Total synthesis of cryptophycins and their 16-(3-phenylacryloyl) derivatives

Article abstract of DOI:10.1021/jo960816b

Cryptophycin A, a cyclic depsipeptide isolated from the blue-green alga (cyanobacterium) Nostoc sp.GSV 224, has shown excellent activity against solid tumors implanted in mice. The benzylic epoxide, which was shown to be very important for biological activity, is also fairly unstable under both acidic and alkaline conditions. The high doses needed to observe in vivo activity might be a result of this instability. In order to solve this problem while preserving the electrophilic character of the benzylic position, enones 1 and 2 have been proposed as promising analogs of the natural product, and a convergent total synthesis of these compounds is described. In addition, the same strategy was used to prepare Cryptophycins A,B, C, and D.

Full text of DOI:10.1021/jo960816b

J . Org. Chem. 1996, 61, 6289-6295
6289
Tota l Syn th esis of Cr yp top h ycin s a n d Th eir 16-(3-P h en yla cr yloyl)
Der iva tives
Rabindra Rej, Dieu Nguyen, Brian Go, Samuel Fortin, and J ean-Franc¸ois Lavalle´e*
BioChem Therapeutic Inc. 275, Boul. Armand-Frappier, Laval, Que´bec, Canada H7V 4A7
Received May 3, 1996X
Cryptophycin A, a cyclic depsipeptide isolated from the blue-green alga (cyanobacterium) Nostoc
sp.GSV 224, has shown excellent activity against solid tumors implanted in mice. The benzylic
epoxide, which was shown to be very important for biological activity, is also fairly unstable under
both acidic and alkaline conditions. The high doses needed to observe in vivo activity might be a
result of this instability. In order to solve this problem while preserving the electrophilic character
of the benzylic position, enones 1 and 2 have been proposed as promising analogs of the natural
product, and a convergent total synthesis of these compounds is described. In addition, the same
strategy was used to prepare Cryptophycins A, B, C, and D.
In 1994, Moore and co-workers isolated from the blue-
green alga (cyanobacterium) Nostoc sp. GSV 224, a series
of metabolites known as Cryptophycins (Figure 1).1
These compounds displayed very potent in vitro cytotox-
icity against several human tumor cell lines and experi-
mental evidence shows that the effect is due to irrevers-
ible inhibition of tubulin polymerization into microtubules.2
Both in vitro1 and in vivo3 data suggest that the presence
of the benzylic epoxide moiety is very important for
biological activity. For instance, Cryptophycin A shows
a much better in vitro profile than its deoxy counterpart
Cryptophycin C in the KB (human nasopharyngeal cell
line)(IC50 A: 5 pg/mL; IC50 C: 3000 pg/mL).1 The in vivo
studies follow the same trend but despite its very high
in vitro potency, Cryptophycin A displays very good
activity only at relatively high doses (30-132 mg/kg).3
One of the possible reasons for this poor correlation may
be the inherent instability of the benzylic epoxide which
might generate inactive compounds. In order to solve
this problem while preserving the electrophilic character
of the benzylic position, enones 1 and 2 were envisioned
as promising analogs of the natural products.
Retrosynthetic analysis of 2 led to four subunits (A-
D).4 D-tyrosine (B) and (S)-(-)-2-hydroxyisocaproic acid
(D) are commercially available. Since the â-amino acid
subunit (C) is available only in its racemic form, a
synthetic route to the desired enantiomer was developed.
Finally, an enantioselective synthesis of fragment A was
also elaborated. Subunits B, C, and D were preas-
sembled, and coupling with A was done through ester
F igu r e 1.
bond formation between A and D. Cyclization was then
carried out by a macrolactamization reaction between A
and B.
The synthesis of fragment A (Scheme 1) was realized
in five practical steps. Phenylacetylene (3) was treated
with n-butyllithium and added to a solution of (S)-(-)-
2-acetoxysuccinic anhydride5 in tetrahydrofuran at -78
°C. After 10 min, sodium borohydride was added, fol-
lowed by an aqueous solution of sodium hydroxide, to
produce a diastereomeric mixture of carboxylic acids 4.
Interestingly, the anhydride opening was regioselective,6
whereas the ketone reduction led a 1:1 mixture of both
isomers. Heating this mixture with p-toluenesulfonic
X Abstract published in Advance ACS Abstracts, August 1, 1996.
(1) Trimurtulu, G.; Ohtani, I.; Patterson, G. M. L.; Moore, R. E.;
Corbett, T. H.;Valeriote, F. A.; Demchik, L. J . Am. Chem. Soc. 1994,
116, 4729. Cryptophycin A was first isolated from Nostoc sp. ATCC
53789 by researchers at Merck. See: Schwartz, R. E.; Hirsch, C. F.;
Sesin, D. F.; Flor, J . E.; Chartrain, M.; Fromtling, R. E.; Harris, G.
H.; Salvatore, M. J .; Liesch, J . M.; Yudin, K. J . Ind. Microbiol. 1990,
5, 113.
(2) Smith, C. D.; Zhang, X.; Mooberry, S. L.; Patterson, G. M. L.;
Moore, R. E. Cancer Res. 1994, 54, 3779.
(3) Trimurtulu, G.; Ogino, J .; Heltzel, C. E.; Husebo, T. L.; J ensen,
C. M.; Larsen, L. K.; Patterson, G. M. L.; Moore, R. E.; Mooberry, S.
L.; Corbett, T. H.;Valeriote, F. A. J . Am. Chem. Soc. 1995, 117, 12030.
(4) Barrrow, R. A.; Hemscheidt, T.; Liang, J .; Paik, S.; Moore, R.
E.; Tius, M. A. J . Am. Chem. Soc. 1995, 117, 2479.
(5) Commercially available from Aldrich Co.
(6) The same regioselectivity was observed with an alcohol as
nucleophile; See: Shiuey, S.-J .; Partridge, J . J .; Uskokovic, M. R. J .
Org. Chem. 1988, 53, 1040.
S0022-3263(96)00816-X CCC: $12.00 © 1996 American Chemical Society

6290 J . Org. Chem., Vol. 61, No. 18, 1996
Rej et al.
Sch em e 1a
a
(a) BuLi, THF, -78 °C; then (S)-(-)-2-acetoxysuccinic anhydride; (b) NaBH4, EtOH, -78 °C; then NaOH 0 °C; PTSA, benzene, 50 °C,
63% from 3; (d) ethyl vinyl ether, PTSA, ether, 0 °C to rt; then LAH, 0 °C to rt; (e) (COCl)2, DMSO, Et3N, CH2Cl2, -78 °C to 0 °C; then
(tert-butoxycarbonylmethylene)triphenylphosphorane, 65% from 6; (f) AcOH, H2O, rt, 73%.
de by 1H NMR). This product was reacted with 1-[3-
(dimethylamino)propyl]-3-ethylcarbodiimide hydrochlo-
ride (EDCI) and N-hydroxysuccinimide in dimethoxy-
ethane and dichloromethane. The activated ester was
then treated with (S)-(-)-2-hydroxyisocaproic acid and
(dimethylamino)pyridine (DMAP) in acetonitrile to pro-
duce the fragment (BCD) 15 in 85% yield after purifica-
tion. The coupling reaction between fragments A and
(BCD) was carried out with trichlorobenzoyl chloride,
triethylamine, and DMAP9 to produce 16 in 84% yield
and >95% de. The protecting groups were then cleaved
by a treatment with trifluoroacetic acid in dichlo-
romethane. The resulting amino acid was cyclized with
O-benzotriazol-1-yl-N,N,N′,N′-bis(pentamethylene)uro-
nium hexafluorophosphate10 and diisopropylethylamine
in acetonitrile at 0 °C. Compound 2 was obtained in 69%
yield from 16. Due to some epimerization during the
deprotection or the cyclization step, 5-10% of the 16-epi
diastereomer was isolated from the reaction mixture. The
macrocyclic structure 2 was prepared in five steps and
46% overall yield from the four subunits A-D.
