Total syntheses of lyngbyabellins A and B, potent cytotoxic lipopeptides from the marine cyanobacterium Lyngbya majuscula

Article abstract of DOI:10.1016/S0040-4020(02)01224-3

The first total syntheses of lyngbyabellins A and B, Lyngbya majuscula derived lipopeptides, are described. The functionalized thiazole carboxylic acid units were prepared by the oxidative dehydrogenation of the corresponding thiazolidines with chemical manganese dioxide. The asymmetric synthesis of the dichlorinated β-hydroxy acid by a chiral oxazaborolidinone mediated aldol reaction. Finally, fragment condensation followed by macrolactamization provided lyngbyabellin A. The total synthesis of lyngbyabellin B was accomplished by formation of the sensitive thiazoline ring after the macrolactamization.

Full text of DOI:10.1016/S0040-4020(02)01224-3

Tetrahedron 58 (2002) 9445–9458
Total syntheses of lyngbyabellins A and B, potent cytotoxic
lipopeptides from the marine cyanobacterium Lyngbya majuscula
Fumiaki Yokokawa,† Hirofumi Sameshima, Daichi Katagiri, Toyohiko Aoyama
*
and Takayuki Shioiri
Graduate School of Pharmaceutical Sciences, Nagoya City University, Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan
Received 8 March 2002; revised 4 September 2002; accepted 26 September 2002
Abstract—The first total syntheses of lyngbyabellins A and B, Lyngbya majuscula derived lipopeptides, are described. The functionalized
thiazole carboxylic acid units were prepared by the oxidative dehydrogenation of the corresponding thiazolidines with chemical manganese
dioxide. The asymmetric synthesis of the dichlorinated b-hydroxy acid by a chiral oxazaborolidinone mediated aldol reaction. Finally,
fragment condensation followed by macrolactamization provided lyngbyabellin A. The total synthesis of lyngbyabellin B was accomplished
by formation of the sensitive thiazoline ring after the macrolactamization. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
Lyngbyabellin A (1) was isolated from the marine
cyanobacterium Lyngbya majuscula collected at Apra
Harbor, Guam.3 It exhibited attractive cytotoxic properties
against the human cancer cell lines and was shown to be a
potent disrupter of the cellular microfilament network. The
subsequent isolation of lyngbyabellin B (2) was reported
simultaneously from collections of Lyngbya from Guam4a
and the Dry Tortugas National Park, Florida.4b The structure
of lyngbyabellin B (2) is closely related to lyngbyabellin A
(1). The isoleucine-derived unit in 1 is replaced by a valine-
derived moiety in 2, and one thiazole unit in 1 is replaced by
a thiazoline ring in 2. The in vitro cytotoxic activities of 2
are slightly weaker than 1. Interestingly, these novel
Marine cyanobacteria have recently been recognized to be
rich sources of numerous structurally diverse and bio-
logically active secondary metabolites.1 Moreover, as the
rate of re-isolation of known natural products, or the
isolation of metabolites closely related to known com-
pounds from marine cyanobacteria increases, recognition
continues to grow that a substantial number of metabolites
isolated from and attributed to the metabolism of marine
animals, such as sea hares and sponges, actually derive from
marine cyanobacteria. However, often only small quantities
of marine cyanobacteria derived natural products can be
isolated from an exploration site, and many species have
been resistant to laboratory culturing. Therefore, the
evaluation of the biological potential of promising bioactive
compounds frequently has to await the development of a
suitable synthetic route.2
lipopeptides are structurally related to dolabellin (3),5
a
metabolite isolated from the sea hare Dolabella auricularia,
and this striking structural relationship strongly supports a
cyanobacterial origin for the latter metabolite (Fig. 1). The
structural features of lyngbyabellins A and B that attracted
Figure 1. Structures of lyngbyabellins A and B, and dolabellin.
Keywords: lipopeptide; total synthesis; chemical manganese dioxide; macrolactamization.
*
Corresponding author. Address: Graduate School of Environmental and Human Sciences, Meijo University, Shiogamaguchi, Tempaku, Nagoya 468-8502,
Japan. Tel./fax: þ81-52-832-1555; e-mail: shioiri@ccmfs.meijo-u.ac.jp
†
Tsukuba Research Institute, Novartis Pharma K. K., Ohkubo 8, Tsukuba, Ibaraki 300-2611, Japan.
0040–4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)01224-3

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F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
Scheme 1. Retrosynthetic analysis of lyngbyabellin A.
our interest are the functionalized thiazoles and thiazoline
heterocycles, the dichlorinated b-hydroxy acid, and their
cyclic natures. Therefore, their structural uniqueness as well
as interesting biological activities have led us to focus on the
total syntheses of lyngbyabellins A and B. In this paper, we
wish to disclose our synthetic efforts toward lyngbyabellins
A and B.6
macrolactamization at the less hindered C22–C21NH amide
bond was chosen among the two amide bonds to provide
the protected linear precursor 4. The linear peptide 4 was
further divided into the isoleucine-derived thiazole amino
acid (Boc-L-(ile)Thz-OMe, 5), the thiazole derivative 6, the
dichlorinated b-hydroxy acid 7, and Boc-glycine (8).
For the synthesis of lyngbyabellin B (2), as the thiazoline
ring is sensitive under acidic conditions and readily
epimerized at the a-centers attached to the heterocycle
under mild acidic or basic conditions, the final formation of
the thiazoline ring by Wipf’s oxazoline–thiazoline inter-
conversion method7 was employed to give the serine
derived cyclic peptide 9. Macrolactamization at the
C19 –C15NH amide bond of 9 was chosen to avoid
epimerization at the C terminus to provide the linear
2. Synthetic strategy
Our retrosynthetic analysis of lyngbyabellin A (1) is shown
in Scheme 1. For the macrocyclization of the linear
precursor, macrolactamization will be much superior to
macrolactonization due to the higher nucleophilicity of
amino groups compared to hydroxy groups. Therefore,
Scheme 2. Retrosynthetic analysis of lyngbyabellin B.

F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
9447
Scheme 3. Syntheses of Boc-L-(ile)Thz-OMe (5) and Boc-L-(val)Thz-OMe (11).
peptide 10. The linear precursor 10 was further separated
into the valine-derived thiazole amino acid (Boc-L-
(val)Thz-OMe, 11), the dichlorinated b-hydroxy acid 7,
the dihydroxy ester (12), and Boc-D-Ser(DPS)-Gly-OAllyl
(13) (Scheme 2).
ology. Condensation of 3,3-dimethylacrolein (20) with the
cysteine methyl ester gave the corresponding thiazolidine,
which was directly used for the CMD oxidation to afford the
desired thiazole 21 in 7% yield. Although we were unable to
improve the yield of the oxidation due to the instability of
the thiazolidine, the thiazole 21 was obtained in only two
steps from the commercially available aldehyde 20.
Alternatively, we synthesized the thiazole 21 via the
thiazoline 25 from the cysteine N-amide 24. The fully
protected cysteine N-amide 24 was prepared from
(R)-Fmoc-S-trityl cysteine (22) through (1) methyl ester-
ification using TMSCHN2,13 (2) deprotection of the Fmoc
group, and (3) coupling with 3-methylcrotonic acid (23)
using DEPC in 65% yield. The titanium(IV)-mediated
tandem deprotection–dehydrocyclization of 2414 produced
the thiazoline 25 in 88% yield, which was dehydrogenated
3. Synthesis of the thiazole fragments
Since we have developed the synthesis of thiazolidines from
N-protected a-amino aldehydes and cysteine methyl ester
which were subsequently dehydrogenated to thiazoles using
chemical manganese dioxide (CMD) manufactured indust-
rially for batteries,8,9 we applied this methodology to the
synthesis of the thiazole amino acid fragments 5, 11. The
N-Boc protected a-amino aldehydes were prepared by
coupling the corresponding N-Boc protected a-amino acids
14, 15 with N,O-dimethylhydroxyl amine using diethyl
phosphorocyanidate (DEPC, (EtO)2P(O)CN),10 followed by
reduction with lithium aluminum hydride.11 Condensation
of the amino aldehydes with cysteine methyl ester smoothly
afforded the thiazolidines 18, 19 as a mixture of C-2
epimers. Subsequent oxidation of the thiazolidines 18 and
19 to the thiazoles 5 and 11 was, respectively, performed
with CMD, which was activated by azeotropic removal of
water with benzene (Scheme 3).12
15
with 1,8-diazabicyclo[5.4.0]-7-undecene (DBU)/BrCCl3
to give the thiazole 21 in 81% yield. Replacement of the
methyl ester function with the trimethylsilylethyl (TMSE)
one quantitatively afforded 26 in two steps. Asymmetric
dihydroxylation16 of the thiazole 26 with Sharpless’
AD-mix-b in the presence of methanesulfonamide gave
the required a,b-dihydroxy thiazole fragment 6 with 91%
enantiomeric excess (ee)17 in 90% yield (Scheme 4).
4. Synthesis of the dichlorinated b-hydroxy acid
Next, we attempted the synthesis of the a,b-dihydroxy
thiazole fragment 6 according to the same CMD method-
The stereoselective synthesis of the dichlorinated
Scheme 4. Synthesis of the a,b-dihydroxy thiazole 6.

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F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
Scheme 5. Synthesis of the dichlorinated b-hydroxy acid 7.
b-hydroxy acid fragment was achieved by the enantio-
selective aldol reaction developed by Kiyooka.18 The aldol
reaction of the aldehyde 275 with commercially available
methyl trimethylsilyl ketene acetal (28) using a stoichio-
metric amount of the chiral oxazaborolidinone 29 derived
from (R)-valine in THF proceeded to give the (S)-b-hydroxy
ester 30 with 97% ee in 58% yield.19 Although the 3S
stereochemistry of the b-hydroxy acid residue, obtained by
hydrolysis of one of methanolysis products of natural
products, has been determined from the close compatibility
of its [a]D with that of (S)-3-hydroxy-2,2-dimethyl-octanoic
acid, we confirmed the absolute stereochemistry of the
synthetic 30 by transformation into the corresponding (S)
and (R)-MTPA esters, and comparison of the 1H NMR
spectra as shown in Fig. 2.20 Due to the diamagnetic effect
of the benzene ring, Dd values (dS2dR ppm) on the right
side of the MTPA plane must have positive values (Dd.0)
and D values on the left side of the plane must have negative
values (Dd,0). These results established that the absolute
stereochemistry of 30 was S. Finally, replacement of
the methyl ester with the allyl ester provided the desired
b-hydroxy acid fragment 7 in 94% yield (Scheme 5).
5. Total synthesis of lyngbyabellin A
The total synthesis of lyngbyabellin A (1) was initiated by
deprotection of the Boc group in 5 with hydrogen chloride
Figure 2. Dd (dS2dR) values (ppm) obtained from 1H NMR spectral data in
CDCl3.
Scheme 7. Synthesis of the a,b-dihydroxy ester (12).
Scheme 6. Total synthesis of lyngbyabellin A (1).

