Total Synthesis of Cryptophycins-1, -3, -4, -24 (Arenastatin A), and -29, Cytotoxic Depsipeptides from Cyanobacteria of the Nostocaceae

Article abstract of DOI:10.1021/jo9907585

A convergent synthesis of cryptophycins has been developed in which (5S,6R)-5-hydroxy-6-methyl-8-phenylocta-2(E),7(E)-dienoic acid (A) is coupled with an amino acid segment (B). Two stereo-selective routes to A are described, the first employing allylatio

Full text of DOI:10.1021/jo9907585

6206
J . Org. Chem. 1999, 64, 6206-6216
Tota l Syn th esis of Cr yp top h ycin s-1, -3, -4, -24 (Ar en a sta tin A), a n d
-29, Cytotoxic Dep sip ep tid es fr om Cya n oba cter ia of th e
Nostoca cea e
J ames D. White,* J ian Hong, and Lonnie A. Robarge
Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003
Received May 6, 1999
A convergent synthesis of cryptophycins has been developed in which (5S,6R)-5-hydroxy-6-methyl-
8-phenylocta-2(E),7(E)-dienoic acid (A) is coupled with an amino acid segment (B). Two stereo-
selective routes to A are described, the first employing allylation of an R-homochiral aldehyde and
the second using asymmetric crotylation of an achiral aldehyde to establish the two stereogenic
centers present in A. The styryl moiety of A was attached either via Stille coupling or through a
Wadsworth-Emmons condensation with diethyl benzylphosphonate. The amino acid subunit B
was prepared from benzyl (2S)-2-hydroxyisocaproate by connection first to N-Boc-â-alanine or its
(2R)-methyl-substituted derivative and then to (2R)-N-Boc-O-methyltyrosine or its m-chloro
derivative. Fusion of the A and B subunits was accomplished by initial esterification of the former
with the latter, followed by macrocyclization using diphenyl phosphorazidate. In this way,
cryptophycin-3, -4, and -29 were obtained along with the nonnatural cyclic depsipeptide 52.
Epoxidation of cryptophycin-3 with dimethyldioxirane gave cryptophycin-1; analogous epoxidation
of 52 afforded arenastatin A (cryptophycin-24).
The cryptophycins are macrocyclic depsipeptides1 that
cin-29) was also isolated from this same Nostoc species
that has now yielded more than 20 members of the
cryptophycin family.3 Structural variation within the
subset of macrocyclic cryptophycins is centered on three
sites: (a) the styryl residue in 3, 4, and 6 that is
epoxidized in 1, 2, and 5, (b) the â-alanine residue in 5
and 6 that is methylated at the R-carbon in 1-4, and (c)
the (R)-O-methyltyrosinyl residue of 2, 4, and 5 that
bears a m-chloro substituent in 1, 3, and 6. A compre-
hensive study of in vivo structure-activity relationships
among these cryptophycins indicates that all three of
these modifications contribute positively to their cytotoxic
action.3
The first synthesis of a cryptophycin was completed
by Kitagawa who prepared both arenastatin A (crypto-
phycin-24, 5) and its epoxide stereoisomer.9 Shortly
thereafter, Moore and Tius reported syntheses of “cryp-
tophycins C” (3) and “D” (4), which resulted in revision
of the configuration of 3 (and by correlation that of 1) at
the O-methyltyrosinyl moiety to (9′R).5 Syntheses of the
four cryptophycins 1-4 have been described by La-
valle´e,10 and Sih has completed syntheses of 1 and 3 by
a chemoenzymatic route.11 Leahy has also synthesized 1
using the chlorohydrin, cryptophycin-8, as precursor to
the epoxide.12 Formal syntheses of 1 and 5 have been
claimed by Georg13 and by Shimizu,14 each of whom
prepared the (5S,6S)-5-hydroxy-6-methyl-8-phenyl-2(E),
7(E)-octadienoic acid moiety of cryptophycins in stereo-
typically exhibit potent tumor-selective cytotoxicity.2 For
example, cryptophycin-1 (1) has an IC50 value of 20 pM
against SKOV3 human ovarian carcinoma and has shown
excellent activity against solid tumors implanted in mice,
including a drug-resistant tumor.3 The first cryptophycin
was isolated by a team of scientists at Merck from a blue-
green alga (cyanobacterium) belonging to the Nosto-
caceae.4 Its structure was established as 1 by Moore et
al.,5 who had isolated this and six additional cytotoxic
cryptophycins independently from Nostoc sp. GSV 224.
Among these were cryptophycins-2 (2), -3 (3), and -4 (4).6
At approximately the same time, Kitagawa isolated a
powerfully cytotoxic depsipeptide that he named arena-
statin A from the Okinawan marine sponge Dysidea
arenaria.7 This compound was subsequently found to be
identical with cryptophycin-24 (5) isolated by Moore and
has been shown to strongly inhibit tubulin assembly in
vitro.8 A closely related cyclic depsipeptide 6 (cryptophy-
(1) Subbaraju, G. V.; Galakoti, T.; Patterson, G. M. L.; Moore, R. E.
J . Nat. Prod. 1997, 60, 302.
(2) Smith, C. D.; Zhang, X.; Mooberry, S. L.; Patterson, G. M. L.;
Moore, R. E. Cancer Res. 1994, 54, 3779.
(3) Golakoti, T.; 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) 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.
(5) Barrow, R. A.; Hemscheidt, T.; Liang, J .; Paik, S.; Moore, R. E.;
Tius, M. A. J . Am. Chem. Soc. 1995, 117, 2479.
(6) 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.
(9) (a) Kobayashi, M.; Kurosu, M.; Wang, W.; Kitagawa, I. Chem.
Pharm. Bull. (J apan) 1994, 42, 2394. (b) Kobayashi, M.; Wang, W.;
Ohyabu, N.; Kurosu, M.; Kitagawa, I. Chem. Pharm. Bull. (J apan)
1995, 43, 1598.
(7) (a) Kobayashi, M. Aoki, S.; Ohyabu, N.; Kurosu, M.; Wang, W.;
Kitagawa, I. Tetrahedron Lett. 1994, 35, 7969. (b) Kobayashi, M.;
Kurosu, M.; Ohyabu, N.; Wang, W.; Fujii, S.; Kitagawa, I. Chem.
Pharm. Bull. (J apan) 1994, 42, 2196.
(8) (a) Koiso, Y.; Morita, K.; Kobayashi, M.; Wang, W.; Ohyabu, N.;
Iwasaki, S. Chem.-Biol. Interact. 1996, 102, 183. (b) Morita, K.; Koiso,
Y.; Hasimoto, Y.; Kobayashi, M.; Wang, W.; Ohyabu, N.; Iwasaki, I.
Biol. Pharm. Bull. (J apan) 1995, 43, 1598.
(10) Rej, R.; Nguyen, D.; Go, B.; Fortin, S.; Lavalle´e, J .-F. J . Org.
Chem. 1996, 61, 6289.
(11) Salamonczyk, G. M.; Han, K.; Guo, Z.-W.; Sih, C. J . Org. Chem.
1996, 61, 6893.
(12) Leahy, J . W.; Gardinier, K. M. J . Org. Chem. 1997, 62, 7098.
(13) Ali, S. M.; Georg, G. I. Tetrahedron Lett. 1997, 38, 1703.
(14) Furuyama, M.; Shimizu, I. Tetrahedron: Asymmetry 1998, 9,
1351.
10.1021/jo9907585 CCC: $18.00 © 1999 American Chemical Society
Published on Web 08/04/1999