In order to validate our synthetic route and generate
positive controls for the biological evaluation of our
analogs, we used our synthetic strategy to prepare
Cryptophycins A-D. The A fragment of these com-
pounds could be obtained independently from either
butyrolactone 5 or its epimer 6 via separate routes
(Schemes 4 and 5). In the first approach, butyrolactone
5 (Scheme 4), was treated with dihydropyran and PTSA,
in tetrahydrofuran, followed by lithium aluminum hy-
dride (LAH) reduction in ether affording diol 17 in 92%
overall yield. The primary alcohol was selectively pro-
tected as a pivaloyl ester, and then the secondary
hydroxyl was acetylated (59% overall): The dimethyl
cuprate reaction on the fully protected compound failed
and led to a mixture of conjugated dienes (results not
shown), probably by a reduction-elimination mechanism.
In order to avoid this process, the tetrahydropyranyl
group was cleaved and the reaction was carried out on
18. In this case, the reaction led to a 1:1 mixture of SN2
and SN2′ products from which the desired product 19 was
isolated by flash chromatography in 34% yield. The
secondary alcohol was reprotected as tetrahydropyranyl
Sch em e 2a
a
(a) NaN3, DMF, 100 °C; (b) J ones reagent, acetone, rt, 93%
from 10; (c) Pd/C, H2, EtOAc, EtOH, rt, 70%.
acid (PTSA) in benzene at 50 °C, afforded butyrolactones
5 and 6, easily separated by flash chromatography, in
63% combined yield from 3. Both lactones could be used
to complete the synthesis of fragment A. For example,
6 was treated with ethyl vinyl ether and a catalytic
amount of p-toluenesulfonic acid in ether. After 1 h,
lithium aluminum hydride was added, and the reaction
mixture was then stirred at room temperature for 24 h.
The resulting diol 7 was immediately treated with 2.5
equiv of Swern reagent followed by 1.4 equiv of (tert-
butoxycarbonylmethylene)triphenylphosphorane to give
8 in 65% overall from 6. The ethoxy ethyl group was then
cleaved in acetic acid and water affording alcohol 9 in
73% yield after trituration of the crude product in
hexanes.
The â-amino acid 12 (fragment C, Scheme 2), was
prepared from the commercially available (S)-(+)-3-
bromo-2-methyl-1-propanol7 (10) in three steps. The
bromide was displaced with sodium azide in dimethyl-
formamide at 100 °C, and the resulting azido alcohol was
oxidized with J ones reagent in acetone to produce the
carboxylic acid 11 in 93% overall yield from 10. Subse-
quent hydrogenation over palladium afforded the â-amino
acid 12 in 70% yield.
Having the four subunits in hand, the synthesis of 2
(Scheme 3) was undertaken. The use of N-hydroxysuc-
cinimide esters8 as activated intermediates, allowed us
to prepare the (BCD)-fragment in two steps, minimizing
the use of protecting groups. Thus, N-protected D-
tyrosine (13) was treated with dicyclohexylcarbodiimide
(DCC) and N-hydroxysuccinimide in dry dimethoxy-
ethane at 0 °C. Then 12 and triethylamine in water were
added to the reaction mixture affording, after workup,
adduct 14 in 93% yield as a single diastereomer (>95%
(7) 10 could also be prepared by reduction of methyl (S)-(+)-3-bromo-
2-methyl propionate with LAH in ether at -50 °C.
(8) Anderson, G. W.; Zimmerman, J . E.; Callahan, F. M. J . Am.
Chem. Soc. 1963, 85, 3039.
(9) Inanaga, J .; Hirata, K.; Saeki, H. Katsuki, T.; Yamaguchi, M.
Bull. Chem. Soc. J pn. 1979, 52, 1989.
(10) Ehrlich, A.; Rothemund, S.; Brudel, M.; Beyermann, M.; Car-
pino L. A.; Bienert, M. Tetrahedron Lett. 1993, 30, 4781.

Total Synthesis of Cryptophycins
J . Org. Chem., Vol. 61, No. 18, 1996 6291
Sch em e 3a
a
(a) DCC, N-hydroxysuccinimide, DME, 0 °C; then 12, Et3N, H2O, rt, 93%; (b) EDCl, N-hydroxysuccinimide, DME, CH2Cl2; then (S)-
(-)-2-hydroxyisocaproic acid; DMAP, CH3CN, rt, 85%; (c) trichlorobenzoyl chloride, Et3N, THF, rt, 84%; (d) TFA, CH2Cl2; (e) O-benzotriazol-
1-yl-N,N,N′,N′-bis(pentamethylene)uronium hexafluorophosphate, DIPEA, CH3CN, 0 °C, 69% from 16.
Sch em e 4a
a
(a) DHP, PTSA, THF, rt, 92%; (b) LAH, Et2O, rt, 100%; (c) PvCl, pyr, DMAP, 0 °C to rt; then Ac2O, 59%; (d) AcOH, H2O, 100%; (e)
(Me)2CuLi, Et2O, 0 °C, 34%; (f) DHP, PTSA, THF, rt, 98%; (g) LAH, THF, 0 °C, 97%; (h) (COCl)2, DMSO, Et3N, CH2Cl2, -78 °C to 0 °C;
then (tert-butoxycarbonylmethylene)triphenylphosphorane, 73% (for two steps); (i) AcOH, H2O, 40 °C, 80%.
Sch em e 5a
a
(a) H2, Lindlar catalyst, quinoline, EtOAc, MeOH, 0 °C, 85%; (b) CuBr (Me)2S, MeLi, Et2O, -35 °C; (c) DHP, PTSA, THF, rt, then
LAH, 0 °C; (d) (COCl)2, DMSO, Et3N, CH2Cl2, -78 °C to 0°; then (tert-butoxycarbonylmethylene)triphenylphosphorane; (e) AcOH, H2O,
40 °C, 23% from 21.
derivative, and the pivaloate group was then cleaved with
LAH. Swern oxidation of the resulting alcohol followed
by reaction with (tert-butoxycarbonylmethylene)triph-
enylphosphorane afforded, after treatment with acetic
acid and water, the desired alcohol 20 in 58% overall yield
from 19. The second approach starts with butyrolactone
6 (Scheme 5), which was partially hydrogenated over
Lindlar catalyst, to produce 21 in 85% yield. Addition
of dimethyl cuprate on 21 resulted in retention of
stereochemistry at the electrophilic center and complete
isomerization of the double bond.11 The SN2′ product, also
present in this case, was separated only at the last step.