F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
9449
the a,b-dihydroxy thiazole fragment 6 was accomplished
under Keck conditions21 to produce the linear precursor 33
in 64% yield. Finally, after removal of the TMSE group at
the C terminus of 33 by tetra n-butylammonium fluoride
(TBAF) and then deprotection of the Boc group at the N
terminus with p-toluenesulfonic acid (TsOH), the macro-
lactamization was efficiently achieved using diphenyl
phosphorazidate (DPPA, (PhO)2P(O)N3)10,22 in the pre-
sence of sodium hydrogen carbonate to provide lyngbya-
bellin A (1) in 58% yield. The 1H and 13C NMR spectra as
well as the specific rotation of our synthetic lyngbyabellin
A (1) were completely identical with those published for
the natural product (Scheme 6).
Scheme 8. Synthesis of Boc-D-Ser(DPS)-Gly-OAllyl (13).
followed by coupling with Boc-glycine (8) using DEPC to
give the dipeptide 31 in 65% yield. Ester saponification of
31 followed by condensation with the b-hydroxy acid
fragment 7 using dicyclohexyl carbodiimide (DCC) in the
presence of N,N-(dimethylamino)pyridine (DMAP) pro-
duced the depsipeptide 32 in 90% yield. After cleavage of
the allyl ester in 32 with Pd(Ph3P)4 in the presence of
morpholine, coupling of the resulting carboxylic acid with
6. Total synthesis of lyngbyabellin B
For the total synthesis of lyngbyabellin B (2), it was
Scheme 9. Total synthesis of lyngbyabellin B (2).

9450
F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
necessary to prepare the remaining two fragments 12 and 13
before the segment condensation.
recorded on a SHIMADZU FT IR-8100 spectrometer.
Optical rotations were measured on a DIP-1000 digital
polarimeters with a sodium lamp (l¼589 nm, D line) and
are reported as follows: [a]TD (cg/100 mL, solvent).
The Sharpless AD reaction of benzyl 3,3-dimethyl acrylate
(34) provided the known diol 35,23 which was subjected
to hydrogenolysis conditions followed by re-protection
with the allyl group to give the required diol fragment 12
(Scheme 7).
1H NMR spectra were recorded on a JEOL EX-270
(270 MHz) or ALPHA 500 (500 MHz) spectrometer.
Chemical shifts are reported in ppm from tetramethylsilane
as the internal standard. Data are reported as follows:
chemical shift, integration, multiplicity (s¼singlet, d¼
doublet, t¼triplet, q¼quartet, br¼broad, m¼multiplet),
coupling constants (Hz), and assignment. Lyngbyabellin
numbering is used for assignments on all intermediates. 13C
NMR spectra were recorded on a JEOL EX-270 (67.8 MHz)
or ALPHA 500 (125.7 MHz) spectrometer with complete
proton decoupling. Chemical shifts are reported in ppm
from tetramethylsilane with the solvent as the internal
standard (chloroform: d 77.0 ppm).
The dipeptide 13 was prepared by coupling Boc-D-Ser-OH
(36) with HCl·H-Gly-OAllyl (37) using DEPC and protec-
tion of the alcohol with a DPS (tert-butyldiphenylsilyl)
group (Scheme 8).
The stage was now set for the total synthesis of
lyngbyabellin B. Saponification of the methyl ester in 11
followed by esterification with b-hydroxy ester 7 using
DCC-DMAP conditions afforded the ester 39 in 91% yield.
After removal of the allyl ester in 39, the initial attempt of
the coupling with diol 12 using Keck conditions gave a
complex mixture. After considerable experimentation, we
found that Yamaguchi’s esterification protocol24 was
suitable for this condensation to afford the coupled product
40 in 66% yield. Deprotection of the allyl group in 40 and
the Boc group in 13 followed by coupling of the two
deprotected fragments using DEPC afforded the protected
linear peptide 41 in 90% yield. Deprotection of the allyl
ester at the C terminus of 41, acidic cleavage of the Boc
group at the N terminus, and then the macrolactamization
using pentafluorophenyl diphenylphosphinate (FDPP)25
afforded the macrocycle 42 in 59% yield, which was
subjected to desilylation of the serine residue with TBAF to
provide 43 in 86% yield. After cyclodehydration of the
serine residue in 43 with (diethylamino)sulfur trifluoride
(DAST) to the oxazoline 44,26 we applied Wipf’s oxazo-
line–thiazoline interconversion protocol for the conversion
of 44 to the target heterocycle 2.7 Thiolysis of the oxazoline
44 with hydrogen sulfide in a solution of methanol/
triethylamine (2:1) provided the thioamide intermediate
45 in 89% yield. Finally, a second cyclodehydration with
DAST27 proceeded to the desired lyngbyabellin B (2) in
99% yield. The synthetic lyngbyabellin B was identical in
all respects with spectra provided for the natural product
(Scheme 9).
Analytical thin layer chromatography were performed on
Merck Art. 5715, Kieselgel 60F254/0.25 mm thickness
plates. Visualization was accomplished with UV light,
phosphomolybdic acid, or ninhydrin solution followed by
heating. Preparative thin layer chromatography were
performed on Merck Art. 5744, Kiselgel 60F254/0.5 mm
thickness plates. Elementary analysis (Anal) and high-
resolution mass spectra (HRMS) were performed at the
Analytical Facility at Nagoya City University.
Solvents for extraction and chromatography were reagent
grade. Liquid chromatography was performed with forced
flow (flash chromatography of the indicated solvent mixture
on silica gel BW-820MH or BW-200 (Fuji Silysia Co.)).
Tetrahydrofuran (THF) was distilled from sodium metal/
benzophenone ketyl. Diethyl ether was distilled from
lithium aluminum hydride. Dichloromethane (CH2Cl2)
and hexamethylphosphoramide (HMPA) were distilled
from calcium hydride. Toluene, acetonitrile (CH3CN), and
˚
N,N-dimethylformamide (DMF) were dried over 4 A
molecular sieves. Triethylamine and N,N-diisopropylethyl-
amine were dried over potassium hydroxide. All other
commercially available reagents were used as received.
8.1.1. N a-(t-Butoxycarbonyl)-L-isoleucine N-methoxy-
N-methylamide (16). To a solution of Boc-L-Ile-OH (14)
(10 g, 43.2 mmol) and N,O-dimethylhydroxylamine hydro-
chloride (4.6 g, 47.2 mmol) in DMF (130 mL) at 08C were
successively added dropwise DEPC (7.2 mL, 47.5 mmol)
and triethylamine (13.2 mL, 95.1 mmol). The resulting
solution was stirred at 08C for 2 h and at room temperature
for 12 h. After dilution with EtOAc, the mixture was washed
with 1 M aq. KHSO4, water, sat. aq. NaHCO3, water, and
brine. The organic layer was dried (Na2SO4), filtered, and
concentrated. The residue was purified by silica gel column
chromatography (hexane/EtOAc¼3:1) to afford the desired
product 16 as a colorless oil (9.6 g, 81%): 1H NMR
spectrum was identical with the reported data (Ref. 11).
7. Conclusion
In summary, we achieved the first total syntheses of the
structurally and biologically attractive lyngbyabellins A and
B. Our syntheses involve the oxidative dehydrogenation of
thiazolidines to thiazoles using CMD, efficient fragment
condensation, macrolactamization, and finally formation of
the sensitive thiazoline ring. This strategy will be useful for
the synthesis of other heterocycle containing cyclic peptides.28
8. Experimental
8.1.2. N a-(t-Butoxycarbonyl)-L-valine N-methoxy-N-
methylamide (17). According to the procedure for the
synthesis of 16, Boc-L-Val-OH (15) (10 g, 46.0 mmol)
provided 17 as a colorless oil (10.2 g, 85%): 1H NMR
spectrum was identical with the reported data (Ref. 11).
8.1. General information
Melting points were measured on a YANACO melting point
apparatus and are uncorrected. Infrared spectra were

