9.10 (brs, 1H). HRMS (TOF) (Mþ þ 1), Found:
m=z 340.1775. Calcd for C17H26NO6: 340.1760.
solution of DBU (83 mg, 0.56 mmol) in THF (2 mL). The reaction
mixture was allowed to stir for 4 h at room temperature. The sol-
vent was removed under reduced pressure, and the residue was
partitioned between EtOAc and water. The organic layer was
washed with a saturated aqueous solution of NH4Cl and with
brine, and dried over MgSO4. The solvent was evaporated, and
the residue was separated by flash column chromatography (SiO2,
hexane/EtOAc = 4/1, v/v) to give 8b as a yellow solid mixture
(175 mg, 98%) of (Z)- (14%) and (E)-isomers (84%). IR (KBr)
3335, 2974, 2931, 1733, 1693, 1654, 1450, 1392, 1368, 1281,
1162, 1136, 1080, 987, 847, 779, 717, 685 cmꢂ1. The (Z)- and
(E)-isomers were further separated by repeating the flash column
chromatography with a longer column under the same conditions.
1H NMR (CDCl3, 400 MHz) (E)-8b: ꢀ 1.07 (t, J ¼ 7:6 Hz, 3H),
1.54 (s, 9H), 2.11 (s, 3H), 2.44 (q, J ¼ 7:6 Hz, 2H), 2.59 (t,
J ¼ 7:6 Hz, 2H), 3.00 (t, J ¼ 7:6 Hz, 2H), 3.01 (t, J ¼ 7:6 Hz,
2H), 3.45 (t, J ¼ 7:6 Hz, 2H), 4.58 (d, J ¼ 5:6 Hz, 2H), 5.22 (dd,
J ¼ 10:5, 1.2 Hz, 1H), 5.30 (dd, J ¼ 17:1, 1.5 Hz, 1H), 5.91 (ddt,
J ¼ 16:9, 10.0, 5.6 Hz, 1H), 5.94 (s, 1H), 10.04 (s, 1H), 10.33 (s,
1H). (Z)-8b: ꢀ 1.07 (t, J ¼ 7:6 Hz, 3H), 1.56 (s, 9H), 1.78 (s, 3H),
2.33 (q, J ¼ 7:6 Hz, 2H), 2.61 (t, J ¼ 8:0 Hz, 2H), 2.91 (t, J ¼ 7:5
Hz, 2H), 3.01 (t, J ¼ 8:0 Hz, 2H), 3.53 (t, J ¼ 7:5 Hz, 2H), 4.59
(dt, J ¼ 5:9, 1.4 Hz, 2H), 5.23 (dq, J ¼ 10:5, 1.2 Hz, 1H), 5.31
(dq, J ¼ 17:1, 1.4 Hz, 1H), 5.92 (ddt, J ¼ 17:3, 10.2, 5.9 Hz, 1H),
6.20 (s, 1H), 9.08 (s, 1H), 9.56 (s, 1H). Compound (E)-8b was
converted to its isomer (Z)-8b as follows: A mixed solution of
compound (E)-8b (26 mg, 0.05 mmol) and iodine (5 mg, 0.015
mmol) in CH2Cl2 (3 mL) was stirred for 24 h at room temperature.
The solvent was removed under reduced pressure, and the residue
was partitioned between EtOAc and water. The organic layer was
washed with both a saturated aqueous solution of NaHSO3 and
brine, and dried over MgSO4. The solvent was evaporated, and
the residue was separated by flash column chromatography (SiO2,
hexane/EtOAc = 4/1, v/v) to give compound (Z)-8b in 80%
yield (21 mg). Mp 137–138 ꢁC (from EtOAc/hexane). Found: C,
62.90; H, 6.97; N, 5.81%. Calcd for C25H33ClN2O5: C, 62.95;
H, 6.97; N, 5.87%.
t-Butyl (Z)-3-(3-Allyloxy-3-oxopropyl)-8-ethyl-9-methyl-7-
oxo-1,4,5,7-tetrahydrodipyrrolo[1,2-a:20,30-d]azepine-2-carbox-
ylate (21). To a solution of compound (Z)-8b (490 mg, 1.0 mmol)
in THF (20 mL), DBU (0.46 mL, 3.0 mmol) was added under N2,
and the mixture was allowed to stir at 50 ꢁC overnight. The sol-
vent was removed under reduced pressure, and the residue was
partitioned between EtOAc and water. The organic layer was
washed with brine and dried over MgSO4. The solvent was evapo-
rated, and the residue was separated by flash column chromatog-
raphy (SiO2, hexane/EtOAc = 4/1, v/v) to give the product 21 in
76% yield (335 mg) as a yellow solid. Mp 73–75 ꢁC (from EtOAc/
hexane). IR (KBr) 3261, 2974, 2933, 1736, 1656, 1559, 1450,
1367, 1327, 1283, 1166, 1135, 1094, 993 cmꢂ1; 1H NMR (CDCl3,
400 MHz) ꢀ 1.07 (t, J ¼ 7:6 Hz, 3H), 1.60 (s, 9H), 2.05 (s, 3H),
2.39 (q, J ¼ 7:6 Hz, 2H), 2.59 (t, J ¼ 7:8 Hz, 2H), 2.87 (brt, J ¼
4:6 Hz, 2H), 3.04 (t, J ¼ 7:8 Hz, 2H), 3.94 (br, 2H), 4.59 (d,
J ¼ 5:6 Hz, 2H), 5.22 (dd, J ¼ 10:5, 1.2 Hz, 1H), 5.30 (dd, J ¼
17:1, 1.5 Hz, 1H), 5.91 (ddt, J ¼ 17:1, 10.4, 5.6 Hz, 1H), 6.12
(s, 1H), 10.10 (s, 1H). Found: C, 68.09; H, 7.24; N, 6.32%. Calcd
for C25H32N2O5: C, 68.16; H, 7.32; N, 6.36%.
t-Butyl 3-(3-Allyloxy-3-oxopropyl)-4-(2-hydroxyethyl)-1H-
pyrrole-2-carboxylate (20).