The sequence was completed in a similar manner as
described for the previous approach. Protection of the
hydroxyl group followed by reduction of the carboxylic
acid afforded alcohol 23. Swern oxidation followed by
Wittig reaction and finally deprotection of the secondary
alcohol afforded 20 in 23% overall yield from 21.
Chlorination of the aromatic ring of the tyrosine moiety
was needed in order to prepare Cryptophycins A and C
as well as our enone analog 1. Introduction of the
chlorine atom could be done directly on the BCD frag-
ment 15 (Scheme 6) by treament with sulfuryl chloride
in acetic acid,4 followed by BOC-ON and triethylamine
to reprotect the amino group. The chloro derivative 24
was obtained in 68% yield from 15. The synthesis of 1
and Cryptophycin C was easily completed by first cou-
(11) Goering, H. L.; Kantner, S. S. J . Org. Chem. 1984, 49, 422.

6292 J . Org. Chem., Vol. 61, No. 18, 1996
Rej et al.
Sch em e 6a
a
(a) SO2Cl2, AcOH, 55 °C; then BOC-ON, Et3N, CH2Cl2 68%; (b) trichlorobenzoyl chloride, Et3N, THF, rt; then 20, DMAP, Et3N,
toluene, rt, 58-68%; (c) TFA, CH2Cl2; (d) O-benzotriazol-1-yl-N,N,N′,N′-bis(pentamethylene)uronium hexafluorophosphate, DIPEA, DMF,
0 °C, 85% for two steps; (e) condition b with 9 instead of 20; (f) condition d, 51% from 24; (g) condition d with DMF replaced by acetonitrile,
35% from 15.
was extracted with ethyl acetate (3 × 300 mL), and the
pling 24 with the appropriate subunit A (9 or 20). The
combined organic phases were washed with water and brine
protecting groups were then cleaved, and the resulting
and then dried over Na2SO4 and evaporated to give 10.1 g
acyclic precursors were cyclized using the same procedure
(73%) of 4. 1H NMR (400 MHz, CDCl3) 7.45 (m, 2H), 7.34 (m,
as described for enone 2. Cryptophycin D was obtained
by coupling 15 with 20, followed by the usual deprotec-
tion and cyclization steps. Finally, Cryptophycins A and
B were prepared from Cryptophycins C and D, respec-
3H), 4.73 and 4.56 (2d, J ) 3.9 and 6.3 Hz, 1H), 4.28 and 4.23
(2m, 1H), 2.88 and 2.73 (2m, 2H); HRMS (M + NH4+) calcd
for C12H16NO4: 238.1079, found: 238.1078.
(4S,5S) a n d (4S,5R) 4-Hyd r oxy-5-(p h en yleth yn yl)d ih y-
tively, by epoxidation with m-chloroperbenzoic acid4 or
d r ofu r a n -2-on e (5 a n d 6). A stirred mixture of 4 (5.0 g, 22.7
dimethyldioxirane.12 The spectroscopic data and the
mmol) and PTSA (200 mg, 1.0 mmol) in benzene (300 mL) was
biological activities of all synthetic Cryptophycins are in
perfect agreement with the reported values.1,4
heated to 50 °C for 1.5 h. The mixture was cooled and
neutralized with pyridine (85 mL), and then the solvent was
evaporated. The residue was purified by flash chromatography
(hexane:EtOAc 3:2) to give 5 (2.0 g, 43%) and 6 (2.1 g, 45%).
Compound 5: mp: 133-135 °C; [R]D -52.2° (c 0.5, CHCl3); IR
(neat film) 3400, 1795, 1156 cm-1; 1H NMR (400 MHz, CDCl3)
7.51 (m, 2H), 7.40 (m, 3H), 5.36 (d, J ) 3.9 Hz, 1H), 4.63 (m,
1H), 2.80 (dd, J ) 5.2, 17.6 Hz, 1H), 2.73 (dd, J ) 2.4, 17.6
Hz, 1H), 2.62 (d, J ) 2.5 Hz, 1H); 13C NMR (75 MHz, CDCl3)
174.1, 132.0, 129.6, 128.5, 120.7, 91.4, 79.7, 75.3, 68.7, 37.1;
HRMS (M+) calcd for C12H10O3: 202.0630, found: 202.0637.
Anal. Calcd for C12H10O3: C, 71.28; H, 4.98. Found: C, 71.16;
H, 5.05. Compound 6: mp 66-68 °C; [R]D +53.6° (c 0.5,
Con clu sion
In summary, we have developed a convergent total
synthesis of Cryptophycins and their 16-(3-phenylacry-
loyl) derivatives. The use of N-hydroxysuccinimide esters
as activated intermediates allowed us to minimize the
use of protecting groups. Compounds 1 and 2, where the
benzylic epoxide of Cryptophycins A and B was replaced
by an enone moiety, were found to be very poor cytotoxic
agents.13 Consequently, the biological activity of Cryp-
tophycin A is not solely related to the electrophilic
character of the benzylic position.
1
CHCl3); IR (neat film) 3430, 1780, 1154 cm-1; H NMR (400
MHz, CDCl3) 7.45 (m, 2H), 7.37 (m, 3H), 5.23 (d, J ) 1.4 Hz,
1H), 4.74 (m, 1H), 3.04 (dd, J ) 5.9, 17.7 Hz, 1H), 2.58 (dd, J
) 2.4, 17.6 Hz, 1H), 2.24 (d, J ) 4.2 Hz, 1H); 13C NMR (75
MHz, CDCl3) 174.7, 131.8, 129.3, 128.4, 121.1, 89.1, 82.2, 76.7,
73.4, 36.9; HRMS (M+) calcd for C12H10O3: 202.0630, found:
202.0637. Anal. Calcd for C12H10O3: C, 71.28; H, 4.98.
Found: C, 71.44; H, 5.08.
Exp er im en ta l Section
Gen er a l Meth od s. Unless otherwise noted, all common
reagents and solvents were used as obtained from commercial
suppliers without further purification. Elemental analysis
were carried out by Canadian Microanalytical Service Ltd.,
Delta, BC. Melting points were determined on a Digital
Melting Point Apparatus and are uncorrected. Merck pre-
coated silica gel 60 F254 plates were used for thin-layer
chromatography (TLC). EM Science silica gel 60 (230-400
mesh ASTM) was used for flash chromatography. All reactions
requiring anhydrous conditions were conducted under a posi-
tive pressure of nitrogen.
