Total synthesis and NMR conformational study of signal peptidase II inhibitors, globomycin and SF-1902 A5

Article abstract of DOI:10.1016/S0040-4020(03)00110-8

A stereoselective total synthesis of an antibiotic, globomycin (1a), and its congener, SF-1902 A₅ (1b), was achieved. Two convergent macrocyclization routes via macrolactamization or macrolactonization to form 1a are described. A conformational study by means of NMR spectroscopy was performed in several solvents. The ¹H NMR spectrum of 1a indicated that the amide proton of only the L-allo-Thr residue was involved in the hydrogen bonding. The structure in solution phase was different from the X-ray structure.

Full text of DOI:10.1016/S0040-4020(03)00110-8

Tetrahedron 59 (2003) 1685–1697
Total synthesis and NMR conformational study of signal
peptidase II inhibitors, globomycin and SF-1902 A5
*
Toshihiro Kiho, Mizuka Nakayama and Hiroshi Kogen
Exploratory Chemistry Research Laboratories, Sankyo Co., Ltd., 2-58, Hiromachi 1-chome, Shinagawa-ku Tokyo 140-8710, Japan
Received 12 December 2002; revised 20 January 2003; accepted 20 January 2003
Abstract—A stereoselective total synthesis of an antibiotic, globomycin (1a), and its congener, SF-1902 A5 (1b), was achieved. Two
convergent macrocyclization routes via macrolactamization or macrolactonization to form 1a are described. A conformational study by
means of NMR spectroscopy was performed in several solvents. The 1H NMR spectrum of 1a indicated that the amide proton of only the
L-allo-Thr residue was involved in the hydrogen bonding. The structure in solution phase was different from the X-ray structure. q 2003
Elsevier Science Ltd. All rights reserved.
1. Introduction
minor components, SF-1902 A2–A5 (1b–f), share four or
five amino acids with 1a, as shown in Figure 1.
Globomycin (1a)1 and its congeners, SF-1902 A2–A5
(1b–f),2 first isolated from four different strains of
actinomycetes (Streptomyces halstedii No. 13912 among
others) in 1978, are 19-membered cyclic depsipeptides.
The major component, 1a, is the first natural product1c,3
which contains both, an L-allo-Ile and L-allo-Thr, and
has a biologically unique activity as an antibiotic against
Gram-negative bacteria.1,2 Globomycin (1a) has only been
proven to be a specific inhibitor of signal peptidase II, a
prolipoprotein-processing enzyme,4 that processes the
acylated precursor form of lipoprotein into apolipoprotein
and a signal peptide in Escherichia coli.6 A breakthrough
in lipoprotein research was the finding that signal peptidase
II is specifically inhibited by 1a.5,6 Inhibition of signal
peptidase II by 1a leads to the accumulation of the acylated
form of lipoprotein in the cytoplasmic membrane and
consequently to the death of the cell.7a Signal peptidase II
represents an attractive target for developing a new class of
antibiotics that function by a different mechanism from
currently available drugs. Globomycin, which is known
to inhibit the processing of lipoproteins, has been used
routinely to demonstrate the acylation of newly identified
lipoproteins.8 It has been widely used for controlling the
maturation of lipopeptides7 and as an invaluable tool in
studies of lipoprotein biosynthesis.9 Structurally, 1a–f
commonly contain four natural amino acids, one N-Me
amino acid and a b-hydroxy-a-methyl carboxylic acid
which greatly contributes to the antibacterial activity.2 The
The congeners, 1e and 1f, have an L-Val in place of an
L-allo-Ile and the other congeners, 1b–1d, have a shorter or
longer alkyl side-chain in the fatty acid unit than 1a. The
relative and absolute stereochemistry of the 3-hydroxy-2-
methylnonanoyl-N-Me-Leu moiety in 1a remained ambigu-
ous for a long time. However, we reported the absolute
structure as determined by X-ray analysis and the first total
synthesis of 1a in a recent communication.1d Since then, we
obtained more details on the structural conformation of
1a in some solvents, which indicate a structure different
from the X-ray structure. We present here the asymmetric
total synthesis of 1a and its congener 1b based on the
macrolactamization method, and an alternative convergent
route via macrolactonization.
Keywords: globomycin; macrolactamization; antibiotics; signal peptidase II;
macrolactonization.
*
Corresponding author. Tel.: þ81-334-923131; fax: þ81-354-368570;
e-mail: hkogen@shinasankyo.co.jp
Figure 1. Globomycin (1a) and its congeners.
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00110-8

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T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
Scheme 1. Retro synthetic analysis.
2. Results and discussion
particularly important as it is the only non-amino acid
containing part.
2.1. Synthetic plan
Thus, we choose the anti-selective boron-mediated asym-
metric aldol reaction developed by Abiko and Masamune10
for its preparation as shown in Scheme 2. The commercially
available ester 2 was enolized with a dicyclohexylboron
triflate in the presence of triethylamine, and then this was
reacted with an aldehyde at 2788C to afford anti-aldol
product 3 in high yield and with high selectivity (87–93%,
89–94% de).
Our approach to the synthesis of 1 began by dividing
the compound into three fragments as shown in Scheme 1:
(i) (2R, 3R)-3-hydroxy-2-methylcarboxylic acid unit,
Fragment A; (ii) L-allo-Thr-Gly unit, Fragment B; and
(iii) N-Me-L-Leu-L-allo-Ile-L-Ser unit, Fragment C. These
fragments were then combined to construct 1 with
macrolactamization or macrolactonization as the key
reaction. According to our strategy, the difficult N-acylation
step between Fragment A and C was introduced early
for both routes. In the route with macrolactamization,
esterification to form the b-acyloxy acid moiety was carried
out later to avoid a b-elimination reaction and a ring closure
was attempted between the C terminus of Fragment C and
the amine of Fragment B which was considered to be one of
the less-hindered sites. On the other hand, the macrolacto-
nization route has the great advantage that no epimerization
occurs even under severe conditions because the C terminus
is Gly.
Finally, hydroxy ester 3 was hydrolyzed with aqueous
LiOH in THF to give (þ)-An without epimerization in good
yield (90–99%). The relative stereochemistry of (þ)-An
1
was confirmed from the H NMR coupling constant11 and
NOESY experiment after the conversion to acetonide 4
(73%, 2 steps). Two large axial–axial coupling constants
(J¼11.0, 11.5 Hz) for the HD proton and NOESY
correlations among HA, HC and the axial methyl group in
4 were observed as shown in Figure 2. These results
indicated that the relative stereochemistry of C(2)–C(3) in 4
was anti. Thereafter, the absolute configuration of C(3) in
(þ)-A3 was established by the modified Mosher’s method.12
An acid (þ)-A3 was treated with TMSCHN213 followed by
esterification with (R)- or (S)-MTPA chloride to afford
2.2. Preparation of fragments
2.2.1. Fragment A. Of the three fragments, Fragment A is
Scheme 2. Synthesis of Fragment A.

T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
1687
stereochemistry of fatty acid (þ)-A3 was (2R, 3R). The
absolute configuration of (þ)-A5 was also confirmed in the
same manner with (R)- and (S)-5b, and the same result was
obtained.
2.2.2. Fragment B and C. The dipeptide unit, Fragment B,
was prepared from commercially available L-allo-threonine
(L-allo-Thr-OH) (6) and glycine benzyl ester (Gly-OBn) (7)
as shown in Scheme 3. The protection of 6 with Boc2O
(88%) and then with TBSOTf (82%) gave N-Boc-L-allo-
Thr(TBS)-OH. This acid was condensed with 7 to afford
fully protected dipeptide 8 (93%). Compound 8 was
hydrogenolyzed to give the dipeptide Fragment B (100%).
L-Serine derivative (Boc-L-Ser(Bn)-OH) (9) was employed
as the starting material for the synthesis of tripeptide
Fragment C. The allylation of 9 followed by the deprotec-
tion of the Boc group with 4N HCl in EtOAc gave allyl ester
Figure 2. NOE experiment of acetonide 4.
(R)- or (S)-MTPA ester ((R)- or (S)-5a), respectively. The
Dd (d(S)-MTPA ester2d(R)-MTPA ester) values of the C(4)H2–
C(11)H3 group were positive and the same values of the
C(2)H, C(3)0H3 and OCH3 group were negative, indicating
that the configuration of C(3) in 5 was (R). Hence, the
Scheme 3. Synthesis of Fragment B and C.
Scheme 4. Total synthesis of 1a via macrolactamization. Reagents and conditions: (a) cat Pd(PPh3)4, morpholine (b) TBAF, AcOH (c) H2, Pd(OH)2.

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T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
Table 1. Yield of macrolactamized product
Tripeptide C was condensed with (þ)-A3 mediated by
diethylcyanophosphate (DEPC)15 and without protection of
the hydroxyl group in (þ)-A3, to give the acylated tripeptide
15a (99%). Esterification of 15a was performed with
diisopropylcarbodiimide (DIPC) and Fragment B under
Keck’s condition16 to afford 16a (96%). The treatment of
the fully protected seco-acid 16a with TBAF and AcOH
provided 18a (99%). The removal of the allyl group in 18a
with Pd(PPh3)4 and morpholine gave acid 19a (99%). The
macrocyclic precursor obtained by the deprotection of the
Boc group was used for macrolactamization. As well other
macrocyclic precursors were prepared from 17a and
debenzylated derivative 20a and deprotected in the same
manners as described above. The coupling reagent, O-(7-
azabenzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexa-
fluorophosphate (HATU)17 gave the best result. A dilute
solution of the intermediates was slowly added to the
suspension of HATU and N,N-diisopropylethylamine to
yield globomycin derivatives. In the case of the precursor
derived from 17a, the yield of macrolactam 22a was very
poor because of steric hindrance between TBS and the
benzyl group during the cyclization step (Table 1).
However, the derivatives in which the TBS group was
removed gave cyclized products 21a in moderate yield
(45%, 2 steps). The benzyl group was not affected in the
cyclization reaction (1a, 39% 2 steps from 20a). O-Bn
globomycin (21a) was treated with Pd(OH)2 under H2
atmosphere to produce 1a (96%).
Product
Yield (%) (2 steps)
22a
21a
1a
trace
45
39
10 as an HCl salt (95%, 2 steps). This salt was coupled with
Boc-L-allo-isoleucine (Boc-L-allo-Ile-OH) (11) mediated
by (benzotriazolyloxy) tris(pyrrolydino)phosphonium hexa-
fluorophosphate (PyBOP)14 to give dipeptide 12 (97%). The
removal of the Boc group in 12 followed by the coupling
with Boc-N-methyl-leucine (Boc-N-Me-L-Leu-OH) (13)
produced tripeptide 14 (94%, 2 steps). The treatment of
14 with HCl in EtOAc and then with saturated NaHCO3
aqueous solution afforded Fragment C as a free amine
(96%).
2.3. Macrolactamization route
With the three Fragments A–C, the formation of a linear
depsipeptide was attempted via two routes for macrolacta-
mization. First, we tried coupling Fragment C and the ester
synthesized from Fragment A and B. However, the reaction
failed due to a b-elimination of the Fragment B unit from
the depsipeptide. Successful synthesis of the target macro-
cyclic precursor was achieved by a coupling Fragment A and
C followed by a esterification with Fragment B (Scheme 4).
The congener 1b was also obtained from (þ)-A5 as a
starting material via the same synthetic route (Scheme 5).18
All the physical properties (1H, 13C, IR, [a]D) of synthetic
1a and b were identical to those of natural globomycin and
SF-1902 A5, respectively.19
Synthetic 1a against Escherichia coli ATCC 11303 showed
the same degree of antimicrobial activity (MIC¼0.2
mg/mL) as that initially observed for natural 1a. On the
other hand, synthetic 1b showed weaker activity than 1a
(MIC¼0.4 mg/mL). However, the activity of the O-Bn
derivative (21a) and the acyclic macrocyclization precursor
were extremely diminished (MIC.50 mg/mL).20 These
Scheme 5.
Scheme 6. Synthesis of 1a via macrolactonization.