To a solution of compound 19
(1.565 g, 4.6 mmol) in MeOH (20 mL), a 3 M KOH solution in
MeOH (7.7 mL, 23 mmol) was added dropwise at 0 ꢁC. After stir-
ring for 2 h, the solvent was evaporated. The residue was acidified
(pH 3–4) with 1 M HCl and extracted with EtOAc. The extract
was washed with brine and dried over MgSO4. The solvent was
evaporated to afford a crude product. To a solution of the product
in THF/DMF (20/10 mL), DBU (0.7 mL, 4.6 mmol) was added
dropwise at 0 ꢁC under N2, followed by dropwise addition of allyl
bromide (0.44 mL, 5.1 mmol), and the mixture was allowed to stir
for 1.5 h at room temperature. The solvent was removed under re-
duced pressure, and the residue was partitioned between EtOAc
and water. The organic layer was washed with brine and dried
over MgSO4. The residue that was obtained by evaporating the
solvent was separated by flash column chromatography (SiO2,
hexane/EtOAc = 3/1, v/v) to afford compound 20 (0.89 g, 60%
in two steps) as an oil. IR (neat) 3346, 2978, 2935, 1738, 1714,
1
1407, 1223, 1172, 1133, 1051, 933 cmꢂ1; H NMR (CDCl3, 300
MHz) ꢀ 1.57 (s, 9H), 2.58 (t, J ¼ 8:1 Hz, 2H), 2.71 (t, J ¼ 6:5 Hz,
2H), 3.02 (t, J ¼ 8:1 Hz, 2H), 3.75 (t, J ¼ 6:5 Hz, 2H), 4.58 (dt,
J ¼ 5:7, 1.3 Hz, 2H), 5.22 (dq, J ¼ 10:5, 1.5 Hz, 1H), 5.29 (dq,
J ¼ 17:2, 1.5 Hz, 1H), 5.91 (ddt, J ¼ 17:2, 10.5, 5.7 Hz, 1H), 6.73
(d, J ¼ 2:9 Hz, 1H), 9.34 (brs, 1H). HRMS (TOF) (Mþ þ 1),
Found: m=z 324.1835. Calcd for C17H26NO5: 324.1811.
t-Butyl 3-(3-Allyloxy-3-oxopropyl)-4-(2-chloroethyl)-5-for-
myl-1H-pyrrole-2-carboxylate (10b). To DMF (8 mL) was add-
ed POCl3 (0.26 mL, 2.8 mmol) dropwise, and the mixture was stir-
red for 10 min at 0 ꢁC and for additional 10 min at room temper-
ature. A solution of compound 20 (362 mg, 1.12 mmol) in DMF
(8 mL) was then added dropwise at 0 ꢁC and the mixture was stir-
red for 10 min at 0 ꢁC and 2 h at 80 ꢁC. The reaction mixture was
quenched by addition of a 10% aqueous NaOAc and stirred for 2 h
at room temperature. The mixture was partitioned between EtOAc
and water, and the organic extract was washed with brine and
dried over MgSO4. The solvent was evaporated, and the product
was purified by flash column chromatography (SiO2, hexane/
EtOAc = 3/1, v/v) to give compound 10b (393 mg, 94%) as an
oil. IR (neat) 3284, 2978, 2359, 1735, 1705, 1667, 1458, 1369,
1272, 1158, 1078, 932, 844 cmꢂ1 1H NMR (CDCl3, 400 MHz)
;
ꢀ 1.59 (s, 9H), 2.63 (t, J ¼ 7:8 Hz, 2H), 3.02 (t, J ¼ 7:7 Hz, 2H),
3.24 (t, J ¼ 6:8 Hz, 2H), 3.67 (t, J ¼ 6:9 Hz, 2H), 4.58 (dt, J ¼
5:6, 1.5 Hz, 2H), 5.23 (dq, J ¼ 10:3, 1.2 Hz, 1H), 5.30 (dq, J ¼
17:3, 1.4 Hz, 1H), 5.90 (ddt, J ¼ 17:3, 10.5, 5.6 Hz, 1H), 9.67 (brs,
1H), 9.77 (s, 1H). HRMS (TOF) (Mþ þ 1), Found: m=z 370.1501
(35Cl), 372.1491 (37Cl). Calcd for C18H2535ClNO5: 370.1421,
C18H2537ClNO5: 372.1392.
t-Butyl 3-(3-Allyloxy-3-oxopropyl)-4-(2-chloroethyl)-5-[(4-
ethyl-3-methyl-5-oxo-1H-pyrrol-2(5H)-ylidene)methyl]-1H-pyr-
role-2-carboxylate (8b). To a mixed solution of 5-tosylpyrroli-
none 9a (125 mg, 0.44 mmol) and formylpyrrole 10b (138 mg,
0.37 mmol) in THF (8 mL), nBu3P (0.23 mL, 0.93 mmol) was add-
ed dropwise at 0 ꢁC under N2, followed by dropwise addition of a
Allyl (Z)-3-(8-Ethyl-2-formyl-9-methyl-7-oxo-1,4,5,7-tetra-
hydrodipyrrolo[1,2-a:20,30-d]azepin-3-yl)propanoate (6). Af-
ter treating compound 21 (270 mg, 0.61 mmol) in TFA (6 mL) at
room temperature for 30 min under N2, (CH3O)3CH (3 mL) was
added dropwise at 0 ꢁC, and the mixture was allowed to stir at

M. A. S. Hammam et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006) 1569
room temperature for 1 h. The reaction mixture was quenched
with water and extracted with EtOAc. The organic layer was
washed with both a saturated aqueous solution of NaHCO3 and
brine, and dried over MgSO4. The solvent was evaporated, and
the residue was separated by flash column chromatography (SiO2,
hexane/EtOAc = 3/1, v/v) to give compound 6 in quantitative
yield (221 mg) as a yellow solid. Mp 97–99 ꢁC (from EtOAc/
hexane). IR (KBr) 3249, 2925, 2875, 1739, 1695, 1612, 1453,
(s, 1H), 6.61 (s, 1H), 6.76 (dd, J ¼ 17:8, 11.5 Hz, 1H), 7.57 (s,
1H). NH and CO2H protons were not observed clearly; UV–vis
(MeOH) ꢁmax 385 (" ¼ 23355), 645 (" ¼ 17729) nm; HRMS
(FAB) (Mþ þ 1), Found: m=z 597.2706. Calcd for C34H37N4O6:
597.2713.
