The synthesis and evaluation of 10- and 12-membered ring benzofused enediyne amino acids

Article abstract of DOI:10.1016/j.bmc.2005.07.016

The enediyne moiety is a versatile functional group found in natural anticancer and anti-infective agents, undergoing the Bergman cyclization reaction to afford a diradical which cleaves double-stranded DNA. We have incorporated the enediyne group into 10

Full text of DOI:10.1016/j.bmc.2005.07.016

Bioorganic & Medicinal Chemistry 13 (2005) 5936–5948
The synthesis and evaluation of 10- and 12-membered ring
benzofused enediyne amino acids
Yanming Du, Christopher J. Creighton, Zhengyin Yan, Diane A. Gauthier,
John P. Dahl,à Boyu Zhao, Stanley M. Belkowski and Allen B. Reitz*
Drug Discovery Division, Johnson & Johnson Pharmaceutical Research and Development, Spring House, PA 19477, USA
Received 4 April 2005; revised 8 July 2005; accepted 8 July 2005
Available online 2 September 2005
Abstract—The enediyne moiety is a versatile functional group found in natural anticancer and anti-infective agents, undergoing the
Bergman cyclization reaction to afford a diradical which cleaves double-stranded DNA. We have incorporated the enediyne group
into 10- (4–10) and 12-membered ring (11) cyclic amino acids and dipeptides, respectively, and explored their relative reactivity
toward cyclization, varying N-substitution in the case of the 10-membered ring substrate, which gave the expected cyclization prod-
ucts in good yields when using either thermal conditions in the presence or absence of microwave irradiation. The N-tosyl substi-
tuted derivative (4) was shown to nick double-stranded supercoiled DNA. N-Arylsulfonyl substitution on the ring promoted the
cyclization, when compared to N-mesyl or acyl substitution, possibly because of a p–p stacking effect as an endo-relationship of
the aryl group with the enediyne was demonstrated in both the solid state and in solution. The 12-membered ring enediyne dipeptide
(11) was inert to the Bergman cyclization under a variety of conditions. When this substrate was irradiated with ultraviolet light,
regio- and stereospecific reduction was observed in which one of the alkynes was reduced to a Z-olefin (47).
ꢀ 2005 Elsevier Ltd. All rights reserved.
1. Introduction
target such as conjugation with steroids and then bind-
ing and inactivation of the human estrogen A receptor.3
Few enediynes incorporating amino acids or peptides
have been prepared. In one example, Basak et al. found
that the association of two pendant tripeptide chains via
the b-sheet hydrogen bonding of 2 promoted the
thermal Bergman cyclization of the central core
enediyne.4 Jones and co-workers described an acyclic
enediyne 3 bearing a tri-aspartic acid side chain that
cleaved the basic protein histone I specifically into one
observed component.5
cis-1,2-Enediyne anticancer and antibiotic agents such
as calicheamicin c, dynemicin, and neocarzinostatin
have attracted much interest because the enediyne sys-
tem 1 undergoes the Bergman aromatization reaction
forming a diradical intermediate which nicks and cleaves
double-stranded DNA.1 The Bergman reaction is pro-
moted either thermally, photochemically, or by metal
catalysis, and the study of substituted model enediynes
has provided insight into the factors which influence
reactivity and selectivity.2 In addition to the well-studied
nicking of double-stranded DNA, proteins are also
attractive targets for enediyne radical-mediated cleav-
age. Enediynes have been attached to a substructure
which directs the reactive portion to a specific molecular
.
.
1
Keywords: Enediynes; Bergman cyclization; Peptidomimetics; Micro-
wave-assisted chemistry.
O
+
NH3
N
H
m
CO2H
H
N
CO2H
CO2H
*
Corresponding author. Tel.: +1 215 628 5615; fax: +1 215 540
4776; e-mail: areitz@prdus.jnj.com
R1
R2
O
O
O
N
H
N
H
Present address: Rib-X Pharmaceuticals, New Haven, CT, USA.
Present address: University of Pennsylvania, School of Medicine,
Philadelphia, PA, USA.
-
O
N
H
CO2
à
n
CO2H
2
3
0968-0896/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2005.07.016

Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
5937
As part of a program looking at constrained peptidom-
imetics and structure-function relationships,6 we rea-
soned that incorporation of an enediyne into a cyclic
peptide scaffold might afford useful structures with
defined and characteristic secondary structures such as
the b-turn. In addition, cyclic enediyne amino acids
may display affinity for biological targets such as recep-
tors or transcriptional regulators thereby promoting
nicking and degradation. Such interactions could also
provide information as to the location of ligand binding
by inspection of where the target is cleaved. We have
investigated the incorporation of benzofused enediynes
into 10- and 12-membered cyclic a-amino acids 4–10
and dipeptide 11, respectively, and examined their reac-
tivity and conformational preferences.
to give a bicyclic system which facilitated the Bergman
reaction.14
We envisioned that construction of enediyne 4 could be
achieved by using either Sonogashira alkynyl coupling
or C–N bond formation as the key step. Although intra-
molecular Sonogashira coupling has been used in the
construction of enediyne 10-membered rings, the yields
were modest (ca. 30%).15 Alternatively, C–N bond for-
mation during the construction of an enediyne ring
has been accomplished by sulfonamide displacement of
a mesylate.10 We decided to explore the use of the
Mitsonobu reaction to form the required C–N bond
because it is simple and compatible with diverse func-
tional groups.16 Intramolecular Mitsonobu reactions
have been used to prepare three- to six-membered cyclic
amines and b-lactams even when the amine or amide
precursors were not activated,17 but it had not yet been
used in the preparation of enediynes. We reasoned that
the required acyclic enediyne precursor to the Mitson-
obo reaction could be assembled by two consecutive
Sonogashira couplings of both propargyl glycine deriva-
tive 12 and propargyl alcohol with 1,2-diiodobenzene.
H
CO2Me
N
R
4 R = Ts
5 R = H
6 R = Ac
7 R = Ms
8 R = Ns
9 R = 4-(MeO)PhSO2
10 R = 3,4-(MeO)2PhSO2
NHMe
N
CbzHN
H
O
O
11
Sonogashira coupling is an efficient way to prepare con-
jugated enynes from alkenyl halides or triflates with 1-
alkynes.18 Applications of this method to the coupling
of propargyl amino acid derivatives with phenyl or vinyl
halides has been reported when using Pd(PPh3)4,19
PdCl2(dppf)2,20 and Pd/C.21 Recently, it was reported
that certain alkynes could couple with aryl halides under
the catalysis of PdCl2(PPh3)2 in THF at room tempera-
ture using aqueous ammonia as base.22 We have used
these later conditions on the amino acid substrate 12
in coupling to aryl iodides with either electron with-
drawing or donating substitution to afford enynes 13–
16 in good yields (Table 1). When 1,2-diiodobenzene
was used, the use of DME was found to be preferred
over MeCN and THF (entries 4–6).
2. Results and discussion
2.1. Ten membered cyclic enediyne amino acids
Cyclic enediynes containing a 10-membered ring have
been the most widely investigated because the distances
between their terminal alkyne carbons are optimally dis-
7
˚
posed for Bergman cyclization (2.9–3.2 A). Among the
enediyne model systems that have been prepared are
carbocyclic with pendant substitution5c,8 and incorpora-
tion of a heteroatom directly into the ring as an ether,3,9
secondary amine,10 thioether,11 or sulfone.12 Insertion
of the enediyne into a ring has proven to be a general
way to change strain energy and modulate enediyne
reactivity.13 In the calicheamycin system, addition of a
thiol to an sp2 center transformed it to sp3 which altered
the conformation of the ring sufficiently enough to pro-
mote the reaction.1 A similar effect was recently reported
in the transannular reaction of a reactive functionality
Alkyne 16 was coupled in a second Sonogashira reaction
with propargyl alcohol to form 1,2-diynylbenzene 17
(Fig. 1, 94%). Intramolecular Mitsunobu reaction of
17 conducted at 0 ꢁC provided enediyne 4 (90%). Com-
pound 4 and 1,4-cyclohexadiene (100 mol equiv) were
dissolved in DMF, and subjected to microwave irradia-
tion producing cyclized product 18 in 84% yield after
Table 1. Sonogashira coupling of L-propargylglycine 12 with iodobenzenes
R1
R2
NHR
CH2
H
NHR
CH2
H
R1
O
I
R2
O
OMe
OMe
PdCl2(PPh3)4
CuI, NH3.
12
13-16
Entry
R1
R2
Solvent
Time (h)
Product
Yield (%)
1
2
3
4
5
6
H
H
H
H
I
THF
THF
14
14
14
24
24
4
13
14
15
16
16
16
80
55
77
50
50
60
OMe
CF3
H
THF
THF
H
I
CH3CN
DME
H
I