F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
9451
8.1.3. 2-[(1S,2S)-1-tert-Butoxycarbonylamino-2-methyl-
butyl]-thiazolidin-4-carboxylic acid methyl ester (18).
To a solution of the amide 16 (9.21 g, 33.6 mmol) in ether
(100 mL) at 08C was added LiAlH4 (1.59 g, 41.9 mmol).
The resulting solution was stirred at 08C for 15 min and
quenched by dropwise addition of 1 M aq. KHSO4. The
mixture was extracted with ether (£3). The combined
organic extracts were washed with brine, dried (Na2SO4),
filtered, and concentrated to afford the aldehyde (6.95 g,
32.3 mmol). The aldehyde and HCl·H-L-Cys-OMe (6.10 g,
35.5 mmol) were dissolved in toluene (100 mL), and to this
suspension was added triethylamine (6.7 mL, 48.3 mmol)
at 08C. The resulting suspension was stirred at room
temperature for 3 h, filtered, and concentrated. The residue
was purified by silica gel column chromatography
(hexane/EtOAc¼3:1) to afford the desired product 18 as a
yellow oil (7.65 g, 69%), which was used for the next step.
The NMR and thin-layer chromatography reveal 18 is a
mixture of C-2 epimers.
5.59 mmol), DEPC (0.85 mL, 5.60 mmol) and triethylamine
(1.56 mL, 11.2 mmol) were sequentially added at 08C and
the resulting mixture was stirred at room temperature
overnight. After dilution with EtOAc, the mixture was
washed with 1 M aq. KHSO4, water, sat. aq. NaHCO3,
water, and brine. The organic layer was dried (Na2SO4),
filtered, and concentrated. The residue was purified by silica
gel column chromatography (hexane/EtOAc¼8:1) to afford
the desired product 24 as a white solid (1.54 g, 65%):
[a]2D3¼þ14.0 (c 1.0, CHCl3); IR n
(cm21) 3330, 1728,
KBr
max
1667, 1634, 1518, 1504, 1489; 1H NMR (270 MHz, CDCl3)
d 1.86 (3H, s, CH3), 2.13 (3H, s, CH3), 2.66 (2H, d, J¼
5.1 Hz, Cys-CbH2), 3.71 (3H, s, CO2CH3), 4.62–4.69 (1H,
m, Cys-CaH), 5.54 (1H, s, (CH3)2CvCH–), 5.80 (1H, d,
J¼7.6 Hz, NH), 7.21–7.39 (15H, m, PhH); 13C NMR
(67.8 MHz, CDCl3) d 20.0, 27.3, 34.0, 50.7, 52.6, 66.8,
117.8, 126.7, 127.8, 129.3, 144.1, 152.2, 165.9, 171.0;
HRMS (EI) m/z calcd for C9H14NO3S: 216.0694 (Mþ2Tr).
Found: 216.0711. Calcd for C19H15: 243.1174 (Trþ). Found:
243.1167.
8.1.4. 2-[(1S)-1-tert-Butoxycarbonylamino-2-methyl-
propyl]-thiazolidin-4-carboxylic acid methyl ester (19).
According to the procedure for the synthesis of 18, the
amide (17) (10.2 g, 39.1 mmol) provided 18 as a white solid
(9.97 g, 65%), which was used for the next step. The NMR
and thin-layer chromatography reveal 19 is a mixture of C-2
epimers.
8.1.8. (4R)-2-(2-Methyl-propenyl)-4,5-dihydro-thiazole-
4-carboxylic acid methyl ester (25). A solution of the
cysteine N-amide 24 (315 mg, 0.69 mmol) in CH2Cl2
(14 mL) was treated with TiCl4 (2.1 mL of a 1.0 M solution
in CH2Cl2, 2.1 mmol) at 08C and stirred at room
temperature for 12 h. The reaction mixture was quenched
with cold sat. aq. NaHCO3. The aqueous layer was extracted
with CHCl3 and the combined organic extracts were dried
(MgSO4), filtered, and concentrated. The residue was
purified by silica gel column chromatography (hexane/
EtOAc¼8:1) to afford the desired product 25 as an orange
oil (96 mg, 88%), which was immediately used for the next
step. 25: [a]2D3¼þ62.1 (c 1.1, CHCl3); IR nmneaaxt (cm21) 3342,
1730, 1651, 1645, 1597, 1437; 1H NMR (270 MHz, CDCl3)
d 1.90 (3H, s, CH3), 2.09 (3H, s, CH3), 3.46–3.71 (2H, m,
thiazoline–C5H2), 3.80 (3H, s, CO2CH3), 5.12 (1H, t,
J¼9.0 Hz, thiazoline–C4H), 6.06 (1H, s, (CH3)2CvCH–).
8.1.5. Boc-L-(ile)Thz-OMe (5). A suspension of CMD
(89.6 g, 103 mmol) in benzene (100 mL) was refluxed with
stirring for 2 h using Dean–Stark apparatus (molecular
sieves type 4 A). To the resulting suspension was added a
solution of the thiazolidine 18 (3.43 mg, 10.3 mmol) in
benzene (5 mL), and then the mixture was stirred at 558C for
2 h. The resulting mixture was filtered through the pad of
celite and the filtrate was concentrated. The residue was
purified by silica gel column chromatography (hexane/
EtOAc¼3:1) to afford the thiazole 5 as a pale yellow oil
1
(1.57 g, 47%): H NMR spectrum was identical with the
reported data (Ref. 8a).
8.1.9. 2-(2-Methyl-propenyl)-thiazole-4-carboxylic acid
methyl ester (21). To a solution of the thiazoline 25
(233 mg, 1.17 mmol) in CH2Cl2 (3.9 mL) at 08C were
successively added BrCCl3 (0.14 mL, 1.42 mmol) and DBU
(0.21 mL, 1.40 mmol). The reaction mixture was stirred at
room temperature for 12 h. The mixture was diluted with
EtOAc, washed with sat. aq. NH4Cl, water, and brine, dried
(Na2SO4), filtered, and concentrated. The residue was
purified by silica gel column chromatography (hexane/
EtOAc¼6:1) to afford the desired product 21 as white
8.1.6. Boc-L-(val)Thz-OMe (11). According to the pro-
cedure for the synthesis of 5, the thiazolidine (19) (1 g,
2.53 mmol) provided 11 as white crystals (650 mg, 65%):
1H NMR was identical with the reported data (Ref. 8a).
8.1.7. (2R)-2-(3-Methyl-but-2-enoylamino)-3-tritylsulfa-
nyl-propionic acid methyl ester (24). A solution of
N a-Fmoc-Cys(S-trityl)-OH (22) (3.0 g, 5.12 mmol) in
MeOH/benzene (26 mL; 1:4) was treated with TMSCHN2
(3.1 mL of 2.0 M solution in hexanes, 6.2 mmol) at room
temperature and the reaction progress was monitored by
TLC (ca. 30 min). The reaction mixture was concentrated
and the crude reaction mixture was used in the next step
without purification.
crystals (188 mg, 81%): mp 81–828C (EtOAc/hexane); IR
KBr
max
n
(cm21) 1715, 1640, 1493, 1456, 1435, 1325, 1246,
1
1281; H NMR (270 MHz, CDCl3) d 2.01 (3H, s, CH3),
2.15 (3H, s, CH3), 3.95 (3H, s, CO2CH3), 6.65 (1H, s,
(CH3)2CvCH–), 8.10 (1H, s, Thz-H); 13C NMR
(67.8 MHz, CDCl3) d 20.8, 27.6, 52.4, 119.3, 126.1,
144.2, 146.1, 161.9, 166.0; HRMS (EI) m/z calcd for
C9H11NO2S: 197.0510. Found: 197.0510.
Diethylamine (30.7 mL, 6 mL/mmol) was added to a
solution of the crude methyl ester in CH3CN (31 mL) and
the resulting mixture was stirred at room temperature for
30 min to ensure complete removal of the Fmoc protecting
group. After concentration, the mixture was azeotroped to
dryness with CH3CN (£2) and the residue was dissolved
in DMF (17 mL). 3,3-Dimethylacrylic acid (560 mg,
8.1.10. 2-(2-Methyl-propenyl)-thiazole-4-carboxylic acid
trimethylsilylethyl ester (26). To a solution of the ester 21
(93 mg, 0.40 mmol) in THF (1.6 mL) at 08C was added a
0.5 M aq. LiOH (1.6 mL, 0.8 mmol). The resulting mixture
was stirred at 08C for 15 min and at room temperature for

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F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
1 h. The reaction was quenched by the addition of 1 M aq.
KHSO4, and the resulting mixture was extracted with
CHCl3 (£3). The combined organic extracts were dried
(Na2SO4), filtered, and concentrated to afford the carboxylic
acid (84 mg), which was used for the next step without
purification.
(MgSO4), filtered, and concentrated. The residue was
purified by silica gel column chromatography (hexane/
EtOAc¼15:1) to afford the desired product 30 as a white
solid (629 mg, 58%, 97% ee). The ee of 30 (10.7 mg) was
1
determined by H NMR analysis in the presence of chiral
shift reagent Eu(hfc)3 (8.0 mg). 30: mp 49–508C; [a]2D3¼
220.0 (c 0.13, MeOH) (Ref. 3: [a]2D7¼210.0 (c 0.13,
(cm21
)
max
neat
To a solution of the carboxylic acid, 2-trimethylsilylethanol
(0.060 mL, 0.42 mmol), and DMAP (1 mg, 0.008 mmol) in
toluene (1.5 mL) at 08C was added DCC (103 mg,
0.44 mmol). After being stirred at room temperature for
1 h, the mixture was diluted with ether and filtered through a
pad of celite. The filtrate was concentrated, and purified by
silica gel column chromatography (hexane/EtOAc¼20:1) to
MeOH)), [a]2D3¼217.1 (c 1.0, CHCl3); IR n
3517, 1723, 1470, 1464; 1H NMR (270 MHz, CDCl3) d 1.18
(3H, s, C2–CH3), 1.21 (3H, s, C2–CH3), 1.37–1.60 (2H, m,
C5–CH2), 1.74 (1H, m, C6–CH2), 1.95 (1H, m, C6–CH2),
2.15 (3H, s, C8–CH3), 2.25 (2H, dt, J¼10.8, 5.3 Hz,
C4–CH2), 2.56 (1H, d, J¼6.7 Hz, OH), 3.61–3.67 (1H, m,
C3–CH), 3.71 (3H, s, CO2CH3); 13C NMR (67.8 MHz,
CDCl3) d 20.4, 22.5, 23.1, 30.9, 37.3, 47.2, 49.6, 52.1, 76.4,
90.6, 178.0; Anal. calcd for C11H20Cl2O3: C, 48.72; H, 7.43.
Found: C, 48.71; H, 7.37.
afford the desired product 26 as a white powder (118 mg,
KBr
max
quant.): mp 62–638C; IR n
(cm21) 1719, 1644, 1458,
1204; 1H NMR (270 MHz, CDCl3) d 0.08 (9H, s, (CH3)3Si),
1.16 (2H, t, J¼8.6 Hz, TMSCH2CH2), 2.00 (3H, s, CH3),
2.15 (3H, s, CH3), 4.45 (2H, t, J¼8.6 Hz, TMSCH2CH2),
6.64 (1H, s, (CH3)2CvCH–), 8.05 (1H, s, Thz-H); 13C
NMR (67.8 MHz, CDCl3) d 21.4, 17.6, 20.9, 27.7, 63.7,
119.3, 125.7, 144.0, 146.8, 161.6, 165.9; HRMS (EI) m/z
calcd for C13H21NO2SSi: 283.1062. Found: 283.1058.
8.1.13. (S)-MTPA ester of 30. To a solution of 30 (7.4 mg,
0.027 mmol) and (S)-MTPA (25.6 mg, 0.109 mmol) in
toluene (0.2 mL) at 08C were added DMAP (14.7 mg,
0.12 mmol) and DCC (24.8 mg, 0.12 mmol). After being
stirred at room temperature for 4 days, the mixture was
diluted with ether and filtered through a pad of celite.
The filtrate was concentrated, and purified by silica gel
column chromatography (hexane/EtOAc¼10:1) to afford
8.1.11. 2-[(1S)-1,2-Dihydroxy-2-methyl-propyl]-thiazole-
4-carboxylic acid 2-(trimethylsilyl)ethyl ester (6). To a
solution of the thiazole 26 (29.7 mg, 0.105 mmol) in
tert-butanol/water (1 mL, 1:1) at 08C were added methane-
sulfonamide (10 mg, 0.105 mmol) and AD-mix-b (147 mg).
The reaction mixture was stirred at 08C for 35 h, and then
sodium sulfite was added as solid and the mixture was
stirred for 30 min. The mixture was extracted with EtOAc,
and the extracts were washed with 1 M aq. KHSO4 and
brine, dried (Na2SO4), filtered, and concentrated. The
residue was purified by silica gel column chromatography
(hexane/EtOAc¼2:1) to afford the desired product 6 as a
colorless oil (29.9 mg, 90%, 91% ee). The ee of 6 was
determined by chiral HPLC on a ChiralPak AS column
(hexane/isopropanol¼50:1; flow rate¼1.0 mL/min, reten-
tion time 15.3 min, 18.2 min). 6: [a]2D4¼218.1 (c 0.7,
CHCl3); IR nnmeaaxt (cm21) 3410, 1715, 1485, 1383, 1250; 1H
NMR (270 MHz, CDCl3) d 0.08 (9H, s, (CH3)3Si), 1.14 (2H,
t, J¼8.4 Hz, TMSCH2CH2), 1.20 (3H, s, CH3), 1.33 (3H, s,
CH3), 3.12 (1H, brs, OH), 4.00 (1H, br, OH), 4.43 (2H, t,
J¼8.4 Hz, TMSCH2CH2), 4.85 (1H, d, J¼4.9 Hz, CH), 8.12
(1H, s, Thz-H); 13C NMR (67.8 MHz, CDCl3) d 21.3, 17.5,
25.2, 25.5, 63.8, 73.0, 77.6, 127.7, 146.4, 161.4, 172.4;
Anal. calcd for C13H23NO4SSi: C, 49.18; H, 7.30; N, 4.41.
Found: C, 49.13; H, 7.41; N, 4.35.
1
the (S)-MTPA ester as a colorless oil (13 mg, 98%): H
NMR (270 MHz, CDCl3) d 1.18 (3H, s, C2–CH3), 1.19 (3H,
s, C2–CH3), 1.56–1.64 (5H, m, C4, C5, C6–CH2), 2.08 (3H,
s, C8–CH3), 2.22–2.31 (1H, m, C4–CH2), 3.53 (3H, s,
OCH3), 3.65 (3H, s, CO2CH3), 5.48 (1H, d, J¼7.9 Hz,
C3–CH), 7.26–7.56 (5H, m, PhH); 13C NMR (67.8 MHz,
CDCl3) d 20.9, 21.5, 22.4, 29.8, 37.3, 46.6, 49.3, 52.2, 55.4,
79.6, 90.0, 121.1, 127.5, 128.4, 129.6, 131.6, 165.9, 175.5.
8.1.14. (R)-MTPA ester of 30. According to the procedure
for the synthesis of (S)-MTPA ester, 30 (9.3 mg, 0.034
mmol) provided (R)-MTPA ester as a colorless oil (15 mg,
91%): 1H NMR (270 MHz, CDCl3) d 1.17 (6H, s, C2–CH3£
2), 1.56–1.68 (5H, m, C4, C5, C6–CH2), 2.08 (3H, s,
C8–CH3), 2.25–2.34 (1H, m, C4–CH2), 3.53 (3H, s,
OCH3), 3.65 (3H, s, CO2CH3), 5.49 (1H, d, J¼9.1 Hz,
C3–CH), 7.26–7.57 (5H, m, PhH); 13C NMR (67.8 MHz,
CDCl3) d 20.4, 21.7, 22.5, 30.1, 37.2, 46.7, 49.2, 52.2, 55.3,
79.5, 90.0, 127.4, 128.4, 129.5, 131.7, 165.9, 175.4.
8.1.15. (3S)-7,7-Dichloro-3-hydroxy-2,2-dimethyl-octa-
noic acid allyl ester (7). To a solution of the ester 30
(41 mg, 0.151 mmol) in methanol (0.2 mL) at 08C was
added 4N aq. NaOH (0.2 mL, 0.8 mmol). The reaction
mixture was stirred at 08C for 30 min, and then at room
temperature for 11.5 h. The reaction was quenched by the
addition of 1N HCl and the mixture was extracted with
ether. The organic extracts were washed with brine, dried
(MgSO4), filtered, and concentrated to afford the carboxylic
acid (45 mg).
8.1.12. (3S)-7,7-Dichloro-3-hydroxy-2,2-dimethyl-octa-
noic acid methyl ester (30). To a solution of N-tosyl-D-
Val-OH (1.19 g, 4.38 mmol) in THF (40 mL) at room
temperature under Ar was added BH3–THF (4.4 mL of
1.0 M solution in THF, 4.4 mmol). The solution was stirred
at room temperature for 30 min. To the resulting solution
were successively added the aldehyde 275 (676 mg,
4.00 mmol) and 1-(trimethylsiloxy)-1-methoxy-2-methyl-
1-propene (28) (0.89 mL, 4.38 mmol) at 2788C. After being
stirred at 2788C for 1 h, the reaction mixture was quenched
by the addition of pH 7 buffer solution. The mixture was
extracted with ether (£1), and the organic layer was washed
with sat. aq. NaHCO3 and brine. The organic layer was dried
The hydroxy acid was dissolved in DMF (0.5 mL), and
KHCO3 (31 mg, 0.31 mmol) was added, followed by the
addition of allyl bromide (0.018 mL, 0.212 mmol). The
mixture was stirred at room temperature for 10 h. After
dilution with ether, the mixture was washed with with 1 M
aq. KHSO4, water, sat. aq. NaHCO3, water, and brine. The