3-Oxopropyl Acetate (22).15 To a dispersion of Zn(OAc)2
ꢃ
2H2O (2.2 g, 10 mmol) in AcOH (3.0 mL, 50 mmol) was added
propenal (5.0 mL, 75 mmol) dropwise at 40 ꢁC under N2, and
the mixture was allowed to stir for 3 h. After filtration through cel-
ite and washing the solid with EtOAc, the filtrate was partitioned
between EtOAc and water. Then, the organic layer was washed
with a saturated aqueous solution of NaHCO3 and brine, and dried
over Na2SO4. The solvent was evaporated to give compound 22 in
40% yield (2.3 g, a colorless oil), which was used for the next step
without further purification. IR (neat) 3062, 2968, 2938, 2853,
2738, 1738, 1650, 1431, 1358, 1367, 1241, 1135, 1050, 956, 864,
1411, 1388, 1327, 1184, 1142, 964, 936, 853, 836, 778, 748 cmꢂ1
;
1H NMR (CDCl3, 400 MHz) ꢀ 1.12 (t, J ¼ 7:5 Hz, 3H), 2.10 (s,
3H), 2.40 (q, J ¼ 7:5 Hz, 2H), 2.62 (t, J ¼ 7:3 Hz, 2H), 2.86 (brt,
2H), 3.07 (t, J ¼ 7:3 Hz, 2H), 3.94 (br, 2H), 4.56 (d, J ¼ 5:7 Hz,
2H), 5.22 (dd, J ¼ 10:4, 1.4 Hz, 1H), 5.28 (dd, J ¼ 17:2, 1.4 Hz,
1H), 5.88 (ddt, J ¼ 17:2, 10.4, 5.7 Hz, 1H), 6.30 (s, 1H), 9.59 (s,
1H), 11.07 (s, 1H). Found: C, 68.38; H, 6.51; N, 7.54%. Calcd for
C21H24N2O4: C, 68.46; H, 6.57; N, 7.60%.
1
Allyl 3-{(Z)-2-[(Z)-{3-(3-Allyloxy-3-oxopropyl)-4-methyl-5-
[(Z)-(4-methyl-5-oxo-3-vinyl-1H-pyrrol-2(5H)-ylidene)methyl]-
2H-pyrrol-2-ylidene}methyl]-8-ethyl-9-methyl-7-oxo-1,4,5,7-
tetrahydrodipyrrolo[1,2-a:20,30-d]azepin-3-yl}propanoate (2b).
To a mixed solution of compounds 6 (135 mg, 0.36 mmol) and
4 (100 mg, 0.31 mmol) in MeOH (13 mL), a solution of H2SO4
(60 mg, 0.62 mmol) in MeOH (2 mL) was added dropwise at room
temperature under N2. After stirring for 1 h, the reaction mixture
was quenched with a buffer solution (pH 7.0) and extracted with
EtOAc. The organic layer was washed with brine and dried over
Na2SO4. The solvent was evaporated, and the blue residue was
separated by thin layer chromatography (SiO2, hexane/CHCl3/
MeOH = 7/4/0.5, v/v/v) to afford compound 2b in 87%
yield (181 mg) as a blue solid. Mp 181–183 ꢁC (from CH2Cl2/
hexane); IR (KBr) 3444, 2925, 1730, 1686, 1589, 1456, 1415,
793, 733 cmꢂ1; H NMR (CDCl3, 400 MHz) ꢀ 2.00 (s, 3H), 2.70
(dt, J ¼ 6:1, 1.5 Hz, 2H), 4.53 (t, J ¼ 6:1 Hz, 2H), 9.73 (t, J ¼ 1:5
Hz, 1H). HRMS (FAB) (Mþ þ 1), Found: m=z 117.0554. Calcd
for C5H9O3: 117.0552.
3-(2-Acetoxyethyl)-4-ethyl-2-tosylpyrrole (24). To a mixture
of compound 22 (1.263 g, 10.8 mmol) and 1-nitropropane (8.0 mL,
89 mmol) was added 0.5 mL of 1 M KOH (0.5 mmol) in MeOH at
0 ꢁC. The reaction mixture was stirred for 2 h at room temperature.
The mixture was quenched with 1 M HCl (0.5 mL), and the sol-
vent was evaporated. The residue was partitioned between EtOAc
and water, and the organic layer was washed with a saturated
aqueous solution of NaHCO3 and then brine, and dried over
Na2SO4. The solvent was evaporated to give the crude nitro-alco-
hol as an oil. To a mixed solution of the resulting nitro-alcohol
(2.09 g, 10.2 mmol) and DMAP (124 mg, 1.02 mmol) in THF (8.0
mL) was added dropwise acetic anhydride (1.1 mL, 12.2 mmol) at
0 ꢁC under N2. After stirring for 2 h at room temperature, the mix-
ture was quenched with MeOH (1.7 mL), and then, the solvent
was removed under reduced pressure. The residue was partitioned
between EtOAc and water, and the organic layer was washed with
both a saturated aqueous solution of NaHCO3 and brine, and dried
over Na2SO4. The solvent was evaporated to give 4-nitrohexane-
1,3-diyl diacetate (23) as an oil in 85% yield (2.28 g) in two steps
as a mixture of diastereomers. IR (neat) 2977, 2941, 1746, 1555,
1459, 1373, 1225, 1097, 1048, 948, 809, 732 cmꢂ1. HRMS (FAB)
(Mþ þ 1), Found: m=z 248.1140. Calcd for C10H18NO6: 248.1134.