T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
1689
Table 2. Solvent effect on the ratio of rotamers
hydroxy acid (95%), this seco-acid was used in the
lactonization reaction by the Yamaguchi’s method.23 To
the refluxed toluene solution of DMAP, was slowly added
mixed-acid anhydride prepared with 2,4,6-Cl3C6H2COCl
and triethylamine in THF, to give protected globomycin 22
(51%).24 The removal of TBS and the benzyl group by
conventional methods provided 1a.
Structure
Solvent
Ratio of the rotamersa
1a
1a
1a
1a
CDCl3
CD3CN
CD3OD
DMSO-d6
5.9:1
4.4:1
2.8:1
1.9:1
Single isomerb
a
The ratio of the rotamers was determined by 1H NMR analysis at the
N-Me position (16 mM) at 278C.
2.5. Spectroscopic analysis
b
1H NMR analysis at 1008C.
The 1H NMR spectrum indicates that 1a exists as a mixture
of two rotational isomers and that the proportion of each is
dependent on the solvent (major/minor¼5.9:1 in CDCl3,
1.9:1 in DMSO-d6, at 278C). On the other hand, 1a exists as
a single isomer in DMSO-d6 at 1008C (Table 2).
Table 3. Temperature coefficient values of NH proton
Residue
2Dd/dT (ppb/K)
Gly
6.40
1.07
4.90
10.5
These results suggested that there is an equilibrium between
the two isomers whose activation energies are not very high.
Furthermore, the temperature-dependence of NH proton
chemical shifts was measured in the range from 30 to 608C
increasing every 108C (CDCl3, 8 mM) in order to estimate
the conformation of the major isomer. Temperature
coefficients values (2Dd/dT) were evaluated from least-
squares plots (Table 3).25
L-allo-Thr
L-Ser
L-allo-Ile
results suggest that the hydroxyl group in the Ser residue
and the cyclic structure of 1 with an inner hydrophilic cavity
were quite essential for the antimicrobial activity.2b
2.4. Macrolactonization route
As a result, the NH proton only in the L-allo-Thr residue
seemed to participate in the hydrogen bonding in contrast
with the results of the X-ray structure.1d Consequently, the
conformation in the solution phase is suspected to be
different from the crystal X-ray structure. Further analyses
on the conformation are being carried out based on
molecular dynamics calculations. Interestingly, the chemi-
cal shifts of 1a in the NMR spectra change with increasing
concentrations only in CDCl3 but those of O-benzyl
derivative 21a do not. Figure 3 shows the 1H NMR spectra
of 1a at five different concentrations (4, 8, 16, 24, 40 mM).
Large shifts (Dd ppm) were observed for the C(3)H proton
of the fatty acid moiety and the a proton of the L-Ser residue
as well as for several amide NH protons. On the other hand,
the protons of N-Me-Leu residue are shifted hardly. These
results suggest the existence of intermolecular interactions
such as a hydrogen bond among the OH group, the amide
NH and the amide CvO group of 1a. In particular, the
primary hydroxyl group of the Ser residue was necessary.
1H and 13C NMR data in CDCl3 for the major isomer of 1a
are summarized in Table 4, in which all of the protons and
carbons were assigned based on DQF-COSY, HMQC and
HMBC experiments.
In the total synthesis of 1a via macrolactonization, the Gly
at the C terminus did not cause any epimerization under
severe conditions during the cyclization step. The common
intermediate 15 was used as a starting material in the
macrolactonization route (Scheme 6). The removal of the
allyl group in 15 afforded hydroxy acid 23 (Pd(PPh3)4 and
morpholine, 99%). Hydroxy acid 23 was then coupled with
freshly prepared dipeptide 2421 synthesized from 8 with
TBSOTf and 2,6-lutidine22 to give linear peptide 25 (95%).
After the treatment of 25 with aqueous LiOH to provide a
The NOESY experiments indicated that these rotational
isomers were derived from the rotation of the acyl N-methyl
amide group. Since correlations among the N-methyl group,
C(3)H and C(19)H were observed, the major isomer was
ascribed to be in the trans form like in the conformation
obtained by X-ray analysis while the minor isomer was
considered to adopt a cis form as there was a correlation
between C(3)H and C(19)H (Fig. 4).
3. Conclusion
We have completed the first total synthesis of globomycin
as well as its congener, SF-1902 A5, by a convergent
Figure 3. 1H NMR spectra of 1a at five different concentrations in CDCl3.

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T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
Table 4. 1H and 13C NMR data for the major isomer of 1a in CDCl3
1Ha
13Cb
1Ha
13Cb
Fatty acid
CvO
N-Me-Leu
CvO
a-CH
b-CH2
g-CH2
d-CH3
d-CH3
N-Me
allo-Ile
CvO
a-CH
b-CH
g-CH2
g-CH3
d-CH3
Ser
176.9
41.2
77.0
15.0
31.3
24.3
29.1
31.6
22.6
14.0
173.2
67.8
38.2
25.3
21.9
23.1
40.1
2-CH
3-CH
3-CH3
4-CH2
5-CH2
6-CH2
7-CH2
8-CH2
9-CH3
allo-Thr
CvO
a-CH
b-CH
g-CH
NH
3.12–3.20 (m)
5.08 (dt, 3.3, 8.8)
1.10 (d, 6.9)
1.57–1.71 (m)
1.25–1.43 (m)
1.25–1.43 (m)
1.25–1.43 (m)
1.25–1.43 (m)
0.88 (t, 7.0)
3.63 (br s)
1.57–1.71 (m) 2.11–2.17 (m)
1.49–1.56 (m)
0.96 (d, 6.6)
3.22 (s)
174.7
56.6
36.6
27.1
14.6
11.7
4.53 (dd, 2.8, 7.4)
2.17–2.24 (m)
1.25–1.43 (m)
0.91 (t, 7.3)
170.4
59.1
66.9
18.9
4.24–4.28 (m)
4.38 (qu, 6.4)
1.25 (d, 6.4)
7.12 (d, 7.3)
0.93 (t, 7.3)
CvO
a-CH
b-CH2
NH
170.7
57.6
61.5
Gly
4.12 (t, 6.5)
3.94 (d, 4.5)
7.63 (d, 4.5)
CvO
a-CH2
NH
168.8
40.5
3.73 (dd, 4.1, 17.3) 4.33 (dd, 8.0, 17.3)
7.68 (br t, 4.1)
a
500 MHz; d in ppm, J in Hz (16 mM).
100 MHz; d in ppm (47 mM).
b
internal standard. All 13C NMR spectra are reported in ppm
relative to the central line for CDCl3 (d 77.0) or CD3OD (d
49.0). 13C NMR spectra of 1a and 1b were obtained on a
Brucker AVANCE 500 spectrometer with a CryoProbe. In
the NMR spectral lists, chemical shifts which are assigned
to the minor conformer are marked with an asterisk. Melting
¨
points (mp) measured with BUCHI Schmelzpunktbestim-
mungs Apparat were uncorrected. Optical rotations
measured on JASCO P-1030 are reported in g/100 mL.
Infrared (IR) spectra are reported in wave number (cm21
)
measured on a JASCO FT-IR-350, FT-IR-8300 or FT-IR-
8900 spectrometer. High-resolution mass spectra were
obtained on a JEOL JMS-BU20, JMS-700 or JMS-700QQ
spectrometer. Elemental analysis was performed on Yanaco
MT-5 or MT-6. Preparative HPLC was performed using a
GILSON liquid chromatography system equipped with a
Model 305 and 306 pump, Model 119 UV detector, Model
811C dynamic mixture, Model 806 manometric module and
Model 503 degasser. Two types of column (NOMURA
CHEMICAL Develosil ODS-HG5; 10 mm£250 mm,
20 mm£250 mm) were used. Analytical HPLC was per-
formed on a HITACHI D-6100 interface equipped with a
HITACHI L-4000 UV detector, a HITACHI L-6200
intelligent pump and a HITACHI L-5025 column oven
using a DAICEL CHIRALCEL OD (4.6 mm£250 mm) for
3a or CHIRALCEL AD column (4.6 mm£250 mm) for 3b.
Figure 4. Selected NOESY correlations of 1a in CD2OD.
coupling of three fragments via two possible routes. A
conformational study in solution was also performed.
Further synthetic investigations examining the structure–
activity relationship (SAR) and determining the exact
conformation are currently underway.
4. Experimental
4.1. General procedure
All moisture-sensitive reactions were carried out under a
N2 atmosphere. Tetrahydrofuran (THF) was distilled from
sodium-benzophenone ketyl. Dichloromethane (CH2Cl2)
was distilled from calcium hydride. Other anhydrous
solvents were purchased from Aldrich or Kanto Kagaku.
All reagents were commercially available and used as
obtained unless otherwise stated. Analytical thin-layer
chromatography (TLC) was performed using TLC plates
precoated with Merck Silica gel 60 F254 (0.25 mm layer
thickness). Preparative flash column chromatography was
performed using Merck Silica gel 60 (230–400 mesh).
NMR spectra were obtained on a JEOL ECP-500, JNM-
GSX-400, Varian Inova-500, Mercury-400 or Brucker
AVANCE 500 spectrometer. All 1H NMR spectra are
reported in ppm downfield from tetramethylsilane as an
4.2. Determination of the relative and absolute
stereochemistry of (1)-A3
4.2.1. Reduction of 3a. To a suspension of LiAlH4 (101 mg,
2.66 mmol) in ether (3 mL) was added dropwise a solution
of 3a (157 mg, 0.264 mmol) in ether (2 mL) at 08C. The
reaction mixture was stirred at the same temperature for 3 h.
After an addition of EtOAc (5 mL), the mixture was
acidified with 5% aqueous HCl solution. The organic layer
was separated and the aqueous layer was extracted with
EtOAc. The combined organic extracts were dried over
Na2SO4, filtered and evaporated. The oil residue was