F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
9453
organic layer was dried (MgSO4), filtered, and concentrated.
The residue was purified by silica gel column chroma-
tography (hexane/EtOAc¼10:1) to afford the desired
product 7 as a colorless oil (42 mg, 94%): [a]2D4¼216.8 (c
1.1, CHCl3); IR nmneaaxt (cm21) 3517, 1717, 1649, 1470, 1271,
1169, 1138, 1105; 1H NMR (270 MHz, CDCl3) d 1.20
(3H, s, C2–CH3), 1.22 (3H, s, C2–CH3), 1.37–1.56 (2H, m,
C5–CH2), 1.75 (1H, m, C6–CH2), 1.91–2.04 (1H, m,
C6–CH2), 2.15 (3H, s, C8–CH3), 2.22 (2H, dt, J¼10.6,
5.2 Hz, C4–CH2), 2.55 (1H, d, J¼6.4 Hz, OH), 3.66
(1H, br, C3–CH), 4.60 (2H, d, J¼5.4 Hz, CH2CHvCH2),
5.23–5.36 (2H, m, CH2CHvCH2), 5.84–5.99 (1H, m,
CH2CHvCH2); 13C NMR (67.8 MHz, CDCl3) d 20.4, 22.4,
23.1, 30.9, 37.3, 47.2, 49.6, 65.3, 76.4, 90.6, 118.3, 131.8,
177.1; Anal. calcd for C13H22Cl2O3: C, 52.53; H, 7.46.
Found: C, 52.41; H, 7.47.
(4:1, 0.5 mL) at room temperature were added DMAP
(15 mg, 0.123 mmol) and DCC (25 mg, 0.121 mmol). The
reaction mixture was stirred at room temperature for 9 h,
and then concentrated. The residue was purified by
preparative thin layer chromatography (0.5 mm thickness,
hexane/EtOAc¼1:1) to afford the desired product 32 as a
colorless oil (57 mg, 90%): [a]2D5¼217.2 (c 1.0, CHCl3); IR
(cm21) 3320, 1732, 1682, 1526; H NMR (270 MHz,
neat
max
1
n
CDCl3) d 0.90 (3H, t, J¼7.4 Hz, Ile-CdH3), 0.91 (3H, d,
J¼6.6 Hz, Ile-CgH3), 1.16–1.27 (2H, m, C4–CH2), 1.28
(3H, s, CH3), 1.29 (3H, s, CH3), 1.46 (9H, s, (CH3)3C),
1.62–1.81 (2H, m, C5–CH2), 2.10 (3H, s, C8–CH3), 2.17
(2H, m, C6–CH2), 3.27–3.28 (1H, m, Ile-CbH), 3.81 (1H,
d, J¼6.1 Hz, Gly-CH2), 3.88 (1H, dd, J¼16.7, 5.8 Hz,
Gly-CH2), 4.55 (2H, d, J¼5.3 Hz, CH2CHvCH2), 5.18–
5.33 (4H, m, CH2CHvCH2, BocNH, C3–CH), 5.44 (1H, d,
J¼9.4 Hz, Ile-CaH), 5.79–5.94 (1H, m, CH2CHvCH2),
7.03 (1H, br, NH), 8.04 (1H, s, Thz-H); 13C NMR
(67.8 MHz, CDCl3) d 11.5, 15.9, 20.8, 22.2, 22.4, 24.8,
28.3, 30.0, 37.3, 39.6, 47.0, 47.0, 49.3, 55.5, 65.6, 77.2,
77.8, 90.2, 118.6, 127.1, 131.7, 146.6, 160.4, 169.1, 174.8;
Anal. calcd for C29H45Cl2N3O7S: C, 53.53; H, 6.97; N, 6.46.
Found: C, 53.82; H, 7.09; N, 6.27.
8.1.16. 2-[(1S,2S)-1-(2-tert-Butoxycarbonylamino-acetyl-
amino)-2-methyl-butyl]-thiazole-4-carboxylic acid
methyl ester (31). Boc-L-(ile)Thz-OMe (5) (132 mg,
0.402 mmol) was treated with 4N HCl/dioxane (1 mL) at
08C. The mixture was stirred at room temperature for
20 min. The mixture was concentrated and dried to afford
the crude hydrochloride salt. To a solution of Boc-Gly-OH
(8) (77 mg, 0.439 mmol) and the above crude hydrochloride
salt in DMF (1.4 mL) at 08C were successively added
dropwise DEPC (0.075 mL, 0.494 mmol) and triethylamine
(0.14 mL, 1.01 mmol). The resulting solution was stirred at
08C for 2 h and at room temperature for 10 h. After dilution
with EtOAc, the mixture was washed with 1 M aq. KHSO4,
water, sat. aq. NaHCO3, water, and brine. The organic layer
was dried (Na2SO4), filtered, and concentrated. The residue
was purified by silica gel column chromatography
(hexane/EtOAc¼2:1–1:1) to afford the desired product 31
8.1.18. Protected linear precursor (33). To a solution of
the allyl ester 32 (33 mg, 0.051 mmol) in THF (0.6 mL)
were added morpholine (0.045 mL, 0.516 mmol) and
Pd(Ph3P)4 (6 mg, 0.005 mmol). After being stirred at
room temperature for 15 min, the mixture was diluted
with ether, and washed with 1 M aq. KHSO4, and brine. The
organic layer was dried (MgSO4), filtered and concentrated
to afford the corresponding carboxylic acid, which was used
for the next step without further purification.
as white crystals (101 mg, 65%): mp 183–1848C (EtOAc);
To a solution of the above carboxylic acid and the diol 6
(12 mg, 0.037 mmol) in toluene (0.5 mL) at room tempera-
ture were added DMAP (2 mg, 0.016 mmol), CSA (2 mg,
0.009 mmol), and DCC (20 mg, 0.086 mmol). After being
stirred at room temperature for 19 h, the mixture was diluted
with ether and filtered through a pad of celite. The filtrate
was concentrated, and purified by silica gel column
chromatography (hexane/acetone¼5:1) to afford the desired
product 33 as a colorless oil (22 mg, 64%): [a]2D5¼249.1 (c
0.6, CHCl3); IR nmneaaxt (cm21) 3346, 1738, 1717, 1682, 1505;
1H NMR (270 MHz, CDCl3) d 0.08 (9H, s, (CH3)3Si), 0.81
(3H, d, J¼6.8 Hz, Ile-CgH3), 0.92 (3H, t, J¼7.3 Hz,
Ile-CdH3), 1.15 (2H, t, J¼8.9 Hz, TMSCH2CH2), 1.20
(3H, s, CH3), 1.24–1.26 (4H, m, Ile-CgH2, C4–CH2), 1.28
(3H, s, CH3), 1.29 (3H, s, CH3), 1.40 (9H, s, (CH3)3C), 1.44
(3H, s, CH3), 1.68–1.85 (2H, m, Ile-CbH, C5–CH2), 2.09
(3H, s, C8–CH3), 2.10–2.12 (1H, m, C6–CH2), 2.23–2.34
(1H, m, C6–CH2), 3.58 (1H, dd, J¼16.8, 4.9 Hz, Gly-CH2),
3.83 (1H, br, Gly-CH2), 4.45 (1H, dd, J¼9.6, 6.9 Hz,
TMSCH2CH2), 4.87 (1H, br, OH), 5.05 (1H, br, BocNH),
5.14 (1H, t, J¼8.9 Hz, C3–CH), 5.32 (1H, br, Ile-CaH), 6.20
(1H, s, C26–CH), 7.98 (1H, d, J¼9.2 Hz, NH), 8.18 (1H, s,
Thz-H), 8.27 (1H, s, Thz-H); 13C NMR (67.8 MHz, CDCl3)
d 21.36, 0.12, 11.2, 16.1, 17.7, 22.1, 22.8, 22.9, 25.4, 25.6,
27.8, 28.3, 37.5, 39.6, 46.5, 46.7, 49.0, 54.7, 63.8, 72.2,
76.3, 76.4, 77.2, 90.0, 128.6, 128.8, 146.6, 150.4, 161.1,
161.2, 161.2, 166.5, 168.7, 172.6, 177.7; Anal. calcd for
C39H62Cl2N4O10S2Si·acetone: C, 52.11; H, 7.08; N, 5.79.
Found: C, 52.43; H, 7.08; N, 5.90.
KBr
[a]2D4¼249.8 (c 1.0, MeOH); IR n
(cm21) 3410, 1736,
max
1701, 1655; 1H NMR (270 MHz, CDCl3) d 0.88–0.93
(6H, m, Ile-CdH3 and CgH3), 1.46 (11H, s and m, (CH3)3C,
Ile-CgH2), 2.20 (1H, br, Ile-CbH), 3.83 (2H, t, J¼5.7 Hz,
Gly-CH2), 3.94 (3H, s, CO2CH3), 5.16 (1H, br, BocNH),
5.20–5.25 (1H, dd, J¼8.9, 8.7 Hz, Ile-CaH), 7.02 (1H, br,
NH), 8.09 (1H, s, Thz-H); 13C NMR (67.8 MHz, CDCl3) d
11.3, 15.9, 24.7, 28.3, 39.5, 44.7, 52.5, 55.6, 80.5, 127.1,
146.8, 156.0, 161.6, 169.1, 171.3; Anal. calcd for
C17H27N3O5S: C, 52.97; H, 7.06; N, 10.90. Found: C,
52.76; H, 7.00; N, 10.61.
8.1.17. [2(1S,2S),1S]-2-[1-(2-tert-Butoxycarbonylamino-
acetylamino)-2-methyl-butyl]-thiazole-4-carboxylic acid
1-(1-allyloxycarbonyl-1-methyl-ethyl)-5,5-dichloro-hexyl
ester (32). To a solution of the ester 31 (99 mg,
0.257 mmol) in THF/methanol (2:1, 1.5 mL) at 08C was
added 0.5N aq. LiOH (1.5 mL, 0.75 mmol). The reaction
mixture was stirred at 08C for 15 min, and then at room
temperature for 70 min. The reaction was quenched by the
addition of 1 M aq. KHSO4 and the mixture was extracted
with CHCl3. The organic extracts were dried (MgSO4),
filtered, and concentrated to afford the carboxylic acid
(105 mg) as a white amorphous solid, which was used for
the next step without purification.
To a solution of the carboxylic acid (40 mg, 0.108 mmol)
and the alcohol 7 (29 mg, 0.097 mmol) in toluene/CH2Cl2