To a mixed solution of nitro-diacetate 23 (3.64 g, 14.7 mmol)
and TosMIC (2.866 g, 14.7 mmol) in MeCN (30 mL) under N2,
DBU (4.6 mL, 30.9 mmol) was added dropwise at ꢂ40 ꢁC, and
then, the mixture was allowed to stir for 5 h at room temperature.
The mixture was quenched with aqueous NH4Cl, and then, the
solvent was removed under reduced pressure. The residue was
partitioned between EtOAc and water, and the organic layer was
successively washed with 6 M HCl, a saturated aqueous solution
of NaHCO3 and brine, and dried over Na2SO4. The solvent was
evaporated, and the product 24 was isolated by flash column chro-
matography (SiO2, hexane/EtOAc = 4/1, v/v) as an oil in 59%
yield (2.47 g); IR (neat) 3323, 2965, 2934, 2876, 1738, 1596,
1548, 1494, 1455, 1383, 1365, 1316, 1302, 1241, 1175, 1140,
1274, 1177, 1098, 960, 916, 833 cmꢂ1 1H NMR (CDCl3, 400
;
MHz) ꢀ 1.11 (t, J ¼ 7:6 Hz, 3H), 2.08 (s, 3H), 2.09 (s, 3H), 2.21
(s, 3H), 2.40 (q, J ¼ 7:6 Hz, 2H), 2.58 (t, J ¼ 7:6 Hz, 4H), 2.87
(brt, J ¼ 5:1 Hz, 2H), 2.92 (t, J ¼ 7:7 Hz, 2H), 2.96 (t, J ¼ 7:6
Hz, 2H), 3.94 (br, 2H), 4.56 (d, J ¼ 5:6 Hz, 2H), 4.57 (d, J ¼ 5:7
Hz, 2H), 5.20 (d, J ¼ 10:4 Hz, 2H), 5.26 (dd, J ¼ 17:2, 1.5 Hz,
1H), 5.28 (dd, J ¼ 17:2, 1.5 Hz, 1H), 5.68 (d, J ¼ 10:8 Hz, 1H),
5.71 (d, J ¼ 17:5 Hz, 1H), 5.87 (ddt, J ¼ 17:2, 10.4, 5.6 Hz, 1H),
5.89 (ddt, J ¼ 17:2, 10.4, 5.7 Hz, 1H), 6.07 (s, 1H), 6.28 (s, 1H),
6.64 (dd, J ¼ 17:5, 10.8 Hz, 1H), 6.81 (s, 1H). NH protons were
not observed clearly. Found: C, 70.95; H, 6.51; N, 8.23%. Calcd
for C40H44N4O6: C, 70.99; H, 6.55; N, 8.28%.
3-{(Z)-2-[(Z)-{3-(2-Carboxyethyl)-4-methyl-5-[(Z)-(4-methyl-
5-oxo-3-vinyl-1H-pyrrol-2(5H)-ylidene)methyl]-2H-pyrrol-2-
ylidene}methyl]-8-ethyl-9-methyl-7-oxo-1,4,5,7-tetrahydrodi-
pyrrolo[1,2-a:20,30-d]azepin-3-yl}propanoic Acid (2a). To a
mixed solution of compound 2b (50 mg, 0.074 mmol) and
[Pd(PPh3)4] (17 mg, 0.015 mmol) in THF (1.9 mL), a solution of
NaTs (27 mg, 0.155 mmol) in MeOH (1.9 mL) was added under
N2 at room temperature. After stirring for 10 min, the solvent was
evaporated, and the residue was separated by flash column chro-
matography (SiO2, CHCl3/MeOH/AcOH = 200/15/1, v/v/v).
The blue fraction was evaporated, and the resulting solid residue
was recrystallized from CHCl3/hexane to afford free acid 2a in
90% yield (40 mg) as a blue solid. Decomposed above 300 ꢁC; IR
(KBr) 3400, 3232, 2968, 2933, 1702, 1601, 1458, 1416, 1292,
1094, 954, 890, 839 cmꢂ1; 1H NMR (C5D5N, 400 MHz) ꢀ 1.11 (t,
J ¼ 7:5 Hz, 3H), 2.10 (s, 3H), 2.13 (s, 3H), 2.35 (s, 3H), 2.40 (q,
J ¼ 7:5 Hz, 2H), 2.83 (t, J ¼ 7:1 Hz, 2H), 2.85–2.90 (m, 4H), 3.14
(t, J ¼ 7:1 Hz, 2H), 3.20 (t, J ¼ 7:1 Hz, 2H), 4.01 (br, 2H), 5.61
(dd, J ¼ 11:7, 1.2 Hz, 1H), 5.70 (dd, J ¼ 17:8, 1.2 Hz, 1H), 6.31
1108, 1088, 1067, 1041, 975, 934, 911, 813, 706, 685 cmꢂ1
;
1H NMR (CDCl3, 400 MHz) ꢀ 1.15 (t, J ¼ 7:6 Hz, 3H), 2.02 (s,
3H), 2.38 (s, 3H), 2.41 (q, J ¼ 7:6 Hz, 2H), 2.93 (t, J ¼ 7:8 Hz,
2H), 4.06 (t, J ¼ 7:8 Hz, 2H), 6.74 (d, J ¼ 2:9 Hz, 1H), 7.27 (d,
J ¼ 8:5 Hz, 2H), 7.77 (d, J ¼ 8:5 Hz, 2H), 9.37 (brs, 1H). HRMS
(FAB) (Mþ þ 1), Found: m=z 336.1272. Calcd for C17H22NO4S:
336.1270.

