Total synthesis of (+)-FR-900493 and establishment of its absolute stereochemistry

Article abstract of DOI:10.1016/j.tet.2007.01.055

The first total synthesis of (+)-FR-900493, an antibacterial nucleoside antibiotic possessing a 6′-N-alkyl-5′-O-aminoribosyl-glycyluridine structure, is described, and its relative and absolute stereochemistries were established. Key elements of the appro

Full text of DOI:10.1016/j.tet.2007.01.055

Tetrahedron 63 (2007) 2798–2804
Total synthesis of (D)-FR-900493 and establishment of its
absolute stereochemistry*
*
Shinpei Hirano, Satoshi Ichikawa and Akira Matsuda
*
Faculty of Pharmaceutical Sciences, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
Received 9 January 2007; revised 24 January 2007; accepted 25 January 2007
Available online 30 January 2007
Abstract—The first total synthesis of (+)-FR-900493, an antibacterial nucleoside antibiotic possessing a 60-N-alkyl-50-O-aminoribosyl-
glycyluridine structure, is described, and its relative and absolute stereochemistries were established. Key elements of the approach include
the early-stage introduction of the aminoribose moiety and two sequential reductive alkylations of an amino group at the 60-position. This
synthetic strategy could be applicable to the synthesis of related nucleoside antibiotics, such as the more potent antibacterial nucleoside
antibiotics, muraymycins.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
therefore, has been focused on MraY as a new target for
the development of antibacterial agents4,5 since this
enzyme is highly conserved across bacterial species and is es-
sential for the growth of the bacteria.6 Because of their struc-
tural and biological similarities, it has been suggested that
FR-900493 might possess the same mode of action as the
MRYs. Having the lowest molecular weight and simplest
chemical structure of these natural inhibitors, FR-900493
theoretically should be a good lead for the development of
novel antibacterial agents. It possesses a 60-N-alkyl-50-O-
aminoribosyl-glycyluridine structure, and chemical studies
on the compound have established its two-dimensional struc-
ture but not its relative and absolute stereochemistries. We
anticipated that 1 would possess a similar stereochemistry
to that of the MRYs at the 50- and 60-position, as shown in
Figure 1. Herein, we report the first total synthesis of
As modern clinical settings and practices change, the conse-
quent spread of infectious diseases caused due to drug-resis-
tant bacterial strains is causing considerable concern to the
world public health community.1 The need for antibacterial
drugs with new mechanisms of actions is critical given the
global implications. FR-900493 (Fig. 1, 1), which was iso-
lated from the culture broth of Bacillus cereus in 1989,
belongs to a class of antibacterial nucleoside antibiotics
that are active against both Gram-positive and Gram-nega-
tive bacteria.2 Muraymycins (MRYs), which are structurally
related antibiotics,3 exhibited more promising antibacterial
activity, and the mode of action is considered to be inhibitors
of MraY (translocase I), which is involved in the biosyn-
thesis of the bacterial cell wall peptidoglycan. Attention,
HO
HO
NH2
NH2
O
HO
MeO
O
O
O
O
O
O
O
O
Me
H
H
N
H
N
H2N
N
6'
HO2C
O
5'
NH
O
HO2C
NH
N
6'
HO2C
O
5'
NH
O
N
H
N
N
O
O
HN
HN
HO
HO
OH
N
H
OH
FR-900493 (1)
muraymycin B1
Figure 1. Structures of FR-900493 and muraymycin B1.
*
This work was supported financially by a Grant-in-Aid from the Ministry of Education, Science, Sports, and Culture. We thank Fujisawa Pharmaceutical for
generous supply of a sample of natural FR-900493. This paper constitutes Part 246 of Nucleosides and Nucleotides: for part 245 in this series, see: Hikishima,
S.; Minakawa, N.; Kuramoto, K.; Ogata, S.; Matsuda, A. Chembiochem 2006, 7, 1970–1975.
* Corresponding authors. Tel.: +81 11 706 3228; fax: +81 11 706 4980 (A.M.); tel.: +81 11 706 3763; fax: +81 11 706 4980 (S.I.); e-mail addresses: ichikawa@
pharm.hokudai.ac.jp; matuda@pharm.hokudai.ac.jp
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.01.055

S. Hirano et al. / Tetrahedron 63 (2007) 2798–2804
2799
FR-900493, and the determination of its relative and absolute
stereochemistries.
b-elimination might have been thermodynamically favored
because steric hindrance was reduced by releasing the
ste0rically encumbered aminoribose moiety installed at the
O5 -position. Previous study revealed that this class of com-
pounds including 5 was also unstable toward basic conditions
2. Results and discussions
The initial attempts to synthesize 1 are outlined in Scheme 1.
During the course of our first total synthesis of (+)-caprazol,
a core structure of the antituberculosis antibiotics capraza-
mycins, a precursor of the key 50-O-aminoribosyl-glycyluri-
dine 4 was synthesized by b-selective ribosylation of 2 with
a fluoride donor 3 as previously reported.7 Namely, the ribo-
syl fluoride 38 protected with a 3-pentylidene group was
activated with BF3$Et2O9 at ꢀ30 ꢁC in the presence of 2,
and the corresponding ribosides were obtained in 80% yield
with good b-selectivity (a/b¼4/96). The pure b-riboside 4
was easily obtained by simple crystallization from AcOEt.