9454
F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
8.1.19. Lyngbyabellin A (1). To a solution of the linear
peptide 33 (24 mg, 0.026 mmol) in THF (0.3 mL) at 08C
was added TBAF (21 mg, 0.080 mmol). The reaction
mixture was stirred at 08C for 10 min, and then at room
temperature for 1.5 h. After dilution with EtOAc, the
mixture was washed with 1 M aq. KHSO4, and brine. The
organic layer was dried (Na2SO4), filtered, and concen-
trated. The residue was dissolved in CH2Cl2 (0.5 mL), and
treated with p-TsOH·H2O (25 mg, 0.129 mmol) at room
temperature for 1 h. After the reaction was quenched by the
addition of triethylamine, the mixture was azeotroped to
dryness with toluene (£3) and the residue was dissolved in
DMF (13 mL). Solid NaHCO3 (44 mg, 0.524 mmol) and
DPPA (0.012 mL, 0.056 mmol) were sequentially added at
08C and the resulting mixture was stirred at 08C for 48 h.
After concentration, the residue was purified by preparative
thin layer chromatography (hexane/acetone¼3:2) to afford
the desired product 1 as a white amorphous solid (10 mg,
58%): [a]2D5¼267.0 (c 0.4, CHCl3) (Ref. 3: [a]2D7¼274.0 (c
0.5, CHCl3)); IR nmKBaxr (cm21) 3453, 1726, 1655, 1543, 1237;
1H NMR (500 MHz, CDCl3) d 0.76 (3H, d, J¼6.7 Hz, C19–
CH3), 0.91 (3H, t, J¼7.3 Hz, C18–CH3), 1.11–1.17 (1H, m,
C17–CH2), 1.25 (3H, s, C28–CH3), 1.32 (3H, s, C9–CH3),
1.31–1.34 (1H, m, C4–CH2), 1.35 (3H, s, C10–CH3), 1.38
(3H, s, C29–CH3), 1.47–1.52 (1H, m, C17–CH2), 1.57–
1.64 (2H, m, C5–CH2), 1.69–1.76 (1H, m, C4–CH2), 1.95–
1.97 (1H, m, C16–CH), 1.98–2.02 (1H, m, C6–CH2), 2.05
(3H, s, C8–CH3), 2.22 (1H, ddd, J¼14.4, 11.0, 5.2 Hz,
C6–CH2), 3.69 (1H, dd, J¼17.1, 4.3 Hz, C21–CH2), 4.72
(1H, dd, J¼17.1, 9.2 Hz, C21–CH2), 5.25 (1H, dd, J¼8.9,
6.7 Hz, C15–CH), 5.30 (1H, dd, J¼10.7, 2.1 Hz, C3–CH),
6.14 (1H, d, J¼0.6 Hz, C26–CH), 7.13 (1H, d, J¼8.9 Hz,
C15–NH), 7.90 (1H, dd, J¼9.2, 4.3 Hz, C21–NH), 8.09 (1H,
s, C13–CH), 8.23 (1H, d, J¼0.9 Hz, C24–CH); 13C NMR
(125.7 MHz, CDCl3) d 11.3, 14.9, 20.5, 22.3, 24.1, 25.4,
25.8, 27.0, 29.4, 37.1, 40.1, 42.9, 46.6, 49.3, 55.1, 71.8,
77.0, 78.1, 90.0, 126.4, 127.8, 146.8, 148.1, 161.0, 161.5,
C8H14O4·1/5H2O: C, 54.04; H, 8.16. Found: C, 54.42; H,
8.05.
8.1.21. Boc-D-Ser-Gly-OAllyl (38). A mixture of Boc-Gly-
OAllyl (197 mg, 0.195 mmol) in 4N HCl/dioxane (3 mL)
was stirred at room temperature for 25 min and concen-
trated. The residue was azeotropically concentrated with
toluene. The resulting HCl·(S)-Thr-OAllyl (37) and Boc-D-
Ser-OH (36) (185 mg, 0.902 mmol) were dissolved in DMF
(3 mL) and cooled to 08C. DEPC (0.15 mL, 0.989 mmol)
and Et3N (0.30 mL, 2.16 mmol) were successively added,
and the mixture was stirred at 08C for 2 h and at room
temperature for 10 h. After dilution with EtOAc, the
mixture was washed with 1 M aq. KHSO4, water, saturated
aqueous NaHCO3, water, and brine. The organic layer was
dried (Na2SO4), filtered and concentrated. The residue was
purified by silica gel column chromatography (hexane/
EtOAc¼1:1–1:2) to afford the desired product 38 as a
colorless oil (154 mg, 56%): [a]2D4¼þ21.5 (c 1.2, CHCl3);
neat
max
1
IR n
(cm21) 3346, 1748, 1715, 1671, 1534, 1167; H
NMR (270 MHz, CDCl3) d 1.46 (9H, s, (CH3)3C), 3.06 (1H,
dd, J¼8.1, 5.1 Hz, disappeared with D2O, OH), 3.63–3.73
(1H, br, changed to dd with D2O, J¼11.4, 5.1 Hz,
Ser-CbH2), 4.06–4.22 (3H, m, Ser-CbH2, Gly-CH2), 4.65
(2H, d, J¼5.8 Hz, CH2CHvCH2), 4.66 (1H, br, Ser-CaH),
5.26–5.37 (2H, m, CH2CHvCH2), 5.55 (1H, br, BocNH),
5.84–5.98 (1H, m, CH2CHvCH2), 7.09 (1H, br, NH); 13
C
NMR (67.8 MHz, CDCl3) d 28.2, 41.3, 55.5, 62.9, 66.1,
80.3, 118.9, 131.2, 155.8, 169.5, 171.5; Anal. calcd for
C13H22N2O6·1/12CHCl3: C, 50.32; H, 7.13; N, 8.97. Found:
C, 50.63; H, 7.36; N, 8.91.
8.1.22. Boc-D-Ser(DPS)-Gly-OAllyl (13). To a solution of
the alcohol 38 (81 mg, 0.268 mmol) in CH2Cl2 (0.9 mL) at
08C were successively added triethylamine (0.074 mL,
0.533 mmol), DMAP (1 mg, 0.008 mmol), and tert-butyl-
diphenylchlorosilane (DPSCl, 0.084 mL, 0.323 mmol). The
reaction mixture was stirred at 08C for 3 min, and then at
room temperature for 7 h. After concentration, the residue
was purified by silica gel column chromatography
(hexane/EtOAc¼5:1) to afford the desired product 13 as
164.6, 168.1, 168.5, 173.0; HRMS (EI) m/z calcd for
35
40
C29H Cl2N4O7S2: 690.1715. Found: 690.1716.
8.1.20. (2S)-2,3-Dihydroxy-3-methyl-butyric acid allyl
ester (12). To a solution of the benzyl ester 3523 (302 mg,
1.48 mmol) in THF (3 mL) was added 5% Pd on carbon
(40 mg) at room temperature. The black slurry was stirred
under 1 atm H2 for 30 min. The reaction mixture was
filtered through a pad of celite and the filtrate was
concentrated. The residue was dissolved in DMF (3 mL),
and KHCO3 (300 mg, 3 mmol) was added, followed by the
addition of allyl bromide (0.18 mL, 2.13 mmol). The
mixture was stirred at room temperature for 7 h. After
dilution with EtOAc, the mixture was washed with with 1 M
aq. KHSO4, water, and brine. The organic layer was
dried (Na2SO4), filtered, and concentrated. The residue was
purified by silica gel column chromatography (hexane/
white crystals (123 mg, 85%): mp 83–848C (ether/pentane);
[a]2D5¼25.4 (c 1.0, CHCl3); IR n
(cm21) 3424, 3387,
KBr
max
1
1746, 1713, 1651, 1553, 1204, 1113; H NMR (270 MHz,
CDCl3) d 1.05 (9H, s, (CH3)3C), 1.44 (9H, s, (CH3)3C), 3.79
(1H, dd, J¼10.1, 5.8 Hz, Ser-CbH2), 4.06–4.11 (3H, m,
Ser-CbH2, Gly-CH2), 4.30 (1H, br, Ser-CaH), 4.64
(2H, d, J¼5.8 Hz, CH2CHvCH2), 5.24–5.36 (3H, m,
CH2CHvCH2, BocNH), 5.83–5.95 (1H, m, CH2CHvCH2),
6.92 (1H, br, NH), 7.36–7.43 (6H, m, PhH), 7.62–7.64 (4H,
m, PhH); 13C NMR (67.8 MHz, CDCl3) d 19.3, 26.8, 28.3,
41.4, 55.8, 64.0, 66.0, 80.3, 118.9, 127.7, 129.8, 131.3,
132.3, 132.7, 135.3, 135.4, 155.3, 168.9, 170.3; Anal. calcd
for C29H40N2O6Si: C, 64.42; H, 7.46; N, 5.18. Found: C,
64.22; H, 7.43; N, 5.48.
EtOAc¼2:1) to afford the desired product 12 as a colorless
neat
oil (129 mg, 50%): [a]2D5¼þ10.3 (c 0.7, CHCl3); IR n
max
(cm21) 3453, 1732, 1649, 1375, 1275, 1200, 1092; 1H NMR
(270 MHz, CDCl3) d 1.23 (3H, s, CH3), 1.31 (3H, s, CH3),
2.69 (1H, brs, OH), 3.27 (1H, br, OH), 4.00 (1H, t, J¼
6.8 Hz, CH), 4.72 (2H, d, J¼5.6 Hz, CH2CHvCH2),
5.29–5.42 (2H, m, CH2CHvCH2), 5.89–6.02 (1H, m,
CH2CHvCH2); 13C NMR (67.8 MHz, CDCl3) d 25.0, 25.8,
66.5, 72.1, 77.2, 119.7, 130.9, 172.7; Anal. calcd for
8.1.23. [1(1S),2(1S)]-2-(1-tert-Butoxycarbonylamino-2-
methyl-propyl)-thiazole-4-carboxylic acid 1-(1-allyloxy-
carbonyl-1-methyl-ethyl)-5,5-dichloro-hexyl ester (39).
To a solution of the ester 11 (229 mg, 0.728 mmol) in THF
(1 mL)–MeOH (1.4 mL) at 08C was added 1 M aq. NaOH
(1.4 mL, 1.4 mmol). The resulting mixture was stirred at
08C for 10 min and then at room temperature for 1 h. After