1570 Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006)
Syntheses of Locked Biliverdin Derivatives
2-Bromo-3-ethyl-4-(2-hydroxyethyl)-5-tosylpyrrole (25). To
a solution of the tosylpyrrole 24 (2.466 g, 7.35 mmol) in CH2Cl2
(45 mL), a trimethylphenylammonium tribromide (3.3 g, 8.82
mmol) was added portionwise at 0 ꢁC, and the mixture was al-
lowed to stir for 1 h. The solvent was removed under reduced pres-
sure, and the residue was partitioned between EtOAc and water.
The organic layer was washed with a saturated aqueous solution
of NaHSO3, NaHCO3, and brine, and then dried over Na2SO4.
The solvent was evaporated, and the product was separated by
flash column chromatography (SiO2, EtOAc/hexane = 3/1, v/v)
to give the brominated compound in 85% yield (3.71 g) as a solid.
Mp 108–109 ꢁC (from EtOAc/hexane); IR (neat) 3208, 2961,
2929, 2895, 2868, 2360, 1715, 1596, 1547, 1455, 1375, 1321,
1294, 1268, 1207, 1184, 1163, 1139, 1118, 1093, 1065, 1030, 969,
946, 916, 813, 719, 685, 670 cmꢂ1; 1H NMR (CDCl3, 400 MHz) ꢀ
1.07 (t, J ¼ 7:6 Hz, 3H), 2.03 (s, 3H), 2.39 (q, J ¼ 7:6 Hz, 2H),
2.41 (s, 3H), 2.93 (t, J ¼ 7:4 Hz, 2H), 4.06 (t, J ¼ 7:4 Hz, 2H),
7.30 (d, J ¼ 8:3 Hz, 2H), 7.79 (d, J ¼ 8:3 Hz, 2H), 9.29 (brs, 1H).
Found: C, 49.21; H, 4.88; N, 3.38%. Calcd for C17H20BrNO4S: C,
49.28; H, 4.87; N, 3.38%. To a solution of the resulting brominat-
ed compound (1.9 g, 4.59 mmol) in MeOH (5 mL) was added 1 M
NaOH (23 mL, 23 mmol) dropwise at 0 ꢁC under N2. After stirring
for 1 h at room temperature, the mixture was neutralized with 1 M
HCl, and the solvent was removed under reduced pressure. The or-
ganic residue was dissolved in EtOAc and washed with brine and
dried over Na2SO4. The solvent was evaporated, and the residue
was separated by flash column chromatography (SiO2, hexane/
EtOAc = 3/1, v/v) to give compound 25 in 85% yield (1.38 g)
(72% in two steps) as a solid. Mp 204–205 ꢁC (from EtOAc/THF/
hexane); IR (KBr) 3451, 3079, 3010, 2966, 2890, 2703, 1735,
1596, 1550, 1479, 1455, 1374, 1300, 1259, 1227, 1196, 1161,
1135, 1091, 1062, 1036, 1015, 987, 837, 813, 788, 764, 705, 684,
664 cmꢂ1; 1H NMR (CDCl3, 400 MHz) ꢀ 1.06 (t, J ¼ 7:6 Hz, 3H),
1.78 (brs, 1H), 2.38 (q, J ¼ 7:6 Hz, 2H), 2.41 (s, 3H), 2.86 (t, J ¼
6:7 Hz, 2H), 3.72 (t, J ¼ 6:7 Hz, 2H), 7.31 (d, J ¼ 8:4 Hz, 2H),
7.78 (d, J ¼ 8:4 Hz, 2H), 9.17 (brs, 1H). Found: C, 48.47; H, 4.95;
N, 3.70%. Calcd for C15H18BrNO3S: C, 48.40; H, 4.87; N, 3.76%.
3-Ethyl-4-[2-(mesyloxy)ethyl]-2-oxo-5-tosyl-1,5-dihydro-2H-
pyrrole (9b). To a solution of the brominated tosylpyrrole 25
(1.37 g, 3.9 mmol) in THF (10 mL) at 0 ꢁC, Et3N (1.1 mL, 7.8
mmol) was added under N2, followed by addition of MeSO2Cl
(0.36 g, 4.7 mmol) in THF (2 mL), and the mixture was allowed
to stir at room temperature for 30 min. The solvent was removed
under reduced pressure, and the residue was partitioned between
EtOAc and water. The organic layer was washed with a saturated
aqueous solution of NaHCO3 and with brine, and dried over
Na2SO4. The solvent was evaporated, and the residue was separat-
ed by flash column chromatography (SiO2, hexane/EtOAc = 3/1,
v/v) to give the mesylated product in 85% yield (1.48 g) as a solid,
which was used for the next reaction without further purification.
IR (KBr) 3276, 3024, 2964, 2940, 2869, 1594, 1550, 1490, 1455,
1382, 1343, 1319, 1292, 1256, 1204, 1169, 1138, 1119, 1092,
pressure, and the residue was partitioned between EtOAc and
water. The organic layer was washed with a saturated aqueous
solution of NaHCO3 and with brine, and dried over Na2SO4.