(3S,4S) a n d (3S,4R)-3,4-Dih yd r oxy-6-p h en ylh ex-5-yn o-
ic Acid (4). To a stirred solution of (S)-(-)-2-Acetoxysuccinic
anhydride (10 g, 63.2 mmol) in THF (50 mL) at -78 °C was
added dropwise during 25 min a freshly prepared solution of
lithiated phenylacetylene (prepared by treating phenylacety-
lene (6.38 mL, 57.0 mmol) with n-butyllithium (2.5 M, 23 mL)
at -78°C in THF (40 mL)). After the addition, the mixture
was stirred for 10 min. A solution of sodium borohydride (2.5
g) in ethanol (50 mL) was slowly added to the reaction mixture
at -78°C. After 15 min, water (5 mL) was added followed by
a solution of 1 N NaOH (63 mL). The reaction mixture was
warmed up to 0°C, and after 20 min, carefully acidified to pH
4 with 3 N HCl (and 1 N HCl toward the end). The mixture
(5S)-5-H yd r oxy-6-oxo-8-p h en yloct a -2(E),7(E)-d ien oic
Acid ter t-Bu tyl Ester (9). To a stirred solution of butyro-
lactone 6 (519 mg, 2.57 mmol) in ether (25 mL) were added
ethyl vinyl ether (918 mL, 9.60 mmol) and PTSA (17 mg, 0.09
mmol) at 0 °C. After 30 min, the reaction mixture was warmed
up to room temperature and stirred for 1 h. Then lithium
aluminum hydride (273 mg, 7.2 mmol) was added at 0 °C, and
the reaction mixture was stirred at room temperature for 24
h. Methanol (1 mL) was then added, and the reaction mixture
was worked up in ethyl acetate and 5% NaHCO3. The solvents
were evaporated, and the crude diol 7 was dissolved in CH2-
Cl2 (4.5 mL) and added to a solution of DMSO (933 mL, 13.1
mmol) and (COCl)2 (573 mL, 6.57 mmol) in CH2Cl2 (20 mL) at
-78 °C. After 20 min, triethylamine (2.7 mL, 19.4 mmol) was
added and after a few min, the temperature was raised to 0
°C and (tert-butoxycarbonylmethylene)triphenylphosphorane
(1.40 g, 3.72 mmol) was added. After 15 min, the solvent was
evaporated, and the product was purified by flash chromatog-
raphy (hexane-EtOAc 8:1) to give 8 (621 mg, 65% from 6).
The ethoxy ethyl derivative 8 (608 mg, 1.62 mmol) was
dissolved in acetic acid (4 mL) and water (2 mL). After 1 h at
room temperature, the reaction mixture was extracted in CH2-
Cl2 and water. The crude product was purified by trituration
in hexane to give 9 (356 mg, 73%) as a beige solid: mp 72.5-
73.5 °C; [R]D -80.2° (c 1.21, CHCl3); IR (neat film) 3450, 2950,
1711, 1690, 1656, 1610, 1154 cm-1; 1H NMR (400 MHz, CDCl3)
7.76 (d, J ) 16.0 Hz, 1H), 7.58 (m, 2H), 7.43 (m, 3H), 6.85 (d,
(12) Kobayashi, M.; Kurosu, M.; Wang, W.; Kitagawa, I. Chem.
Pharm. Bull. 1994, 42, 2394.
(13) De Muys, J .-M.; Rej, R.; Nguyen, D.; Go, B.; Fortin, S.; Lavalle´e,
J .-F. BioMed. Chem. Lett. 1996, 6, 1111.

Total Synthesis of Cryptophycins
J . Org. Chem., Vol. 61, No. 18, 1996 6293
J ) 16.0 Hz, 1H), 6.84 (m, 1H), 5.86 (d, J ) 15.7 Hz, 1H), 4.58
(dd, J ) 4.4, 7.2 Hz, 1H), 3.71 (broad singlet, 1H), 2.79 (m,
1H), 2.51 (m, 1H), 1.49 (s, 9H); 13C NMR (75 MHz, CDCl3)
199.1, 165.2, 145.4, 141.4, 133.8, 131.3, 129.1, 128.7, 126.4,
120.1, 80.4, 74.4, 37.0, 28.1; HRMS (MH+) calcd for C18H23O4:
303.1596, found: 303.1603. Anal. Calcd for C18H22O4: C,
71.50; H, 7.33. Found: C, 71.26; H, 7.19.
(2R)-3-Azid o-2-m eth ylp r op ion ic Acid (11). (S)-(+)-3-
bromo-2-methyl-1-propanol (9.52 g, 62.3 mmol) and NaN3 (8.1
g, 125 mmol) were heated in DMF (65 mL) at 90-100°C for 3
h. The reaction was worked up by cooling down to room
temperature adding ether, filtering off the solid, and washing
the filtrate several times with water. The ether phase was
washed with brine, dried over MgSO4, and evaporated to give
6.71 g (94%). The residue was then dissolved in acetone (270
mL), and J ones reagent was added in portions until the
mixture permanently turned orange. 2-propanol was added
to quench excess of reagent. The precipitate was filtered off
and rinsed with ether. The filtrate was then washed with
brine and dried over MgSO4. Evaporation of the solvent gave
7.50 g (100%) of azido acid 11: 1H NMR (400 MHz, CDCl3) 3.59
and 3.45 (2dd, J ) 12.2 Hz, 7.1 Hz, 2H), 2.75 (m, 1H), 1.28 (d,
J ) 7.2 Hz, 3H).
(2R)-3-Am in o-2-m eth ylp r op ion ic Acid (12). A solution
of azido acid 11 (7.5 g, 58.1 mmol) and Pd/C 10% (2 g) was
stirred under H2 in EtOAc (200 mL) and EtOH (50 mL) at
room temperature for 48 h. The mixture was then filtered over
Celite. The first organic filtrate was separated and discarded.
The filtration pad was rinsed with water and the aqueous
filtrate evaporated to dryness. The crude solid residue was
recrystallized from methanol and EtOAc yielding 4.17 g (70%)
of the desired â-amino acid 12 as a colorless solid: mp 179-
181 °C; [R]D -14.7° (c 2.60, H2O); 1H NMR (400 MHz, CD3-
OD) 4.9 (bs, 3H), 2.95 (m, 2H), 2.48 (m, 1H), 1.2 (d, J ) 7.2
Hz, 3H); 13C NMR (75 MHz, CD3OD) 179.0, 41.6, 37.7, 13.9;
HRMS (M+) calcd for C4H9NO2: 103.0633, found: 103.0631.
Anal. Calcd for C4H9NO2: C, 46.59; H, 8.80; N, 13.58. Found:
C, 46.44; H, 8.73; N, 13.34.
ate was next dissolved in CH3CN (2.6 mL), and DMAP (135
mg, 1.1 mmol) and (2S)-2-hydroxy-4-methylpentanoic acid (87
mg, 0.66 mmol) were then added at room temperature. After
15 h, 0.1 N HCl was added to the reaction mixture until pH 2,
and then the solution was extracted with EtOAc. The organic
phase was washed with water and brine, and dried over
MgSO4. After evaporation of the solvents, the residue was
purified by flash chromatography (CH2Cl2:MeOH:EtOAc 90:
5:5) to give 15 (110 mg, 85%) as a ligh beige solid: mp 100-
110 °C; [R]D -21.0° (c 4.8, MeOH); IR (neat film) 3315, 2960,
1730, 1668, 1612, 1514, 1463, 1370, 1250 cm-1; 1H NMR (400
MHz, DMSO-d6) 8.78 (broad s, 1H), 7.13 (d, J ) 8.5 Hz, 2H),
6.90 (d, J ) 8.7 Hz, 1H), 6.79 (d, J ) 8.5 Hz, 2H), 4.81 (dd, J
) 3.7, 9.2 Hz, 1H), 4.04 (m, 1H), 3.70 (s, 3H), 3.24 (bt, J ) 5.0
Hz, 2H), 2.82 (dd, J ) 4.8 Hz, 13.7 Hz, 1H), 2.66 (m, 1H), 2.55
(m, 1H), 1.65 (m, 3H), 1.29 (s, 9H), 1.02 (d, J ) 7.0 Hz, 3H),
0.89 (d, J ) 6.2 Hz, 3H), 0.85 (d, J ) 6.2 Hz, 3H); 13C NMR
(75 MHz, DMSO-d6) 173.2, 172.2, 171.5, 157.2, 154.6, 129.7,
129.5, 112.9, 77.4, 72.0, 56.0, 54.4, 40.9, 36.6, 27.7, 27.4, 24.1,
22.6, 21.0, 13.8; HRMS (MH+) calcd for C25H39N2O8: 495.2706,
found: 495.2714.