T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
1691
1
purified by column chromatography with a 3:1 mixture of
hexane and EtOAc used as an eluent to give a diol (33.6 mg,
0.193 mmol, 73%) as a colorless oil. H NMR (400 MHz,
oil. H NMR (400 MHz, CDCl3) d ppm: 0.88 (t, 3H, J¼
6.9 Hz), 1.09 (d, 3H, J¼7.1 Hz), 1.24–1.30 (m, 8H), 1.63–
1.68 (m, 2H), 2.84 (qu, 1H, J¼7.1 Hz), 3.53 (d, 3H, J¼
1.1 Hz), 3.58 (s, 3H), 5.37 (q, 1H, J¼6.1 Hz), 7.38–7.41 (m,
3H), 7.52–7.54 (m, 2H); 13C NMR (100 MHz, CDCl3) d
ppm: 12.3, 14.0, 22.5, 24.6, 29.0, 30.3, 31.6, 42.4, 51.8,
55.4, 77.4, 84.5 (q, J¼29 Hz), 123.3 (q, J¼288 Hz), 127.4,
128.3, 129.6, 132.1, 165.9, 173.5; IR (CHCl3) cm21: 2954,
2931, 2859, 1743, 1460, 1438, 1272, 1171, 1122, 1017;
HRMS calcd for C21H30F3O5 (MþH)þ calcd 419.2045,
found: 419.2039; [a]2D5¼225.8 (c 1.02, CHCl3).
1
CDCl3) d ppm: 0.890 (t, 3H, J¼6.9 Hz), 0.892 (d, 3H, J¼
7.1 Hz), 1.25–1.35 (m, 7H), 1.41–1.51 (m, 2H), 1.54–1.61
(m, 1H), 1.66–1.76 (m, 1H), 2.74 (br s, 1H), 2.97 (br s, 1H),
3.51 (dt, 1H, J¼3.2, 7.7 Hz), 3.62 (dd, 1H, J¼7.2, 10.8 Hz),
3.77 (dd, 1H, J¼3.6, 10.8 Hz); 13C NMR (100 MHz,
CDCl3) d ppm: 14.0, 14.1, 22.6, 25.2, 29.4, 31.9, 35.4,
39.9, 67.7, 77.4; IR (CHCl3) cm21: 3623, 3502, 2959, 2930,
2873, 2858, 1467, 1247, 1025, 959; HRMS calcd for
C10H23O2 (MþH)þ calcd 175.1712, found: 175.1698;
[a]2D4¼þ29.5 (c 1.02, CHCl3).
For (R)-5a. By combining the ester (60.3 mg, 0.298 mmol),
DMAP (55.5 mg, 0.454 mmol) and (S)-MTPACl (67 mL,
0.358 mmol), (R)-5a (124 mg, 0.295 mmol, 99%) was
4.2.2. The acetonide of (2S, 3R)-2-methyl-1, 3-nonanediol
(4). To a solution of the diol (11.0 mg, 63.1 mmol) in
acetone (1.0 mL) were added p-toluenesulfonic acid
(2.2 mg), dimethoxypropane (100 mL) and MgSO4 (50 mg).
After being stirred at room temperature for 27 h, the
reaction mixture was filtered and evaporated. The residue
was purified by column chromatography with a 6:1 mixture
of hexane and EtOAc used as an eluent to give 4 (13.4 mg,
62.5 mmol, 99%) as a colorless volatile oil. 1H NMR
(400 MHz, CDCl3) d ppm: 0.74 (d, 3H, J¼6.6 Hz), 0.88 (t,
3H, J¼6.7 Hz), 1.22–1.52 (m, 9H), 1.38 (s, 3H), 1.42 (s,
3H), 1.55–1.70 (m, 2H), 3.42 (dt, 1H, J¼2.2, 8.4 Hz), 3.48
(t, 1H, J¼11.7 Hz), 3.68 (dd, 1H, J¼5.1, 11.7 Hz); 13C
NMR (100 MHz, CDCl3) d ppm: 12.8, 14.1, 19.1, 22.6,
24.9, 29.3, 29.8, 31.9, 33.0, 34.1, 66.2, 75.0, 98.1; IR
(CHCl3) cm21: 2957, 2931, 2859, 1460, 1383, 1369, 1265,
1167, 1112, 1055; HRMS calcd for C13H27O2 (MþH)þ
calcd 215.2011, found: 215.2015; [a]2D4¼þ41.9 (c 0.49,
CHCl3).
1
obtained as a colorless oil. H NMR (400 MHz, CDCl3) d
ppm: 0.86 (t, 3H, J¼6.8 Hz), 1.08–1.27 (m, 8H), 1.17 (d,
3H, J¼7.2 Hz), 1.58–1.63 (m, 2H), 2.85 (qu, 1H, J¼
7.2 Hz), 3.54 (d, 3H, J¼1.1 Hz), 3.64 (s, 3H), 5.37 (q, 1H,
J¼6.1 Hz), 7.38–7.41 (m, 3H), 7.52–7.55 (m, 2H); 13C
NMR (100 MHz, CDCl3) d ppm: 12.8, 14.0, 22.5, 24.1,
29.0, 30.3, 31.5, 42.6, 51.9, 55.4, 77.4, 84.5 (q, J¼28 Hz),
123.3 (q, J¼288 Hz), 127.4, 128.3, 129.5, 132.2, 166.0,
173.7; IR (CHCl3) cm21: 2955, 2930, 2858, 1743,
1459, 1437, 1271, 1171, 1123, 1017; HRMS calcd for
C21H29F3O5Na (MþNa)þ calcd 441.1865, found: 441.1871;
[a]2D5¼þ25.1 (c 1.06, CHCl3).
4.2.4. The (S)-MTPA ester of methyl (2R, 3R)-3-hydroxy-
2-methylundecanoate ((S)-5b). From 3b (452 mg,
2.09 mmol) and TMSCHN2 was obtained a methyl ester
(431 mg, 1.87 mmol, 90%) as a colorless oil. 1H NMR
(500 MHz, CDCl3) d ppm: 0.88 (t, 3H, J¼7.0 Hz), 1.21 (d,
3H, J¼6.6 Hz), 1.27–1.53 (m, 14H), 2.49–2.57 (m, 2H),
3.63–3.68 (m, 1H), 3.71 (s, 3H); 13C NMR (125 MHz,
CDCl3) d ppm: 14.1, 14.3, 22.7, 25.5, 29.2, 29.5, 29.6, 31.9,
34.8, 45.2, 51.7, 73.4, 176.5; IR (CHCl3) cm21: 3459, 2952,
2927, 2855, 1740, 1461, 1437, 1377, 1263, 1172; HRMS
calcd for C13H26O3Na (MþNa)þ calcd 253.1780, found:
253.1770; [a]2D4¼22.5 (c 1.61, CHCl3).
4.2.3. The (S)-MTPA ester of methyl (2R, 3R)-3-
hydroxy-2-methylnonanoate ((S)-5a). To a solution of
(þ)-A3 (157 mg, 0.834 mmol) in CH3OH (4 mL) was added
dropwise trimethylsilyl diazomethane (2.0 M in hexane) at
08C until the reaction mixture turned light yellow. The
mixture was evaporated and the residue was purified
by column chromatography with a 10:1 mixture of hexane
and EtOAc used as an eluent to give an ester (165 mg,
By combining the ester (56.0 mg, 0.243 mmol), DMAP
(59 mg, 0.486 mmol) and (R)-MTPACl (68 mL, 0.365 mmol),
(S)-5b (105 mg, 0.235 mmol, 97%) was obtained as a
colorless oil. 1H NMR (400 MHz, CDCl3) d ppm: 0.88
(t, 3H, J¼7.0 Hz), 1.09 (d, 3H, J¼7.3 Hz), 1.24–1.29
(m, 12H), 1.63–1.67 (m, 2H), 2.84 (qu, 1H, J¼7.3 Hz), 3.53
(d, 3H, J¼1.5 Hz), 3.58 (s, 3H), 5.37 (q, 1H, J¼6.1 Hz),
7.38–7.41 (m, 3H), 7.52–7.54 (m, 2H); 13C NMR
(100 MHz, CDCl3) d ppm: 12.3, 14.1, 22.6, 24.7, 29.2,
29.4, 30.3, 31.8, 42.4, 42.6, 51.8, 55.4, 77.4, 84.5 (q, J¼
28 Hz), 123.3 (q, J¼288 Hz), 127.4, 128.4, 129.6, 132.1,
165.9, 173.5; IR (CHCl3) cm21: 2954, 2928, 2856, 1743,
1460, 1438, 1271, 1172, 1122, 1017; HRMS calcd for
C23H33F3O5Na (MþNa)þ calcd 469.2178, found: 469.2181;
[a]2D6¼224.1 (c 1.17, CHCl3).
1
0.816 mmol, 98%) as a colorless oil. H NMR (400 MHz,
CDCl3) d ppm: 0.88 (t, 3H, J¼6.8 Hz), 1.21 (d, 3H, J¼
7.3 Hz), 1.24–1.54 (m, 10H), 2.50–2.57 (m, 2H), 3.63–
3.69 (m, 1H), 3.71 (s, 3H); 13C NMR (100 MHz, CDCl3) d
ppm: 14.0, 14.3, 22.6, 25.5, 29.2, 31.8, 34.8, 45.2, 51.7,
73.4, 176.5; IR (CHCl3) cm21: 3606, 2955, 2930, 2859,
1720, 1460, 1438, 1378, 1260, 1173; HRMS calcd for
C11H23O3 (MþH)þ calcd 203.1647, found: 203.1644;
[a]2D5¼26.9 (c 1.03, CHCl3).
The ester (49.6 mg, 0.245 mmol) was dissolved in CH2Cl2
(1.5 mL). To this solution were added DMAP (60.2 mg,
0.493 mmol) and (R)-MTPACl (69 mL, 0.369 mmol) at
room temperature. The mixture was stirred at the same
temperature, and 5% aqueous HCl solution was added. The
organic layer was separated and washed with a saturated
K2CO3 aqueous solution and brine. The combined organic
extracts were dried over Na2SO4, filtered and evaporated.
The oil residue was purified by column chromatography
with a 10:1 mixture of hexane and EtOAc used as an eluent
to give (S)-5a (99.2 mg, 0.237 mmol, 97%) as a colorless
For (R)-5b. By combining the ester (60.4 mg, 0.262 mmol),
DMAP (64 mg, 0.524 mmol) and (S)-MTPACl (73 mL,
0.393 mmol), (R)-5b (116 mg, 0.260 mmol, 99%) was
1
obtained as a colorless oil. H NMR (400 MHz, CDCl3) d
ppm: 0.88 (t, 3H, J¼7.0 Hz), 1.10–1.29 (m, 12H), 1.17 (d,
3H, J¼7.2 Hz), 1.54–1.63 (m, 2H), 2.85 (qu, 1H,