The solvent was evaporated, and the residue was separated by
flash column chromatography (SiO2, hexane/EtOAc = 2/1, v/v)
to give compound 9b in 65% yield (1.03 g) (55% in two steps) as a
white solid. Mp 140–141 ꢁC (from EtOAc/hexane); IR (KBr)
3196, 3081, 2969, 1703, 1596, 1460, 1354, 1317, 1259, 1176,
1131, 1080, 990, 975, 906, 830, 721, 668 cmꢂ1; 1H NMR (CDCl3,
400 MHz) ꢀ 0.66 (t, J ¼ 7:6 Hz, 3H), 2.06 (dq, J ¼ 14:8, 7.6 Hz,
1H), 2.11 (dq, J ¼ 14:8, 7.6 Hz, 1H), 2.40 (s, 3H), 3.00 (s, 3H),
3.07 (dt, J ¼ 15:4, 4.9 Hz, 1H), 3.11 (dt, J ¼ 15:4, 4.9 Hz, 1H),
4.41 (dt, J ¼ 9:8, 5.4 Hz, 1H), 4.51 (dt, J ¼ 9:8, 4.9 Hz, 1H),
5.22 (s, 1H), 6.48 (brs, 1H), 7.30 (d, J ¼ 8:2 Hz, 2H), 7.64 (d,
J ¼ 8:2 Hz, 2H). Found: C, 49.35; H, 5.50; N, 3.58%. Calcd for
C16H21NO6S2: C, 49.60; H, 5.46; N, 3.61%.
t-Butyl (E)-8-(3-Allyloxy-3-oxopropyl)-3-ethyl-9-methyl-2-
oxo-1,2,4,5-tetrahydrodipyrrolo[1,2-a:20,30-d]azepine-7-carbox-
ylate (26). To a mixed solution of 5-tosylpyrrolinone 9b (25 mg,
0.08 mmol) and formylpyrrole 10a (40 mg, 0.1 mmol) in THF
n
(10 mL), a solution of Bu3P (32 mg, 0.16 mmol) in THF (1 mL)
was added dropwise at 0 ꢁC under N2, followed by dropwise addi-
tion of DBU (37 mg, 0.25 mmol) in THF (2 mL). After stirring
overnight at room temperature, the solvent was removed under re-
duced pressure, and the residue was partitioned between EtOAc
and water. The organic layer was washed with both a saturated
aqueous solution of NH4Cl and brine, and then dried over
Na2SO4. The solvent was evaporated, and the residue was separat-
ed by flash column chromatography (SiO2, hexane/EtOAc = 3/1,
v/v) to afford compound 26 as a yellow solid in 65% yield
(20 mg). Mp 180–181 ꢁC (from EtOAc/hexane); IR (KBr) 3213,
2973, 2933, 2553, 1736, 1682, 1538, 1481, 1455, 1414, 1396,
1368, 1348, 1284, 1250, 1176, 1129, 1082, 1055, 987, 956, 855,
1
817, 773, 735, 667 cmꢂ1; H NMR (CDCl3, 400 MHz) ꢀ 1.11 (t,
J ¼ 7:7 Hz, 3H), 1.58 (s, 9H), 2.06 (s, 3H), 2.38 (q, J ¼ 7:1 Hz,
2H), 2.52 (t, J ¼ 7:9 Hz, 2H), 2.98 (t, J ¼ 8:8 Hz, 2H), 4.59 (d,
J ¼ 5:8 Hz, 2H), 5.26 (d, J ¼ 10:2 Hz, 1H), 5.30 (d, J ¼ 17:3 Hz,
1H), 5.91 (ddt, J ¼ 17:3, 10.2, 5.8 Hz, 1H), 6.28 (s, 1H), 9.12 (brs,
1H). The protons of the bridged ethylene were not observed clear-
ly. HRMS (FAB) (Mþ þ 1), Found: m=z 441.2383. Calcd for
C25H33N2O5: 441.2389.
Allyl (E)-3-(3-Ethyl-7-formyl-9-methyl-2-oxo-1,2,4,5-tetra-
hydrodipyrrolo[1,2-a:20,30-d]azepin-8-yl)propanoate (7).
A
solution of compound 26 (20 mg, 0.043 mmol) in TFA (0.43
mL) was allowed to stir at room temperature under N2 for 30 min.
Then, (CH3O)3CH (0.22 mL) was added dropwise, and the mix-
ture was allowed to stir at room temperature for 1 h. The reaction
mixture was quenched by water and extracted with EtOAc, and
then, the organic layer was washed with a saturated aqueous solu-
tion of NaHCO3 and with brine, and dried over Na2SO4. The sol-
vent was evaporated, and the residue was separated by flash col-
umn chromatography (SiO2, hexane/EtOAc = 3/1, v/v) to afford
compound 7 as a yellow solid in 85% yield (16 mg). Mp 175–
176 ꢁC (from EtOAc/hexane). IR (KBr) 3019, 2361, 1728, 1688,
1639, 1502, 1457, 1421, 1381, 1342, 1325, 1302, 1278, 1161,
1050, 983, 850, 734, 719, 674 cmꢂ1; 1H NMR (CDCl3, 400 MHz)
ꢀ 1.12 (t, J ¼ 7:6 Hz, 3H), 2.08 (s, 3H), 2.39 (q, J ¼ 7:6 Hz, 2H),
2.57 (t, J ¼ 7:7 Hz, 2H), 2.90 (brs, 2H), 3.03 (t, J ¼ 7:7 Hz, 2H),
4.58 (d, J ¼ 5:9 Hz, 2H), 5.24 (dd, J ¼ 10:5, 1.3 Hz, 1H), 5.29
(dd, J ¼ 17:2, 1.3 Hz, 1H), 5.90 (ddt, J ¼ 17:2, 10.5, 5.9 Hz, 1H),
6.18 (s, 1H), 8.00 (brs, 1H), 9.71 (s, 1H). The protons of the ethyl-
ene bridge were not observed clearly. Found: C, 68.20; H, 6.53; N,
1059, 1014, 980, 948, 859, 817, 782, 770, 714 cmꢂ1 1H NMR
;
(CDCl3, 400 MHz) ꢀ 1.17 (t, J ¼ 7:5 Hz, 3H), 2.39 (q, J ¼ 7:5 Hz,
2H), 2.42 (s, 3H), 2.95 (s, 3H), 3.04 (t, J ¼ 7:5 Hz, 2H), 4.27 (t,
J ¼ 7:5 Hz, 2H), 7.32 (d, J ¼ 8:3 Hz, 2H), 7.78 (d, J ¼ 8:4 Hz,
2H), 9.31 (brs, 1H). The resulting product (1.03 g, 2.3 mmol)
was dissolved in TFA (10 mL) at room temperature under N2. Af-
ter stirring for 15 min, DMSO (0.65 mL, 9.2 mmol) was added
dropwise, and the mixture was allowed to stir overnight. Zn
(0.3 g, 4.7 mmol) was then added portionwise, and the reaction
mixture was stirred for 1 h. The TFA was removed under reduced

M. A. S. Hammam et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006) 1571
7.47%. Calcd for C21H24N2O4: C, 68.46; H, 6.57; N, 7.60%.