5938
Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
H
CO Me
2
H
CO Me
2
propargyl
alcohol
NHTs
NHTs
Pd(PPh ) Cl
3 2
2
I
OH
CuI, NH
94%
3
16
17
DEAD
PPh
3
90%
H
H
CO Me
2
CO Me
2
Figure 3. Cleavage of /-X DNA mediated by differing concentrations
of 4. The compound was dissolved in 100% DMSO and incubated with
the DNA for 24 h followed by analysis on a 1% agarose gel and
visualization using ethidium bromide.
N
N
Microwaves
Ts
Ts
o
DMF, 120 C, 84%
18
4
Figure 1. Synthesis of 10-membered cyclic enediyne amino acid 4.
concentration from 1 lM to 50 mM and evaluated the
progress of the reaction by agarose gel electrophoresis
(Fig. 3).24 Cleavage of supercoiled DNA was seen at
concentrations 10 lM and higher, with many fragments
being observed at the highest concentrations.
10 min at 120 ꢁC. Although microwaves have been used
in organic synthesis extensively,23 this appears to be
their first application to the Bergman reaction. Alterna-
tively, the reaction was also achieved under heating in
the absence of microwaves. We compared the conver-
sion of 4 to 18 by either heating or microwave irradia-
tion at different temperatures during a 10 min period.
Although it appeared that the use of microwaves accel-
erated the reaction to a modest extent when compared
with thermal conditions alone, there was not a dramatic
difference between the two.
Several factors are known to influence Bergman cycliza-
tion such as the distance between the bond-forming
alkynyl carbons, electronic effects, and strain energy.
However, the effect of pendant substitution on stabiliza-
tion of a diradical intermediate is not well characterized.
We prepared NH compound 5 and N-substituted deriv-
atives 6–10 to complement 4, to investigate the effect of
N-substitution upon the Bergman cyclization. Since the
tosylate of 4 was in an endo-orientation relative to the
enediyne ring by X-ray structure determination and in
solution, we reasoned that varying the tosylate to other
groups would influence the rate of the Bergman reaction.
The synthesis of 7–10 was initiated by conducting con-
secutive Sonagashira coupling reactions starting with
N-substituted L-propargyl glycines 19–22 and 1,2-diiod-
obenzene to give 23–26, followed by reaction with prop-
argyl alcohol to give 33–36 (Fig. 4). Subsequent ring
closing via the Mitsunobu reaction on 33–36 provided
enediynes 7–10 (62–85% yield). Treatment of N-nosyl
compound 8 with thiophenol provided amine 5, which
furnished 6 upon treatment with acetyl chloride.10,25
Compound 4 was stable for several months at room
temperature in the solid state. We carefully monitored
the rate of conversion of 4 to 18 at 0.1 mM in DMF with
1,4-cyclohexadiene (100 mol equiv), and determined
that the half-life (t1/2) for depletion of 4 and formation
of 18 was 131 h at 37 ꢁC and 9.5 h at 55 ꢁC without
any other products being detected. A single-crystal
X-ray structure of 4 was obtained and revealed that
the tosyl group adopts an endo-orientation placing it
above the enediyne ring (Fig. 2). A NOESY NMR
experiment of 4 in CDCl3 was conducted revealing a po-
sitive NOE between hydrogens on the tosylate methyl
and phenyl hydrogens on the benzo group of the fused
enediyne ring, as well as the phenyl hydrogens ortho to
sulfonyl of the tosylated with methylene hydrogens of
the enediyne ring. Therefore, the endo-conformation
revealed in the X-ray structure of 4 in the solid state
was also observed for the compound in solution.
The Bergman cyclizations of enediynes 4, and 6–10 were
compared at 55 ꢁC and the half-lives for conversion are
presented in Table 2. Sulfonamides 4 and 7–10 were ob-
served to react with a faster rate (t1/2 = 4.0–18.5 h) than
acetamide 6 (t1/2 = 55.4 h). Mesylate 7 had a longer rate
of reaction (t1/2 = 18.5 h) than the aryl sulfonamides 4
and 8–10 (t1/2 of 4.0–9.4 h). Therefore, aryl substitution
increased the rate of the reaction, and N-sulfonyl mesy-
late 7 reacted ca. 3· faster than N-acetyl 6. The reaction
was not influenced by either electron withdrawing (viz.,
8) or electron donating substitution on the aryl ring
(viz., 9 and 10). Since arylsulfonamides promoted the
reaction to the greatest degree, it is possible that p–p
stacking could stabilize the Bergman diradical interme-
diates, as documented for through-space radical stabil-
ization.26 The rate-limiting step of the enediyne
cycloaromatization of benzofused enediynes such as 4
has been determined to be hydrogen abstraction by the
diradical intermediate,27 so that stabilization of this
intermediate would be expected to promote the reaction.
To investigate the possibility that 4 could cleave double-
stranded DNA, we incubated it with supercoiled DNA
at 37 ꢁC for a period of 24 h while varying the
Figure 2. X-ray crystal structure of 4 revealing an endo-orientation of
the tosylate group with the enediyne ring.

Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
5939
HO
I
NHR
H
NHR
propargyl
alcohol
NHR
H
CH2
CH2
H
OMe
1,2-diiodobenzene
CH2
O
O
PdCl2(PPh3)4
CuI, NH3.
O
PdCl2(PPh3)4
CuI, NH3.
OMe
OMe
19 R = Ms
20 R = Ns
21 R = 4-(MeO)PhSO2
22 R = 3,4-(MeO)2PhSO2
23 R = Ms (43%)
24 R = Ns (68%)
25 R = 4-(MeO)PhSO2 (45%)
26 R = 3,4-(MeO)2PhSO2 (60%)
33 R = Ms (87%)
34 R = Ns (79%)
35 R = 4-(MeO)PhSO2 (87%)
36 R = 3,4-(MeO)2PhSO2 (93%)
DEAD
Ph3P
H
CO2Me
N
R
H
H
AcCl
Et3N
CO2Me
CO2Me
PhSH
8
7 R = Ms (62%)
8 R = Ns (93%)
N
N
93%
72%
Ac
H
9 R = 4-(MeO)PhSO2 (64%)
10 R = 3,4-(MeO)2PhSO2 (85%)
6
5
Figure 4. Synthesis of enediynes 5–10.
bered ring enediyne 11 (Fig. 6). N-Cbz propargyl glycine
42 was coupled in the Sonogashira reaction with 1,2-di-
iodobenzene using ammonia as a base at room tempera-
ture to give alkyne 43. Consecutive coupling of 43 with
propargyl glycinamide 44 furnished acyclic enediyne 45
(69%). Removal of the Boc group of 45 followed by pep-
tide coupling with HATU/HOAT or DPPA did not afford
desired 11. However, treatment of 45 with thionyl chlo-
ride in methanol removed the Boc group and the corre-
sponding methyl ester was formed. Further reaction
with trimethylaluminum (2 mol equiv)29 provided desired
product 11 (37%). Trimethylaluminum has recently been
reported to convert carbamates to acetamides by substitu-
tion of the oxygen substituent of the carbamate with
Me;30 however, no acetamides were isolated upon reac-
tion of 45.
Table 2. Half life for the Bergman reactions of enediynes 4 and 6–10
(55 ꢁC in DMF)
H
H
CO2Me
R
CO2Me
R
N
N
DMF, 55oC
18
18 R = Ts
4, 6-10
37 R = Ac
38 R = Ms
39 R = Ns
40 R = 4-(MeO)PhSO2
41 R = 3,4-(MeO)2PhSO2
Enediyne
t1/2 (h)
4
6
7
8
9
10
5.9
9.5
55.4
18.5
7.6
4.0
The nitrogen atom of sulfonamides can adopt either
pyramidal or planar geometry (sp3 vs sp2 hybridization),
and sulfonamides exhibit the pyramidal form more fre-
quently than do amides.28 Single-crystal X-ray struc-
tures were obtained for acetamide 6 and mesylate 7.
However, in both cases the nitrogens involved adopt
the planar sp2 configuration (Fig. 5). As with enediyne
4, the methyl group of mesylate 7 is positioned endo rel-
ative to the enediyne system.
A single crystal X-ray structure of enediyne 11 was
obtained, revealing a reversed turn structure with hydro-
gen bonding between the carbonyl on the benzyloxycar-
bonyl group, and NHs on both the N-methyl amide
terminus and the bridging internal amide (Fig. 7). A b-
turn will fall into a particular defined class if three of
the four backbone torsional angles do not deviate more
than 30 ꢁC and the other not more than 45 ꢁC from ideal
values. Evaluation of the torsional angles of 11 indicated
that it adopts a Type II b-turn conformation in the solid
state.31 The Type II b-turn comprises ca. 13% of b-turns
among structures deposited in the Protein Data Bank.32
2.2. Twelve membered cyclic enediyne amino acids
We employed a route in which the amide bond was con-
structed in the last step for the preparation of 12-mem-
Figure 5. X-ray structures for enediyne acetamide 6 (left) and mesylate 7 (right).

5940
Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
I
PdCl2(PPh3)2, CuI
I
O
1.5 DME / 1 (0.5M NH3/H2O)
OH
+
O
N
H
55% (4 hrs)
I
O
CH2
OH
42
CbzHN
O
43
PdCl2(PPh3)2
CuI, NH3
CH2
NHMe
BocHN
69%
O
44
O
CH2
1. MeOH / SOCl2
2. AlMe3
NHMe
NHBoc
CH2
NHMe
37%
N
H
CbzHN
OH
CbzHN
O
O
O
11
45
Figure 6. Synthesis of 12-membered ring enediyne 11.
have longer terminal alkyne carbon distances than are
required for the thermal reaction.34 When 11 was
irradiated with ultraviolet light in the presence of 1,4-
cyclohexadiene in DMF, Bergman product 46 was not
observed but Z-alkene 47 was obtained (58%, Fig. 8).
Although expected product 46 and alkene 47 have the
same molecular weight, the presence of only one alkyne
in 47 could be seen by the presence of characteristic res-
onances at 83.1 and 89.6 ppm in the 13C NMR spec-
trum. The combination of HMBC and COSY allowed
for unambiguous assignment of a highly regioselective
reduction as shown and no reduction of the other alkyne
was observed. The cis bond geometry was determined by
a strong, positive NOE between the two vinyl protons,
along with an 11 Hz coupling constant. Turro and co-
workers have observed that photoirradiation of an acy-
clic 1,2-dialkynylbenzene substrate reduced only one
of the olefins to afford a single Z-olefin product.35
Although we do not fully understand the factors leading
to the formation of 47 upon irradiation of 11, we pro-
pose that the distance between the alkynes was too long
for the Bergman cyclization allowing for the competing
addition of a hydrogen radical to the exo face of the
alkyne at the b-position providing an aryl-stabilized
radical. Computational analysis has suggested that
a-alkyl vinylic radicals are generally sp2-hybridized-rad-
icals, whereas a-phenyl vinylic radicals are the linear
sp-hybridized p-radicals.36 An unpaired electron in the
p orbital of sp-hydridized intermediate could suffer at-
tack of an additional hydrogen radical from both sides
of the alkene and this process would be expected to be
diffusion controlled showing a strong preference for
the kinetic Z-product.
Figure 7. X-ray structure of enediyne 11 revealing a Type II b-turn
conformation in the solid state.
The distance between the two reacting alkynyl carbons
generally required for spontaneous Bergman cyclization
7
˚
is 2.9–3.3 A. Accordingly, we were not surprised that 11
was thermally stable either with or without microwave
activation because the distance between the two relevant
alkynyl carbons of 11 (C11 and C8) in the solid state is
33
˚
Since radicals were proposed to be generated in the
photoreduction process, we incubated bovine serum
3.86 A. The photochemical variant of the Bergman
reaction has been used for acyclic enediynes that

Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
5941
H
H
h
58%
NHMe
NHMe
NHMe
CbzNH
N
H
N
H
CbzNH
CbzHN
NH
O
O
O
O
O
O
46
11
47
Figure 8. Regioselective photoreduction of enediyne 11.
Figure 9. Cleavage of BSA by photoirradiation of enediyne 11 (units in Dalton).
albumin with 11 (at 1.0 lM), irradiated the mixture at
ambient temperature for a period of 1 h, and evaluated
the reaction mixture by SELDI-MS analysis (Fig. 9).
Fragmentation to several protein species of lower mass
(e.g., 9703 Da) was observed when 11 was present with
UV irradiation, when compared to controls in the ab-
sence of 11 or irradiation. Therefore, photoreduction
of enediyne 11 could also lead to non-specific protein
degradation in addition to formation of Z-olefin 47.
with the formation of radical intermediates under
these conditions.
4. Experimental
4.1. General
1H NMR spectra were obtained on either Bruker 500-
MHz DRX500 or 300-MHz DPX300 Bruker NMR
spectrometers with Me4Si as an internal standard. Stan-
dard conditions (300 MHz, CDCl3 for 1H, and 75 MHz,
CDCl3 for 13C) were used unless otherwise noted. Ele-
mental analyses were determined by Robertson Micro-
lit, Madison, NJ, and QTI Quantitative Technologies
INC, Whitehouse, NJ. X-ray crystallographic analysis
was done by Crystalytics, Lincoln, NE. Mass spectra
were generated using a MicroMass Platform LC electro-
spray mass spectrometer or by chemical ionization on a
Hewlett–Packard 5989A mass spectrometer. HRMS was
measured by Micromass LCT (ES-TOT). Most reagents
and solvents were purchased, and used without further
purification. UX174 RF I DNA was purchased from
New England Biolabs and BSA fraction V protein was
purchased from J. T. Baker. Protected propargyl glycine
12, 19–22, 42, and 44 were prepared according to general
and accepted methods.
3. Conclusions
We here, report the synthesis of benzofused enediynes,
which are incorporated onto a cyclic amino acid scaf-
fold. The synthesis entailed the Sonogashira and Mits-
unobu reactions, which appears to be the first time in
which a Mitsunobu reaction has been used in the con-
struction of a cyclic enediyne system. N-Acyl and sul-
fonyl substituted variants of 5 were prepared to study
the Bergman cyclization to give 18 and 37–41. We
found that N-arylsulfonyl substitution promoted the
reaction, which may be due to p–p stacking and sta-
bilization of the Bergman diradical intermediate. The
Bergman cyclization of 4 was also carried out in high
yield using microwave radiation. In addition,
4
cleaved double-stranded DNA upon heating in a dose
dependent manner. We then prepared and studied the
12-membered enediyne substrate 11, which we found
to adopt a Type II b-turn conformation in the solid
state. It did not undergo the Bergman cyclization pos-
sibly because the terminal alkynes are too far apart.
Upon irradiation with light, regioselective reduction
provided Z-olefin 47. In addition, 11 induced fragmen-
tation of the protein BSA when irradiated, consistent
4.2. Bergman cyclization of 4 in the presence and absence
of microwaves
A quantity of 3.9 mg of 4 was dissolved in degassed
DMF (10 mL) to give a 1 mM stock solution and
1.8 mg acetophenetidin was dissolved in degassed
DMF (100 mL) to give a 0.1 mM stock solution. The

5942
Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
reaction solution was prepared by mixing the enediyne 4
stock solution (1 mM, 2 mL) and the acetophenetidin
stock solution (0.1 mM, 2 mL) in degassed DMF
(16 mL) to give enediyne 4 at a concentration of
0.1 mM, and acetophenetidin at 0.01 mM concentra-
tion. The reaction solution (2 mL) prepared above was
added to a 10-mL CEM vial containing a magnetic
stir bar and then sealed. After purging with nitrogen
and vacuum degassing, 1,4-cyclohexadiene (0.01 mL,
0.1 mmol, 500 mol equiv) was added into the vacuumed
system via syringe. The mixture was then submitted to
either microwave irradiation (CEM Discovery appara-
tus setting: 150 W) or an oil bath at the temperature
indicated and kept at this temperature for 10 min. The
vial was then removed from the appropriate heating
sources and frozen immediately on dry ice, and then
thawed immediately before analysis. LC/MS–MS was
used to follow the formation of 18 with acetophenetidin
as an internal standard. The relative conversion of 4 to
18 under these conditions was very similar in the pres-
ence or absence of microwaves, with the microwave-
assisted reactions proceeding to a slightly higher degree.
(459.1 mg, 1.75 mmol) and DEAD (40% in toluene,
0.79 mL, 1.75 mmol) to afford compound 7 (150.4 mg,
62%) as a white solid: H NMR d 7.41–7.25 (m, 4H),
4.78 (d, J = 20.0 Hz, 1H), 4.28 (dd, J = 10.3, 4.5, 1H),
4.19 (d, J = 20.0, 1H), 3.81 (s, 3H), 3.38 (dd, J = 18.7,
10.1 Hz, 1H), 3.29 (dd, J = 18.9, 4.4 Hz, 1H), 3.08 (s,
3H). 13C NMR d 170.2, 129.1, 129.0, 128.8, 128.3
(2C), 127.9, 95.2, 93.6, 87.9, 84.7, 64.7, 53.4, 43.9,
42.4, 21.4. Anal. Calcd for C16H15NO4S: C, 60.55; H,
4.76; N, 4.41. Found: C, 60.33; H, 4.57; N, 4.46.
1
4.6. S-1-(2-Nitrobenzenesulfonyl)-[6,7]-benz-1-aza-cyclo-
dec-4,8-diyne-2- carboxylic methyl ester (8)
According to the procedure described for 4, compound 34
(1.25 g, 2.84 mmol) was treated with PPh3 (1.49 g,
5.67 mmol) and DEAD (40% in toluene, 2.57 mL,
5.67 mmol) to afford compound 3 (930.0 mg, 77%) as a
1
white solid: H NMR (DMSO-d6) d 8.24 (d, J = 7.4 Hz,
1H), 7.94 (d, J = 7.8 Hz, 1H), 7.76 (td, J = 7.7, 0.6 Hz,
1H), 7.57 (t, J = 7.7 Hz, 1H), 7.43–7.32 (m, 4H), 4.99
(dd, J = 10.9, 3.9 Hz, 1H), 4.72 (d, J = 19.4, 1H), 4.46
(d, J = 19.2, 1H), 3.65 (s, 3H), 3.22 (dd, J = 18.5,
4.0 Hz, 1H), 3.13 (dd, J = 18.7, 10.2 Hz, 1H). 13C NMR
d 169.6, 148.1, 135.1, 132.3, 132.2, 129.9, 129.0, 128.6
(2C), 128.3, 128.1, 127.3, 124.5, 96.4, 94.5, 87.1, 84.0,
64.3, 52.9, 42.6, 21.6. Anal. Calcd for C21H16N2O6S: C,
59.43; H, 3.80; N, 6.60. Found: C, 59.18; H, 3.61; N, 6.32.
4.3. Kinetic studies
Reaction solutions (30 mL) prepared as described above
containing 4 or 6–10 were added to a 250 mL flask con-
taining a magnetic stir bar and then sealed. After vacuum
degassing and refilling with nitrogen, 1,4-cyclohexadiene
(0.028 mL, 0.3 mmol, 100 mol equiv) was added. The
mixture was then submitted to an oil bath at 55 ꢁC. After
defined periods of time, a sample from the reaction mix-
ture (0.8 mL) was taken via syringe and immediately fro-
zen on dry ice, and thawed before analysis. LC/MS–MS
was used to follow the reaction with acetophenetidin as
an internal standard to detect the amount of product
formed and starting material consumed.
4.7. S-[6,7]-Benz-1-azacyclodec-4,8-diyne-2-carboxylic
methyl ester (5)
To a solution of 8 (85.0 mg, 0.20 mmol) in DMF (4 mL)
were added potassium carbonate (82.9 mg, 0.60 mmol)
and thiophenol (0.025 mL, 0.24 mmol). The resulting
mixture was stirred at ambient temperature for 2 h
and loaded onto a silica gel column. Purification with
gradient elution (EtOAc/heptane gradient from 1:9 to
4:6) afforded 5 (44.6 mg, 93%) as a white solid: 1H
NMR (500 MHz, DMSO-d6) d 7.40–7.30 (m, 4H), 3.73
(dd, J = 18.4, 2.9 Hz, 1H), 3.69–3.65 (m, 1H), 3.65 (s,
3H), 3.54 (dd, J = 18.4, 8.0, 1H), 3.08–2.98 (m, 1H),
2.78 (dd, J = 17.4, 2.2 Hz, 1H), 2.62 (dd, J = 17.3,
11.3 Hz, 1H); 13C NMR (DMSO-d6) d 173.0, 128.5,
128.4, 127.8, 127.8 (2C), 127.5, 100.1, 98.3, 84.3, 82.5,
61.7, 51.8, 39.5, 24.2. HRMS (ES) m/z: calcd for
(M+H)+ C15H14NO2, 240.1025; found, 240.1028.
4.4. S-1-(4-Toluenesulfonyl)-[6,7]-benz-1-azacyclodec-4,8-
diyne-2-carboxylic methyl ester (4)
To a solution of 17 (132.7 mg, 0.32 mmol) and PPh3
(169.0 mg, 0.64 mmol) in THF (35 mL) was added
DEAD (40% in toluene, 0.29 mL, 0.64 mmol) slowly at
0 ꢁC. The resulting mixture was stirred at this temperature
for 1 h and the solvent was then removed in vacuo. The
residue was purified on silica gel (EtOAc/heptane gradient
from 1:9 to 5:5) afforded 4 (114.0 mg, 90%) as a white sol-
id: 1H NMR d7.86–7.79 (m, 2H), 7.30–7.22 (m, 4H), 7.16–
7.10 (m, 2H), 4.78 (d, J = 19.0 Hz, 1H), 4.33 (dd, J = 10.4,
4.0 Hz, 1H), 4.22 (d, J = 19.1, 1H), 3.86 (s, 3H), 3.33 (dd,
J = 18.3, 10.2 Hz, 1H), 3.23 (dd, J = 18.7, 4.0 Hz, 1H),
2.25 (s, 3H). 13C NMR d 170.4, 143.8, 138.2, 129.7 (2C),
129.2, 128.5, 128.4, 128.1, 128.0, 127.9, 127.6 (2C), 95.7,
93.1, 87.6, 84.4, 64.6, 53.3, 42.7, 22.0, 21.7. Anal. Calcd
for C22H19NO4S: C, 67.16; H, 4.87; N, 3.56. Found: C,
66.98; H, 4.85; N, 3.58.
4.8. S-1-(2-Acetyl)-[6,7]-benz-1-azacyclodec-4,8-diyne-2-
carboxylic methyl ester (6)
To a solution of 5 (120.0 mg, 0.50 mmol) and Et3N
(0.35 mL, 2.51 mmol) in CH2Cl2 (20 mL) was added
acetyl chloride (0.18 mL, 2.51 mmol) at 0 ꢁC. The result-
ing mixture was stirred at ambient temperature for over-
night. The mixture was diluted with CH2Cl2, washed
with saturated aqueous NaHCO3, and dried over MgSO4.
The residue was purified on silica gel (heptane/EtOAc gra-
dient from 6:4 to 3:7) affording 6 (101.3 mg, 72%) as a
white solid: 1H NMR d 7.40–7.23 (m, 4H), 4.61 (d,
J = 19.1 Hz, 1H), 4.22 (d, J = 19.2 Hz, 1H), 4.07 (dd,
J = 11.3, 2.8 Hz, 1H), 3.76 (s, 3H), 3.63 (dd, J = 18.3,
11.2 Hz, 1H), 3.14 (dd, J = 18.1, 2.9 Hz, 1H), 2.24 (s,
4.5. S-1-Methanesulfonyl-[6,7]-benz-1-azacyclodec-4,8-diyne-
2-carboxylic methyl ester (7)
According to the procedure described for 4, compound
33 (293.2 mg, 0.88 mmol) was treated with PPh3

Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
5943
3H). 13C NMR d 170.6, 170.0, 129.9, 128.8, 128.7, 128.0,
127.9 (2C), 97.0, 93.3, 88.5, 83.2, 64.4, 53.0, 43.7, 22.2,
20.2. Anal. Calcd for C17H15NO3: C, 72.58; H, 5.37; N,
4.98. Found: C, 72.42; H, 5.19; N, 4.77.
54.8, 53.2, 25.4, 21.9. Anal. Calcd for C19H19NO4S: C,
63.85; H, 5.36; N, 3.92. Found: C, 63.59; H, 5.07; N,
3.69.
4.12. S-2-(4-Toluenesulfonylamino)-5-(4-methoxyphenyl)-
pent-4-ynoic acid methyl ester (14)
4.9. S-1-(4-Methoxybenzenesulfonyl)-[6,7]-benz-1-azacy-
clodec-4,8-diyne-2-carboxylic methyl ester (9)
Compound 12 (141.0 mg, 0.5 mmol) was coupled with 1-
iodo-4-methoxybenzene (140.4 mg, 0.6 mmol) under the
same conditions as described for 13 to furnish compound
14 (106.5 mg, 55%) as white needles: 1H NMR d 7.81–7.74
(m, 2H), 7.33–7.25 (m, 4H), 6.86–6.78 (m, 2H), 5.48 (d,
J = 9.1 Hz, 1H), 4.25–4.13 (m, 1H), 3.82 (s, 3H), 3.64 (s,
3H), 2.92 (dd, J = 17.2, 5.1 Hz, 1H), 2.85 (dd, J = 17.4,
5.5 Hz, 1H), 2.42 (s, 3H). 13C NMR d 170.7, 160.0,
144.1, 137.4, 133.5 (2C), 130.1 (2C), 127.6 (2C), 115.2,
114.3 (2C), 84.5, 81.5, 55.7, 54.9, 53.2, 25.4, 21.9. Anal.
Calcd for C20H21NO5S: C, 62.00; H, 5.46; N, 3.62. Found:
C, 61.88; H, 5.32; N, 3.38.
According to the procedure described for 4, compound 35
(361.8 mg, 0.85 mmol) was treated with PPh3 (445.9 mg,
1.70 mmol) and DEAD (40% in toluene, 0.77 mL,
1.70 mmol) to afford compound 6 (222.0 mg, 64%) as a
1
white solid: H NMR d 7.91–7.85 (m, 2H), 7.29–7.21
(m, 4H), 6.83–6.76 (m, 2H), 4.75 (d, J = 19.5 Hz, 1H),
4.32 (dd, J = 10.5, 3.9 Hz, 1H), 4.20 (d, J = 19.0 Hz,
1H), 3.86 (s, 3H), 3.69 (s, 3H), 3.34 (dd, J = 18.4,
10.5 Hz, 1H), 3.23 (dd, J = 18.2, 3.9 Hz, 1H); 13C NMR
d 170.4, 163.2, 132.7, 129.9 (2C), 129.2, 128.5, 128.4,
128.1, 128.0, 127.9, 114.3, 95.7, 93.3, 87.6, 84.3, 64.6,
55.8, 53.3, 42.6, 22.0. Anal. Calcd for C22H19NO5S: C,
64.53; H, 4.68; N, 3.42. Found: C, 64.39; H, 4.71; N, 3.39.
4.13. S-2-(4-Toluenesulfonylamino)-5-(4-trifluoromethyl-
phenyl)pent-4-ynoic acid methyl ester (15)
4.10. S-1-(3,4-Dimethoxybenzenesulfonyl)-[6,7]-benz-1-aza-
cyclodec-4,8-diyne-2- carboxylic methyl ester (10)
Compound 12 (141.0 mg, 0.5 mmol) was coupled with 1-
iodo-4-trifluoromethylbenzene (0.088 mL, 0.6 mmol) un-
der the same condition as for 13 to afford 15 (163.3 mg,
According to the procedure described for 4, compound
36 (293.2 mg, 0.88 mmol) was treated with PPh3
(459.1 mg, 1.75 mmol) and DEAD (40% in toluene,
0.79 mL, 1.75 mmol). The residue was purified on silica
gel (CH2Cl2) afforded 10 (663.6 mg, 85%) as a white sol-
1
77%) as a light yellow solid: H NMR d 7.81–7.74 (m,
2H), 7.55 (d, J = 8.1 Hz, 2H), 7.45 (d, J = 8.2 Hz, 2H),
7.29 (d, J = 8.4 Hz, 2H), 5.59 (d, J = 8.9 Hz, 1H), 4.22
(dt, J = 8.5, 5.5 Hz, 1H), 3.65 (s, 3H), 2.94 (d, J =
5.5 Hz, 2H), 2.41 (s, 3H). 13C NMR d 170.6, 144.2,
137.3, 132.4 (2C), 130.4 (q, J = 32.6 Hz), 130.1 (2C),
127.6 (2C), 127.0 (q, J = 1.2 Hz), 125.5 (q, J = 3.9 Hz,
2C), 124.3 (q, J = 272.3 Hz), 86.1, 83.3, 54.7, 53.3, 25.4,
21.9. Anal. Calcd for C20H18F3NO4S: C, 56.46; H, 4.26;
N, 3.29; F, 13.40. Found: C, 56.28; H, 4.03; N, 3.16; F,
13.78.
1
id: H NMR d 7.59 (dd, J = 8.7, 2.3 Hz, 1H), 7.41 (d,
J = 1.8 Hz, 1H), 7.30–7.20 (m, 4H), 6.80 (d,
J = 8.8 Hz, 1H), 4.74 (d, J = 19.6 Hz, 1H), 4.35 (dd,
J = 9.8, 4.4 Hz, 1H), 4.23 (d, J = 19.4 Hz, 1H), 3.88 (s,
3H), 3.81 (s, 3H), 3.74 (s, 3H), 3.34 (dd, J = 18.8,
9.6 Hz, 1H), 3.26 (dd, J = 18.4, 4.6 Hz, 1H). 13C NMR
d 170.4, 153.0, 149.4, 132.6, 128.8, 128.4, 128.4, 128.0,
127.9, 127.8, 121.9, 110.6, 110.0, 95.9, 93.3, 87.5, 84.3,
64.5, 56.2, 56.1, 53.2, 42.4, 21.8. Anal. Calcd for
C23H21NO6S: C, 62.86; H, 4.82; N, 3.19. Found: C,
62.64; H, 4.72; N, 3.02.
4.14. S-2-(4-Toluenesulfonylamino)-5-(2-iodophenyl)pent-
4-ynoic acid methyl ester (16)
To a solution of compound 12 (783.0 mg, 2.78 mmol) in
DME (19.0 mL) were added 1,2-diiodobenzene (0.44
mL, 3.34 mmol), PdCl2(PPh3)4 (60.0 mg, 0.085 mmol),
and CuI (27.0 mg, 0.14 mmol) at ambient temperature
under nitrogen. A solution of aqueous ammonia
(0.5 M, 2 mL, 11.0 mmol) was then added dropwise
and the resulting mixture was stirred for 4 h. The sol-
vent was then removed in vacuo. The residue was dis-
solved in ethyl acetate (60 mL), washed with saturated
NH4Cl, NaHCO3, and brine sequentially, and then
dried over MgSO4. After concentration, purification
on silica gel (EtOAc/heptane gradient from 1:9 to 5:5)
afforded 16 (800.8 mg, 60%) as a light yellow liquid:
1H NMR d 7.83–7.74 (m, 3H), 7.38–7.22 (m, 4H), 6.98
(td, J = 7.5, 1.7 Hz, 1H), 5.75 (d, J = 9.0 Hz, 1H), 4.25
(dt, J = 9.2, 4.8 Hz, 1H), 3.64 (s, 3H), 3.00 (dd,
J = 17.0, 4.5 Hz, 1H), 2.92 (dd, J = 17.1, 5.4 Hz, 1H),
2.39 (s, 3H). 13C NMR d 170.5, 144.1, 138.9, 137.5,
133.3, 130.1 (2C), 129.9, 129.7, 128.2, 127.6 (2C),
101.1, 87.5, 86.5, 54.7, 53.4, 25.4, 21.9. Anal. Calcd
for C19H18INO4S: C, 47.22; H, 3.75; N, 2.90. Found:
C, 47.41; H, 3.77; N, 2.76.
4.11. S-2-(4-Toluenesulfonylamino)-5-phenylpent-4-ynoic
acid methyl ester (13)
To a solution of compound 12 (141.0 mg, 0.50 mmol) in
THF (3.3 mL) were added iodobenzene (98%, 0.068 mL,
0.6 mmol), PdCl2(PPh3)4 (10.5 mg, 0.015 mmol), and
CuI (4.8 mg, 0.025 mmol) at room temperature under
nitrogen. A solution of aqueous ammonia (0.5 M,
2 mL, 1.0 mmol) was then added dropwise and the
resulting mixture was stirred at ambient temperature
for 14 h. The solvent was then removed in vacuo. The
residue was dissolved in ethyl acetate (30 mL), washed
with saturated NH4Cl, NaHCO3, and brine sequentially,
and then dried over MgSO4. After concentration, purifi-
cation on silica gel (EtOAc/heptane gradient from 2:8 to
1
5:5) afforded 13 (143.5 mg, 80%): H NMR d 7.81–7.74
(m, 2H), 7.39–7.26 (m, 7H), 5.49 (d, J = 9.0 Hz, 1H),
4.26–4.15 (m, 1H), 3.65 (s, 3H), 2.95 (dd, J = 17.0,
4.5 Hz, 1H), 2.87 (dd, J = 16.9, 5.3 Hz, 1H), 2.42 (s,
3H). 13C NMR d 170.7, 144.1, 137.4, 132.1 (2C), 130.1
(2C), 128.6, 122.6 (2C), 127.6 (2C), 123.1, 84.7, 83.1,