1692
T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
J¼7.2 Hz), 3.53 (d, 3H, J¼1.5 Hz), 3.64 (s, 3H), 5.37 (q,
1H, J¼6.1 Hz), 7.38–7.41 (m, 3H), 7.52–7.54 (m, 2H); 13C
NMR (100 MHz, CDCl3) d ppm: 12.8, 14.1, 22.6, 24.2,
29.1, 29.3, 30.3, 31.8, 42.6, 51.9, 55.4, 77.4, 84.6 (q, J¼
28 Hz), 123.3 (q, J¼289 Hz), 127.4, 128.3, 129.6, 132.2,
166.0, 173.7; IR (CHCl3) cm21: 2954, 2928, 2856, 1743,
1461, 1438, 1271, 1171, 1122, 1017; HRMS calcd for
C23H33F3O5Na (MþNa)þ calcd 469.2178, found: 469.2167;
[a]2D6¼þ26.9 (c 1.17, CHCl3).
27.4, 28.7, 30.3, 31.3, 31.6, 32.7, 32.9, 37.8, 38.6, 41.2,
42.2, 55.9, 56.1, 57.7, 61.3, 62.9, 68.9, 77.3, 80.8, 170.7,
173.1, 173.5, 176.8; IR (KBr) cm21: 3328, 2961, 2934,
2875, 1726, 1659, 1525, 1369, 1201, 1170; HRMS m/z
(MþK)þ calcd 812.4423, found: 812.4436. Anal. Calcd for
C37H67N5O12·H2O: C, 56.11; H, 8.78; N, 8.84. Found: C,
56.34; H, 8.65; N, 8.59; [a]2D5¼255.3 (c 0.52, CH3OH).
Globomycin (1a)1d from 20a. To a solution of 20a
(42.5 mg, 54.9 mmol) in CH2Cl2 (1.5 mL), was added
TFA (0.3 mL) at room temperature. After being stirred at
the same temperature, the solvents were removed in vacuo.
The residue was dissolved in CH2Cl2 and reconcentrated
repeatedly to remove excess TFA. The crude product was
dried under reduced pressure to afford a TFA salt (43.8 mg)
and used for macrocyclization without further purification.
This salt (15.6 mg, 19.6 mmol) was dissolved in THF
(10 mL) and the solution was slowly added to a suspension
of HATU (75.5 mg, 0.199 mmol) and DIEA (52 mL,
0.298 mmol) in THF (10 mL) for over 3.5 h at 08C with a
syringe pump under highly diluted conditions. The reaction
mixture was stirred at the same temperature for an
additional 2 h, warmed to room temperature and stirred
for 16 h. This mixture was evaporated, diluted with 3:1
mixture of CH3OH and EtOAc and filtered. The filtrate was
concentrated, dissolved in EtOAc and washed with 1%
aqueous HCl solution, saturated NaHCO3 aqueous solution
and then brine. The organic layer was dried over Na2SO4,
filtered and evaporated. The residue was purified by pre-
parative HPLC (column: Develosil ODS-HG5 (10 mm£
250 mm); wavelength: 210 nm; flow rate: 5.0 mL/min) with
a 70:30 mixture of CH3OH and 1% aqueous triethylammo-
nium acetate used as an eluent to give 1a (5.0 mg, 7.6 mmol,
39% (2 steps)) as a colorless solid.
4.3. Macrolactamization route to obtain 1a
4.3.1. (2R, 3R)-3-[Boc-L-allo-Thr(TBS)-GlyO]-2-methyl-
nonanoyl-N-methyl-L-Leu-L-allo-Ile-L-Ser(Bn)OH
(17a). Compound 16a1d (48.9 mg, 48.0 mmol) and morpho-
line (8.5 mL, 97.5 mmol) were dissolved in THF (4.0 mL).
To this solution was added Pd(PPh3)4 (5.5 mg, 4.8 mmol),
and the reaction mixture was stirred at room temperature for
2.5 days. The mixture was concentrated and purified by
column chromatography with EtOAc and then a 10:1
mixture of CH2Cl2 and CH3OH used as eluents to give 17a
(44.9 mg, 45.9 mmol, 96%) as a pale yellow amorphous
1
foam. H NMR (400 MHz, CD3OD, major conformer) d
ppm: 0.06 (s, 3H), 0.09 (s, 3H), 0.85–0.95 (m, 12H), 0.88
(s, 9H), 0.96 (d, 3H, J¼6.6 Hz), 1.10 (d, 3H, J¼7.0 Hz),
1.13–1.18 (m, 4H), 1.28–1.45 (m, 10H), 1.45 (s, 9H),
1.56–1.66 (m, 3H), 1.73–1.81 (m, 1H), 1.91–1.97 (m, 1H),
3.06 (s, 3H), 3.23 (qu, 1H, J¼6.8 Hz), 3.74 (d, 1H, J¼
17.7 Hz), 3.75 (dd, 1H, J¼3.6, 9.7 Hz), 3.88 (dd, 1H, J¼4.9,
9.7 Hz), 4.01 (d, 1H, J¼17.7 Hz), 4.10–4.16 (br, 2H),
4.44–4.47 (m, 1H), 4.51 and 4.55 (AB type d’s, each 1H,
J¼11.9 Hz), 4.63 (t, 1H, J¼4.2 Hz), 5.08 (dt, 1H, J¼3.8,
7.4 Hz), 5.19 (dd, 1H, J¼5.4, 10.4 Hz), 7.24–7.33 (m, 5H);
13C NMR (100 MHz, CD3OD, both rotamers) d ppm: 24.9,
24.5, 11.9, 12.8, 14.4, 14.8, 15.1, 18.8, 20.1, 22.2, 23.7,
26.1, 26.2, 26.3, 26.4, 27.4, 28.7, 30.3, 30.7, 31.2, 31.5,
32.9, 37.8, 38.5, 41.2, 42.2, 54.1, 55.8, 57.7, 57.8, 61.8,
69.9, 70.7, 74.2, 77.2, 80.8, 97.2, 128.7, 128.8, 129.4, 139.2,
157.7, 170.4, 172.8, 173.0, 173.1, 173.3, 173.5, 176.7; IR
(KBr) cm21: 3326, 2959, 2932, 2860, 1725, 1663, 1520,
1253, 1200, 835; HRMS m/z Mþ calcd 978.6198, found:
978.6205. Anal. Calcd for C50H87N5O12Si·1/2H2O: C,
60.82; H, 8.98; N, 7.09. Found: C, 60.64; H, 8.88; N,
6.98; [a]2D3¼236.4 (c 0.99, CHCl3).
4.4. Total synthesis of SF-1902 A5 (1b)
4.4.1. anti-Selective asymmetric aldol reaction. Major
isomer 3b. To a stirred solution of (1R, 2S)-2 (575 mg,
1.20 mmol) in CH2Cl2 (14 mL) was added Et3N (0.40 mL,
2.88 mmol). The solution was cooled to 2788C and to this
was transferred via cannula a solution of c-Hex2BOTf
(1.0 M in hexane, 2.52 mL, 2.52 mmol), which was pre-
cooled to 2788C. The resulting solution was stirred at
2788C for 1.5 h to complete enolization. A solution of
nonylaldehyde (0.41 mL, 2.40 mmol) in CH2Cl2 (3 mL)
was added dropwise to the enolate solution and the reaction
mixture was stirred at 2788C for 3 h and at 08C for 2 h. The
reaction was quenched by the addition of pH 7 buffer
solution (5.7 mL) followed by CH3OH (10 mL) and 30%
H2O2 (1 mL). The mixture was stirred overnight vigorously
at room temperature. The resulting solution was extracted
with ether (70 mL£3). The organic extracts were combined,
dried over MgSO4, and concentrated in vacuo. The resulting
crude product was partially purified by silica gel flash
column chromatography (n-hexane/AcOEt¼10:1) to afford
a mixture of aldol products (694 mg, 1.12 mmol, 93%). The
ratio of the diastereomers (94.3:5.7) was determined by
HPLC analysis (DAICEL CHIRALCEL AD 0.46 cm£
25 cm, n-hexane/i-PrOH¼90:10, 1.0 mL/min, 408C). Puri-
fication of the diastereomers by silica gel flash column
chromatography (n-hexane/AcOEt¼10:1) gave compound
4.3.2. (2R, 3R)-3-(Boc-L-allo-Thr-GlyO)-2-methyl-nona-
noyl-N-methyl-L-Leu-L-allo-Ile-L-SerOH (20a). Com-
pound 19a1d (48.9 mg, 56.6 mmol) was dissolved in
CH3OH (1.5 mL). To this solution, Pd(OH)2 (20 wt%,
20.2 mg) was added and the resulting mixture was stirred at
room temperature for 2.5 h under H2 atmosphere. Pd(OH)2
was removed by filtration and the filtrate was evaporated to
give 20a (42.5 mg, 54.9 mmol, 97%) as colorless needles
(mp 104–1068C). 1H NMR (400 MHz, CD3OD, major
conformer) d ppm: 0.87–0.93 (m, 12H), 0.98 (d, 3H, J¼
6.6 Hz), 1.11 (d, 3H, J¼6.8 Hz), 1.18–1.45 (m, 11H), 1.20
(d, 3H, J¼6.2 Hz), 1.45 (s, 9H), 1.52–1.66 (m, 3H), 1.75–
1.82 (m, 1H), 1.90–2.00 (m, 1H), 3.07 (s, 3H), 3.24 (qu, 1H,
J¼6.9 Hz), 3.82 (dd, 1H, J¼3.9, 11.2 Hz), 3.89 (d, 1H, J¼
17.7 Hz), 3.89–4.03 (m, 3H), 4.08 (br d, 1H, J¼5.3 Hz),
4.44–4.50 (m, 2H), 5.10 (dt, 1H, J¼3.6, 7.4 Hz), 5.20 (dd,
1H, J¼5.4, 10.3 Hz); 13C NMR (125 MHz, CD3OD) d ppm:
12.0, 12.8, 14.4, 14.8, 19.4, 22.1, 23.64, 23.66, 26.1, 26.2,
1
3b as a viscous oil (650 mg, 1.05 mmol, 87%). H NMR