Allyl 3-{(Z)-2-({(E)-8-(3-Allyloxy-3-oxopropyl)-3-ethyl-9-
methyl-2-oxo-1,2,4,5-tetrahydrodipyrrolo[1,2-a:20,30-d]azepin-
7-yl}methylene)-4-methyl-5-[(Z)-(4-methyl-5-oxo-3-vinyl-1H-
pyrrol-2(5H)-ylidene)methyl]-2H-pyrrol-3-yl}propanoate (3b).
To a mixed solution of compounds 4 (180 mg, 0.6 mmol) and 7
(110 mg, 0.3 mmol) in MeOH (13 mL), a solution of H2SO4 (59
mg, 0.6 mmol) in MeOH (2 mL) was added dropwise at room tem-
perature under N2. After stirring for 1 h, the reaction mixture was
quenched by a buffer solution (pH 7.0) and extracted by EtOAc.
The organic layer was washed with brine and dried over Na2SO4.
The solvent was evaporated, and the blue residue was separated
by thin layer chromatography (hexane/CHCl3/MeOH = 7/4/0.5,
v/v/v) to give compound 3b as a greenish blue solid in 45%
yield (20 mg). Decomposed above 200 ꢁC (from EtOAc/hexane).
IR (KBr) 3224, 2933, 1734, 1698, 1676, 1584, 1508, 1419, 1348,
Briggs, Science 1997, 278, 2120; J. M. Christie, P. Reymond,
G. K. Powell, P. Bernasconi, A. A. Raibekas, E. Liscum, W. R.
Briggs, Science 1998, 282, 1698; W. R. Briggs, J. M. Christie,
Trends Plant Sci. 2002, 7, 204; S. M. Harper, L. C. Neil, K. H.
Gardner, Science 2003, 301, 1541; R. Fedorov, I. Schlichting,
E. Hartmann, T. Domratcheva, M. Fuhrmann, P. Hegemann,
Biophys. J. 2003, 84, 2474. c) W. Rudiger, F. Thummler, Photo-
¨
¨
morphogenesis of Plants, 2nd ed., ed. by R. E. Kendrick, G. H. M.
Kronenberg, Kluwer Academic Publishers, Dordrecht, The
Netherlands, 1994; C. R. Nathan, S. Yi-Shin, J. C. Lagarias, Annu.
Rev. Plant Biol. 2006, 57, 837.
2
M. A. Mroginski, D. H. Murgida, D. von Stetten, C. Kneip,
F. Mark, P. Hildebrandt, J. Am. Chem. Soc. 2004, 126, 16734.
T. Lamparter, N. Michael, O. Caspani, T. Miyata, K.
Shirai, K. Inomata, J. Biol. Chem. 2003, 278, 33786.
H. Falk, The Chemistry of Linear Oligopyrroles and Bile
Pigments, Springer Verlag, Wien, New York, 1989.
F. Andel, III, J. T. Murphy, J. A. Haas, M. T. McDowell,
3
4
1272, 1227, 1158, 984, 958, 669 cmꢂ1 1H NMR (CDCl3, 400
;
MHz) ꢀ 1.07 (t, J ¼ 7:6 Hz, 3H), 2.06 (s, 3H), 2.10 (s, 3H), 2.13
(s, 3H), 2.36 (q, J ¼ 7:3 Hz, 2H), 2.52 (t, J ¼ 7:8 Hz, 2H), 2.59 (t,
J ¼ 7:8 Hz, 2H), 2.97 (t, J ¼ 7:8 Hz, 2H), 2.98 (t, J ¼ 7:8 Hz,
2H), 3.12 (m, 2H), 4.52 (d, J ¼ 5:6 Hz, 2H), 4.56 (d, J ¼ 5:6 Hz,
2H), 5.18–5.30 (m, 4H), 5.68 (d, J ¼ 11:7 Hz, 1H), 5.71 (d, J ¼
17:0 Hz, 1H), 5.78–5.94 (m, 1H), 6.07 (s, 1H), 6.16 (s, 1H), 6.54
(dd, J ¼ 18:0, 11.7 Hz, 1H), 6.92 (s, 1H), 7.14 (s, 1H). One NH
and bridged ethylene protons were not appeared clearly. HRMS
(FAB) (Mþ þ 1), Found: m=z 677.3334. Calcd for C40H45N4O6:
677.3339.
5
I. van der Hoef, J. Lugtenburg, J. C. Lagarias, R. A. Mathies,
Biochemistry 2000, 39, 2667.
6 Y. Mizutani, S. Tokutomi, T. Kitagawa, Biochemistry
1994, 33, 153.