5(S)-[[2(S)-[[3-[[2(R)-(ter t-Bu t oxyca r b on yla m in o)-3-
(4-m eth oxyp h en yl)p r op ion yl]a m in o]-2(R)-m eth ylp r op io-
n yl]oxy]-4-m et h ylp en t a n oyl]oxy]-6-oxo-8-p h en yloct a -
2(E),7(E)-d ien oic Acid ter t-Bu tyl Ester (16). To a stirred
solution of 15 (104 mg, 0.21 mmol) in THF (1.3 mL) were added
trichlorobenzoyl chloride (37mL, 0.24 mmol) and triethylamine
(37mL, 0.27 mmol). After 3 h, the solvent was evaporated,
and a solution of 9 (53 mg, 0.18 mmol) in toluene (2.5 mL)
was added to the residue. Triethylamine (30 mL, 0.18 mmol)
and DMAP (3 mg, 0.02 mmol) were then added. After 1 h,
the reaction mixture was extracted in CH2Cl2 and 0.1 N HCl,
and the organic phase was washed with brine and dried over
MgSO4. After evaporation of the solvents, the residue was
purified by flash chromatography (hexane:EtOAc 2:1) to give
16 (110 mg, 85%) as a colorless solid. [R]D -42.6° (c 2.2,
CHCl3); IR (neat film) 3350, 2980, 1741, 1713, 1680, 1612,
1514, 1368, 1249, 1171 cm-1; 1H NMR (400 MHz, CDCl3) 7.74
(d, J ) 16.0 Hz, 1H), 7.59 (d, J ) 6.1 Hz, 2H), 7.43 (m, 3H),
7.06 (d, J ) 8.0 Hz, 2H), 6.85 (d, J ) 16.0 Hz, 1H), 6.80 (m,
1H), 6.77 (d, J ) 8.0 Hz, 2H), 6.67 (broad s, 1H), 5.87 (d, J )
15.7 Hz, 1H), 5.51 (broad s, 1H), 5.23 (broad d, 1H), 5.14 (dd,
J ) 4.0, 9.1 Hz, 1H), 4.31 (m, 1H), 3.75 (s, 3H), 3.62 (m, 1H),
3.15 (m, 1H), 3.00 (m, 1H), 2.92 (m, 1H), 2.84 (m, 1H), 2.72
(m, 2H), 1.82 (m, 3H), 1.47 (s, 9H), 1.38 (s, 9H), 1.16 (d, J )
7.0 Hz, 3H), 0.99 (d, J ) 6.1 Hz, 3H), 0.96 (d, J ) 6.0 Hz, 3H);
13C NMR (75 MHz, CDCl3) 192.7, 173.9, 171.5, 170.4, 164.9,
158.2, 155.1, 145.4, 139.7, 133.8, 131.1, 130.1, 128.9, 128.7,
128.6, 126.8, 120.5, 113.7, 80.4, 76.3, 70.6, 55.8, 55.0, 41.6, 40.0,
39.3, 37.9, 33.2, 28.1, 27.9, 24.6, 22.8, 21.4, 14.4; HRMS (MH+)
calcd for C43H59N2O11: 779.4119, found: 779.4114.
3-[[2(R )-(t er t -Bu t oxyca r b on yla m in o)-3-(4-m e t h oxy-
ph en yl)pr opion yl]am in o]-2(R)-m eth ylpr opion ic Acid (14).
To a stirred solution of Boc-D-Tyr(Me)OH (5.00 g, 16.9 mmol)
and N-hydroxysuccinimide (2.92 g, 25.4 mmol) in DME (130
mL) at 0 °C was added DCC (4.37 g, 21.2 mmol). After 36 h,
a solution of (R)-(-)-3-amino-2-methylpropionic acid (2.10 g,
20.3 mmol) and TEA (4.72 mL, 34 mmol) in water (50 mL)
was added, and the reaction mixture was warmed up to room
temperature. After 30 min, the solid was filtered and rinsed
with water. The filtrate was evaporated, and an aqueous
solution of 5% K2CO3 was added to the residue until pH 9 and
extracted with CH2Cl2. The aqueous phase was acidified to
pH 2 and extracted with CH2Cl2. The CH2Cl2 phase was then
washed with brine, dried over MgSO4, and evaporated to give
an oily residue. Ether was added and 14 (6.02 g, 93%)
precipitated out as a colorless solid: mp 119-122 °C; [R]D
-6.9° (c 1.00, H2O); IR (neat film) 3314, 2980, 2940, 1710, 1660,
(3S,6R,10S,16S) 3-Isob u t yl-10-(4-m et h oxyb en zyl)-6-
m eth yl-16-(3-p h en yla cr yloyl)-1,4-d ioxa -8,11-d ia za cyclo-
h exa d ec-13(E)-en e-2,5,9,12-tetr a on e (2). To a stirred so-
lution of compound 16 (106 mg, 0.136 mmol) in CH2Cl2 (3.2
mL) at room temperature was added trifluoroacetic acid (1.6
mL). After 45 min, toluene was added and the solvents were
evaporated. The residue was dissolved in CH3CN (14 mL).
To the stirred solution at 0 °C were added O-benzotriazol-1-
yl-N,N,N′,N′-bis(pentamethylene)uronium hexafluorophos-
phate (75 mg, 0.163 mmol), followed by diisopropylethylamine
(71 mL, 0.408 mmol). After 30 min, the reaction mixture was
extracted in CH2Cl2 and 0.1 N HCl. The organic phase was
washed with brine and dried over MgSO4. The solvents were
evaporated, and the residue was purified by flash chromatog-
raphy (CH2Cl2: acetone 5:1) to give 2 and its 16-epimer (65
mg, 79%) as a 7:1 mixture, respectively. The products were
separated by flash chromatography (hexane:acetone 2:1).