The azide group in 4 was reduced to the corresponding amine
with PPh3 in aqueous THF, which was protected with a Boc
group to give 5. Hydrogenolysis of the Cbz group of 5 cata-
resulting in the abovementioned b-elimination.11 Therefore,
0
we planned to introduce the 3-aminopropyl group at the N6 -
position by reductive alkylation conducted under weakly
acidic conditions.12 Treatment of the amine 6 and 1 equiv
of N-Boc-3-aminopropanal 7 with sodium triacetoxyborohy-
dride in dichloromethane in the presence of acetic acid gave
selectively the desired mono-alkylated compound 8 in 92%
yield. In this reaction, the use of excess 7 resulted in dialkyl-
ation of 6. Subsequent N-methylation by a second reductive
alkylation of 8 with paraformaldehyde gave the fully pro-
tected FR-900493 9 in 80% yield. However, deprotection
of 9 under various conditions was unsuccessful due to the dif-
ficulties in deprotection of the BOM group at the N3-position
of the uracil moiety and hydrolysis of the methyl ester at the
70-position. Catalytic hydrogenation of 9 to remove the BOM
group was a slow process, and elongation of the reaction time
and/or harsher conditions resulted in the formation of 5,6-di-
hydrouridine derivative due to over-reduction of the uracil
moiety. Presumably, the tertiary amine at the 60-position
poisons the catalysis. For the hydrolysis of the methyl ester
moiety, treatment of 9 with Ba(OH)2 in aqueous THF re-
sulted in decomposition of the material to give the elimina-
tion products. Thus, treatment of 9 under basic conditions
should be avoided throughout the synthesis.
lyzed by Pd(OH)2–C afforded the amine 6 in 90% yield.
0
For the installation of the 3-aminopropyl group at the N6 -
position of 6, first we 0attempted a Mitsunobu reaction using
the corresponding N6 -o-nitrobenzenesulfonyl (Ns) deriva-
tive of 6, the chemistry of which was developed by Fukuyama
et al.10 However, sulfonylation of 6 with NsCl and Et3N in
CH2Cl2 resulted in elimination at the 50- and 60-position. It
was suggested that the increased acidity at the 60-proton
by sulfonylation of the 60-amino group promoted the b-
elimination of the aminoribosyloxy group. In addition, the
O
R
O
O
O
O
O
N3
O
CbzHN
MeO2C
OH
O
NH
O
F
NBOM
O
CbzHN
MeO2C
O
O
a
N
N
+
O
O
O
O
O
3
4: R = N3
5: R = NHBoc
2
b
NHBoc
N
NHBoc
O
O
O
O
O
O
O
O
O
O
H2N
NBOM
O
BocHN
NH
NBOM
N
c
d
O
O
MeO2C
MeO2C
O
O
O
O
O
8
6
NHBoc
N
O
O
N
O
O
O
Me
deprotection
e
BocHN
NBOM
O
1
O
MeO2C
O
O
9
˚
Scheme 1. Reagents and conditions: (a) BF3$Et2O, MS 4 A, CH2Cl2 (80%); (b) Ph3P, aq THF–benzene, then Boc2O (two steps, 95%); (c) H2, Pd(OH)2–C,
MeOH (90%); (d) BocHNCH2CH2CHO 7, NaBH(OAc)3, AcOH, CH2Cl2 (92%); (e) (CH2O)n, NaBH(OAc)3, AcOH, CH2Cl2 (80%).

2800
S. Hirano et al. / Tetrahedron 63 (2007) 2798–2804
Table 1. Optimization of deprotection conditions of BOM group
In order to avoid problems associated with deprotection, we
next planned to remove the BOM group at the N3-position
before the N-alkylations of the 60-amino group and deprotect
all the protecting groups under acidic conditions as shown in
Scheme 2. The methyl ester of 5 was first converted to the
tert-butyl ester 10 by hydrolysis followed by tert-butylation
of the resulting carboxylic acid with O-tert-butyl trichloro-
acetimidate13 in the presence of BF3$Et2O in CH2Cl2 (two
steps, 46%). Hydrogenation of 10 resulted in selective
deprotection of the Cbz group and the BOM group was not
removed. The liberated amine moiety was then protected
with a Troc group to give 11 in 79% yield in two steps.
The reduction of 10 under more forcing conditions gave
results similar to those mentioned above. Next, selective
hydrogenolysis of the BOM group at the N3-position without
affecting the Troc group possessing chlorine atoms was
examined (Table 1). Under standard conditions using
Pd(OH)2–C catalyst in AcOEt or MeOH (entries 1 and 2),
reduction of the chlorine atom(s) of the Troc group was
observed in addition to the desired BOM deprotection, and
a complex mixture of products resulted. It has been reported
that the O-benzyl group was selectively deprotected in the
presence of a Troc group by hydrogenolysis using trichloro-
acetic acid (TCA) as an additive.14 Therefore, we carried out
the deblocking of the BOM group in the presence of 2,2,2-
trichloroethanol (TCE) and obtained 12 in 45% yield
(entry 3). Moreover, the use of 2,2,2-trichloroethyl chloro-
formate (TrocCl) improved the yield of 12 to 77% yield (en-
try 4). The use of 10 equiv of TCA as an additive proved to
be most effective suppressing the collapse of the Troc group
to furnish the desired 12 in 92% yield (entry 5). From these
results, it would appear that the additive acts not only as
a dummy of the Troc group but also as a promoter of the re-
action. Treatment of 12 with Zn powder to deprotect the Troc
Entry
Solvent
Additive (equiv)
Time (min)
Yield of
12 (%)
1
2
3
4
5
AcOEt
MeOH
MeOH
MeOH
MeOH
None
None
TCE (20)
TrocCl (10)
TCA (10)
120
20
20
20
8
30
45
77
92
20
TCE: 2,2,2-trichloroethanol; TrocCl: 2,2,2-trichloroethyl chloroformate;
TCA: trichloroacetic acid.
group smoothly afforded the amine 13. As in the procedure
described in the synthesis of 9, the amine 13 was alkylated
by two sequential reductive alkylations to give 15 (80 and
70%, respectively). Finally, a global deprotection of 15
with aqueous 80% TFA successfully afforded (+)-(1), [a]D25
+9.4 (c 0.3, H2O) [lit.2 [a]D19 +11 (c 0.7, H2O)], the properties
of which were identical in all respects to those of the natural
material. Especially, chemical shifts and coupling constants
of H-50 and H-60 of synthetic 1 are in good accordance with
those of the natural material. Under global deprotection con-
ditions, the conversion was clean and quantitative, and there
was no problem with b-elimination. Thus, the correlations of
the synthetic and natural 1 confirm the two-dimensional
structural assignments, and establish the relative and abso-
lute stereochemistries as those shown in Figure 1.