T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
1693
(400 MHz, CDCl3, major isomer) d ppm: 0.88 (t, 3H,
J¼6.9 Hz), 1.13 (d, 3H, J¼7.3 Hz), 1.18 (d, 3H, J¼6.8 Hz),
1.26–1.47 (m, 14H), 2.28 (s, 3H), 2.42–2.53 (m, 2H, 1H
D2O exchangeable), 2.48 (s, 6H), 3.59–3.65 (m, 1H), 4.10
(dq, 1H, J¼4.5, 6.9 Hz), 4.54 and 4.76 (AB type d’s, each
1H, J¼16.5 Hz), 5.83 (d, 1H, J¼4.4 Hz), 6.86–6.88 (m,
2H), 6.86 (s, 2H), 7.16–7.30 (m, 8H); 13C NMR (100 MHz,
CDCl3) d ppm: 13.5, 14.11, 14.13, 20.9, 22.7, 22.9, 25.4,
29.3, 29.57, 29.61, 31.6, 31.9, 34.5, 45.5, 48.3, 56.7, 73.2,
78.2, 126.0, 127.2, 127.7, 128.0, 128.3, 128.4, 132.1, 133.4,
138.2, 138.4, 140.3, 142.6, 174.6; IR (CHCl3) cm21: 3619,
3544, 2928, 2856, 1728, 1605, 1456, 1322, 1153, 1012;
HRMS calcd for C37H51O5NSNa (MþNa)þ 644.3386,
found: 644.3378; [a]2D4¼þ20.4 (c 1.55, CHCl3).
24.7, 26.0, 26.3, 26.4, 29.27, 29.33, 29.49, 29.55, 29.66,
29.71, 31.1, 31.6, 31.8, 31.9, 34.4, 35.6, 35.8, 36.8, 37.5,
37.7, 40.9, 41.3, 52.60, 52.62, 56.1, 56.6, 59.2, 66.2, 66.2,
69.5, 73.4, 73.6, 74.5, 75.7, 77.2, 118.76, 118.85, 127.7,
127.91, 127.92, 128.2, 128.5, 128.6, 131.3, 131.4, 136.8,
137.3, 169.3, 169.6, 170.71, 170.74, 170.8, 171.5, 176.8,
178.1; IR (CHCl3) cm21: 3431, 2961, 2930, 2858, 1746,
1672, 1622, 1502, 1464, 1273, 1103, 1048; HRMS calcd for
C38H64O7N3 (MþH)þ 674.4744, found: 674.4724; [a]2D4¼
259.4 (c 1.46, CHCl3).
4.4.4. (2R, 3R)-3-[Boc-L-allo-Thr(TBS)-GlyO]-2-methyl-
undecanoyl-N-methyl-L-Leu-L-allo-Ile-L-Ser(Bn)OAllyl
(16b). To a solution of 15b (244 mg, 0.361 mmol) and
Fragment B1d ((212 mg, 0.542 mmol) in CH2Cl2 (1.5 mL),
were added DMAP (44 mg, 0.36 mmol), CSA (42 mg,
0.18 mmol) followed by DIC (113 mL, 0.722 mmol) at
room temperature. The reaction mixture was stirred at the
same temperature. Moreover, Fragment B and other
reagents were sometimes added in order to finish the
reaction. The mixture was concentrated and diluted with
hexane and EtOAc. The mixture was filtered and washed
with 10% aqueous citric acid, saturated NaHCO3, aqueous
solution and brine. The organic layer was dried over
Na2SO4, filtered and evaporated. The residue was purified
by column chromatography with a gradient elution system,
a 3:1–1:1 mixture of hexane and EtOAc used as eluents
to give 16b (310 mg, 0.296 mmol, 82%) as a colorless
amorphous foam. 1H NMR (400 MHz, CDCl3, two rotamers
(major/minor¼9:1), major conformer) d ppm: 0.02 (s, 3H),
0.05 (s, 3H), 0.78–0.90 (m, 25H), 0.92 (d, 3H, J¼6.6 Hz),
1.08 (d, 3H, J¼6.9 Hz), 1.15 (d, 3H, J¼6.3 Hz), 1.18–1.28
(m, 8H), 1.36–1.43 (m, 3H), 1.42 (s, 9H), 1.55–1.62 (m,
3H), 1.68–1.76 (m, 1H), 1.92–1.98 (m, 1H), 2.97 (s, 3H),
3.06 (t, 1H, J¼6.9 Hz), 3.64 (dd, 1H, J¼3.3, 9.4 Hz), 3.76
(dd, 1H, J¼4.2, 18.4 Hz), 3.89 (dd, 1H, J¼3.0, 9.4 Hz),
4.06–4.16 (m, 3H), 4.39–4.41 (m, 1H), 4.43 and 4.53 (AB
type d’s, each 1H, J¼12.0 Hz), 4.59–4.62 (m, 2H), 4.72 (dt,
1H, J¼3.1, 8.2 Hz), 5.05 (d, 1H, J¼7.6 Hz), 5.08–5.13 (m,
2H), 5.20 (dd, 1H, J¼1.4, 8.5 Hz), 5.28 (dd, 1H, J¼1.4,
16.9 Hz), 5.78–5.89 (m, 1H), 6.61 (d, 1H, J¼8.2 Hz), 6.66–
6.68 (m, 2H), 7.23–7.34 (m, 5H); 13C NMR (100 MHz,
CDCl3) d ppm: 25.0, 24.7, 11.7, 12.2, 14.1, 14.2, 17.9,
19.5, 21.8, 22.6, 23.2, 24.8, 25.1, 25.5, 25.7, 26.3, 28.3,
29.2, 29.3, 29.4, 29.5, 29.9, 30.5, 31.8, 31.9, 35.8, 37.2,
39.9, 41.1, 52.6, 54.3, 56.2, 66.2, 68.7, 69.5, 73.3, 76.4,
77.5, 118.7, 127.7, 127.9, 128.4, 131.5, 137.3, 169.0, 169.6,
170.3, 170.8, 174.4; IR (CHCl3) cm21: 3431, 2959, 2930,
2859, 1743, 1677, 1499, 1369, 1256, 1162, 1106; HRMS
calcd for C55H95O12N5SiNa (MþNa)þ 1068.6644, found:
1068.6702. Anal. Calcd for C55H95O12N5Si·1/2H2O: C,
62.59; H, 9.17; N, 6.64. Found: C, 62.41; H, 8.98; N, 6.80.
[a]2D5¼252.1 (c 1.08, CHCl3).
4.4.2. (2R, 3R)-3-Hydroxy-2-methylundecanoic acid
(A5). A solution of 3b (117 mg, 0.188 mmol) and LiOH·
H2O (47.0 mg, 0.94 mmol) in THF–CH3OH–H2O (1:1:1,
2.7 mL) was stirred at room temperature overnight.
LiOH·H2O (47.0 mg, 0.94 mmol) in H2O (0.5 mL) was
added, and the resulting mixture was stirred for 1 day. The
mixture was poured into water (5 mL) and extracted with
CH2Cl2 to recover the chiral auxiliary. The aqueous layer
was acidified with 10% aqueous KHSO4 solution and
extracted with CH2Cl2. The extracts were washed with brine
and dried with MgSO4. Filtration and concentration gave
1
(þ)-A5 as a colorless oil (36.7 mg, 0.170 mmol, 90%). H
NMR (400 MHz, CDCl3) d ppm: 0.88 (t, 3H, J¼6.8 Hz),
1.20–1.61 (m, 18H), 2.56 (qu, 1H, J¼7.1 Hz), 3.68–3.72
(m, 1H); 13C NMR (100 MHz, CDCl3) d ppm: 14.1, 14.2,
22.7, 25.5, 29.3, 30.0, 31.9, 34.6, 45.2, 73.3, 180.8; IR
(CHCl3) cm21: 3615, 3511, 2928, 2857, 1740, 1704, 1464,
1397, 1380, 1289; HRMS calcd for C12H25O3 (MþH)þ
calcd 217.1804, found: 217.1806; [a]2D3¼þ3.6 (c 1.13,
CHCl3).
4.4.3. (2R, 3R)-3-Hydroxy-2-methyl-undecanoyl-N-
methyl-L-Leu-L-allo-Ile-L-Ser(Bn)OAllyl (15b). Fragment
A5 (192 mg, 0.888 mmol) and Fragment C1d (352 mg,
0.740 mmol) were dissolved in THF (3.0 mL) and then Et3N
(0.52 mL, 3.7 mmol) was added. To the solution was added
DEPC (0.3 mL, 1.85 mmol) at 08C. The reaction mixture
was stirred at 08C for 2 h and at room temperature for an
additional 1 day. After saturated NaHCO3 aqueous solution
was added, the organic layer was separated and the aqueous
layer was extracted with EtOAc. The combined organic
extracts were dried over Na2SO4, filtered and evaporated.
The oil residue was purified by column chromatography
with a 4:1 mixture of hexane and EtOAc used as an eluent
to give 15b (497 mg, 0.296 mmol, 99%) as a pale yellow oil.
1H NMR (400 MHz, CDCl3, two rotamers (major/minor¼
2.4:1)) d ppm: 0.80–0.97 (m, 15H), 1.06–1.22 (m, 2H),
1.22–1.47 (m, 16H), 1.58–1.70 (m, 1H), 1.78–1.85 (m,
2/3H), 1.93–2.01 (m, 4/3H), 2.69–2.77 (m, 2/3H), 2.80p (s,
1H), 2.84–2.93p (m, 1/3H), 2.95 (s, 2H), 3.62 (br, 1H), 3.68
(dd, 1H, J¼3.0, 9.6 Hz), 3.68–3.77 (m, 2H), 3.91–3.95 (m,
1H), 4.56 and 4.47 (AB type d’s, each 1H, J¼12.3 Hz),
4.43–4.68 (m, 11/3H), 4.74–4.78 (m, 4/3H), 5.09 (dd,
2/3H, J¼5.6, 10.0 Hz), 5.22–5.33 (m, 7/3H), 5.81–5.92 (m,
1H), 6.64 (d, 2/3H, J¼8.2 Hz), 6.79–6.84 (m, 1H), 7.24–
7.37 (m, 5H), 7.63p (d, 1/3H, J¼9.6 Hz); 13C NMR
(100 MHz, CDCl3, both rotamers) d ppm: 11.7, 14.1, 14.2,
14.4, 14.8, 14.9, 21.7, 21.8, 22.6, 23.2, 23.4, 24.3, 24.5,
4.4.5. (2R, 3R)-3-(Boc-L-allo-Thr-GlyO)-2-methyl-undeca-
noyl-N-methyl-L-Leu-L-allo-Ile-L-Ser(Bn)OAllyl (18b).
To a solution of 16b (301 mg, 0.288 mmol) in THF
(1.5 mL) was added
a mixture of AcOH (82 mL,
1.43 mmol) and TBAF (1.0 M THF solution, 1.44 mL,
1.44 mmol) at 08C. The solution was stirred at the same
temperature and at room temperature for an additional 22 h.
This reaction mixture was diluted with EtOAc and washed
with a saturated NaHCO3 aqueous solution. The resulting