Compound 2: [R]D -8.9° (c 1.1, CHCl3); IR (neat film) 3490,
1
1514, 1465, 1250 cm-1; H NMR (400 MHz, acetone-d6) 10.8
(broad s, 1H), 7.28 (broad s, 1H), 7.16 (d, J ) 8.6 Hz, 2H),
6.83 (d, J ) 8.6 Hz, 2H), 5.99 (bd, J ) 8.6 Hz, 1H), 4.26 (m,
1H, 1H), 3.75 (s, 3H), 3.44 (m, 1H), 3.27 (m, 1H), 3.06 (dd, J )
5.6, 13.8 Hz, 1H), 2.85 (m, 1H), 2.63 (m, 1H), 1.35 (s, 9H), 1.10
(d, J ) 7Hz, 3H); 13C NMR (75 MHz, acetone-d6) 174.7, 170.9,
157.6, 154.4, 129.3, 128.7, 112.7, 77.5, 55.3, 53.6, 40.5, 38.1,
37.1, 26.7, 13.3; HRMS (MH+) calcd for C19H29N2O6: 381.2025,
found: 381.2023. Anal. Calcd for C19H28N2O6: C, 59.99; H,
7.42; N, 7.36. Found: C, 59.77; H, 7.19; N, 7.37.
2(S)-[[3-[[2(R)-(ter t-Bu toxyca r bon yla m in o)-3-(4-m eth -
oxyph en yl)pr opion yl]am in o]-2(R)-m eth ylpr opion yl]oxy]-
4-m eth ylp en ta n oic Acid (15). To a stirred solution of 14
(100 mg, 0.26 mmol) and N-hydroxysuccinimide (61 mg, 0.53
mmol) in DME/CH2Cl2 (1.5 mL/1.5 mL) was added 1-(3-
dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (66
mg, 0.34 mmol) at room temperature. After 24 h, EtOAc was
added, and the solution was washed with water, 0.1 N HCl,
5% NaHCO3, water, and brine. The organic phase was then
dried over MgSO4 and the solvent evaporated to give the
activated hydroxysuccinimide ester (123 mg). The intermedi-
3280, 2960, 1758, 1727, 1678, 1612, 1514, 1248, 1178 cm-1
;
1H NMR (400 MHz, CDCl3) 7.72 (d, J ) 16.0 Hz, 1H), 7.55 (m,
2H), 7.44 (m, 3H), 7.14 (d, J ) 8.6 Hz, 2H), 7.07 (dt, J ) 4.4,
7.1 Hz, 1H), 6.91 (d, J ) 16.0 Hz, 1H), 6.85 (d, J ) 8.6 Hz,
2H), 6.79 (ddd, J ) 4.6, 6.0, 15.1 Hz, 1H), 5.84 (dd, J ) 1.3,
15.2 Hz, 1H), 5.72 (dd, J ) 2.2, 11.5 Hz, 1H), 5.63 (d, J ) 8.0
Hz, 1H), 5.03 (dd, J ) 4.7, 9.4 Hz, 1H), 4.82 (bq, J ) 7.6 Hz,

6294 J . Org. Chem., Vol. 61, No. 18, 1996
Rej et al.
1H), 3.80 (s, 3H), 3.43 (m, 2H), 3.20 (dd, J ) 5.4, 14.5 Hz, 1H),
3.07 (dd, J ) 7.5, 14.5 Hz, 1H), 2.93 (ddd, J ) 2.2, 4.6, 14.7
Hz, 1H), 2.75 (m, 1H), 2.55 (m, 1H), 1.80 (m, 2H), 1.60 (m,
1H), 1.27 (d, J ) 7.4 Hz, 3H), 0.93 (d, J ) 6.5 Hz, 3H), 0.89 (d,
J ) 6.5 Hz, 3H); 13C NMR (75 MHz, CDCl3) 193.6, 175.9, 171.2,
170.1, 165.1, 158.6, 145.6, 140.1, 133.9, 131.3, 130.1, 129.1,
128.6, 128.5, 126.0, 120.4, 114.1, 76.3, 71.3, 55.2, 54.3, 40.4,
39.6, 37.9, 35.3, 34.8, 24.5, 22.7, 21.7, 14.3. Anal. Calcd for
(5S,6R)-5-Hyd r oxy-6-m eth yl-8-p h en ylocta -2(E),7(E)-d i-
en oic Acid ter t-Bu tyl Ester (20). To a stirred solution of
19 (44 mg, 0.145 mmol) in THF (1.5 mL) at room temperature
were added dihydropyran (80 mL, 0.86 mmol) and PTSA (3
mg, 0.02 mmol). After 2 h, the reaction mixture was worked
up in CH2Cl2 and 5% NaHCO3. The organic phase was washed
brine and dried over MgSO4. The solvent was evaporated, and
the residue was dissolved in THF (1.5 mL). To the stirred
solution at 0°C was added LAH (6.2 mg, 0.16 mmol). After
15 min, the reaction mixture was worked up in CH2Cl2 and
0.1 N HCl. The organic phase was washed NaHCO3 5% and
brine and dried over MgSO4. After evaporation of the solvents,
the residue was dissolved in CH2Cl2 (0.5 mL) and added to a
stirred solution of DMSO (72 mL, 0.52 mmol) and oxalyl
chloride (24 mL, 0.34 mmol) in CH2Cl2 (2 mL) at -78 °C. After
30 min, triethylamine (72 mL, 0.52 mmol) was added and the
solution was warmed up to 0 °C. After 15 min, (tert-butoxy-
carbonylmethylene)triphenylphosphorane (64 mg, 0.17 mmol)
was added and the solution was stirred for another 20 min.
The mixture was then worked up in CH2Cl2 and 0.1 N HCl.
The organic phase was washed 5% NaHCO3 and brine and
dried over MgSO4. After evaporation of the solvent, the
residue was purified by flash chromatography (hexane:EtOAc
5:1) to give 38 mg, (65%) from 19. The product was then
dissolved in acetic acid (1.0 mL) and water (0.5 mL), and the
solution was stirred at 40°C for 30 min. The reaction mixture
was extracted in CH2Cl2 and water. The organic phase was
washed 5% NaHCO3 and brine and dried over MgSO4. The
solvent was evaporated and the residue purified by flash
chromatography (hexane:EtOAc 5:1) to give 20 (24 mg, 80%).
[R]D +46.7° (c 0.83, CHCl3); IR (neat film) 3450, 2930, 1700,
C
34H40N2O8: C, 67.53; H, 6.67; N, 4.63. Found: C, 67.02 H,
6.64; N, 4.62. 16-ep im er [R]D -3.8° (c 0.4, CHCl3); IR (neat
film) 3300, 2960, 1738, 1680, 1612, 1513, 1248, 1178 cm-1; 1H
NMR (400 MHz, CDCl3) 8.16 (d, J ) 16.4 Hz, 1H), 7.72 (m,
2H), 7.43 (m, 3H), 7.16 (d, J ) 8.5 Hz, 1H), 7.06 (d, J ) 8.6
Hz, 2H), 7.01 (d, J ) 16.4 Hz, 1H), 6.75 (m, 2H), 6.68 (d, J )
8.6 Hz, 2H), 6.02 (bd J ) 9.7 Hz, 1H), 5.94 (d, J ) 15.8 Hz,
1H), 4.99 (dd, J ) 5.0, 9.3 Hz, 1H), 4.77 (m, 1H), 3.72 (s, 3H),
3.64 (m, 1H), 3.11 (m, 1H), 2.96 (m, 3H), 2.78 (m, 1H), 2.68
(m, 1H), 1.90 (m, 1H), 1.77 (m, 2H), 1.20 (d, J ) 6.9 Hz, 3H),
1.01 (d, J ) 6.6 Hz, 3H), 0.98 (d, J ) 6.5 Hz, 3H); HRMS (M+)
calcd for C34H40N2O8: 604.2784, found: 604.2789.