3. Conclusions
The first total synthesis of FR-900493 (+)-(1) has been ac-
complished in 17 steps from uridine and its absolute stereo-
chemistry was determined to be 10R,20R,30R,40S,50S,60S,100S,
200R,300R,400R. This synthetic strategy could be applicable to
NHBoc
NHBoc
O
NHBoc
O
O
O
O
O
O
O
O
O
O
O
O
O
O
TrocHN
tBuO2C
NH
O
CbzHN
tBuO2C
NBOM
O
TrocHN
tBuO2C
NBOM
O
e
c,d
a,b
N
5
O
N
N
O
O
O
O
O
O
O
O
10
11
12
NHBoc
N
O
NHBoc
NHBoc
N
O
O
O
O
O
O
O
O
O
O
Me
O
O
O
O
BocHN
N
NH
O
H
H2N
NH
O
BocHN
N
NH
h
f
g
O
O
tBuO2C
N
O
tBuO2C
tBuO2C
O
O
O
O
O
O
O
15
14
13
i
(+)-FR-900493 (1)
Scheme 2. Reagents and conditions: (a) Ba(OH)2$8H2O, aq THF; (b) tBuOC(NH)CCl3, BF3$Et2O, CH2Cl2 (two steps, 46%); (c) H2, Pd–C, MeOH; (d) TrocCl,
Et3N, CH2Cl2 (two steps, 79%); (e) H2, Pd(OH)2–C, TCA, MeOH (92%, see Table 1); (f) activated Zn powder, NH4Cl, MeOH (95%); (g) 8, NaBH(OAc)3,
AcOH, CH2Cl2 (80%); (h) (CH2O)n, NaBH(OAc)3, AcOH, AcOEt (70%); (i) aq 80% TFA (quant).

S. Hirano et al. / Tetrahedron 63 (2007) 2798–2804
2801
the synthesis of the MRYs, more potent antibacterial nucleo-
side antibiotics. Continuous efforts to develop novel anti-
bacterial agents are underway and will be reported in due
course.
column chromatography (1ꢂ5 cm, 50% AcOEt–hexane)
to afford 8 (22 mg, 92%) as a white foam: [a]2D1 +13.1
(c 0.5, CHCl3); H NMR (CDCl3, 500 MHz) d 7.38–7.28
1
(m, 5H, Ar–H), 7.17 (d, 1H, H-6, J6,5¼8.0 Hz), 5.71 (d,
1H, H-5, J5,6¼8.0 Hz), 5.63 (m, 1H, NHBoc), 5.46 (d, 1H,
–NCHaO–, J¼9.9 Hz), 5.44 (s, 1H, H-10), 5.41 (d, 1H,
–NCHbO–, J¼9.9 Hz), 5.15 (d, 1H, H-20, J2 ,3 ¼6.1 Hz),
0
0
4. Experimental
4.92 (s, 1H, H-100), 4.87 (dd, 1H, H-30, J3 ,2 ¼6.1 Hz, J3 ,4
¼
0
0
0
0
4.1. General experimental methods
4.4 Hz), 4.68 (s, 2H, benzyl), 4.59 (m, 1H, H-400), 4.53 (d,
1H, H-200, J2 ,3 ¼5.9 Hz), 4.48 (d, 1H, H-3 , J3 ,2 ¼5.9 Hz),
4.19 (m, 1H, H-40), 4.18 (m, 1H, H-50), 3.74 (s, 3H, OMe),
3.41 (m, 1H, H-60), 3.19 (m, 3H, H-500a, H-500b, H-100a),
3.03 (m, 1H, H-100b), 2.87 (m, 1H, H-80a), 2.35 (m, 1H, H-
80b), 1.57 (s, 3H, acetonide), 1.51 (m, 2H, H-90a, H-90b),
1.44 (m, 22H, t-Buꢂ2, CH2CH3ꢂ2), 1.38 (s, 3H, acetonide),
0.76 (m, 3H, CH2CH3), 0.70 (m, 3H, CH2CH3); 13C NMR
(CDCl3, 125 MHz) d 173.52, 162.36, 155.94, 150.73,
142.17, 137.58, 128.20, 127.69, 115.92, 114.49, 113.18,
101.97, 97.70, 88.94, 86.64, 86.32, 84.89, 82.59, 81.99,
81.80, 78.90, 72.32, 70.22, 62.21, 52.44, 45.22, 43.33,
37.57, 29.42, 28.66, 28.50, 28.46, 28.41, 28.37, 26.76,
25.14, 8.50, 7.20; FABMS-LR m/z 948 (MH+); FABMS-
HR (NBA) calcd for C46H70N5O16 948.4817, found
948.4827.
00
00 00
00 00
NMR spectra were obtained on a JEOL EX270, JEOL
GX270, JEOL AL400, or Bruker ARX-500, and reported
in parts per million (d) relative to tetramethylsilane
(0.00 ppm) as internal standard otherwise noted. Coupling
constant (J) was reported in hertz (Hz). Abbreviations of
multiplicity were as follows: s, singlet; d, doublet; t, triplet;
q, quartet; m, multiplet; br, broad. Data were presented as
follows: chemical shift (multiplicity, integration, coupling
constant). Assignment was based on 1H–1H COSY,
HMBC, and HMQC NMR spectra. Optical rotations were
recorded on JASCO DIP-370 digital polarimeter or JASCO
P-1030 polarimeter. FABMS was obtained on a JEOL
JMS-HX101 or JEOL JMS-700TZ. Analytical thin layer
chromatography (TLC) was performed on Merck silica gel
60F254 plates. Normal-phase column chromatography was
performed on Merck silica gel 5715 or Kanto Chemical
silica gel 60N (neutral). Flash column chromatography
was performed on Merck silica gel 60.