5944
Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
4.15. S-2-(4-Toluenesulfonylamino)-5-[2-(3-hydroxyprop-
1-ynyl)phenyl]pent-4-ynoic acid methyl ester (17)
25.5. Anal. Calcd for C13H14INO4S: C, 38.34; H, 3.47;
N, 3.44. Found: C, 38.46; H, 3.16; N, 3.36.
To a solution of 16 (166.0 mg, 0.34 mmol) in DME
(2.2 mL) were added propargyl alcohol (0.040 mL,
0.69 mmol), PdCl2(PPh3)4 (7.2 mg, 0.01 mmol), and
CuI (3.2 mg, 0.017 mmol) at ambient temperature under
nitrogen. A solution of aqueous ammonia (0.5 M,
1.36 mL, 0.68 mmol) was then added dropwise and the
resulting mixture was stirred at rt for 4 h. The solvent
was then removed in vacuo. The residue was dissolved
in ethyl acetate (30 mL), washed with saturated NH4Cl,
NaHCO3, and brine sequentially, and then dried over
MgSO4. After concentration, purification on silica gel
(EtOAc/heptane gradient from 1:9 to 5:5) afforded 17
(132.7 mg, 94%) as a clear liquid: 1H NMR d 7.74–
7.66 (m, 2H), 7.38–7.10 (m, 6H), 6.16 (d, J = 9.2 Hz,
1H), 4.53 (s, 2H), 4.14 (dt, J = 9.1, 4.7 Hz, 1H), 3.56
(s, 3H), 3.22 (br s, 1H), 2.92 (dd, J = 17.0, 4.2 Hz,
1H), 2.84 (dd, J = 16.6, 5.2 Hz, 1H), 2.30 (s, 3H). 13C
NMR d 170.8, 144.1, 137.4, 132.4, 132.2, 130.1 (2C),
128.4, 128.4, 127.5 (2C), 125.8, 125.6, 92.3, 87.1, 84.3,
83.5, 54.6, 53.4, 51.8, 25.5, 21.9. Anal. Calcd for
C22H21NO5S: C, 64.22; H, 5.14; N, 3.40. Found: C,
63.96; H, 5.32; N, 3.38.
4.18. S-2-(2-Nitrobenzenesulfonylamino)-5-(2-iodophe-
nyl)pent-4-ynoic acid methyl ester (24)
Compound 20 (1.56 g, 5.01 mmol) was coupled with 1,2-
diiodobenzene (1.31 mL, 10.03 mmol) under the similar
conditions as described for 16 to afford 24 (1.58 g, 61%)
1
as a light yellow liquid: H NMR d 8.17–8.08 (m, 1H),
7.93–7.87 (m, 1H), 7.81 (dd, J = 8.1, 0.8 Hz, 1H),
7.77–7.66 (m, 2H), 7.38 (dd, J = 7.7, 1.7 Hz, 1H), 7.28
(ddd, J = 7.5, 7.5, 1.1 Hz, 1H), 7.00 (ddd, J = 8.1, 8.1,
1.8 Hz, 1H), 6.54 (d, J = 9.0 Hz, 1H), 4.53 (dt, J = 9.0,
5.0 Hz, 1H), 3.65 (s, 3H), 3.15 (dd, J = 17.2, 4.6 Hz,
1H), 3.07 (dd, J = 17.2, 5.1 Hz, 1H). 13C NMR d
169.7, 147.6, 138.6, 134.5, 133.6, 132.9, 132.9, 130.3,
129.5, 129.1, 127.8, 125.6, 100.7, 86.6, 86.4, 55.3, 53.0,
25.0. Anal. Calcd for C18H15IN2O6S: C, 42.04; H,
2.94; N, 5.45. Found: C, 42.25; H, 2.76; N, 5.37.
4.19. S-2-(4-Methoxybenzenesulfonylamino)-5-(2-iodophe-
nyl)pent-4-ynoic acid methyl ester (25)
Compound 25 (1.66 g, 5.60 mmol) was prepared using
the conditions described in the synthesis of 16 in cou-
pling with 1,2-diiodobenzene (1.46 mL, 11.20 mmol) to
4.16. S-2-(4-Toluenesulfonyl)-1,2,3,4-tetrahydrobenzo[g]iso-
quinoline-3-carboxylic acid methyl ester (18)
1
afford 25 (1.26 g, 45%) as a white solid: H NMR d
7.88–7.79 (m, 2H), 7.40–7.25 (m, 2H), 7.05–6.92 (m,
3H), 5.63 (d, J = 9.1 Hz, 1H), 4.25 (dt, J = 9.1, 4.8 Hz,
1H), 3.87 (s, 3H), 3.68 (s, 3H), 3.02 (dd, J = 16.9,
4.3 Hz, 1H), 2.93 (dd, J = 17.1, 5.3 Hz, 1H), 2.39 (s,
3H). 13C NMR d 170.5, 163.4, 139.0, 133.2, 132.0,
129.8, 129.8 (2C), 129.7, 128.1, 114.6 (2C), 101.1, 87.4,
86.5, 56.0, 54.6, 53.4, 25.4. Anal. Calcd for C19H18I-
NO5S: C, 45.70; H, 3.63; N, 2.81. Found: C, 45.94; H,
3.71; N, 2.56.
A 10-mL CEM vial containing a magnetic stir bar was
charged with enediyne 4 (11.8 mg, 0.03 mmol) and
DMF (3 mL), and then sealed. After purging with nitro-
gen and vacuum degassing, 1,4-cyclohexadiene
(0.30 mL, 3.1 mmol) was added via syringe. The mixture
was then submitted to microwave irradiation (CEM
Discovery apparatus setting 120 ꢁC, 150 W), and kept
at this temperature for 10 min. The crude reaction mix-
ture was concentrated, and the residue was separated on
silica gel (EtOAc/heptane from 15:85 to 45:55) to afford
compound 18 (10.0 mg, 84%) as a white solid: 1H NMR
d 7.78–7.70 (m, 4H), 7.58 (s, 1H), 7.54 (s, 1H), 7.48–7.40
(m, 2H), 7.25 (overlapped doublet, J = 8.0 Hz, 2H), 5.01
(t, J = 5.1 Hz, 1H), 4.86 (d, J = 15.0, 1H), 4.69 (d,
J = 15.6, 1H), 3.52 (s, 3H), 3.38–3.32 (m, 2H), 2.37 (s,
3H). 13C NMR d 171.4, 143.9, 136.3, 132.8, 132.7,
130.6, 129.9 (2C), 129.8, 127.8 (2C), 127.8, 127.6,
127.3, 126.3, 126.3, 125.2, 55.0, 52.7, 45.5, 32.8, 21.8.
HRMS (ES) m/z: calcd for (M+H)+ C22H22NO4S,
396.1270; found, 396.1272.
4.20. S-2-(3,4-Dimethoxybenzenesulfonylamino)-5-(2-
iodophenyl)pent-4-ynoic acid methyl ester (26)
According to the procedure described for compound 16,
compound 22 (500.0 mg, 1.52 mmol) was coupled with
1,2-diiodobenzene (0.40 mL, 3.05 mmol) under the sim-
ilar conditions to afford compound 26 (0.97 g, 60%) as a
1
white solid: H NMR d 7.83 (d, J = 8.2 Hz, 1H), 7.53
(dd, J = 8.5, 2.1 Hz, 1H), 7.54–7.25(m, 3H), 7.02 (td,
J = 7.7, 1.6 Hz, 1H), 6.92 (d, J = 8.2 Hz, 1H), 5.67 (d,
J = 8.9 Hz, 1H), 4.25 (dt, J = 9.0, 4.6 Hz, 1H), 3.94 (s,
3H), 3.92 (s, 3H), 3.70 (s, 3H), 3.02 (dd, J = 17.1,
3.9 Hz, 1H), 2.92 (dd, J = 17.3, 5.3 Hz, 1H). 13C NMR
d 170.5, 153.2, 149.6, 139.0, 133.2, 132.0, 129.9, 129.6,
128.2, 121.6, 110.9, 110.1, 101.1, 87.4, 86.6, 56.6, 56.6,
54.6, 53.4, 25.4. Anal. Calcd for C20H20INO6S: C,
45.38; H, 3.81; N, 2.65. Found: C, 45.33; H, 3.76; N,
2.61.
4.17. S-2-(Methanesulfonylamino)-5-(2-iodophenyl)pent-
4-ynoic acid methyl ester (23)
Compound 19 (335.2 mg, 1.63 mmol) was coupled with
1,2-diiodobenzene (0.43 mL, 3.27 mmol) under similar
conditions as described for 16 to afford compound 23
(284 mg, 43%) as a light yellow liquid: 1H NMR d
7.84 (dd, J = 8.0, 0.8 Hz, 1H), 7.42 (dd, J = 7.7,
1.7 Hz, 1H), 7.31 (ddd, J = 7.5, 7.5, 1.0 Hz, 1H), 7.03
(ddd, J = 8.0, 8.0, 1.9 Hz 1H), 5.45 (d, J = 9.1 Hz, 1H),
4.47 (dt, J = 9.0, 4.8 Hz, 1H), 3.87 (s, 3H), 3.21–3.02
(m, 2H), 3.09 (s, 3H); 13C NMR d 171.0, 139.0, 133.2,
130.0, 129.5, 128.2, 101.1, 87.3, 86.8, 54.9, 53.6, 42.6,
4.21. S-2-(Methanesulfonylamino)-5-[2-(3-hydroxyprop-
1-ynyl)phenyl]pent-4-ynoic acid methyl ester (33)
Compound 23 (548.4 mg, 1.35 mmol) was coupled un-
der similar conditions as described for 17 using propar-
gyl alcohol (0.16 mL, 2.70 mmol) to afford compound

Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
5945
1
33 (391.3 mg, 87%) as a light yellow liquid: H NMR d
7.47–7.36 (m, 2H), 7.31–7.22 (m, 2H), 5.95 (d,
J = 9.6 Hz, 1H), 4.60 (s, 2H), 4.47 (dt, J = 9.4, 4.6 Hz,
1H), 3.84 (s, 3H), 3.20–3.03 (m, 6H); 13C NMR d
171.5, 132.4, 132.2, 128.5 (2C), 125.7, 125.4, 92.2, 87.1,
84.3, 83.6, 54.9, 53.7, 51.8, 42.3, 25.8. Anal. Calcd for
C16H17NO5S: C, 57.30; H, 5.11; N, 4.18. Found: C,
57.14; H, 5.36; N, 3.99.
4.25. S-2-Acetyl-1,2,3,4-tetrahydrobenzo[g]isoquinoline-3-
carboxylic acid methyl ester (37)
According to the procedure described for 18, compound
6 (10.5 mg, 0.037 mmol) was treated with 1,4-cyclohex-
adiene (0.30 mL, 3.2 mmol) and subjected to microwave
irradiation for 60 min at 200 ꢁC. The crude reaction
mixture was concentrated, and the residue was separat-
ed on silica gel (EtOAc/heptane gradient from 20:80 to
70:30) to afford 37 (8.4 mg, 79%) as a sticky clear oil:
1H NMR (500 MHz, mixture of rotamers) d 7.82–7.74
(m, 2H), 7.69–7.61 (m, 2H), 7.50–7.42 (m, 2H), 5.36 (t,
J = 5.5 Hz, 1H), 5.10–4.74 (m, 2H), 3.63 & 3.61 (s, 3H
in total), 3.48–3.23 (m, 2H), 2.29 & 2.15 (s, 3H in total).
HRMS (ES) m/z: calcd for (M+H)+ C17H18NO3,
284.1287; found, 284.1291.
4.22. S-2-(2-Nitrobenzenesulfonylamino)-5-[2-(3-hydroxy-
prop-1-ynyl)phenyl]pent-4-ynoic acid methyl ester (34)
According to the procedure described for 17, com-
pound 24 (1.87 g, 3.49 mmol) was coupled with propar-
gyl alcohol (0.42 mL, 6.99 mmol) to afford 34 (1.25 g,
79%) as a light yellow liquid: 1H NMR d 8.18–8.09
(m, 1H), 7.91–7.82 (m, 1H), 7.75–7.65 (m, 2H), 7.46–
7.39 (m, 1H), 7.38–7.30 (m, 1H), 7.30–7.20 (m, 2H),
6.68 (d, J = 8.9 Hz, 1H), 4.60–4.47 (m, 3H), 3.66 (s,
3H), 3.14 (dd, J = 17.5, 4.5 Hz, 1H), 3.06 (dd,
J = 17.1, 5.0 Hz, 1H), 2.88 (br s, 1H). 13C NMR d
170.6, 147.9, 134.8, 134.0, 133.2, 132.5, 132.4, 130.8,
128.5, 128.4, 125.8, 125.8, 125.3, 92.3, 86.6, 84.0, 83.6,
55.6, 53.5, 51.9, 25.4. Anal. Calcd for C21H18N2O7S:
C, 57.01; H, 4.10; N, 6.33. Found: C, 56.98; H, 3.90;
N, 6.06.
4.26. S-2-Methanesulfonyl-1,2,3,4-tetrahydro-benzo[g]-
isoquinoline-3-carboxylic acid methyl ester (38)
According to the procedure described for 18, compound
7 (9.5 mg, 0.03 mmol) was treated with 1,4-cyclohexadi-
ene (0.28 mL, 3.0 mmol) and subjected to microwave
irradiation for 20 min. The crude reaction mixture was
concentrated, and the residue was separated on silica
gel (EtOAc/heptane gradient from 15:85 to 50:50) to af-
ford 38 (7.8 mg, 82%) as a white solid: 1H NMR d 7.84–
7.75 (m, 2H), 7.68 (s, 1H), 7.64 (s, 1H), 7.52–7.43 (m,
2H), 5.02 (t, J = 5.0 Hz, 1H), 4.96 (d, J = 15.2 Hz,
1H), 4.74 (d, J = 15.8 Hz, 1H), 3.67 (s, 3H), 3.48 (d,
J = 4.8 Hz, 1H), 3.03 (s, 3H). 13C NMR d 171.8,
132.9, 132.8, 130.3, 129.8, 127.8, 127.7, 127.5, 126.5,
126.4, 125.2, 55.4, 53.0, 45.2, 38.8, 33.0. Anal. Calcd
for C16H17NO4S: C, 60.17; H, 5.37; N, 4.39. Found:
C, 60.02; H, 5.60; N, 4.16.
4.23. S-2-(4-Methoxybenzenesulfonylamino)-5-[2-(3-hydro-
xyprop-1-ynyl)phenyl]pent-4-ynoic acid methyl ester (35)
According to the procedure described for 17, compound
25 (190.0 mg, 0.38 mmol) was coupled with propargyl
alcohol (0.044 mL, 0.76 mmol) to afford 35 (140.8 mg,
1
87%) as a white solid: H NMR d 7.88–7.81 (m, 2H),
7.48–7.39 (m, 1H), 7.38–7.31 (m, 1H), 7.30–7.20 (m,
2H), 6.96–6.89 (m, 2H), 6.18 (d, J = 9.4 Hz, 1H), 4.62
(s, 2H), 4.22 (dt, J = 9.2, 4.4 Hz, 1H), 3.84 (s, 3H),
3.67 (s, 3H), 3.25 (s, 1H), 3.01 (dd, J = 17.3, 4.1 Hz,
1H), 2.93 (dd, J = 17.1, 5.1 Hz, 1H). 13C NMR d
170.8, 163.4, 132.5, 132.2, 131.9, 129.7 (2C), 128.4,
128.4, 125.8, 125.6, 114.6 (2C), 92.3, 87.1, 84.3, 83.5,
56.0, 54.5, 53.4, 51.8, 25.5. Anal. Calcd for
C22H21NO6S: C, 61.81; H, 4.95; N, 3.28. Found: C,
61.63; H, 5.15; N, 3.19.
4.27. S-2-(2-Nitrobenzenesulfonyl)-1,2,3,4-tetrahydro-
benzo[g]isoquinoline-3-carboxylic acid methyl ester (39)
According to the procedure described for 18, compound
8 (13.7 mg, 0.03 mmol) was treated with 1,4-cyclohex-
adiene (0.28 mL, 3.0 mmol). The crude reaction mixture
was concentrated, and the residue was separated on sil-
ica gel (EtOAc/heptane gradient from 15:85 to 45:55) to
1
afford 39 (13.5 mg, 98%) as a white solid: H NMR d
4.24. S-2-(3,4-Dimethoxybenzenesulfonylamino)-5-[2-(3-
hydroxyprop-1-ynyl)-phenyl]pent-4-ynoic acid methyl ester
(36)
8.12–8.04 (m, 1H), 7.71–7.53 (m, 6H), 7.51 (s, 1H),
7.40–7.30 (m, 2H), 5.09 (t, J = 4.7 Hz, 1H), 4.86 (d,
J = 15.8 Hz, 1H), 4.80 (d, J = 16.3 Hz, 1H), 3.45 (s,
3H), 3.45–3.41 (m, 2H). 13C NMR d 170.7, 148.0,
133.7, 132.5, 132.4, 132.3, 131.7, 131.1, 129.2, 128.9,
127.3, 127.3, 127.2, 126.1, 126.0, 124.8, 124.3, 55.0,
52.5, 45.1, 32.3. HRMS (ES) m/z: calcd for (M+H)+
C21H19N2O6S: 427.0964, found 427.0967.
According to the procedure described for 17, compound
26 (945.0 mg, 1.78 mmol) was coupled with propargyl
alcohol (0.21 mL, 3.57 mmol) to afford 36 (810.0 mg,
1
93%) as a white solid: H NMR d 7.53–7.46 (m, 1H),
7.41–7.35 (m, 2H), 7.34–7.27 (m, 1H), 7.26–7.17 (m,
2H), 6.87–6.82 (m, 1H), 6.40–6.30 (m, 1H), 4.60 (s,
2H), 4.21 (dt, J = 9.2, 4.5 Hz, 1H), 3.87 (s, 3H), 3.84
(s, 3H), 3.64 (s, 3H), 3.37 (br s, 1H), 2.97 (dd,
J = 16.9, 4.1 Hz, 1H), 2.88 (dd, J = 17.0, 5.0 Hz, 1H).
13C NMR d 170.8, 153.1, 149.5, 132.4, 132.1, 132.0,
128.4, 128.3, 125.7, 125.5, 121.5, 110.8, 110.0, 92.3,
87.2, 84.2, 83.4, 56.5, 56.5, 54.6, 53.4, 51.8, 25.4. Anal.
Calcd for C23H23NO7S: C, 60.38; H, 5.07; N, 3.06.
Found: C, 60.30; H, 4.79; N, 2.79.
4.28. S-2-(4-Methoxybenzenesulfonyl)-1,2,3,4-tetrahydro-
benzo[g]isoquinoline-3-carboxylic acid methyl ester (40)
According to the procedure described for 18, compound
9 (12.3 mg, 0.03 mmol) was treated with 1,4-cyclohex-
adiene (0.28 mL, 3.0 mmol). The crude reaction mixture
was concentrated, and the residue was separated on sil-
ica gel (EtOAc/heptane gradient from 15:85 to 45:55) to
afford compound 40 (11.9 mg, 96%) as a white solid: 1H