(3S,4S)-3-(Tetr ah ydr opyr an -2-yloxy)-6-ph en ylh ex-5(E)-
en e-1,4-d iol (17). To a stirred solution of 5 (265 mg, 1.23
mmol) in THF (4 mL) at room temperature were added
dihydropyran (206 mL, 2.26 mmol) and p-toluenesulfonic acid
(22 mg, 0.12 mmol). After 3 h, the reaction mixture was
worked up in EtOAc and 5% NaHCO3, and the organic phase
was washed with brine and dried over MgSO4. The solvents
were evaporated, and the residue was dissolved in ether (6
mL). The solution was added to a suspension of LAH (160
mg, 4.22 mmol) in ether (26 mL), and the mixture was stirred
at room temperature overnight. Methanol (1 mL) was then
added, and the reaction mixture was worked up with EtOAc
and 0.1 N HCl. The organic phase was washed with brine
and dried over Na2SO4. The solvents were then evaporated
to give the crude diol 17 (346 mg, 92%). 1H NMR (400 MHz,
CDCl3) 7.34 (m, 5H), 6.69 (2d, J ) 13.7 Hz, 1H), 6.18 (2 dd, J
) 6.4, 13.7 Hz, 1H), 4.60 (2d, J ) 7.0, 7.6 Hz, 1H), 4.20 (1m,
1H), 4.10 (1m, 1H), 3.90 (1m, 1H), 3.70 (m, 2H), 3.55 (m, 1H),
1.85 (m, 3H), 1.70 (m, 1H), 1.60 (m, 3H); HRMS (MNH4+) calcd
for C17H28NO4: 310.2018, found: 310.2025.
1
1654, 1368, 1154 cm-1; H NMR (400 MHz, CDCl3) 7.38 (m,
2H), 7.32 (m, 2H), 7.24 (m, 1H), 6.92 (dt, J ) 7.3, 15.6 Hz,
1H), 6.49 (d, J ) 16.0 Hz, 1H), 6.15 (dd, J ) 8.6, 16.0 Hz, 1H),
5.86 (dt, J ) 1.4, 15.6 Hz, 1H), 3.66 (m, 1H), 2.44 (m, 2H),
2.36 (m, 1H), 1.76 (d, J ) 3.9 Hz, 1H), 1.50 (s, 9H), 1.16 (d, J
) 6.9 Hz, 3H); 13C NMR (75 MHz, CDCl3) 165.7, 144.0, 137.0,
131.9, 131.0, 128.5, 127.4, 126.2, 125.5, 80.2, 73.9, 43.2, 37.2,
28.1, 16.8); HRMS (MNH4+) calcd for C19H30NO3: 320.2226,
found: 320.2219.
2(S)-[[3-[[2(R)-(ter t-Bu toxyca r bon yla m in o)-3-(3-ch lor o-
4-m eth oxyp h en yl)p r op ion yl]a m in o]-2(R)-m eth ylp r op io-
n yl]oxy]-4-m eth ylp en ta n oic Acid (24). A mixture of 15
(600 mg, 1.21 mmol) and freshly distilled sulfuryl chloride
(0.107 mL, 1.33 mmol) in glacial acetic acid (6 mL) was heated
at 55 °C for 30 min. The reaction mixture was then cooled
down to room temperature, and the solvent was evaporated
to give 718 mg of the deprotected chloro tyrosine derivative.
This crude product was then dissolved in CH2Cl2 (14 mL) and
BOC-ON (449 mg, 1.82 mmol) and triethylamine (372 mL, 2.69
mmol) were added. After stirring at room temperature
overnight, 0.1 N HCl was added and the reaction mixture
extracted with CH2Cl2. The organic phase was washed with
water and brine and dried over MgSO4. The solvent was
evaporated, and the residue was purified by flash chromatog-
raphy (from CHCl3:EtOAc 95:5 to CHCl3:EtOAc:MeOH 85:10:
5) to give 438 mg (68%) of 24 as a light yellow solid: mp 75-
80 °C; [R]D -21.8° (c 5.55, MeOH); IR (neat film) 3305, 2960,
1733, 1658, 1590, 1504, 1260 cm-1; 1H NMR (400 MHz, DMSO-
d6) 8.60 (broad s, 1H,), 7.29 (s, 1H), 7.16 (d, J ) 8.4 Hz, 1H),
7.02 (d, J ) 8.4 Hz, 1H), 6.91 (d, J ) 8.8 Hz, 1H), 4.81 (m,
1H), 4.05 (m, 1H), 3.80 (s, 3H), 3.27 (m, 2H), 2.81 (m, 1H),
2.65 (m, 1H), 2.57 (m, 1H), 1.65 (m, 3H), 1.29(s, 9H), 1.03 (d,
J ) 7.0 Hz, 3H), 0.88 (d, J ) 6.2 Hz, 3H), 0.85 (d, J ) 6.2 Hz,
3H); 13C NMR (400 MHz, DMSO-d6) 173.3, 171.3, 154.7, 152.5,
130.9, 130.0, 128.6, 128.4, 127.7, 124.8, 119.9, 111.9, 77.5, 71.3,
55.6, 55.5, 40.8, 36.1, 27.6, 24.0, 22.5, 21.0, 13.8; HRMS (MH+)
calcd for C25H38ClN2O8: 529.2317, found: 529.2302.
(3S,4S)-2,2-Dim et h ylp r op ion ic
Acid
4-Acet oxy-3-
h yd r oxy-6-p h en ylh ex-5(E)-en yl Ester (18). To a stirred
solution of compound 17 (320 mg, 1.04 mmol) in CH2Cl2 (2
mL) and pyridine (2 mL) at 0 °C were added trimethylacetyl
chloride (515 mL, 4.18 mmol) and DMAP (32 mg, 0.20 mmol).
After 3 h, acetic anhydride was added and the solution was
stirred another 3 h. After workup, the residue was purified
by flash chromatography (hexane:EtOAc 4:1) to give 264 mg
(59%) of the fully protected compound. The product (208 mg,
0.48 mmol) was dissolved in acetic acid (5 mL) and water (2.5
mL) and stirred at room temperature for 3 h. The reaction
mixture was extracted in CH2Cl2 and water. The organic
phase was washed 5% NaHCO3 and brine and dried over
MgSO4. The solvent was evaporated to give 18 (164 mg,
98%): 1H NMR (400 MHz, CDCl3) 7.41 (m, 2H), 7.33 (m, 3H),
6.72 (d, J ) 16.0 Hz, 1H), 6.19 (dd, J ) 7.6, 16.0 Hz, 1H), 5.38
(m, 1H), 4.34 (m, 1H), 4.22 (m, 1H), 3.85 (m, 1H), 2.38 (broad
d, J ) 4.2 Hz, 1H), 2.14 (s, 3H), 1.89 (m, 1H), 1.76 (m, 1H),
1.21 (s, 9H).