7 C. Kneip, P. Hildebrandt, W. Schlamann, S. E. Braslavsky,
F. Mark, K. Schaffner, Biochemistry 1999, 38, 15185.
8
a) H. Kinoshita, Y. Hayashi, Y. Murata, K. Inomata, Chem.
Lett. 1993, 1437. b) H. Kinoshita, H. Ngwe, K. Kobori, K.
Inomata, Chem. Lett. 1993, 1441. c) K. Kohori, M. Hashimoto,
H. Kinoshita, K. Inomata, Bull. Chem. Soc. Jpn. 1994, 67, 3088.
d) T. Kakiuchi, H. Kato, K. P. Jayasundera, T. Higashi, K.
Watabe, D. Sawamoto, H. Kinoshita, K. Inomata, Chem. Lett.
1998, 1001. e) K. P. Jayasundera, H. Kinoshita, K. Inomata,
Chem. Lett. 1998, 1227. f) T. Kakiuchi, H. Kinoshita, K. Inomata,
Synlett 1999, 901. g) A. Ohta, D. Sawamoto, K. P. Jayasundera,
H. Kinoshita, K. Inomata, Chem. Lett. 2000, 492. h) D. Sawamoto,
H. Nakamura, H. Kinoshita, S. Fujinami, K. Inomata, Chem. Lett.
2000, 1398. See also the references cited therein. i) S. Takeda,
K. P. Jayasundera, T. Kakiuchi, H. Kinoshita, K. Inomata, Chem.
Lett. 2001, 590.
3-{(Z)-2-({(E)-8-(3-Carboxyethyl)-3-ethyl-9-methyl-2-oxo-
1,2,4,5-tetrahydrodipyrrolo[1,2-a:20,30-d]azepin-7-yl}methyl-
ene)-4-methyl-5-[(Z)-(4-methyl-5-oxo-3-vinyl-1H-pyrrol-2(5H)-
ylidene)methyl]-2H-pyrrol-3-yl}propanoic acid (3a).
To a
mixed solution of compound 3b (20 mg, 0.03 mmol) and [Pd-
(PPh3)4] (7 mg, 0.006 mmol) in THF (1.3 mL), a solution of NaTs
(11 mg, 0.06 mmol) in MeOH (1.3 mL) was added at room tem-
perature under N2. After stirring for 10 min, the solvent was
evaporated, and the residue was separated by flash column chro-
matography (SiO2, CHCl3/MeOH/AcOH = 200/15/1, v/v/v).
The greenish blue fraction was concentrated, and the resulting sol-
id was recrystallized from CHCl3/hexane to afford free acid 3a in
42% yield (7 mg) as a greenish blue solid. Decomposed above
250 ꢁC; IR (KBr) 3418, 2934, 1732, 1697, 1585, 1435, 1272,
9 H. Hanzawa, K. Inomata, H. Kinoshita, T. Kakiuchi, K. P.
Jayasundera, D. Sawamoto, A. Ohta, K. Uchida, K. Wada, M.
Furuya, Proc. Natl. Acad. Sci. U.S.A. 2001, 98, 3612; A related
paper was reported: U. Robben, I. Lindner, W. Gartner, K.
¨
1
1158, 1101, 959, 692 cmꢂ1; H NMR (C5D5N, 400 MHz) ꢀ 1.11
(t, J ¼ 7:3 Hz, 3H), 2.06 (s, 6H), 2.19 (s, 3H), 2.67 (q, J ¼ 7:6 Hz,
2H), 2.88 (t, J ¼ 7:6 Hz, 2H), 2.97 (t, J ¼ 7:6 Hz, 2H), 3.32 (t,
J ¼ 7:3 Hz, 4H), 3.43 (br, 2H), 5.60 (d, J ¼ 11:5 Hz, 1H), 5.73 (d,
J ¼ 17:8 Hz, 1H), 6.36 (s, 1H), 6.38 (s, 1H), 6.78 (dd, J ¼ 18:0,
11.2 Hz, 1H), 7.62 (s, 1H), 11.14 (br, 1H). Protons of CO2H,
one NH, and bridged ethylene were not appeared clearly. UV–
vis (MeOH) ꢁmax 388 (" ¼ 28675), 648 (" ¼ 13100) nm; HRMS
(FAB) (Mþ þ 1), Found: m=z 597.2718. Calcd for C34H37N4O6:
597.2713.
Schaffner, Angew. Chem., Int. Ed. 2001, 40, 1048.
10 a) H. Hanzawa, T. Shinomura, K. Inomata, T. Kakiuchi,
H. Kinoshita, K. Wada, M. Furuya, Proc. Natl. Acad. Sci.
U.S.A. 2002, 99, 4725. b) K. Inomata, Chem. Today 2004,
No. 398, 56.
11 M. A. S. Hammam, Y. Murata, H. Kinoshita, K. Inomata,
Chem. Lett. 2004, 33, 1258.
12 The synthesis of BV derivative locked in E-anti configura-
tion and conformation has been reported as a short communica-
tion. See Ref. 17.
13 a) P. Manitto, D. Monti, J. Chem. Soc., Chem. Commun.
1980, 178. b) I. Lindner, B. Knipp, S. E. Braslavslky, W. Gartner,
K. Schaffner, Angew. Chem., Int. Ed. 1988, 37, 1843. c) D.
Sawamoto, K. Inomata, Chem. Lett. 2001, 588.
14 D. H. R. Barton, J. Kervogoret, S. Z. Zard, Tetrahedron
1990, 46, 7587.
The present work was financially supported in part by
Grant-in-Aid for Scientific Research (B) (No. 15350021) from
Japan Society for the Promotion of Science (JSPS).
¨
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1572 Bull. Chem. Soc. Jpn. Vol. 79, No. 10 (2006)
Syntheses of Locked Biliverdin Derivatives
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