4.1.3. Dialkylamine (9).
A mixture of 8 (24 mg,
0.025 mmol), paraformaldehyde (7.5 mg, 0.25 mmol), and
AcOH (14 mL, 0.25 mmol) in CH2Cl2 (1 mL) was treated
with NaBH(OAc)3 (26 mg, 0.14 mmol) at room temperature
for 72 h. The mixture was partitioned between AcOEt and
saturated aqueous NaHCO3. The organic phase was washed
with brine, dried (Na2SO4), and concentrated in vacuo. The
residue was purified by neutral silica gel column chromato-
graphy (1ꢂ10 cm, 40% AcOEt–hexane) to afford 9
(19 mg, 80%) as a white foam: [a]2D1 +10.0 (c 0.5, CHCl3);
1H NMR (CDCl3, 500 MHz) d 7.38–7.27 (m, 5H, Ar–H),
7.18 (d, 1H, H-6, J6,5¼8.0 Hz), 5.71 (d, 1H, H-5,
J5,6¼8.0 Hz), 5.60 (t, 1H, NHBoc, J¼7.5 Hz), 5.50 (d,
1H, –NCH2O–, J¼9.5 Hz), 5.46 (s, 1H, H-10), 5.41 (d, 1H,
–NCH2O, J¼9.5 Hz), 5.32 (br s, 1H, NHBoc), 5.17 (d, 1H,
4.1.1. Amine (6). A mixture of 5 (50 mg, 0.054 mmol) and
10% Pd(OH)2–C (10 mg) in MeOH (2 mL) was vigorously
stirred under H2 atmosphere at room temperature for
30 min. The catalyst was filtered off through Celite pad and
the filtrate was concentrated in vacuo. The residue was puri-
fied by neutral silica gel column chromatography (2ꢂ10 cm,
66% AcOEt–hexane) to afford 6 (38 mg, 90%) as a white
foam: [a]2D1 +79.4 (c 0.8, CHCl3); 1H NMR (CDCl3,
500 MHz) d 7.38–7.22 (m, 6H, Ar–H, H-6), 5.74 (m, 2H,
H-5, NHBoc), 5.53 (s, 1H, H-10), 5.50 (d, 1H, –NCHaO–,
J¼9.9 Hz), 5.42 (d, 1H, –NCHbO–, J¼9.9 Hz), 5.10 (d,
00
00
0
1H, H-20, J2 ,3 ¼6.0 Hz), 5.01 (s, 1H, H-1 ), 4.88 (m, 1H,
H-20, J2 ,3 ¼6.1 Hz), 4.88 (s, 1H, H-1 ), 4.84 (m, 1H, H-3 ),
0
0
0
0
H-30), 4.69 (s, 2H, benzyl), 4.55 (m, 2H, H-200, H-400), 4.48
4.69 (s, 2H, benzyl), 4.58 (d, 1H, H-200, J2 ,3 ¼6.1 Hz),
00 00
(m, 1H, H-300), 4.31 (d, 1H, H-50, J5 ,6 ¼8.3 Hz), 4.22 (m,
1H, H-40), 3.76 (s, 3H, OMe), 3.70 (m, 1H, H-60), 3.20 (m,
1H, H-500a), 3.11 (m, 1H, H-500b), 1.58 (s, 3H, acetonide),
1.53 (m, 4H, CH2CH3ꢂ2), 1.44 (s, 9H, t-Bu), 1.36 (s, 3H,
acetonide), 0.76 (m, 6H, CH2CH3ꢂ2); 13C NMR (CDCl3,
125 MHz) d 174.50, 162.34, 156.01, 150.69, 141.67,
137.63, 128.20, 127.65, 116.14, 114.58, 112.63, 102.08,
96.64, 88.08, 87.01, 86.39, 84.51, 82.05, 81.75, 81.44,
78.99, 72.31, 70.26, 55.57, 52.68, 43.21, 29.38, 28.72,
28.44, 27.14, 25.28, 8.48, 7.28; FABMS-LR m/z 791
(MH+); FABMS-HR (NBA) calcd for C38H55N4O14
791.3715, found 791.3725.
4.47 (d, 1H, H-300, J3 ,2 ¼6.1 Hz), 4.43 (dd, 1H, H-4 , J4 ,3
¼
0
0
0
00 00
0
0
0
0
0
0
0
3.6 Hz, J4 ,5 ¼9.1 Hz), 4.38 (dd, 1H, H-5 , J5 ,4 ¼9.1 Hz,
00
0
0
J5 ,6 ¼4.8 Hz), 4.24 (m, 1H, H-4 ), 3.71 (s, 3H,0O0 Me), 30.62
(d, 1H, H-60, J6 ,5 ¼4.8 Hz), 3.24 (m, 2H, H-5 a, H-10 a),
3.01 (m, 2H, H-100b, H-500b), 2.79 (m, 1H, H-80a), 2.53 (m,
1H, H-80b), 2.48 (s, 3H, NMe), 1.64 (m, 2H, H-90a, H-90b),
1.43 (s, 9H, t-Bu), 1.42 (s, 9H, t-Bu), 1.40 (s, 3H, acetonide),
1.38 (m, 4H, CH2CH3ꢂ2), 1.37 (s, 3H, acetonide), 0.74 (m,
6H, CH2CH3ꢂ2); 13C NMR (CDCl3, 125 MHz) d 172.00,
162.50, 156.11, 150.94, 142.11, 137.79, 128.32, 127.78,
116.07, 114.56, 114.21, 102.22, 97.56, 89.00, 86.61, 86.49,
84.83, 82.50, 82.06, 81.90, 78.98, 78.74, 72.40, 70.37,
67.50, 51.45, 43.32, 36.33, 29.43, 28.71, 28.52, 28.44,
26.73, 26.70, 24.94, 8.45, 7.19; FABMS-LR m/z 962
(MH+); FABMS-HR (NBA) calcd for C47H72N5O16
962.4975, found 962.4971.