(3S,4S)-2,2-Dim eth ylpr opion ic Acid 3-Hydr oxy-4-m eth -
yl-6-p h en ylh ex-5(E)-en yl Ester (19). To a stirred suspen-
sion of CuI (446 mg, 2.23 mmol) in ether (10 mL) at 0 °C was
slowly added a solution of methyllithium in ether (3.1 mL, 1.4
M). After 10 min, 18 (147 mg, 0.42 mmol) in ether (2 mL)
was added. After 20 min, the reaction mixture was extracted
in CH2Cl2 and 0.1 N HCl. The organic phase was washed 5%
NaHCO3 and brine and dried over MgSO4. The solvent was
evaporated and the residue was purified by flash chromatog-
raphy (hexane:EtOAc 6:1) to give 19 (44 mg, 34%): 1H NMR
(400 MHz, CDCl3) 7.37 (m, 2H), 7.25 (m, 3H), 6.47 (d, J ) 16.0
Hz, 1H), 6.17 (dd, J ) 8.5, 16.0 Hz, 1H), 4.32 (m, 1H), 4.22
(m, 1H), 3.60 (m, 1H), 2.40 (m, 1H), 2.08 (d, J ) 4.0 Hz), 1.90
(m, 1H), 1.74 (m, 1H), 1.22 (s, 9H), 1.17 (d, J ) 6.8 Hz, 3H);
13C NMR (75 MHz, CDCl3) 178.8, 137.1, 131.5, 131.4, 128.7,
127.3, 126.1, 72.1, 61.8, 43.6, 38.7, 33.6, 27.2, 16.7.
(3S,6R,10S,16S)-3-Isobu tyl-10-(3-ch lor o-4-m eth oxyben -
zyl)-6-m eth yl-16-(3-p h en yla cr yloyl)-1,4-d ioxa -8,11-d ia za -
cycloh exa d ec-13(E)-en e-2,5,9,12-tetr a on e (1). 9 and 24
were coupled with the same procedure used for the preparation
of 16 and gave the coupling product in 79% (64 mg): [R]D
-41.2° (c 2.0, CHCl3); IR (neat film) 3350, 3000, 1741, 1713,
1685, 1662, 1610, 1504, 1258, 1170 cm-1; 1H NMR (400 MHz,
CDCl3) 7.74 (d, J ) 16.0 Hz, 1H), 7.58 (d, J ) 6.6 Hz, 1H),

Total Synthesis of Cryptophycins
J . Org. Chem., Vol. 61, No. 18, 1996 6295
7.42 (s, 1H), 7.02 (d, J ) 7.5 Hz, 1H), 6.82 (m, 2H), 6.79 (d, J
) 8.3 Hz, 1H), 5.89 (d, J ) 15.6 Hz, 1H), 5.54 (broad s, 1H),
5.32 (broad s, 1H), 5.16 (dd, J ) 4.0, 9.1 Hz, 1H), 4.34 (m,
1H), 3.86 (s, 3H), 3.68 (m, 1H), 3.17 (m, 1H), 3.01 (m, 1H),
2.86 (m, 2H), 2.73 (m, 2H), 1.83 (m, 3H), 1.60 (m, 1H), 1.49 (s,
9H), 1.39 (s, 9H), 1.19 (d, J ) 7.0 Hz, 3H), 1.00 (d, J ) 5.9 Hz,
3H), 0.97 (d, J ) 6.0 Hz, 3H); 13C NMR (400 MHz, CDCl3)
193.6, 173.9, 171.3, 170.9, 165.1, 155.2, 153.7, 145.6, 139.8,
133.9, 131.2, 131.0, 130.1, 129.0, 128.7, 128.5, 127.0, 121.9,
120.6, 112.1, 80.6, 79.7, 76.4, 70.7, 56.0, 55.7, 41.8, 40.3, 39.5,
37.7, 33.4, 28.2, 28.0, 24.8, 23.0, 21.5, 14.5; HRMS (M+) calcd
for C43H58ClN2O11: 813.3729, found: 813.3735. The depro-
tection and the cyclization steps were run as compound 2 (31
mg, 64%): [R]D -10.0° (c 1.07, CHCl3); IR (neat film) 3405,
3280, 3000, 1758, 1725, 1674, 1610, 1504, 1172 cm-1; 1H NMR
(400 MHz, CDCl3) 7.70 (d, J ) 16.0 Hz, 1H), 7.55 (m, 1H),
7.40 (m, 3H), 7.24 (d, J ) 2.0 Hz, 1H), 6.92 (d, J ) 16.0 Hz,
1H), 6.85 (d, J ) 8.4 Hz, 1H), 6.77 (ddd, J ) 4.7, 10.5, 15.2
Hz, 1H), 5.98 (d, J ) 8.3 Hz, 1H), 5.89 (d, J ) 15.2 Hz, 1H),
5.69 (dd, J ) 2.1, 11.5 Hz, 1H), 5.02 (dd, J ) 4.7, 9.5 Hz, 1H),
4.82 (m, 1H), 3.87 (s, 3H), 3.47 (m, 1H), 3.41 (m, 1H), 3.18
(dd, J ) 5.2, 14.5 Hz, 1H), 2.99 (dd, J ) 8.0, 14.5 Hz, 1H),
2.93 (dd, J ) 2.4, 12.4 Hz, 1H), 2.74 (m, 1H), 2.53 (m, 1H),
1.77 (m, 2H), 1.58 (m, 1H), 1.26 (d, J ) 7.2 Hz, 3H), 0.91 (d, J
) 6.5 Hz, 3H), 0.87 (d, J ) 6.4 Hz, 3H); 13C NMR (400 MHz,
CDCl3) 193.5, 175.6, 171.0, 170.1, 165.3, 153.9, 145.6, 140.2,
133.9, 131.3, 130.9, 129.8, 129.1, 128.6, 128.3, 126.0, 122.4,
120.4, 112.2, 76.3, 71.3, 56.1, 54.1, 40.7, 39.6, 37.9, 35.0, 34.8,
24.6, 22.8, 21.7, 14.2; IRMS (M+) calcd for C34H39ClN2O8:
638.2395, found: 638.2388.
Cr yp t op h ycin C. Cryptophycin C was prepared by the
coupling between 20 and 24 followed by the deprotection and
the cyclization steps (37 mg, 58% overall). 1H NMR, 13C NMR,
IR, HRMS, and [R]D are in perfect agreement with the reported
values.4
Cr yp top h ycin D. Cryptophycin D was prepared by the
coupling between 15 and 20 followed by the deprotection and
the cyclization steps (7 mg, 35% overall). 1H NMR, 13C NMR,
IR, HRMS, and [R]D are in perfect agreement with the reported
values.4
Ack n ow led gm en t. We would like to thank the
Natural Sciences and Engineering Research Council of
Canada (NSERC) for an undergraduate research award
to B.G., Dr. S. Lamothe for his help in preparing this
manuscript, and Dr. G. Attardo for his support.
Su p p or tin g In for m a tion Ava ila ble: Copies of 1H and/
or 13C NMR spectra for 1, 2, 4-9, 11, 12, 14-20, 24 and
Cryptophycins A, C, D (36 pages). This material is contained
in libraries on microfiche, immediately follows this article in
the microfilm version of the journal, and can be ordered from
the ACS; see any current masthead page for ordering
information.
J O960816B