F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
9455
neat
dilution with water, the mixture was washed with ether. The
aqueous layer was acidified to pH 3 by the addition of 1 M
aq. KHSO4 and salted out. The mixture was extracted with
ether (£3). The combined organic extracts were dried
(MgSO4), filtered, and concentrated to afford the corre-
sponding carboxylic acid (224 mg), which was used for the
next step without further purification.
[a]2D5¼275.8 (c 1.0, CHCl3); IR n
(cm21) 3475, 3368,
max
1740, 1717, 1503, 1478, 1233, 1204, 1169; 1H NMR
(270 MHz, CDCl3) d 0.85 (3H, d, J¼6.6 Hz, Val-CgH3),
0.96 (3H, d, J¼6.8 Hz, Val-CgH3), 1.30 (3H, s, CH3), 1.31
(3H, s, CH3), 1.37 (3H, s, CH3), 1.40 (3H, s, CH3), 1.45 (9H,
s, (CH3)3C), 1.67–1.70 (4H, m, C4 and C5–CH2), 2.07 (3H,
s, C8–CH3), 2.14–2.19 (1H, m, C6–CH2), 2.24–2.31 (2H,
m, Val-CbH, C6–CH2), 3.79 (1H, s, C26–OH), 4.65 (2H, d,
J¼5.8 Hz, CH2CHvCH2), 4.77–4.81 (1H, m, Val-CaH),
4.81 (1H, s, C25–CH), 5.24–5.38 (3H, m, CH2CHvCH2,
BocNH), 5.82–5.94 (1H, m, CH2CHvCH2), 6.26 (1H, d,
J¼9.6 Hz, C3–CH), 8.16 (1H, s, Thz-H); 13C NMR
(67.8 MHz, CDCl3) d 18.3, 19.5, 22.2, 22.3, 22.5, 24.8,
26.0, 28.5, 29.8, 33.9, 37.3, 46.7, 49.1, 57.7, 66.0, 71.1,
77.2, 78.0, 79.7, 90.1, 119.2, 127.7, 131.1, 146.6, 155.3,
To a solution of the carboxylic acid (86 mg, 0.286 mmol)
and the alcohol 7 (85 mg, 0.286 mmol) in toluene/CH2Cl2
(4:1, 1 mL) at 08C were added DMAP (42 mg, 0.344 mmol)
and DCC (71 mg, 0.344 mmol). The reaction mixture was
stirred at 08C for 10 min, and then at room temperature for
4 h, and then concentrated. The mixture was diluted with
ether and filtered through a pad of celite. The filtrate was
concentrated, and purified by silica gel column chroma-
tography (hexane/ether¼2:1) to afford the desired product
161.1, 167.7, 172.3, 174.0; HRMS (EI) m/z calcd for
C31H Cl2N2O9S: 694.2458. Found: 694.2457.
35
48
39 as white crystals (151 mg, 91%): mp 108–1098C
KBr
(EtOAc/pentane); [a]2D7¼223.2 (c 1.2, CHCl3); IR n
8.1.25. [1(1S),2(1S)]-2-(1-tert-Butoxycarbonylamino-2-
methyl-propyl)-thiazole-4-carboxylic acid 1-(1-{(1S)-1-
[(2R)-1-(allyloxycarbonylmethyl-carbamoyl)-2-(tert-
butyl-diphenyl-silanyloxy)-ethylcarbamoyl]-2-hydroxy-
2-methyl-propoxycarbonyl}-1-methyl-ethyl)-5,5-
dichloro-hexyl ester (41). To a solution of the allyl ester
40 (30 mg, 0.043 mmol) in THF (0.5 mL) were added
morpholine (0.038 mL, 0.436 mmol) and Pd(Ph3P)4 (5 mg,
0.004 mmol). After being stirred at room temperature for
30 min, the mixture was diluted with ether, and washed with
1 M aq. KHSO4, water, and brine. The organic layer was
dried (MgSO4), filtered and concentrated to afford the
corresponding carboxylic acid, which was used for the next
step without further purification.
max
(cm21) 3397, 1723, 1489, 1211; 1H NMR (270 MHz,
CDCl3) d 0.92 (3H, d, J¼6.8 Hz, Val-CgH3), 0.99 (3H, d,
J¼6.8 Hz, Val-CgH3), 1.28 (6H, s, CH3£2), 1.45 (9H, s,
(CH3)3C), 1.63–1.75 (4H, m, C4 and C5–CH2), 2.10 (3H, s,
C8–CH3), 2.17–2.19 (1H, m, C6–CH2), 2.28–2.37 (1H, m,
C6–CH2), 2.41–2.49 (1H, m, Val-CbH), 4.57 (2H, d,
J¼5.6 Hz, CH2CHvCH2), 4.90 (1H, br, Val-CaH), 5.19–
5.34 (3H, m, CH2CHvCH2, BocNH), 5.46 (1H, d,
J¼9.4 Hz, C3–CH), 5.81–5.94 (1H, m, CH2CHvCH2),
8.03 (1H, s, Thz-H); 13C NMR (67.8 MHz, CDCl3) d 17.3,
19.4, 20.6, 22.3, 22.4, 28.3, 29.9, 33.3, 37.2, 46.9, 49.3,
58.0, 65.5, 77.2, 80.0, 90.2, 118.5, 126.9, 131.7, 146.6,
155.2, 160.4, 173.1, 174.8; HRMS (EI) m/z calcd for
35
40
C20H Cl2N2O6S: 578.1984. Found: 578.1989.
A mixture of Boc-D-Ser(DPS)-Gly-OAllyl (13) (44 mg,
0.081 mmol) in 4N HCl/dioxane (0.8 mL) was stirred at
room temperature for 30 min and concentrated. The residue
was azeotropically concentrated with toluene. The resulting
HCl salt and the above carboxylic acid were dissolved in
DMF (0.3 mL) and cooled to 08C. DEPC (0.013 mL,
0.086 mmol) and triethylamine (0.021 mL, 0.151 mmol)
were successively added, and the mixture was stirred at 08C
for 2 h and at room temperature for 17 h. After dilution with
EtOAc, the mixture was washed with 1 M aq. KHSO4,
water, saturated aqueous NaHCO3, water, and brine. The
organic layer was dried (Na2SO4), filtered and concentrated.
The residue was purified by silica gel column chroma-
tography (hexane/EtOAc¼2:1) to afford the desired product
8.1.24. [1S,2(1S)]-2-(1-tert-Butoxycarbonylamino-2-
methyl-propyl)-thiazole-4-carboxylic acid 1-[(1S)-1-(1-
allyloxycarbonyl-2-hydroxy-2-methyl-propoxycarbo-
nyl)-1-methyl-ethyl]-5,5-dichloro-hexyl ester (40). To a
solution of the allyl ester 39 (100 mg, 0.173 mmol) in
THF (1.7 mL) were added morpholine (0.13 mL,
1.49 mmol) and Pd(Ph3P)4 (20 mg, 0.017 mmol). After
being stirred at room temperature for 25 min, the
mixture was diluted with ether, and washed with 1 M aq.
KHSO4, water, and brine. The organic layer was dried
(MgSO4), filtered and concentrated. The residue was
purified by silica gel column chromatography
(hexane/EtOAc¼4:1–2:1) to afford the corresponding
carboxylic acid (90 mg).
41 as a white amorphous solid (42 mg, 90%): [a]2D4¼235.3
(c 0.7, CHCl3); IR n
(cm21) 3346, 1736, 1719, 1684,
1
neat
max
The above carboxylic acid and triethylamine (0.031 mL,
0.223 mmol) were dissolved in toluene (0.6 mL) and
treated with 2,4,6-trichlorobenzoyl chloride (0.031 mL,
0.198 mmol) dropwise at room temperature. After 30 min
at room temperature, a solution of the alcohol 12 (41 mg,
0.235 mmol) and DMAP (42 mg, 0.344 mmol) in toluene
(0.4 mL, þ0.4 mL rinse) was added via cannula and
warmed up to 608C and stirring was continued for 13 h.
After dilution with ether, the mixture was washed with 1 M
aq. KHSO4, water, saturated aqueous NaHCO3, water, and
brine. The organic layer was dried (MgSO4), filtered and
concentrated. The residue was purified by silica gel column
chromatography (hexane/EtOAc¼5:1–4:1) to afford the
desired product 40 as a colorless oil (80 mg, 66%):
1509, 1233, 1200, 1169; H NMR (270 MHz, CDCl3) d
0.90–1.05 (6H, m, Val-CgH3£2), 1.01 (9H, s, (CH3)3C),
1.26 (3H, s, CH3), 1.29 (3H, s, CH3), 1.33 (3H, s, CH3£2),
1.44 (9H, s, (CH3)3C), 1.60–1.85 (4H, m, C4 and C5–CH2),
2.07 (3H, s, C8–CH3), 2.10–2.20 (1H, m, C6–CH2), 2.25–
2.27 (1H, m, C6–CH2), 2.32–2.40 (1H, m, Val-CbH), 3.75
(1H, dd, J¼10.1, 5.1 Hz, Ser-CbH2), 3.88 (1H, s, C26–OH),
3.96–4.16 (2H, m, Gly-CH2), 4.20 (1H, dd, J¼10.2, 3.3 Hz,
Ser-CbH2), 4.55 (1H, m, Ser-CaH), 4.63 (2H, d, J¼5.8 Hz,
CH2CHvCH2), 4.80–4.85 (1H, br, Val-CaH), 4.87 (1H, s,
C25–CH), 5.23–5.36 (3H, m, CH2CHvCH2, BocNH),
5.80 (1H, d, J¼11.0 Hz, C3–CH), 5.84–5.95 (1H, m,
CH2CHvCH2), 6.94 (1H, d, J¼7.4 Hz, NH), 7.18 (1H, br,
NH), 7.39–7.42 (6H, m, PhH), 7.59–7.61 (4H, m, PhH),