1694
T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
organic layer was dried over Na2SO4, filtered and
evaporated. The residue was purified by column chroma-
tography with a 1:1 mixture of hexane and EtOAc used as
an eluent to give 18b (225 mg, 0.216 mmol, 94%) as a
same temperature, the solvents were removed in vacuo.
The residue was dissolved in CH2Cl2 and reconcentrated
repeatedly to remove excess TFA. The crude products were
dried under reduced pressure to afford a TFA salt (113 mg)
and which was used for macrocyclization without further
purification. This salt (52.1 mg, 58.0 mmol) was dissolved
in THF (29 mL) and the solution was slowly added to a
suspension of TBTU (185 mg, 0.575 mmol) and DIEA
(200 mL) in THF (29 mL) for over 9 h at room temperature
with a syringe pump under highly diluted condition. After
being stirred at the same temperature for an additional 3
days, the mixture was evaporated, diluted with a 3:1 mixture
of CH3OH and EtOAc and filtered. The filtrate was
concentrated, dissolved in EtOAc and washed with 1%
aqueous HCl solution, saturated NaHCO3 aqueous solution
and then brine. The organic layer was dried over Na2SO4,
filtered and evaporated. The residue was purified by pre-
parative HPLC (column: Develosil ODS-HG5 (10 mm£
250 mm); wavelength: 210 nm; flow rate: 4.0 mL/min) with
an 86:14 mixture of CH3OH and 1% aqueous ammonium
acetate used as an eluent to give 21b (17.6 mg, 22.7 mmol,
1
colorless amorphous foam. H NMR (400 MHz, CDCl3,
major conformer) d ppm: 0.82–0.98 (m, 16H), 0.95 (d, 3H,
J¼6.6 Hz), 1.11 (d, 3H, J¼7.1 Hz), 1.21–1.32 (m, 11H),
1.27 (d, 3H, J¼6.2 Hz), 1.41–1.49 (m, 1H), 1.45 (s, 9H),
1.58–1.66 (m, 3H), 1.73–1.81 (m, 1H), 1.94–1.99 (m, 1H),
3.00 (s, 3H), 3.07 (t, 1H, J¼6.9 Hz), 3.67 (dd, 1H, J¼3.1,
9.5 Hz), 3.74 (br d, 1H, J¼5.9 Hz), 3.92 (dd, 1H, J¼3.1,
9.5 Hz), 3.95 (br s, 1H), 4.03 (br d, 1H, J¼4.9 Hz), 4.08 (br
s, 1H), 4.42–4.46 (m, 1H), 4.46 and 4.56 (AB type d’s, each
1H, J¼12.2 Hz), 4.62–4.64 (m, 2H), 4.75 (dt, 1H, J¼3.1,
8.1 Hz), 5.06 (dd, 1H, J¼5.9, 9.7 Hz), 5.12–5.17 (m, 1H),
5.23 (dd, 1H, J¼1.4, 8.4 Hz), 5.30 (dd, 1H, J¼1.4, 17.6 Hz),
5.48 (d, 1H, J¼7.7 Hz), 5.81–5.91 (m, 1H), 6.67 (d, 1H,
J¼8.1 Hz), 6.73 (d, 1H, J¼8.3 Hz), 6.92 (br, 1H), 7.26–
7.36 (m, 5H); 13C NMR (100 MHz, CDCl3) d ppm: 11.7,
12.6, 14.1, 14.3, 19.8, 20.2, 21.9, 22.6, 23.2, 24.9, 25.1,
26.3, 28.3, 29.2, 29.4, 29.5, 30.3, 31.6, 31.8, 35.9, 37.3,
40.0, 41.3, 52.7, 54.9, 56.3, 66.2, 69.2, 69.5, 73.3, 76.6,
77.5, 118.8, 127.7, 127.9, 128.5, 131.5, 137.4, 169.2, 169.6,
170.75, 170.84, 171.5, 174.5; IR (CHCl3) cm21: 3433,
2961, 2930, 2873, 1744, 1674, 1498, 1369, 1254, 1161;
HRMS calcd for C49H81O12N5Na (MþNa)þ 954.5799,
found: 954.5791; [a]2D5¼269.6 (c 1.43, CHCl3).
1
39% (2 steps)) as a pale yellow solid (mp 57–598C). H
NMR (400 MHz, CDCl3, two rotamers (major/minor¼
3.5:1)) d ppm: 0.86–0.96 (m, 15H), 1.10 (d, 12/5H, J¼
6.9 Hz), 1.16 (d, 3/5H, J¼6.9 Hz), 1.26–1.54 (m, 20H),
1.55–1.67 (m, 1H), 1.70–1.77 (m, 1H), 2.01–2.07 (m, 1H),
2.08–2.18 (m, 1H), 2.79 (s, 3/5H), 3.09–3.14 (m, 1H), 3.17
(s, 12/5H), 3.62 (dd, 4/5H, J¼3.5, 17.1 Hz), 3.68–3.77 (br,
4/5H), 3.79–4.00 (m, 12/5H), 4.02p (t, 1/5H, J¼6.0 Hz),
4.08–4.17 (m, 1H), 4.19–4.23 (m, 4/5H), 4.27–4.29 (m,
4/5H), 4.31–4.47 (m, 2H), 4.53 and 4.57 (AB type d’s, each
1H, J¼11.9 Hz), 4.77p (dd, 1/5H, J¼3.5, 9.3 Hz), 4.84p (br
d, 1/5H, J¼10.6 Hz), 5.10–5.14 (m, 4/5H), 6.82–6.89 (m,
11/5H), 7.18p (br d, 1/5H, J¼8.4 Hz), 7.30–7.38 (m, 5H),
7.63 (br d, 4/5H, J¼5.1 Hz), 7.91 (br, 4/5H); 13C NMR
(100 MHz, CDCl3, both rotamers) d ppm: 11.77, 11.81,
14.1, 14.7, 14.8, 15.1, 19.8, 19.9, 21.8, 22.5, 22.6, 23.08,
23.14, 24.2, 24.8, 25.2, 26.3, 26.9, 27.1, 28.8, 29.2, 29.4,
29.49, 29.54, 29.7, 31.3, 31.8, 31.9, 36.9, 37.5, 38.1, 38.4,
39.5, 40.5, 40.8, 41.3, 55.4, 55.7, 56.2, 56.9, 57.4, 58.0,
59.3, 67.7, 68.0, 73.4, 73.9, 76.6, 78.2, 127.9, 128.2, 128.5,
128.65, 128.72, 136.6, 137.1, 169.1, 169.3, 169.8, 170.1,
170.9, 171.0, 171.5, 172.4, 172.8, 173.9, 174.3, 176.7; IR
(CHCl3) cm21: 3691, 3421, 3342, 2961, 2929, 1666, 1543,
1502, 1468, 1101; HRMS m/z (MþNa)þ calcd 796.4836,
found: 796.4838; [a]2D4¼þ6.9 (c 1.65, CHCl3).
4.4.6. (2R, 3R)-3-(Boc-L-allo-Thr-GlyO)-2-methyl-undeca-
noyl-N-methyl-L-Leu-L-allo-Ile-L-Ser(Bn)OH (19b). Com-
pound 18b (217 mg, 0.233 mmol) and morpholine (46 mL,
0.52 mmol) were dissolved in THF (1.0 mL). To this
solution, was added Pd(PPh3)4 (cat.), and the reaction
mixture was stirred at room temperature for 3 days. The
mixture was concentrated and purified by column chroma-
tography with EtOAc and then 10:1 mixture of CH2Cl2
and CH3OH used as an eluents to give 19b (193 mg,
0.216 mmol, 93%) as a slightly yellow amorphous foam. 1H
NMR (400 MHz, CD3OD, major conformer) d ppm: 0.85–
0.96 (m, 14H), 0.96 (d, 3H, J¼6.6 Hz), 1.10 (d, 3H, J¼
6.8 Hz), 1.20 (d, 3H, J¼6.4 Hz), 1.10–1.49 (m, 14H), 1.45
(s, 9H), 1.58–1.63 (m, 2H), 1.74–1.81 (m, 1H), 1.89–1.99
(m, 1H), 3.06 (s, 3H), 3.23 (qu, 1H, J¼6.8 Hz), 3.75 (dd,
1H, J¼3.6, 9.6 Hz), 3.85–3.96 (m, 1H), 3.88 and 3.96 (AB
type d’s, each 1H, J¼14.6 Hz), 3.98–4.03 (m, 1H), 4.08 (d,
1H, J¼6.0 Hz), 4.44–4.74 (m, 1H), 4.51 and 4.56 (AB type
d’s, each 1H, J¼11.9 Hz), 4.62–4.65 (m, 1H), 5.01 (dt, 1H,
J¼3.9, 7.3 Hz), 5.19 (dd, 1H, J¼5.4, 10.4 Hz), 7.24–7.36
(m, 5H); 13C NMR (100 MHz, CD3OD) d ppm: 11.9, 12.8,
14.4, 14.8, 19.4, 22.1, 23.6, 23.7, 26.1, 26.2, 27.38, 27.45,
28.7, 30.4, 30.59, 30.60, 31.3, 31.6, 33.0, 37.8, 38.5, 41.2,
42.2, 54.1, 55.8, 57.7, 57.8, 61.3, 68.9, 70.7, 74.2, 77.3,
80.8, 128.7, 128.8, 129.4, 139.2, 170.7, 173.0, 173.1, 173.5,
173.6, 176.7; IR (CHCl3) cm21: 3411, 2962, 2930, 2859,
1726, 1666, 1500, 1394, 1370, 1252, 1162; HRMS calcd for
C46H77O12N5Na (MþNa)þ 914.5466, found: 914.5413.
Anal. Calcd for C46H77O12N5·1/2H2O: C, 61.31; H, 8.72;
N, 7.77. Found: C, 61.31; H, 8.64; N, 7.75. [a]2D4¼246.7
(c 1.16, CH3OH).
4.4.8. SF-1902 A5 (1b). Compound 21b (17.8 mg,
0.0230 mmol) was dissolved in CH3OH (0.5 mL). To this
solution, Pd(OH)2 (cat.) was added and the resulting
mixture was stirred at room temperature for 5.5 h under
H2 atmosphere. Pd(OH)2 was removed by filtration and the
filtrate was evaporated. The residue was purified by column
chromatography with a 10:1 mixture of CH2Cl2 and CH3OH
used as an eluent to give 1b (14.2 mg, 0.0208 mmol, 90%)
as colorless needles (mp 100–1028C). 1H NMR (500 MHz,
CDCl3, 16 mM, two rotamers (major/minor¼5.7:1)) d ppm:
0.82–1.05 (m, 17H), 1.09 (d, 18/7H, J¼6.8 Hz), 1.15p (d,
3/7H, J¼6.8 Hz), 1.13–1.42 (m, 15H), 1.48–1.58 (m,
6/7H), 1.61–1.71 (m, 3H), 1.91 (br, 15/7H), 2.00–2.07p
(m, 2/7H), 2.11–2.16 (m, 6/7H), 2.17–2.21 (m, 6/7H),
2.74p (s, 3/7H), 3.01–3.17 (m, 1H), 3.21 (s, 18/7H), 3.63
(br, 6/7H), 3.70 (dd, 6/7H, J¼3.4, 17.1 Hz), 3.85p (dd, 1/7H,
4.4.7. OBn-SF-1902 A5 (21b). To a solution of 19b
(112 mg, 126 mmol) in CH2Cl2 (1.0 mL) was added TFA
(0.5 mL) at room temperature. After being stirred at the