0
0
4.1.2. Monoalkylamine (8). A mixture of 6 (20 mg,
0.025 mmol), aldehyde 7 (4.3 mg, 0.025 mmol), and AcOH
(7 mL, 0.13 mmol) in CH2Cl2 (500 mL) was treated with
NaBH(OAc)3 (21 mg, 0.10 mmol) at room temperature for
10 min. The mixture was partitioned between AcOEt and
saturated aqueous NaHCO3. The organic phases were
washed with brine, dried (Na2SO4), and concentrated
in vacuo. The residue was purified by neutral silica gel
4.1.4. Cbz-Protected tert-butyl ester (10). Barium hydrox-
ide octahydrate (378 mg, 1.2 mmol) was added to a solution
of 5 (924 mg, 1.0 mmol) in THF–H2O (4:1, 10 mL) at room
temperature, and the resulting reaction mixture was stirred at

2802
S. Hirano et al. / Tetrahedron 63 (2007) 2798–2804
room temperature for 2 h. The reaction mixture was poured
onto 0.3 M aqueous HCl and extracted with AcOEt. The or-
ganic phase was dried (Na2SO4), filtered, and concentrated
in vacuo. The residue was dissolved in CH2Cl2 (10 mL), to
FABMS-LR m/z 1029 (MNa+); FABMS-HR (NBA) calcd
for C44H61N4O16Na 1029.3060, found 1029.3053.
4.1.6. tert-Butyl ester (12). A mixture of 11 (7.4 mg,
7.4 mmol), 10% Pd(OH)2–C (5.0 mg), and 2,2,2-trichloro-
acetic acid (12 mg, 74 mmol) in MeOH (1 mL) was vigor-
ously stirred under H2 atmosphere at room temperature for
20 min. The catalyst was filtered off through Celite pad and
the filtrate was concentrated in vacuo. The residue was puri-
fied by preparative TLC (50% AcOEt–hexane) to afford 12
(6.0 mg, 92%) as a colorless glass: [a]2D1 +8.77 (c 1.22,
CHCl3); 1H NMR (CDCl3, 500 MHz) d 8.99 (br s, 1H, NH-
t
which BuOC(NH)CCl3 (864 mg, 4.0 mmol) and BF$OEt2
(38 mL, 0.3 mmol) were added at 0 ꢁC. The resulting mix-
ture was stirred for 16 h, and partitioned between AcOEt
and saturated aqueous NaHCO3. The organic phase was
washed with brine, dried (Na2SO4), and concentrated in va-
cuo. The residue was purified by neutral silica gel column
chromatography (3ꢂ15 cm, 33% AcOEt–hexane) to afford
10 (444 mg, two steps, 46%) as a white foam: [a]2D5 +29.7
1
(c 1.00, CHCl3); H NMR (CDCl3, 500 MHz) d 7.36–7.22
3), 7.27 (d, 1H, H-6, J6,5¼8.1 Hz), 5.70 (dd, 1H, H-5, J5,6¼
(m, 11H, Ar–H, H-6), 5.72 (d, 1H, H-5, J5,6¼8.0 Hz), 5.53
(br s, 1H, NHBoc), 5.53 (s, 1H, H-10), 5.48 (d, 1H,
–NCHaO–, J¼9.8 Hz), 5.41 (d, 1H, –NCHbO–, J¼9.8 Hz),
5.38 (m, 1H, NHCbz), 5.21 (d, 1H, benzyl, J¼12.3 Hz),
8.1 Hz, J5,NH¼0.3 Hz), 5.65 (m, 1H, NHBoc), 5.54 (s, 1H,
H-10), 5.49 (m, 1H, NHTroc), 5.10 (s, 1H, H-100), 5.07 (d,
0
1H, H-20, J2 ,3 ¼6.6 Hz), 4.96 (d, 1H, H-5 , J5 ,6 ¼12.0 Hz),
0
0
0
0
4.84 (m, 1H, H-30), 4.57 (m, 3H, H-40, H-400, H-60), 4.47 (d,
5.04–5.01 (m, 2H, benzyl, H-100), 4.97 (d, 1H, H-20, J2 ,3
¼
1H, H-200, J2 ,3 ¼9.2 Hz), 4.38 (d, 1H, H-3 , J3 ,2 ¼9.2 Hz),
4.21 (m, 2H, CH2CCl3), 3.27 (m, 1H, H-500a), 3.10 (m, 1H,
H-500b), 1.55 (m, 4H, CH2CH3ꢂ2), 1.50 (s, 9H, t-Bu), 1.48
(s, 3H, acetonide), 1.45 (s, 9H, t-Bu), 1.32 (s, 3H, acetonide),
0.79 (m, 6H, CH2CH3ꢂ2); 13C NMR (CDCl3, 125 MHz)
d 168.96, 162.90, 155.92, 143.14, 116.40, 114.75, 112.20,
102.54, 95.71, 87.40, 86.98, 86.28, 84.24, 83.58, 92.00,
81.36, 79.47, 79.16, 74.63, 55.16, 43.29, 29.43, 28.84,
28.48, 28.09, 28.87, 27.12, 25.34, 8.49, 7.36; FABMS-
LR m/z 909 (MNa+); FABMS-HR (NBA) calcd for
C36H53Cl3N4O15Na 909.2471, found 909.2467.
00
0
0
00 00
00 00
5.3 Hz), 4.84 (m, 1H, H-30), 4.68 (s, 2H, benzyl), 4.51 (m,
3H, H-60, H-200, H-300), 4.37 (d, 1H, H-50, J5 ,6 ¼8.4 Hz),
4.21 (m, 1H, H-40), 4.18 (m, 1H, H-400), 3.23 (m, 1H, H-
500a), 3.08 (m, 1H, H-500b), 1.49 (s, 18H, t-Buꢂ2), 1.46 (m,
4H, CH2CH3ꢂ2), 1.41 (s, 3H, acetonide), 1.33 (s, 3H, aceto-
nide), 0.75 (m, 6H, CH2CH3ꢂ2); 13C NMR (CDCl3,
125 MHz) d 171.06, 162.36, 156.10, 155.96, 150.81,
141.41, 137.75, 136.10, 128.44, 128.26, 128.16, 127.69,
116.48, 114.71, 112.46, 102.22, 96.12, 86.99, 86.16,
84.14, 82.02, 81.14, 79.81, 79.33, 72.34, 70.29, 67.22,
54.86, 52.98, 43.32, 29.34, 28.76, 28.33, 27.01, 25.29,
8.32, 7.21; FABMS-LR m/z 967 (MH+); FABMS-HR
(NBA) calcd for C49H66N4O16 967.4552, found 967.4536.