Total Synthesis of Cryptophycins
J . Org. Chem., Vol. 64, No. 17, 1999 6207
methyltyrosine. Our synthesis plan followed the logic
implied in this dissection, with the objective of first
connecting B to A via an ester linkage before closing the
16-membered ring by macrolactamization. This approach
differs from that of Kitagawa’s in his synthesis of 5,
where an intramolecular Wadsworth-Emmons conden-
sation was used to close the macrocycle at C2-C3.8
However, macrolactamization has been favored as the
finale in subsequent approaches to cryptophycins,9-12
including a synthesis of arenastatin A (5) previously
reported from our laboratories.17
Our first route to fragment A began with allylation of
(R)-aldehyde 7 with stannane 8. Keck’s conditions for this
allylation18 afforded the anti (9) and syn homoallylic
alcohols in a diastereomeric ratio of 11:1, but decreasing
the reaction temperature to -100 °C as recommended
by Linderman19 improved this ratio to 20:1. After puri-
fication, 9 was converted to its tert-butyldimethylsilyl
(TBDMS) ether 10, which underwent oxidative cleavage
of the alkene to yield aldehyde 11. The latter was
subjected to a Wittig reaction with phosphorane 1220 and
afforded trans R,â-unsaturated tert-butyl ester 13 in
excellent yield.
selective fashion, and recently an improved synthesis of
this acid using a [2,3]-Wittig rearrangement was re-
ported.15 A group at Eli Lilly has actively pursued
synthetic analogues of cryptophycins with promising
results.16
A strategy common to many of the approaches to
cryptophycins is one that partitions the structure into
two halves, a δ-hydroxy acid (A) and a peptidic subunit
(B). The latter is comprised of three segments, (2S)-2-
hydroxyisocaproate, a â-alanine derivative, and (2R)-O-
Our intention with 13 was to homologate this sub-
stance at C7 through a pathway that would create the
7(E) olefin of A while permitting incorporation of the
terminal aryl substituent in a manner that could accom-
modate wide structural variation. Although a phenyl
group is required for A, other aryl substituents as well
as alkyl residues are envisioned as surrogates in prospec-
tive cryptophycin analogues. An attractive means for
accessing these structural variants appeared to be a Stille
coupling,21 and 13 was therefore advanced in a direction
that could be adapted to this strategy.
First, the p-methoxybenzyl group was removed from
13 with DDQ in a biphasic solvent system, and the
(15) Ling, J .; Hoard, D. W.; Khao, V. V.; Martinelli, M. J .; Moher,
E. D.; Moore, R. E.; Tius, M. A. J . Org. Chem. 1999, 64, 1459.
(16) Dhotke, U. P.; Khan, V. V.; Hutchison, D. R.; Martinelli, M. J .
Tetrahedron Lett. 1998, 39, 8771.
(17) White, J . D.; Hong, J .; Robarge, L. A. Tetrahedron Lett. 1998,
39, 8779.
(18) Keck, G. E.; Park, M.; Krishnamurthy, D. J . Org. Chem. 1993,
58, 3787.
(19) Linderman, R. J .; Cusack, K. P.; Taber, M. R. Tetrahedron Lett.
1996, 37, 6649.
(20) Chuang, C.-P.; Hart, D. J . J . Org. Chem. 1983, 48, 1782.
(21) Farina, V.; Krishnamurthy, V.; Scott, W. J . Org. React. 1997,
50, 1.