T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
1695
J¼3.9, 18.6 Hz), 3.92 (br, 12/7H), 3.96p (br, 2/7H), 4.05p (d,
1/7H, J¼4.9 Hz), 4.17 (br, 8/7H), 4.23–4.28 (m, 1H), 4.32–
4.41 (m, 12/7H), 4.50–4.54 (m, 1H), 4.76p (dd, 1/7H, J¼
4.4, 9.3 Hz), 4.92p (d, 1/7H, J¼9.8 Hz), 5.09–5.11 (m,
6/7H), 6.91p (d, 1/7H, J¼9.8 Hz), 7.08 (d, 6/7H, J¼6.8 Hz),
7.40p (d, 1/7H, J¼7.8 Hz), 7.46p (br, 1/7H), 7.58–7.65p (m,
1/7H), 7.65 (br, 6/7H), 7.71 (br, 6/7H), 7.67 (br, 6/7H); 13C
NMR (125 MHz, CDCl3, 18 mM, both rotamers) d ppm:
11.7, 12.3, 14.1, 14.6, 14.9, 15.0, 18.8, 19.0, 21.9, 22.6,
22.7, 22.9, 23.1, 24.3, 24.8, 25.2, 25.9, 26.9, 27.1, 29.2,
29.36, 29.43, 29.5, 29.6, 29.7, 31.3, 31.6, 31.8, 36.6, 37.3,
38.1, 38.4, 39.2, 40.2, 40.5, 41.1, 56.2, 56.6, 57.6, 57.8,
57.9, 59.06, 59.15, 60.7, 61.4, 66.8, 67.1, 67.8, 78.0, 168.9,
170.3, 170.7, 170.9, 171.1, 173.2, 173.5, 174.6, 174.7,
176.9; IR (CHCl3) cm21: 3675, 3339, 2962, 2930, 2858,
1736, 1663, 1545, 1467, 1378, 1247, 1190; HRMS calcd for
C34H61O9N5Na (MþNa)þ 706.4367, found: 706.4382.
Anal. Calcd for C34H61N5O9·4/5H2O: C, 58.48; H, 9.04;
N, 10.03. Found: C, 58.37; H, 8.85; N, 9.91. [a]2D5¼27.5 (c
1.10, CHCl3); [a]2D5¼þ20.8 (c 1.04, CH3OH).
8.4 Hz), 4.52, 4.54 and 4.57p (AB type d’s, total 2H, J¼
12.1 Hz), 4.62–4.68 (m, 1H), 4.83–4.87p (m, 1/3H), 5.21
(dd, 2/3H, J¼5.3, 10.2 Hz), 7.24–7.33 (m, 5H); 13C NMR
(100 MHz, CD3OD, both rotamers) d ppm: 14.4, 14.8,
15.22, 15.28, 22.2, 22.5, 23.7, 25.5, 25.9, 26.7, 27.4, 29.9,
30.5, 31.8, 33.0, 35.5, 37.7, 38.0, 38.3, 38.6, 42.5, 43.3,
54.1, 55.9, 57.6, 57.7, 58.8, 58.9, 60.0, 70.7, 74.2, 74.8,
76.2, 128.7, 128.8, 129.4, 139.2, 172.5, 172.6, 172.8, 173.1,
173.2, 173.5, 173.9, 179.2, 179.3; IR (KBr) cm21: 3309,
2959, 2932, 2873, 1736, 1651, 1532, 1456, 1207, 1116;
HRMS m/z (MþK)þ calcd 644.3677, found: 644.3671.
Anal. Calcd for C33H55N3O7·1/2H2O: C, 64.46; H, 9.18; N,
6.83. Found: C, 64.55; H, 8.95; N, 6.79; [a]2D4¼251.2 (c
1.09, CH3OH).
4.5.3. (2R, 3R)-3-Hydroxy-2-methyl-nonanoyl-L-N-
methyl-Leu-L-allo-Ile-L-Ser(OBn)-L-allo-Thr(TBS)-
GlyOBn (25). Compound 23 (59.8 mg, 98.7 mmol) and
compound 24 (40.1 mg, 105 mmol) were dissolved in THF
(1.5 mL) and then Et3N (41 mL, 294 mmol) was added. To
this solution was added DEPC (32 mL, 196 mmol) at 08C.
The reaction mixture was stirred at 08C for 2 h and at room
temperature for an additional 16 h. After saturated NaHCO3
aqueous solution was added, the organic layer was separated
and the aqueous layer was extracted with EtOAc. The
combined organic extracts were dried over Na2SO4, filtered
and evaporated. The oil residue was purified by column
chromatography with a gradient elution system, a 5:1–3:1
mixture of hexane and EtOAc used as eluents to give 25
(92.4 mg, 95.4 mmol, 97%) as a colorless solid (mp 166–
1698C). 1H NMR (400 MHz, CDCl3, major isomer) d ppm:
0.02 (s, 3H), 0.06 (s, 3H), 0.79–0.96 (m, 15H), 0.84 (s, 9H),
1.15 (d, 3H, J¼6.4 Hz), 1.22 (d, 3H, J¼7.1 Hz), 1.27–1.47
(m, 13H), 1.53–1.60 (m, 1H), 1.78–1.85 (m, 1H), 1.90–
2.05 (m, 1H), 2.71–2.74 (m, 1H), 2.93 (s, 3H), 3.56 (dd, 1H,
J¼7.6, 9.2 Hz), 3.61–3.63 (m, 1H), 3.77 (dd, 1H, J¼5.1,
18.2 Hz), 3.84 (dd, 1H, J¼4.5, 9.2 Hz), 3.98 (dd, 1H, J¼5.7,
18.2 Hz), 4.22–4.30 (m, 1H), 4.42 (dd, 1H, J¼4.4, 7.7 Hz),
4.49–4.58 (m, 5H), 5.07 (dd, 1H, J¼5.5, 10.1 Hz), 5.14 (s,
2H), 6.84–4.92 (m, 4H), 7.24–7.39 (m, 10H); 13C NMR
(100 MHz, CDCl3, both rotamers) d ppm: 25.0, 24.7, 11.6,
14.1, 14.3, 14.6, 14.7, 14.8, 16.0, 17.9, 19.5, 19.6, 21.69,
21.74, 22.6, 23.2, 23.4, 24.6, 24.7, 25.7, 25.9, 26.5, 29.2,
29.3, 29.6, 31.2, 31.8, 34.3, 35.7, 36.8, 37.0, 37.4, 41.0,
41.1, 41.7, 52.8, 52.9, 54.9, 56.7, 59.18, 59.24, 65.2, 67.0,
67.1, 68.4, 68.6, 69.3, 73.6, 74.5, 75.5, 127.8, 128.1, 128.4,
128.5, 128.6, 135.3, 137.1, 169.2, 169.4, 169.6, 169.7,
171.2, 171.4, 178.3; IR (KBr) cm21: 3281, 2959,
2931, 2859, 1757, 1640, 1547, 1257, 1123, 834; HRMS
C52H55N5O10K (MþK)þ calcd 1006.5703, found:
1006.5692. Anal. Calcd for C52H85N5O10·1/2H2O: C,
63.90; H, 8.87; N, 7.17. Found: C, 63.86; H, 8.62; N,
7.13; [a]2D4¼243.7 (c 1.04, CHCl3).
4.5. Yamaguchi macrolactonization route
4.5.1. L-allo-Thr(TBS)-GlyOBn (24). To a solution of 81d
(303 mg, 0.630 mmol) in CH2Cl2 (4.0 mL) were added
TBSOTf (290 mL, 1.26 mmol) and 2,6-lutidine (220 mL,
1.89 mmol). After being stirred at room temperature for 1 h,
saturated NH4Cl aqueous solution was added. The organic
layer was separated and the aqueous layer was extracted
with CH2Cl2. The combined organic extracts were dried
over Na2SO4, filtered and evaporated. The residue was
purified by column chromatography with a 30:1 mixture of
CH2Cl2 and CH3OH used as an eluent to give 24 (181 mg,
1
0.474 mmol, 75%) as a colorless oil. H NMR (400 MHz,
CDCl3) d ppm: 0.06 (s, 6H), 0.87 (s, 9H), 1.03 (d, 3H, J¼
6.1 Hz), 3.51 (d, 1H, J¼4.2 Hz), 4.01 (dd, 1H, J¼5.5,
18.3 Hz), 4.11 (dd, 1H, J¼5.9, 18.3 Hz), 4.29 (dq, 1H, J¼
4.2, 6.1 Hz), 5.15 and 5.16 (AB type d’s, each 1H, J¼
12.1 Hz), 7.29–7.37 (m, 5H), 7.77 (br t, 1H, J¼5.1 Hz); 13C
NMR (125 MHz, CDCl3) d ppm: 25.0, 24.7, 17.1, 18.0,
25.8, 40.8, 60.7, 67.1, 68.9, 128.4, 128.5, 128.6, 135.2,
169.7, 173.2; IR (CHCl3) cm21: 3376, 2956, 2931, 2858,
1747, 1670, 1515, 1385, 1358, 1258; HRMS m/z (MþH)þ
calcd 381.2209, found: 381.2205; [a]2D4¼210.7 (c 1.23,
CHCl3).
4.5.2. (2R, 3R)-3-Hydroxy-2-methyl-nonanoyl-L-N-
methyl-Leu-L-allo-Ile-L-Ser(Bn)OH (23). Compound
15a (162 mg, 0.252 mmol) and morpholine (44 mL,
0.505 mmol) were dissolved in THF (4.0 mL). To this
solution was added Pd(PPh3)4 (15.2 mg, 0.013 mmol), and
the reaction mixture was stirred at room temperature for 2.5
days. The mixture was concentrated and purified by column
chromatography with EtOAc and then a 10:1 mixture of
CH2Cl2 and CH3OH used as eluents to give 23 (151 mg,
0.249 mmol, 99%) as a slightly yellow amorphous foam. 1H
NMR (400 MHz, CD3OD, both rotamers) d ppm: 0.86–0.98
(m, 15H), 1.05p (d, 1H, J¼6.6 Hz), 1.10 (d, 2H, J¼6.8 Hz),
1.12–1.23 (m, 1H), 1.31–1.66 (m, 13H), 1.73–1.88 (m,
1H), 1.90–1.99 (m, 1H), 2.75p (s, 1H), 2.90 (qu, 2/3H, J¼
6.9 Hz), 3.01 (s, 2H), 3.04p (dq, 1/3H, J¼2.7, 6.5 Hz), 3.64–
3.71 (m, 1H), 3.75 (dd, 1H, J¼3.6, 9.8 Hz), 3.86p and 3.88
(dd, 1H, J¼5.1, 9.8 Hz), 4.40p and 4.48 (dd, 1H, J¼6.2,
4.5.4. O0TBS-OBn-globomycin (22a). A solution of 25
(30.4 mg, 31.4 mmol) and LiOH·H2O (9.2 mg, 220 mmol) in
THF–CH3OH–H2O (3:1:1, 1.0 mL) was stirred at 08C for
2 h. The mixture was acidified with 10% aqueous KHSO4
solution and extracted with EtOAc. The combined organic
extracts were washed with brine, dried over Na2SO4, filtered
and evaporated. The oil residue was purified by column
chromatography with a gradient elution system, a 20:1–
10:1 mixture of CH2Cl2 and CH3OH used as eluents to give