5946
Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
NMR d 7.73–7.67 (m, 2H), 7.67–7.61 (m, 2H), 7.48 (s,
1H), 7.44 (s, 1H), 7.38–7.31 (m, 2H), 6.85–6.78 (m,
2H), 4.89 (t, J = 5.3 Hz, 1H), 4.76 (d, J = 15.5 Hz, 1H),
4.58 (d, J = 15.3 Hz, 1H), 3.72 (s, 3H), 3.44 (s, 3H),
3.26 (d, J = 5.3 Hz, 2H). 13C NMR d 171.1, 163.0,
132.4, 132.3, 130.5, 130.3, 129.5 (2C), 129.5, 127.4,
127.2, 126.8, 125.9, 125.9, 124.8, 114.0 (2C), 55.5, 54.6,
52.4, 45.1, 32.4. Anal. Calcd for C22H21NO5S: C,
64.22; H, 5.14; N, 3.40. Found: C, 64.03; H, 5.46; N,
3.03.
3.02 (d, J = 6.28 Hz, 0.2H), 2.98 (dd, J = 17.1, 5.5 Hz,
1H), 2.90 (dd, J = 16.7, 8.2 Hz, 1H), 2.85 (dd, J = 16.9,
5.6 Hz, 1H), 2.75 (dd, J = 17.0, 7.9 Hz, 1H), 2.71 (d,
J = 4.8 Hz, 0.3H), 2.62 (d, J = 4.9 Hz, 2.7H), 1.37 (s,
9H). HRMS (ES) m/z: calcd for (M+H)+ C30H34N3O7,
548.2397; found, 548.2384.
4.32. S,S-(8-Methylcarbamoyl-10-oxo-7,8,9,10,11,12-hexa-
hydro-9-azabenzocyclododec-5,13-diyn-11-yl)-carbamic acid
benzyl ester (11)
4.29. S-2-(3,4-Dimethoxybenzenesulfonyl)-1,2,3,4-tetrahy-
dro-benzo[g]isoquinoline-3-carboxylic acid methyl ester (41)
To a stirred solution of 45 (186.0 mg, 0.34 mmol) in
methanol was added thionyl chloride (0.1 mL) at
0 ꢁC. The mixture was stirred at ambient temperature
for overnight and then concentrated. The residue was
dissolved in satd Na2CO3 (10 mL) and extracted with
CH2Cl2 (20 mL) three times. The combined organic
phase was dried over MgSO4 and concentrated. Trim-
ethylaluminum (0.29 mL, 0.58 mmol, 2.0 M in hexane)
was added dropwise to the resulting free amine in
CH2Cl2 (34 mL) at 0 ꢁC. The mixture was then stirred
under reflux for 24 h. The reaction was quenched by
slow addition of aqueous HCl (0.5 M, 10 mL) at
0 ꢁC. The aqueous solution was extracted with CH2Cl2
(34 mL) three times. The combined organic phase was
dried over MgSO4 and concentrated. The residue was
separated by reverse phase HPLC (gradient in
CH3CN/H2O from 40:60 to 80:20) to give 11 (54 mg,
37%) as a white solid. 1H NMR (DMSO-d6) d 8.51
(d, J = 8.0 Hz, 1H), 7.88 (d, J = 4.9 Hz, 1H), 7.72–
7.63 (m, 1H), 7.48–7.26 (m, 9H), 5.13 (d,
J = 12.5 Hz, 1H), 5.04 (d, J = 12.3 Hz, 1H), 4.36 (q,
J = 7.8 Hz, 1H), 4.25–4.14 (m, 1H), 3.03 (dd,
J = 17.5, 4.2 Hz, 1H), 2.98 (d, J = 7.8 Hz, 2H), 2.79
(dd, J = 17.1, 6.0 Hz, 1H), 2.58 (d, J = 4.4 Hz, 3H).
13C NMR (100 MHz) d 169.9, 169.8, 156.5, 136.5,
131.1, 130.5, 128.4 (2C), 128.1, 128.0, 127.9, 127.8
(2C), 126.0, 125.6, 91.7, 89.7, 81.7, 81.4, 66.0, 54.9,
51.9, 25.7, 22.7, 21.5. Anal. Calcd for C25H23N3O4:
C, 69.92; H, 5.40; N, 9.78. Found: C, 69.68; H,
5.15; N, 9.68.
According to the procedure described for 18, compound
10 (13.4 mg, 0.03 mmol) was treated with 1,4-cyclohex-
adiene (0.28 mL, 3.0 mmol). The crude reaction mixture
was concentrated, and the residue was separated on silica
gel (EtOAc/heptane gradient from 15:85 to 45:55) to af-
1
ford 41 (13.4 mg, 100%) as a white solid: H NMR d
7.79–7.70 (m, 2H), 7.58 (s, 1H), 7.55 (s, 1H), 7.49 (dd,
J = 8.8, 2.3 Hz, 1H), 7.47–7.40 (m, 2H), 7.31 (d,
J = 2.5 Hz, 1H), 6.86 (d, J = 8.2 Hz, 1H), 4.97 (t,
J = 5.3 Hz, 1H), 4.86 (d, J = 15.5 Hz, 1H), 4.68 (d,
J = 16.2 Hz, 1H), 3.89 (s, 3H), 3.85 (s, 3H), 3.56 (s, 3H),
3.35 (d, J = 5.1 Hz, 2H). 13C NMR d 171.2, 152.7,
149.0, 132.5, 132.3, 130.5, 130.4, 129.5, 127.3, 127.2,
126.8, 126.0, 126.0, 124.7, 121.5, 110.4, 109.9, 56.1, 56.1,
54.7, 52.4, 45.2, 32.3. Anal. Calcd for C23H23NO6S: C,
62.57; H, 5.25; N, 3.17. Found: C, 62.52; H, 5.57; N, 2.83.
4.30. S-2-Benzyloxycarbonylamino-5-(2-iodophenyl)pent-
4-ynoic acid (43)
According to the procedure described for 16, compound
42 (1.21 g, 4.89 mmol) was coupled with 1,2-diiodoben-
zene (0.77 mL, 5.86 mmol). Purification of the product
on silica gel (EtOAc/AcOH gradient from 100:0 to
200:1) afforded 43 (1.21 g, 55%) as a light yellow liquid:
1H NMR d 10.88 (br s, 1H), 7.78 (d, J = 7.8 Hz, 1H),
7.45–7.30 (m, 6H), 7.26 (t, J = 7.7 Hz, 1H), 6.97 (td,
J = 7.5, 1.3 Hz, 1H), 5.91 (d, J = 8.4 Hz, 1H), 5.23–
5.12 (m, 2H), 4.73 (dt, J = 8.4, 4.7 Hz, 1H), 3.21–3.02
(m, 2H). 13C NMR (100 MHz) d 175.6, 156.4, 139.0,
136.4, 133.2, 129.8, 129.7, 129.0 (2C), 128.6, 128.5
(2C), 128.1, 101.3, 87.9, 86.5, 67.7, 52.8, 24.0. Anal.
Calcd for C19H16INO4: C, 50.80; H, 3.59; N, 3.12.
Found: C, 50.94; H, 3.58; N, 2.87.
4.33. S,S-(8-Methylcarbamoyl-10-oxo-7,8,9,10,11,12-hexa-
hydro-9-aza- benzocyclododec-13-yn-5-cis-ene-11-yl)car-
bamic acid benzyl ester (47)
Photolysis experiments were carried out with a Rayo-
nette photochemical reactor with a carousel unit
˚
equipped with eight 3000 A lamps (RMR-600). A solu-
4.31. S,S-2-Benzyloxycarbonylamino-5-[2-(4-tert-butoxy-
carbonylamino-4-(methylcarbamoyl)-but-1-ynyl)phenyl]pent-
4-ynoic acid (45)
tion of 11 (12.0 mg, 0.028 mmol) and 1,4-cyclohexadi-
ene (0.26 mL) in degassed DMF (2.8 mL) in a quartz
reaction vessel (15 mL) was irradiated for 6 h. The
crude reaction mixture was concentrated, and the resi-
due was separated on a reverse phase HPLC (MeCN/
H2O gradient from 10:90 to 90:10) to afford 47
(7.0 mg, 58%) as a white solid: 1H NMR (500 MHz,
DMSO-d6, 75 ꢁC) d 7.64–7.52 (br, 2H), 7.44–7.39 (m,
2H), 7.38–7.34 (m, 4H), 7.34–7.28 (m, 2H), 7.28–7.23
(m, 1H), 7.05 (d, J = 7.5 Hz, 1H), 6.42 (d, J = 11.2 Hz,
1H), 5.73 (dd, J = 10.1, 5.0 Hz, 1H), 5.71 (dd,
J = 11.2, 5.1 Hz, 1H), 5.07 (s, 2H), 4.56 (td, J = 9.3,
2.5 Hz, 1H), 4.17 (dt, J = 6.7, 4.3 Hz, 1H), 2.94 (dd,
J = 17.0, 4.6 Hz, 1H), 2.65 (dd, J = 16.9, 4.1 Hz, 1H),
According to the procedure described for compound 17,
compound 43 (188.9 mg, 0.42 mmol) was treated with
44 (190.2 mg, 0.84 mmol), PdCl2(PPh3)2 (8.8 mg,
0.013 mmol), CuI (4.0 mg, 0.021 mmol), and NH3
(0.5 M, 2.5 mL). Purification on HPLC (MeCN/H2O
gradient from 40:60 to 60:40) afforded compound 45
1
(0.16 gm, 69%) as a white solid. H NMR (500 MHz,
DMSO-d6, 65 ꢁC, mixture of rotamers) d 7.71–7.62 (m,
1H), 7.41–7.22 (m, 9H), 6.70–6.40 (br s, 1H), 5.07 (s,
2H), 4.30 (td, J = 8.3, 5.4 Hz, 1H), 4.22–4.13 (m, 1H),

Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
5947
2.59 (d, J = 4.6 Hz, 3H), 2.39–2.31 (m, 1H), 2.13–2.01
Supplementary data
(m, 1H). 13C NMR (125 MHz, CDCl3, 75 ꢁC) d 170.4,
168.6, 155.4, 140.5, 136.3, 130.7, 129.8 (2C), 128.0,
127.8 (3C), 127.4, 127.3, 127.1, 126.2, 121.6, 89.6,
83.1, 65.5, 55.1, 51.1, 32.8, 25.0, 22.9. HRMS (ES) m/
z: calcd for (M+H)+ C25H26N3O4, 432.1923; found,
432.1928.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.bmc.2005.07.016.
References and notes
4.34. S,S-16,18-Dioxo-15,17-diaza-tricyclo[13.2.1.05,10]-
octadeca-5(10),6,8-triene-3,11-diyne-14-carboxylic acid
methylamide (48)
1. (a) Lee, M. D.; Dunne, T. S.; Chang, C. C.; Ellestad, G.
A.; Siegel, M. M.; Morton, G. O.; McGahren, W. J.;
Borders, D. B. J. Am. Chem. Soc. 1987, 109, 3466–3468;
(b) Konishi, M.; Ohkuma, H.; Tsuno, T.; Oki, T.;
VanDuyne, G. D.; Clardy, J. J. Am. Chem. Soc. 1990,
112, 3715–3716; (c) Edo, K.; Mizugaki, M.; Koide, Y.;
Seto, H.; Furihata, K.; Otake, N.; Ishida, N. Tetrahedron
Lett. 1985, 26, 331–334.
2. (a) Jones, G. B.; Foad, F. S. Curr. Pharm. Des. 2002, 8,
2415–2440; (b) Grissom, J. W.; Gunawardena, G. U.;
Klingberg, D.; Huang, D. Tetrahedron 1996, 52, 6453–
6518; (c) Smith, A. L.; Nicolaou, K. C. J. Med. Chem.
1996, 39, 2103–2117.
A 10-mL CEM vial containing a magnetic stir bar was
charged with enediyne 11 (4.0 mg, 0.0093 mmol) and
DMF (2 mL), and then sealed. After purging with nitro-
gen and vacuum degassing, 1,4-cyclohexadiene
(0.10 mL) was added into the system via syringe, and
the mixture was stirred at 120 ꢁC in an oil bath for 2
days. The crude reaction mixture was concentrated,
and the residue was separated on silica gel (EtOAc/
methanol gradient from 100:0 to 90:10) to afford 48
1
3. Jones, G. B.; Wright, J. M.; Hynd, G.; Wyatt, J. K.; Warner,
P. M.; Huber, R. S.; Li, A.; Kilgore, M. W.; Sticca, R. P.;
Pollenz, R. S. J. Org. Chem. 2002, 67, 5727–5732.
(2.1 mg, 70%) as a white solid: H NMR d 7.45–7.34
(m, 2H), 7.32–7.23 (m, 2H), 6.78–6.68 (m, 1H), 6.41
(br s, 1H), 4.95 (dd, J = 12.3, 5.2 Hz, 1H), 4.46 (br s,
1H), 3.78 (dd, J = 17.2, 12.9 Hz, 1H), 3.22 (dd,
J = 17.2, 4.9 Hz, 1H), 3.14 (dd, J = 17.7, 2.5 Hz, 1H),
2.84 (d, J = 4.6 Hz, 3H), 2.76 (dd, J = 17.9, 4.1 Hz,
1H). 13C NMR d 173.1, 168.7, 157.9, 131.9, 131.8,
128.7, 128.5, 126.3, 125.8, 89.2, 86.8, 83.2, 82.5, 56.8,
53.8, 27.2, 22.8, 20.5. The structure assignment for 48
was based upon extensive 2-D NMR analysis. For
example, an HMBC study revealed a three-bond corre-
lation between the 2-carbonyl on the hydantoin ring
with both of the amino acid a-hydrogens. HRMS (ES)
m/z: calcd for (M+H)+ C18H16N3O3: 322.1192, found:
322.1188.
4. (a) Basak, A.; Rudra, K. R.; Bag, S. S.; Basak, A. J. Chem.
Soc., Perkin Trans. 1 2002, 1805–1809; (b) Basak, A.; Bag, S.
S.; Bdour, H. M. M. Chem. Commun. 2003, 1, 2614–2615.
5. (a) Plourde, G., II; El-Shafey, A.; Fouad, F. S.; Purohit,
A. S.; Jones, G. B. Bioorg. Med. Chem. Lett. 2002, 12,
2985–2988; (b) Jones, G. B.; Plourde, G. W., II; Wright, J.
Org. Lett. 2000, 2, 811–813; (c) Zein, N.; Solomon, W.;
Casazza, A. W.; Kadow, J. F.; Krishnan, B. S.; Tun, M.
M.; Vyas, D. M.; Doyle, T. W. Bioorg. Med. Chem. Lett.
1993, 3, 1351–1356.
6. (a) Creighton, C. J.; Reitz, A. B. Org. Lett. 2001, 3, 893–895;
(b) Creighton, C. J.; Reynolds, C. H.; Lee, D. H. S.; Leo, G.
C.; Reitz, A. B. J. Am. Chem. Soc. 2001, 123, 12664–12669.
7. (a) Nicolaou, K. C.; Zuccarello, G.; Ogawa, Y.; Schwei-
ger, E. J.; Kumazawa, T. J. Am. Chem. Soc. 1988, 110,
4866–4868; (b) Schreiber, P. R. J. Am. Chem. Soc. 1998,
120, 4184–4190; (c) Lockhart, T. P.; Comita, P. B.;
Bergman, R. G. J. Am. Chem. Soc. 1981, 103, 4082–4090.
8. (a) Selected references: Nicolaou, K. C.; Sorensen, E. J.;
Discordia, R.; Hwang, C. K.; Minto, R. E.; Bharucha, K.
N.; Bergman, R. G. Angew. Chem., Int. Ed. Engl. 1992, 31,
1044–1046; (b) Semmelhack, M. F.; Neu, T.; Foubelo, F.
J. Org. Chem. 1994, 59, 5038–5047; (c) Jones, G. B.;
Wright, J. M.; Plourde, G. W., Jr.; Hynd, G.; Huber, R.
S.; Mathews, J. E. J. Am. Chem. Soc. 2000, 122, 1937–
1944; (d) Comanita, B. M.; Heuft, M. A.; Rietveld, T.;
Fallis, A. G. Isr. J. Chem. 2000, 40, 241–253; (e) Alabugin,
I. V.; Manoharan, M. J. Phys. Chem. A 2003, 107, 3363–
3371.
4.35. DNA nicking study with enediyne 4
The compound was dissolved in 100% DMSO and
diluted to the concentrations listed in Figure 3. The
/X174 RF I DNA (1 lg) was incubated with various
of the compound solutions at the room temperature
for 24 h and then separated on a 1% agarose gel con-
taining ethidium bromide. The DNA bands were visu-
alized using a UV transluminator, and the image was
obtained by a digital gel doc camera (8400 Fluor-
Chem, CA) and processed using Adobe Photo Deluxe
1.1.
4.36. BSA cleavage experiment with enediyne 11
9. Singh, R.; Just, G. Tetrahedron Lett. 1990, 31, 185–188.
10. (a) Shain, J. C.; Khamrai, U. K.; Basak, A. Tetrahedron
Lett. 1997, 38, 6067–6070; (b) Basak, A.; Shain, J. C.;
Khamrai, U. K.; Rudra, K. R.; Basak, A. J. Chem. Soc.,
Perkin Trans. 1 2000, 1955–1964; (c) Basak, A.; Mandal,
S.; Das, A. K.; Bertolasi, V. Bioorg. Med. Chem. Lett.
2002, 12, 873–877.
Enediyne 11 (100 lM, 10 lL) was mixed with BSA (10%
in H2O, 5 lL) and DMSO (50% in H2O, 85 lL). The
mixture was irradiated by UV at ambient temperature
for 1 h and then submitted for SELDI-MS analysis.
11. Sakai, Y.; Nishiwaki, E.; Shishido, K.; Shibuya, M.
Tetrahedron Lett. 1991, 32, 4363–4366.
12. Suzuki, I.; Shigenaga, A.; Manabe, A.; Nemoto, H.;
Shibuya, M. Tetrahedron 2003, 59, 5691–5704.
Acknowledgments
The authors thank Drs. Gregory C. Leo, Brett Tounge,
Rajamani Ramkumar, and Gary Caldwell for advice,
encouragement, and technical support.
13. (a) Pitsch, W.; Klein, M.; Zabel, M.; Ko¨nig, B. J. Org.
Chem. 2002, 67, 6805–6807; (b) Semmelhack, M. F.; Wu,
L., Jr.; Pascal, R. A., Jr.; Ho, D. M. J. Am. Chem. Soc.

5948
Y. Du et al. / Bioorg. Med. Chem. 13 (2005) 5936–5948
2003, 125, 10496–10497; (c) See also: Basak, A.; Roy, S.
K.; Mandal, S. Angew. Chem., Int. Ed. 2004, 44, 132–135.
28. (a) Ohwada, T.; Okamoto, I.; Shudo, K.; Yamaguchi, K.
Tetrahedron Lett. 1998, 39, 7877–7880; (b) Crich, D.;
Bruncko, M.; Natarajan, S.; Teo, B. K.; Tocher, D. A.
Tetrahedron 1995, 51, 2215–2228; (c) Lyapkalo, I. M.;
Reissig, H.-U.; Schafer, A.; Wagner, A. Helv. Chim. Acta
2002, 85, 4206–4215.
14. Basak, A.; Bag, S. S.; Majumder, P. A.; Das, A. K.;
Bertolasi, V. J. Org. Chem. 2004, 69, 6927–6930.
15. Dai, W.-M.; Wu, A. Tetrahedron Lett. 2001, 42, 81–83.
16. (a) Mitsunobu, O.; Yamada, M. Bull. Chem. Soc. Jpn.
1967, 40, 2380–2382; (b) Hughes, D. L. Org. Prep. Proced.
Int. 1996, 28, 127–164.
29. Mladenova, M.; Alami, M.; Linstrumelle, G. Synth.
Commun. 1995, 25, 1401–1410.
17. (a) Bernotas, R. C.; Cube, R. V. Tetrahedron Lett. 1991, 32,
161–164; (b) Miller, M. J. Acc. Chem. Res. 1986, 19, 49–56.
18. (a) For Sonogashira coupling: Sonogashira, K.; Tohda,
Y.; Hagihara, N. Tetrahedron Lett. 1975, 50, 4467–4470;
For couplings with alkynylmetals: (b) Negishi, E.-I.; Qian,
M.; Zeng, F.; Anastasia, L.; Babinski, D. Org. Lett. 2003,
5, 1597–1600; (c) Negishi, E. I.; Anastasia, L. Chem. Rev.
2003, 103, 1979–2017.
30. Kaim, L. E.; Grimaud, L.; Lee, A.; Perroux, Y. Org. Lett.
2004, 6, 381–383.
31. Ball, J. B.; Hughes, R. A.; Alewood, P. F.; Andrews, P. R.
Tetrahedron 1993, 49, 3467–3478.
32. Creighton, C. J.; Leo, G. C.; Du, Y.; Reitz, A. B. Bioorg.
Med. Chem. Lett. 2004, 12, 4275–4285.
33. Upon prolonged heated for 2 days at 120 ꢁC in DMF 11
was converted to hydantoin 48 (70%).
19. Crisp, G. T.; Robertson, T. A. Tetrahedron 1992, 48,
3239–3250.
20. Wallace, E. M.; Moliterni, J. A.; Moskal, M. A.; Neubert,
A. D.; Marcopulos, N.; Stamford, L. B.; Trapani, A. J.;
Savage, P.; Chou, M.; Jeng, A. Y. J. Med. Chem. 1998, 41,
1513–1523.
21. Lopez-Deber, M. P.; Castedo, L.; Granja, J. R. Org. Lett.
2001, 3, 2823–2826.
O
N
O
HN
NHMe
O
48
22. Mori, A.; Ahmed, M. S. Mohamed; Sekiguchi, A.; Masui,
K.; Koike, T. Chem. Lett. 2002, 7, 756–757.
34. For a recent review: Jones, G. B.; Russell, K. C., 2nd ed.
In CRC Handbook of Organic Photochemistry and Photo-
biology, 2004; 29, pp 1–21.
35. (a) Evenzahav, A.; Turro, N. J. J. Am. Chem. Soc. 1998,
120, 1835–1841; (b) Zimmerman, H. E.; Pincock, J. A. J.
Am. Chem. Soc. 1973, 95, 3246–3250. In Ref. 35a
photoinduced reduction of 12-alkynylbenzene derivative
49 produced eneyne 50.
23. (a) For recent reviews see: Perreux, L.; Loupy, A. Tetrahe-
dron 2001, 57, 9199–9223; (b) Lidstrom, P.; Tierney, J.;
Wathey, B.; Westman, J. Tetrahedron 2001, 57, 9225–9283.
24. Strothkamp, K. G.; Strothkamp, R. E. J. Chem. Educ.
1994, 71, 77–79.
25. (a) Fukuyama, T.; Jow, C.-K.; Cheung, M. Tetrahedron
Lett. 1995, 36, 6373–6374; (b) Goodman, M.; Rew, Y. J.
Org. Chem. 2002, 67, 8820–8826; (c) Miller, S. C.; Scanlan,
T. J. Am. Chem. Soc. 1998, 120, 2690–2691.
26. (a) Dumas, F.; Thominiaux, C.; Miet, C.; dÕAngelo, J.;
Desmaele, D.; Nour, M.; Cave, C.; Morgant, G.; Huu-
Dau, M.-E. T. Tetrahedron Lett. 2002, 43, 9649–9652; (b)
Jouikov, V. V.; Fattakhova, D. S. J. Organomet. Chem.
2000, 613, 220–230.
n-Pr
H
n-Pr
hν
H
i-PrOH
n-Pr
n-Pr
49
50
36. (a) Benati, L.; Montevecchi, P. C.; Spagnolo, P. J. Chem.
Soc. Perkin Trans. 1 1991, 2103–2109; (b) Giese, B. Angew.
Chem., Int. Ed. Engl. 1989, 28, 969–980.
27. (a) Kaneko, T.; Takahashi, M.; Hirama, M. Tetrahedron
Lett. 1999, 40, 2015–2018; (b) Koseki, S.; Fujimura, Y.;
Hirama, M. J. Phys. Chem. A 1999, 103, 7672–7675.