0
0
4.1.7. Amine (13). A mixture of 12 (16.1 mg, 0.018 mmol)
and NH4Cl (29.2 mg, 0.54 mmol) in MeOH (1 mL) was
treated with activated Zn powder (85% purity, 19.5 mg,
0.18 mmol) at room temperature for 8 h. The insoluble
was filtered off through Celite pad and the filtrate was con-
centrated in vacuo. The residue was purified by neutral silica
gel column chromatography (1ꢂ7 cm, 66% AcOEt–hexane)
to afford 13 (11.7 mg, 91%) as a white foam: [a]2D1 +79.4
4.1.5. Troc-Protected tert-butyl ester (11). A mixture of 10
(150 mg, 0.16 mmol) and 10% Pd–C (15 mg) in MeOH
(3 mL) was vigorously stirred under H2 atmosphere at
room temperature for 20 min. The catalyst was filtered off
through Celite pad and the filtrate was concentrated in vacuo.
The residue was dissolved in CH2Cl2 (2 mL), to which
TrocCl (29 mL, 0.21 mmol) and triethylamine (29 mL,
0.21 mmol) were added at room temperature. The resulting
mixture was stirred for 2 h. The mixture was partitioned be-
tween AcOEt and saturated aqueous NaHCO3. The organic
phase was washed with brine, dried (Na2SO4), and concen-
trated in vacuo. The residue was purified by silica gel column
chromatography (4ꢂ15 cm, 33% AcOEt–hexane) to afford
11 (127 mg, 79%) as a white foam: [a]2D1 +10.3 (c 0.8,
1
(c 0.8, CHCl3); H NMR (CDCl3, 500 MHz) d 7.34 (d,
1H, H-6, J6,5¼7.3 Hz), 5.90 (br s, 1H, NHBoc), 5.73 (d,
1H, H-5, J5,6¼7.3 Hz), 5.63 (s, 1H, H-10), 5.07 (s, 1H,
H-100), 5.06 (m, 1H, H-10), 4.88 (m, 1H, H-30), 4.63 (m,
1H, H-200), 4.59 (m, 1H, H-300), 4.43 (m, 1H, H-50), 4.30
(m, 1H, 400), 4.25 (m, 1H, H-40), 3.67 (m, 1H, H-60), 3.25
(m, 1H, H-500a), 3.18 (m, 1H, H-500b), 1.58 (s, 3H, acetonide),
1.58 (m, 4H, CH2CH3ꢂ2), 1.52 (s, 9H, t-Bu), 1.45 (s, 9H,
t-Bu), 1.36 (s, 3H, acetonide), 0.81 (m, 6H, CH2CH3ꢂ2);
13C NMR (CDCl3, 125 MHz) d 185.04, 163.08, 156.06,
149.83, 145.16, 142.97, 116.31, 114.84, 112.22, 102.71,
102.53, 94.93, 87.56, 86.89, 86.40, 84.16, 83.09, 81.97,
81.05, 79.08, 77.19, 55.58, 43.26, 43.19, 29.28, 28.83, 28.51,
28.45, 28.10, 27.21, 25.41, 8.50, 7.42; FABMS-LR m/z 713
(MH+); FABMS-HR (NBA) calcd for C33H53N4O13
713.3609, found 713.3615.
1
CHCl3); H NMR (CDCl3, 500 MHz) d 7.37–7.30 (m, 5H,
Ar–H), 7.22 (d, 1H, H-6, J6,5¼7.5 Hz), 5.74 (d, 1H, H-5,
J5,6¼7.5 Hz), 5.60 (m, 1H, NHBoc), 5.50 (s, 1H, H-10),
5.49 (d, 1H, –NCHaO–, J¼10.1 Hz), 5.44 (br s, 1H, NHTroc),
5.42 (d, 1H, –NCHbO–, J¼10.1 Hz), 5.06 (d, 1H, H-20,
00
0
0
0
0
0
J2 ,3 ¼5.8 Hz), 5.02 (s, 1H, H-1 ), 4.97 (d, 1H, H-5 , J5 ,6
¼
12.0 Hz), 4.87 (m, 1H, H-30), 4.68 (s, 2H, benzyl), 4.58 (m,
3H, H-40, H-200, H-400), 4.49 (d, 1H, H-60, J6 ,5 ¼9.6 Hz),
0
0
4.42 (d, 1H, H-300, J3 ,2 ¼7.0 Hz), 4.21 (m, 2H, CH2CCl3),
4.1.8. Monoalkylamine (14). A mixture of 13 (28.7 mg,
0.04 mmol), aldehyde 7 (6.9 mg, 0.04 mmol), and AcOH
(100 mL) in CH2Cl2 (1 mL) was treated with NaBH(OAc)3
(20.4 mg, 0.1 mmol) at room temperature for 1 h. The mix-
ture was partitioned between AcOEt and saturated aqueous
NaHCO3. The organic phase was washed with brine, dried
(Na2SO4), and concentrated in vacuo. The residue was puri-
fied by neutral silica gel column chromatography (2.5ꢂ
10 cm, 60% AcOEt–hexane) to afford 14 (27.6 mg, 80%)
00 00
3.26 (m, 1H, H-500a), 3.09 (m, 1H, H-500b), 1.56 (m, 4H,
CH2CH3ꢂ2), 1.50 (s, 9H, t-Bu), 1.49 (s, 3H, acetonide),
1.46 (s, 9H, t-Bu), 1.37 (s, 3H, acetonide), 0.76 (m, 6H,
CH2CH3ꢂ2); 13C NMR (CDCl3, 125 MHz) d 162.32,
150.73, 141.77, 137.61, 128.21, 127.65, 116.27, 114.63,
112.60, 102.19, 96.76, 87.77, 86.92, 86.26, 84.47, 83.59,
81.98, 81.40, 79.87, 74.63, 72.38, 70.28, 55.19, 43.33,
29.35, 28.81, 28.48, 28.11, 27.11, 25.37, 8.51, 7.32;

S. Hirano et al. / Tetrahedron 63 (2007) 2798–2804
2803
1
as a white foam: [a]D25 +35.4 (c 0.4, CHCl3); H NMR
(CDCl3, 500 MHz) d 8.39 (br s, 1H, NH-3), 7.22 (d, 1H,
H-6, J6,5¼8.0 Hz), 5.81 (m, 1H, NHBoc), 5.68 (d, 1H,
H-5, J5,6¼8.0 Hz), 5.48 (s, 1H, H-10), 5.15 (m, 2H, NHBoc,
H-20), 4.97 (s, 1H, H-100), 4.83 (m, 1H, H-30), 4.56 (m, 2H,
152.20, 143.45, 143.34, 120.15, 118.77, 115.87, 109.50,
109.32, 103.14, 93.56, 83.56, 79.72, 78.35, 78.24, 75.86,
73.85, 73.06, 70.18, 55.48, 43.54, 40.96, 37.60, 23.54;
FABMS-LR m/z 520 (MH+); FABMS-HR (NBA) calcd for
C20H34N5O11 520.2255, found 520.2251.