1696
T. Kiho et al. / Tetrahedron 59 (2003) 1685–1697
the seco-acid (21.6 mg, 29.7 mmol, 95%) as a colorless
1
solid (mp 205–2078C). H NMR (400 MHz, CDCl3, both
24.6, 11.9, 14.17, 14.19, 15.06, 15.15, 15.3, 18.1, 18.4,
19.0, 21.7, 22.6, 22.7, 23.2, 23.3, 24.1, 25.0, 25.3, 25.8,
26.5, 27.0, 27.1, 27.2, 29.07, 29.15, 29.3, 29.4, 29.8, 31.6,
31.7, 31.8, 37.5, 37.6, 38.2, 38.5, 39.6, 40.1, 40.5, 42.1,
56.1, 56.2, 56.3, 56.7, 59.1, 59.3, 59.4, 66.6, 67.0, 67.9,
73.4, 73.8, 76.2, 76.5, 77.2, 78.2, 127.9, 128.0, 128.2, 128.3,
128.4, 128.6, 136.5, 136.6, 168.5, 169.0, 169.1, 169.3,
169.5, 169.7, 171.4, 172.6, 172.8, 174.0, 174.3, 177.0; IR
(KBr) cm21: 3330, 2957, 2928, 2857, 1740, 1656, 1542,
1256, 1118, 834; HRMS calcd for C45H78N5O9Si (MþH)þ
calcd 860.5569, found: 860.5590. Anal. Calcd for
C45H77N5O9Si·2H2O: C, 60.31; H, 9.11; N, 7.81. Found:
C, 60.49; H, 8.77; N, 7.67; [a]2D6¼þ11.9 (c 1.01, CH3OH).
rotamers) d ppm: 0.04 (s, 3H), 0.08 (s, 3H), 0.84–0.98 (m,
15H), 0.87 (s, 9H), 1.05p (d, 1H, J¼6.5 Hz), 1.09 (d, 2H,
J¼6.7 Hz), 1.17 (d, 3H, J¼6.3 Hz), 1.31–1.66 (m, 14H),
1.75–1.83 (m, 1H), 1.84–1.95 (m, 1H), 2.73p (s, 1H), 2.90
(qu, 2/3H, J¼6.9 Hz), 3.01 (s, 2H), 3.04–3.08p (m, 1/3H),
3.61–3.78 (m, 4H), 3.84 and 3.85p (d, 1H, J¼17.8 Hz),
4.15–4.22 (m, 1H), 4.34–4.37p (m, 1/3H), 4.42–4.53 (m,
5/3H), 4.54 and 4.55p (s, 2H), 4.68–4.75 (m, 1H), 5.20 (dd,
2/3H, J¼5.1, 10.4 Hz), 7.24–7.34 (m, 5H); 13C NMR
(100 MHz, CD3OD, both rotamers) d ppm: 24.8, 24.4,
12.0, 14.37, 14.42, 14.9, 15.2, 15.4, 18.8, 20.3, 22.1, 22.6,
23.7, 25.5, 25.8, 26.0, 26.3, 26.7, 27.4, 27.5, 29.9, 30.5,
31.8, 33.0, 33.1, 35.5, 37.7, 38.2, 38.5, 41.8, 42.5, 43.3,
54.4, 55.8, 55.9, 57.8, 57.9, 60.6, 69.9, 70.9, 71.0, 74.4,
74.8, 76.2, 128.8, 128.92, 128.95, 129.5, 139.1, 171.8,
172.2, 173.6, 179.4; IR (KBr) cm21: 3295, 2959, 2931,
2859, 1736, 1642, 1541, 1455, 1120, 834; HRMS calcd for
C45H80N5O10Si (MþH)þ calcd 878.5674, found: 878.5682.
Anal. Calcd for C45H79N5O10Si·1/2H2O: C, 60.92; H, 9.09;
N, 7.89. Found: C, 61.04; H, 8.58; N, 7.90; [a]2D5¼243.2
(c 0.50, CH3OH).
4.6. OBn-Globomycin (21a)1d from 22a
To a solution of 22a (9.4 mg, 10.9 mmol) in THF (0.5 mL),
was added a mixture of AcOH (40 mL, 0.70 mmol) and
TBAF (1.0 M THF solution, 0.5 mL, 0.5 mmol) at 08C. The
solution was stirred at the same temperature for 1 h and at
room temperature for additional 26 h. This reaction mixture
was diluted with EtOAc and washed with a saturated
NaHCO3 aqueous solution. This organic layer was dried
over Na2SO4, filtered and evaporated. The residue was
purified by column chromatography with a gradient elution
system, a 30:1–20:1 mixture of CH2Cl2 and MeOH used as
eluents to give 21a (7.8 mg, 10.4 mmol, 96%) as a colorless
solid.
A solution of the seco-acid (29.7 mg, 33.8 mmol) in THF
(0.7 mL) was treated with 2,4,6-trichlorobenzoyl chloride
(6.9 mL, 44.1 mmol) and Et3N (14 mL, 100 mmol), and
stirred at room temperature for 14.5 h. This mixed
anhydride solution was diluted with toluene (16.1 mL) and
introduced over 5 h via a syringe pump into a refluxed
solution of DMAP (84.1 mg, 688 mmol) in toluene
(17.0 mL). This mixture was refluxed for an additional
3 h. The cooled reaction mixture was evaporated, diluted
with EtOAc, filtered and washed with 5% HCl aqueous
solution, saturated NaHCO3 aqueous solution and then
brine. The organic layer was dried over Na2SO4, filtered and
evaporated. The residue was purified by preparative HPLC
(column: Develosil ODS-HG5 (10 mm£250 mm); wave-
length: 220 nm; flow rate: 4.0 mL/min) with a 94:6 mixture
of CH3OH and 1% aqueous triethylammonium acetate
used as an eluent to give 22a (14.8 mg, 17.2 mmol, 51%) as
a colorless solid (mp 70–728C). 1H NMR (500 MHz,
CDCl3, two rotamers (major/minor¼7:3)) d ppm: 0.059
(s, 21/10H), 0.065p (s, 9/10H), 0.070 (s, 21/10H), 0.08p
(s, 9/10H), 0.84–0.99 (m, 21H), 0.845 (s, 63/10H), 0.855p
(s, 9/10H), 1.07–1.17 (m, 6H), 1.19–1.40 (m, 11H), 1.41–
1.56 (m, 3H), 1.63–1.75 (m, 27/10H), 1.90–1.94 (m, 1H),
2.00–2.02p (m, 3/10H), 2.11–2.14p (m, 3/10H), 2.19–2.24
(m, 7/10H), 2.78p (s, 9/10H), 3.02 (dq, 7/10H, J¼6.9,
9.6 Hz), 3.13–3.16p (m, 3/10H), 3.16 (s, 21/10H), 3.55 (dd,
7/10H, J¼3.7, 17.2 Hz), 3.71 (br s, 7/10H), 3.78 (dd, 7/10H,
J¼6.3, 10.2 Hz), 3.85 (dd, 7/10H, J¼4.8, 10.2 Hz), 3.89p
(dd, 3/10H, J¼5.5, 10.4 Hz), 3.93–3.98 (m, 1H), 4.20–4.23
(m, 7/10H), 4.30 (q, 3/10H, J¼4.6 Hz), 4.39 (dd, 7/10H,
J¼8.9, 17.2 Hz), 4.43–4.49p (m, 18/10H), 4.51 and 4.61
(AB type d’s, each 7/10H, J¼11.8 Hz), 4.55p (dd, 3/10H,
J¼4.6, 7.9 Hz), 4.61–4.65 (m, 14/10H), 4.77p (dd, 3/10H,
J¼3.9, 9.4 Hz), 4.83p (d, 3/10H, J¼10.9 Hz), 5.26–5.31 (m,
7/10H), 6.40 (d, 7/10H, J¼7.7 Hz), 6.45 (d, 7/10H, J¼
2.7 Hz), 6.69–6.73 (m, 6/10H), 6.89p (d, 3/10H, J¼9.4 Hz),
7.05p (t, 3/10H, J¼5.5 Hz), 7.26–7.40 (m, 5H), 7.72 (dd,
7/10H, J¼3.6, 8.7 Hz), 8.22 (br s, 7/10H); 13C NMR
(100 MHz, CDCl3, both rotamers) d ppm: 24.8, 24.7,
Acknowledgements
We thank Drs M. Inukai and S. Miyakoshi (Sankyo Co.,
Ltd.) for the antibacterial assay of globomycin and its
congener, Dr T. Hata, Mr Y. Furukawa and Dr T. Kinoshita
(Sankyo Co., Ltd.) for performing the X-ray crystal-
lographic analysis and Drs K. Ajito and S. Gomi (Meiji
Seika Kaisha, Ltd.) for providing the natural SF-1902 A5.
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