9456
F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
8.17 (1H, s, Thz-H); 13C NMR (67.8 MHz, CDCl3) d 15.4,
19.2, 19.5, 22.0, 22.3, 22.4, 25.8, 25.8, 26.8, 28.4, 29.8, 33.6,
37.3, 41.6, 46.8, 49.1, 54.4, 57.8, 63.5, 66.0, 71.4, 77.2, 77.8,
80.1, 90.1, 118.8, 127.7, 129.9, 129.9, 131.3, 131.9, 132.6,
135.3, 135.5, 146.4, 155.3, 160.9, 168.0, 168.8, 169.5,
172.8, 173.9; Anal. calcd for C52H74Cl2N4O12SSi: C, 57.92;
H, 6.92; N, 5.20. Found: C, 57.64; H, 7.10; N, 5.14.
aza-bicyclo[16.2.1]heneicosa-1(21),18-diene-4,7,10,13,
17-pentaone (43). To a solution of the silyl ether 42
(19.7 mg, 0.0214 mmol) in THF (0.1 mL) at 08C was added
a solution of TBAF (12.0 mg, 0.0459 mmol) in THF
(0.1 mL). The reaction mixture was stirred at 08C for
10 min, and then at room temperature for 80 min. After
dilution with EtOAc, the mixture was washed with water
and brine. The organic layer was dried (Na2SO4), filtered
and concentrated. The residue was purified by silica gel
column chromatography (CHCl3/MeOH¼1:0–30:1) to
8.1.26. [2S,8R,11(1S),15S]8-(tert-Butyl-diphenyl-silanyl-
oxymethyl)-15-(4,4-dichloro-pentyl)-11-(1-hydroxy-1-
methyl-ethyl)-2-isopropyl-14,14-dimethyl-12,16-dioxa-
20-thia-3,6,9,21-tetraaza-bicyclo[16.2.1]heneicosa-1(21),
18-diene-4,7,10,13,17-pentaone (42). To a solution of the
allyl ester 41 (30 mg, 0.028 mmol) in THF (0.3 mL) were
added morpholine (0.025 mL, 0.287 mmol) and Pd(Ph3P)4
(3 mg, 0.003 mmol). After being stirred at room tempera-
ture for 30 min, the mixture was diluted with EtOAc, and
washed with 1 M aq. KHSO4, and brine. The organic layer
was dried (Na2SO4), filtered and concentrated to afford the
corresponding carboxylic acid, which was used for the next
step without further purification.
afford the desired product 43 as a white amorphous solid
neat
max
(12.5 mg, 86%): [a]D24¼255.0 (c 0.5, CHCl3); IR n
(cm21) 3368, 1723, 1674, 1532, 1233, 1154; 1H NMR
(270 MHz, CDCl3) d 0.81 (3H, d, J¼6.8 Hz, Val-CgH3),
1.01 (3H, d, J¼6.8 Hz, Val-CgH3), 1.36 (3H, s, CH3), 1.39
(3H, s, CH3), 1.46 (3H, s, CH3), 1.53 (3H, s, CH3), 1.74–
1.77 (3H, m, C4 and C5–CH2), 1.90–2.00 (1H, m,
C4–CH2), 2.04–2.15 (1H, m, C6–CH2), 2.09 (3H, s,
C8–CH3), 2.24–2.45 (3H, m, C6–CH2, Val-CbH, OH),
3.30–3.45 (1H, br, Ser-CbH2), 3.60 (1H, dd, J¼16.5,
4.8 Hz, Gly-CH2), 4.17–4.25 (2H, m, Gly-CH2, Val-CaH),
4.53 (1H, d, J¼8.9 Hz, Ser-CbH2), 5.09 (1H, t, J¼9.7 Hz,
C3–CH), 5.30 (1H, s, C26–OH), 5.32–5.35 (1H, m,
Ser-CaH), 5.36 (1H, s, C25–CH), 7.15–7.19 (2H, br,
NH£2), 7.90 (1H, d, J¼9.9 Hz, NH), 8.28 (1H, s, Thz-H);
13C NMR (67.8 MHz, CDCl3) d 19.2, 20.0, 21.9, 22.9,
23.9, 25.6, 28.4, 29.8, 33.5, 37.5, 44.1, 46.9, 48.9,
52.1, 55.8, 61.2, 72.8, 78.3, 79.2, 89.9, 129.1,
146.5, 160.8, 167.6, 168.3, 171.0, 171.6, 172.3; HRMS
(EI) m/z calcd for C28H4235Cl2N4O9S: 680.2050. Found:
680.2053.
The carboxylic acid was dissolved in EtOAc (0.2 mL), and
treated with 4N HCl/EtOAc (0.5 mL). After being stirred at
room temperature for 30 min, the mixture was concentrated
and then azeotropically concentrated with toluene to afford
the free peptide.
The above free peptide was dissolved in CH2Cl2 (14 mL)
and cooled to 08C. FDPP (22 mg, 0.057 mmol) and i-Pr2NEt
(0.028 mL, 0.161 mmol) were successively added, and the
mixture was stirred at 08C for 4 h, and then at room
temperature for 38 h. After the bulk of solvent was removed
in vacuo, the residue was diluted with EtOAc. The mixture
was washed with 1 M aq. KHSO4, water, sat. aq. NaHCO3,
water, and brine, dried (Na2SO4), filtered and concentrated.
The residue was purified by silica gel column chroma-
tography (hexane/EtOAc¼1:1–1:2–1:3) to afford the
8.1.28. Oxazoline (44). To a solution of the alcohol 43
(10.1 mg, 0.0148 mmol) in CH2Cl2 (0.2 mL) at 2788C was
added DAST (0.0025 mL, 0.0189 mmol). The reaction
mixture was slowly warmed up to 2208C during 15 min,
and then stirred at same temperature for 15 min. The
reaction was quenched by the addition of sat. aq. NaHCO3,
and the resulting mixture was extracted with CHCl3 (£3).
The combined organic extracts were dried (Na2SO4),
filtered and concentrated. The residue was purified by
silica gel column chromatography (CHCl3/MeOH¼30:1) to
desired product 42 as a white amorphous solid (15 mg,
59%): [a]2D4¼253.2 (c 0.8, CHCl3); IR n
(cm21) 3389,
neat
max
1
1740, 1719, 1686, 1524, 1231, 1113; H NMR (270 MHz,
CDCl3) d 0.67 (9H, s, (CH3)3C), 0.92 (3H, d, J¼6.8 Hz,
Val-CgH3), 1.05 (3H, d, J¼6.8 Hz, Val-CgH3), 1.19 (3H, s,
CH3), 1.30 (3H, s, CH3), 1.49 (3H, s, CH3), 1.50 (3H, s,
CH3), 1.68–1.74 (3H, m, C4 and C5–CH2), 1.90–2.00 (1H,
m, C4–CH2), 2.03–2.15 (1H, m, C6–CH2), 2.10 (3H, s,
C8–CH3), 2.21–2.33 (2H, m, Val-CbH, C6–CH2), 3.72
(1H, d, J¼9.6 Hz, Gly-CH2), 3.78 (1H, dd, J¼7.7, 2.8 Hz,
Ser-CbH2), 4.31 (1H, dd, J¼10.2, 2.8 Hz, Ser-CbH2), 4.47
(1H, dd, J¼16.3, 8.7 Hz, Val-CaH), 4.69 (1H, d, J¼9.4 Hz,
Gly-CH2), 5.24–5.32 (2H, m, C3–CH, Ser-CaH), 5.36 (1H,
s, C26–OH), 5.85 (1H, s, C25–CH), 6.91 (1H, d, J¼9.6 Hz,
NH), 7.30–7.41 (7H, m, PhH, NH), 7.46–7.51 (4H, m,
PhH), 8.22 (1H, d, J¼9.7 Hz, NH), 8.33 (1H, s, Thz-H); 13C
NMR (67.8 MHz, CDCl3) d 18.7, 19.0, 19.7, 22.0, 22.9,
23.6, 25.5, 26.6, 28.0, 29.7, 34.4, 37.6, 44.3, 46.5, 48.9, 54.5,
55.6, 63.5, 73.4, 78.9, 79.0, 89.9, 127.6, 127.7, 129.7, 129.8,
130.0, 131.0, 133.1, 135.0, 135.8, 146.4, 160.8, 167.0, 167.0,
168.7, 171.8, 171.9.
afford the desired product 44 as a white amorphous solid
neat
max
(8.9 mg, 91%): [a]D25¼2159.2 (c 0.26, CHCl3); IR n
(cm21) 3346, 1736, 1663, 1530, 1235; 1H NMR (270 MHz,
CDCl3) d 0.81 (3H, d, J¼6.6 Hz, Val-CgH3), 1.02 (3H, d,
J¼6.6 Hz, Val-CgH3), 1.26 (3H, s, CH3), 1.34 (3H, s, CH3),
1.48 (3H, s, CH3), 1.69–1.77 (3H, m, C4 and C5–CH2), 1.80
(3H, s, CH3), 1.89–2.00 (1H, m, C4–CH2), 2.05–2.16 (1H,
m, C6–CH2), 2.10 (3H, s, C8–CH3), 2.24–2.33 (1H, m,
C6–CH2), 2.39–2.47 (1H, m, Val-CbH), 3.67 (1H, dd,
J¼18.0, 2.8 Hz, Gly-CH2), 4.22 (1H, t, J¼9.9 Hz,
oxz-CH2), 4.52–4.57 (1H, m, oxz-CH2), 4.62 (1H, dd,
J¼18.0, 10.4 Hz, Gly-CH2), 4.71 (1H, dd, J¼10.1, 3.8 Hz,
Val-CaH), 5.13 (1H, t, J¼9.7 Hz, C3–CH), 5.22 (1H, s,
C26–OH), 5.29 (1H, d, J¼10.1 Hz, oxz-CH), 5.52 (1H, s,
C25–CH), 6.94 (1H, d, J¼8.1 Hz, NH), 7.89 (1H, d, J¼
9.6 Hz, NH), 8.27 (1H, s, Thz-H); 13C NMR (67.8 MHz,
CDCl3) d 19.3, 20.1, 22.0, 22.9, 24.3, 26.1, 28.9, 29.7, 33.7,
37.5, 42.5, 47.2, 48.9, 55.7, 68.7, 70.1, 73.0, 74.5, 78.3,
90.0, 129.1, 146.8, 161.1, 166.7, 167.6, 170.7, 171.9, 173.5;
HRMS (EI) m/z calcd for C28H4035Cl2N4O8S: 662.1944.
Found: 662.1945.
8.1.27. [2S,8R,11(1S),15S]-15-(4,4-Dichloro-pentyl)-8-
hydroxymethyl-11-(1-hydroxy-1-methyl-ethyl)-2-isopro-
pyl-14,14-dimethyl-12,16-dioxa-20-thia-3,6,9,21-tetra-