H-40, H-200), 4.50 (d, 1H, H-300, J3 ,2 ¼6.0 Hz), 4.23 (m,
00 00
1H, H-400), 4.06 (d, 1H, H-50, J5 ,6 ¼8.5 Hz), 3.23 (m, 4H,
H-60, H-500a, H-100a, H-100b), 3.07 (m, 1H, H-500b), 2.83
(m, 1H, H-80a), 2.33 (m, 1H, H-80b), 1.63 (m, 4H,
CH2CH3ꢂ2), 1.56 (s, 3H, acetonide), 1.55 (m, 2H, H-90a,
H-90b), 1.52 (s, 9H, t-Bu), 1.45 (s, 9H, t-Bu), 1.43 (s, 9H,
t-Bu), 1.37 (s, 3H, acetonide), 0.77 (m, 6H, CH2CH3ꢂ2);
13C NMR (CDCl3, 125 MHz) d 172.24, 162.82, 156.14,
156.01, 149.89, 143.56, 116.00, 114.74, 112.76, 102.37,
96.48, 88.64, 86.77, 86.67, 84.76, 82.45, 82.07, 81.90,
78.96, 78.80, 77.21, 62.36, 45.32, 43.34, 37.93, 32.94,
29.67, 29.60, 29.47, 29.33, 29.18, 28.82, 28.63, 28.47,
28.36, 28.27, 28.16, 26.89, 25.28, 8.43, 7.30; FABMS-LR
m/z 870 (MH+); FABMS-HR (NBA) calcd for
C41H67N5O15 870.4675, found 870.4670.
For analytical purpose, a part of the TFA salt of 1 was further
purified according to the procedure2 to afford free 1.
0
0
Data for synthetic free 1: 1H NMR (D2O, 500 MHz) d 7.79
(d, 1H, H-6, J6,5¼7.8 Hz), 5.83 (d, 1H, H-5, J5,6¼7.8 Hz),
00
5.75 (d, 1H, H-10, J1 ,2 ¼2.3 Hz), 5.20 (s, 1H, H-1 ), 4.33
0
0
(dd, 1H, H-20, J2 ,3 ¼5.1 Hz, J2 ,1 ¼2.3 Hz), 4.28 (dd, 1H,
0
0
0
0
H-50, J5 ,4 ¼2.4 Hz, J5 ,6 ¼8.4 Hz), 4.21 (m, 2H, H-3 , H-
0
0
0
0
0
200), 4.16 (dd, 1H, H-300, J3 ,2 ¼6.0 Hz, J3 ,4 ¼2.8 Hz),
00 00
00 00
4.10 (m, 2H, H-40, H-400), 3.49 (d, 1H, H-60, J6 ,5 ¼8.4 Hz),
0
0
3.18 (dd, 1H, H-500a, J5 a,5 b¼13.8 Hz, J5 a,4 ¼3.7 Hz),
3.03 (m, 3H, H-500b, H-100a, H-100b), 2.85 (m, 1H, H-80a),
2.62 (m, 1H, H-80b), 2.41 (s, 3H, NMe), 1.91 (m, 1H, H-
90a), 1.80 (m, 1H, H-90b); 13C NMR (D2O, 125 MHz)
d 175.71, 171.32, 155.20, 141.89, 110.07, 102.44, 91.40,
83.76, 80.78, 78.52, 75.40, 74.20, 71.41, 71.34, 69.98,
52.33, 41.80, 39.00, 38.67, 24.99.
00
00
00
00
4.1.9. Dialkylamine (15). A mixture of 14 (5.0 mg,
5.7 mmol), paraformaldehyde (0.5 mg, 16.7 mmol), and
AcOH (50 mL) in AcOEt (500 mL) was treated with
NaBH(OAc)3 (12.0 mg, 56 mmol) at room temperature for
72 h. The mixture was partitioned between AcOEt and satu-
rated aqueous NaHCO3. The organic phase was washed with
brine, dried (Na2SO4), and concentrated in vacuo. The resi-
due was purified by neutral silica gel column chromato-
graphy (1ꢂ5 cm, 50% AcOEt–hexane) to afford 15 (3.5 mg,
50%) as a white foam: [a]2D5 +30.0 (c 1.0, CHCl3); 1H NMR
(CD3CN, 500 MHz) d 9.07 (br s, 1H, NH-3), 7.42 (d, 1H,
H-6, J6,5¼8.0 Hz), 5.89 (m, 1H, NHBoc), 5.65 (s, 1H,
H-10), 5.58 (d, 1H, H-5, J5,6¼8.0 Hz), 5.43 (m, 1H, NHBoc),
Data for authentic free 1: 1H NMR (D2O, 500 MHz) d 7.79
(d, 1H, H-6, J6,5¼7.8 Hz), 5.83 (d, 1H, H-5, J5,6¼7.8 Hz),
00
5.75 (d, 1H, H-10, J1 ,2 ¼2.3 Hz), 5.20 (s, 1H, H-1 ), 4.33
0
0
(dd, 1H, H-20, J2 ,3 ¼5.1 Hz, J2 ,1 ¼2.3 Hz), 4.28 (dd, 1H,
0
0
0
0
H-50, J5 ,4 ¼2.4 Hz, J5 ,6 ¼8.4 Hz), 4.21 (m, 2H, H-3 , H-
0
0
0
0
0
200), 4.16 (dd, 1H, H-300, J3 ,2 ¼6.0 Hz, J3 ,4 ¼2.8 Hz),
00 00
00 00
4.10 (m, 2H, H-40, H-400), 3.49 (d, 1H, H-60, J6 ,5 ¼8.4 Hz),
0
0
3.18 (dd, 1H, H-500a, J5 a,5 b¼13.8 Hz, J5 a,4 ¼3.7 Hz),
3.03 (m, 3H, H-500b, H-100a, H-100b), 2.85 (m, 1H, H-80a),
2.62 (m, 1H, H-80b), 2.41 (s, 3H, NMe), 1.91 (m, 1H, H-
90a), 1.80 (m, 1H, H-90b).