F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
9457
8.1.29. Thioamide (45). A solution of the oxazoline 44
Acknowledgements
(8.9 mg, 0.0134 mmol) in MeOH/triethylamine (2:1, 1 mL)
was saturated with H2S gas at 2108C. The reaction mixture
was stirred at room temperature for 18 h, and concentrated.
The residue was diluted with EtOAc, washed with 1 M aq.
KHSO4, water, and brine. The organic layer was dried
(Na2SO4), filtered and concentrated. The residue was
purified by silica gel column chromatography (CHCl3/
MeOH¼30:1) to afford the desired product 45 as a white
This work was financially supported in part by Grant-in-Aid
for Research in Nagoya City University (to F. Y.), Uehara
Memorial Foundation (to F. Y.), the Fujisawa Foundation
(to F. Y.), and Grant-in-Aids from the Ministry of
Education, Science, Sports and Culture, Japan.
amorphous solid (8.3 mg, 89%): [a]2D5¼þ37.2 (c 0.22,
CHCl3); IR n
(cm21) 3325, 1731, 1669, 1543, 1235;
neat
References
max
1H NMR (270 MHz, CDCl3) d 0.81 (3H, d, J¼6.6 Hz,
Val-CgH3), 1.01 (3H, d, J¼6.6 Hz, Val-CgH3), 1.36 (3H, s,
CH3), 1.37 (3H, s, CH3), 1.51 (3H, s, CH3), 1.58 (3H, s,
CH3), 1.60–1.65 (1H, br, OH), 1.73–1.80 (3H, m, C4 and
C5–CH2), 1.95–2.02 (1H, m, C4–CH2), 2.05–2.15 (1H, m,
C6–CH2), 2.09 (3H, s, C8–CH3), 2.23–2.33 (2H, m,
Val-CbH, C6–CH2), 3.41 (1H, br, Ser-CbH2), 3.61
(1H, dd, J¼16.7, 5.1 Hz, Gly-CH2), 4.19–4.25 (2H, m,
Ser-CbH2, Gly-CH2), 5.09 (1H, t, J¼9.7 Hz, C3–CH), 5.31
(1H, s, C26–OH), 5.31–5.35 (2H, m, Ser-CaH, Val-CaH),
5.76 (1H, s, C25–CH), 7.16 (1H, br, NH), 7.89 (1H,
d, J¼9.9 Hz, NH), 8.27 (1H, s, Thz-H), 8.59 (1H,
d, J¼9.1 Hz, NH); 13C NMR (67.8 MHz, CDCl3) d 19.3,
19.9, 21.9, 23.0, 24.0, 27.4, 28.9, 29.9, 33.5, 37.5, 44.1,
47.0, 48.8, 55.7, 57.2, 60.7, 72.5, 78.3, 85.2, 89.9, 128.8,
146.7, 160.8, 167.5, 169.3, 171.5, 172.0, 195.8; HRMS
(EI) m/z calcd for C28H4235Cl2N4O8S2: 696.1821. Found:
696.1821.
1. (a) Barja, A. M.; Banaigs, B.; Abou-Mansor, E.; Burgess, J. G.;
Wright, P. C. Tetrahedron 2001, 57, 9347–9377. (b) Gerwick,
W. H.; Tan, L. T.; Sitachitta, N. In The Alkaloids; Cordell,
G. A., Ed.; Academic: New York, 2001; pp 75–184.
2. Our synthetic studies of marine cyanobacteria derived natural
products, see: (a) Yokokawa, F.; Fujiwara, H.; Shioiri, T.
Tetrahedron 2000, 56, 1759–1775. (b) Wu, M.; Okino, T.;
Nogle, L. M.; Marquez, B. L.; Williamson, R. T.; Sitachitta,
N.; Berman, F. W.; Murray, T. F.; McGough, K.; Jacobs, R.;
Colsen, K.; Asano, T.; Yokokawa, F.; Shioiri, T.; Gerwick,
W. H. J. Am. Chem. Soc. 2000, 122, 12041–12042. See also
(c) Shioiri, T.; Hamada, Y. Synlett 2001, 184–201.
3. Luesch, H.; Yoshida, W. Y.; Moore, R. E.; Paul, V. J.;
Mooberry, S. L. J. Nat. Prod. 2000, 63, 611–615.
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J. Nat. Prod. 2000, 63, 1437–1439. (b) Milligan, K.; Marquez,
B. L.; Williamson, R. T.; Gerwick, W. H. J. Nat. Prod. 2000,
63, 1440–1443.
8.1.30. Lyngbyabellin B (2). To a solution of the thioamide
45 (8.3 mg, 0.0119 mmol) in CH2Cl2 (0.4 mL) at 2788C
was added DAST (0.0025 mL, 0.0189 mmol). The reaction
mixture was slowly warmed up to 2208C during 10 min,
and then stirred at same temperature for 10 min. The
reaction was quenched by the addition of sat. aq. NaHCO3,
and the resulting mixture was extracted with CHCl3 (£3).
The combined organic extracts were dried (Na2SO4),
filtered and concentrated. The residue was purified by silica
gel column chromatography (CHCl3/MeOH¼1:0–60:1) to
afford the desired product 2 as a white amorphous solid
5. Sone, H.; Kondo, T.; Kiryu, M.; Ishiwata, H.; Ojika, M.;
Yamada, K. J. Org. Chem. 1995, 60, 4774–4781.
6. For a preliminary account of the total synthesis of
lyngbyabellin A, see: Yokokawa, F.; Sameshima, H.; Shioiri,
T. Tetrahedron. Lett. 2001, 42, 4171–4174.
7. Wipf, P.; Miller, C. P.; Venkatraman, S.; Fritch, P. C.
Tetrahedron Lett. 1995, 36, 6395–6398.
8. (a) Hamada, Y.; Shibata, M.; Sugiura, T.; Kato, S.; Shioiri, T.
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N.; Yamauchi, M.; Toriyama, K.; Anzai, A.; Ando, A.; Shioiri,
T. Synlett 1998, 35–36.
(8.0 mg, 99%): [a]2D7¼2207.5 (c 0.15, CHCl3) (Ref. 4a:
9. CMD is commercially available from Wako Pure Chemical
Industries, Ltd. as Manganese (IV) Oxide, Chemicals Treated.
10. Takuma, S.; Hamada, Y.; Shioiri, T. Chem. Pharm. Bull. 1982,
30, 3147–3153, and references therein.
[a]2D5¼2152 (c 0.06, CHCl3));29 IR n
(cm21) 3339,
neat
max
1
1734, 1717, 1682, 1539, 1505, 1472; H NMR (270 MHz,
CDCl3) d 0.78 (3H, d, J¼6.8 Hz, C18–CH3), 1.02 (3H, d,
J¼6.8 Hz, C17–CH3), 1.36 (3H, s, C10–CH3), 1.45 (3H, s,
C9–CH3), 1.48 (3H, s, C27–CH3), 1.64–1.75 (3H, m, C4
and C5–CH2), 1.85 (3H, s, C28–CH3), 1.96–2.00 (1H, m,
C4–CH2), 2.05–2.15 (1H, m, C6–CH2), 2.09 (3H, s,
C8–CH3), 2.22–2.27 (1H, m, C6–CH2), 2.33–2.41 (1H,
m, C16–CH), 3.30 (1H, dd, J¼11.0, 10.1 Hz, C23–CH2),
3.65 (1H, d, J¼17.8 Hz, C20–CH2), 3.77 (1H, d, J¼11.5 Hz,
C23–CH2), 4.67 (1H, dd, J¼18.0, 10.1 Hz, C20–CH2),
5.13 (1H, dd, J¼9.7, 9.6 Hz, C15–CH), 5.29–5.37 (2H,
m, C3–CH, C22–CH), 5.56 (1H, s, C26–OH), 5.75 (1H,
s, C25–CH), 6.71 (1H, d, J¼8.4 Hz, C20–NH), 8.11 (1H,
d, J¼9.6 Hz, C15–NH), 8.30 (1H, s, C13–CH); 13C
NMR (67.8 MHz, CDCl3) d 19.5, 19.8, 21.8, 23.0,
24.6, 26.2, 29.3, 29.5, 34.0, 34.5, 37.5, 43.2, 47.3,
48.8, 55.6, 74.2, 78.5, 78.7, 78.7, 90.0, 129.4,
146.7, 160.9, 167.5, 170.7, 170.8, 172.4, 177.2; HRMS
(EI) m/z calcd for C28H4035Cl2N4O7S2: 678.1715. Found:
678.1725.
11. Fehrentz, J.-A.; Castro, B. Synthesis 1983, 676–678.
12. (a) Sugiyama, H.; Yokokawa, F.; Shioiri, T. Org. Lett. 2000, 2,
2149–2152. (b) Fujiwara, H.; Tojiki, K.; Yokokawa, F.;
Shioiri, T. Pept. Sci. 2000, 1999, 9–12.
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Bull. 1981, 29, 1475–1478. (b) Shioiri, T.; Aoyama, T.
Encyclopedia of Reagents for Organic Synthesis; Paquette,
L. A., Ed.; Wiley: Chichester, 1985; Vol. 7, p 5248.
14. Raman, P.; Razavi, H.; Kelly, J. W. Org. Lett. 2000, 2,
3289–3292.
15. Williams, D. R.; Lowder, P. D.; Gu, Y.-G.; Brooks, D. A.
Tetrahedron Lett. 1997, 38, 331–334.
16. Kolb, H. C.; VanNieuwenhze, M. S.; Sharpless, K. B. Chem.
Rev. 1994, 94, 2483–2547.
17. The ee was determined by chiral HPLC on a ChiralPak AS
column (hexane/isopropanol¼50:1; flow rate¼1.0 mL/min).
18. (a) Kiyooka, S.-I.; Kaneko, Y.; Komura, M.; Matsuo, H.;
Nakano, M. J. Org. Chem. 1991, 56, 2276–2278. (b) Kiyooka,

9458
F. Yokokawa et al. / Tetrahedron 58 (2002) 9445–9458
S.-I. J. Synth. Org. Chem. Jpn 1997, 55, 313–324. See also:
(c) Yokokawa, F.; Izumi, K.; Omata, J.; Shioiri, T.
T. Synthesis 1998, 627–638. (e) Yokokawa, F.; Sameshima,
H.; Shioiri, T. Synlett 2001, 986–988.
Tetrahedron 2000, 56, 3027–3034.
1
26. Lafargue, P.; Guenot, P.; Lellouche, J.-P. Heterocycles 1995,
41, 947–958.
19. The ee was determined by H NMR analysis in the presence
of the chiral shift reagent Eu(hfc)3.
27. Lafargue, P.; Guenot, P.; Lellouche, J.-P. Synlett 1995,
171–172.
20. Ohtani, I.; Kusumi, T.; Kashman, Y.; Kakisawa, H. J. Am.
Chem. Soc. 1991, 113, 4092–4096.
28. After our work has been completed, isolation and synthesis
of hectochlorin, a structurally analogous lipopeptide, were
reported: (a) Isolation Marquez, B. L.; Watts, K. S.; Yokochi,
A.; Roberts, M. A.; Verdier-Pinard, P.; Jimenez, J. I.; Hamel,
E.; Scheuer, P. J.; Gerwick, W. H. J. Nat. Prod. 2002, 65,
866–871. Synthesis (b) Cetusic, J. R. P.; Green, III., F. R.;
Graupner, P. R.; Oliver, M. P. Org. Lett. 2002, 4, 1307–1310.
29. In the Ref. 4b, this paper reports the optical rotation of natural
lyngbyabellin B as [a]2D5¼þ33 (c 0.2, CH2Cl2). Since the
optical rotation of our synthetic material is [a]2D5¼2270.2
(c 0.14, CH2Cl2), the reported value of the natural product
should be revised.
21. Boden, E. P.; Keck, G. E. J. Org. Chem. 1985, 50, 2394–2395.
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Commun. 1993, 23, 349–356. (c) Deng, J.; Hamada, Y.;
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