00
00
00
00
5.04 (m, 2H, H-100, H-20), 4.77 (d, 1H, H-30, J3 ,2 ¼5.5 Hz),
0
0
00
4.67 (d, 1H, H-200, J2 ,3 ¼5.9 Hz), 4.51 (d, 1H, H-3 , J3 ,2
¼
00 00
00 00
5.9 Hz), 4.28 (m, 2H, H-40, H-50), 4.10 (m, 1H, H-400), 3.45
(m, 1H, H-60), 3.19 (m, 1H, H-500a), 3.04 (m, 3H, H-100a,
H-100b, H-500b), 2.76 (m, 1H, H-80a), 2.53 (m, 1H, H-80b),
2.40 (s, 3H, NMe), 1.56 (m, 4H, CH2CH3ꢂ2), 1.53 (m, 2H,
H-90a, H-90b), 1.52 (s, 3H, acetonide), 1.47 (s, 9H, t-Bu),
1.40 (s, 9H, t-Bu), 1.39 (s, 9H, t-Bu), 1.32 (s, 3H, acetonide),
0.77 (m, 6H, CH2CH3ꢂ2); 13C NMR (CD3CN, 125 MHz)
d 170.40, 163.97, 156.89, 151.34, 144.25, 116.67, 115.04,
113.85, 102.89, 94.93, 88.44, 87.43, 87.01, 85.11, 82.91,
82.40, 82.26, 81.43, 79.40, 78.90, 43.95, 38.88, 38.72,
30.31, 29.48, 28.68, 28.62, 28.57, 27.33, 25.50, 8.75, 7.55;
FABMS-LR m/z 884 (MH+); FABMS-HR (NBA) calcd for
C42H70N5O15 884.4868, found 884.4879.
References and notes
1. Meka, V. G.; Pillai, S. K.; Sakoulas, G.; Wennersten, C.;
Venkataraman, L.; DeGirolami, P. C.; Eliopoulos, G. M.;
Moellering, R. C., Jr.; Gold, H. S. J. Infect. Dis. Drug Targets
2004, 190, 311–317.
2. (a) Ochi, K.; Ezaki, M.; Iwani, M.; Komori, T.; Kohsaka, M.
EP-333177, 1989; (b) Yoshida, Y.; Yamanaka, H.; Sakane, K.
JP H05-78385, 1993.
3. McDonald, L. A.; Barbieri, L. R.; Carter, G. T.; Lenoy, E.;
Lotvin, J.; Petersen, P. J.; Siegel, M. M.; Singh, G.;
Williamson, R. T. J. Am. Chem. Soc. 2002, 124, 10260–10261.
4. (a) Bugg, T. D. H.; Lloyd, A. J.; Roper, D. I. Infect. Disord.
Drug Targets 2006, 6, 85–106; (b) Kimura, K.; Bugg,
T. D. H. Nat. Prod. Rep. 2003, 20, 252–273.
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Hyland, S. A.; Anderson, M. S. Anal. Biochem. 2003, 317,
156–165; (c) Zawadzke, L. E.; Wu, P.; Cook, L.; Fan, L.;
Casperson, M.; Kishinani, M.; Calambur, D. S.; Hofstead, J.;
Padmanabha, R. Anal. Biochem. 2003, 314, 243–252; (d)
Stachyra, T.; Dini, C.; Ferrari, P.; Bouhss, A.; van Heijenoort,
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Med. Chem. Lett. 2003, 13, 3345–3350; (f) Sarabia, F.;
4.1.10. (D)-FR-900493 (1). Compound 15 (3.1 mg,
3.5 mmol) was treated with aqueous 80% TFA (1 mL) at
room temperature for 1.5 h. The mixture was concentrated
in vacuo to give FR-900493 as tri-TFA salt (3.0 mg, quant).
[a]2D5 +9.4 (c 0.3, H2O); 1H NMR (D2O, 500 MHz) d 7.70 (d,
1H, H-6, J6,5¼8.2 Hz), 5.89 (d, 1H, H-5, J5,6¼8.2 Hz), 5.81
(s, 1H, H-10), 5.28 (s, 1H, H0-100), 4.70 (d, 1H, H-20,
0
0
0
0
J2 ,3 ¼3.0 Hz), 4.42 (d, 1H, H-3 , J3 ,2 ¼3.0 Hz), 4.33 (m,
2H, H-200, H-300), 4.17 (m, 3H, H-40, H-400, H-50), 3.47–
3.37 (m, 3H, H-500a, H-100a, H-100b), 3.35 (d, 1H, H-60,
00
0
0
J6 ,5 ¼12.5 Hz), 3.19 (m, 1H, H-5 b), 3.12 (s, 3H, NMe),
3.06 (m, 2H, H-80a, H-80b), 2.15 (m, 2H, H-90a, H-90b);
13C NMR (D2O, 125 MHz) d 167.11, 164.03, 163.68,

2804
S. Hirano et al. / Tetrahedron 63 (2007) 2798–2804
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