6208 J . Org. Chem., Vol. 64, No. 17, 1999
White et al.
primary alcohol 14 was oxidized to 15. A Takai reaction22
of this aldehyde using iodoform gave the (E)-iodoalkene
16, which was coupled to phenyltrimethylstannane (17)
in the presence of palladium dichloride bisacetonitrile
complex.23 The resultant styrene derivative 18 was then
deprotected to furnish hydroxy ester 19.
Segment B was initially prepared in its least substi-
tuted version corresponding to the peptidic subunit of
arenastatin A (5). Benzyl (-)-2-hydroxyisocaproate (28)28
was coupled to N-Boc-â-alanine (29), and the resultant
diester 30 was deprotected to give the free amine 31. The
latter was next condensed with N-Boc-O-methyl-D-ty-
rosine (32), affording 33 in quantitative yield. Subsequent
hydrogenolysis of the benzyl ester gave carboxylic acid
34. Analogous treatment of 31 with N-Boc-3-chloro-O-
Although the nine-step pathway leading from 7 to 19
is relatively efficient (14% yield overall), the need to
remove an unwanted stereoisomer from the initial allyl-
ation mixture prompted a search for a fully stereoselec-
tive method for incorporating the two asymmetric centers
of 9. Reagent-controlled crotylation of an achiral aldehyde
in which both diastereo- and enantioselectivity are
orchestrated by a chiral element in the nucleophilic
partner seemed the best option for achieving this objec-
tive. Thus, coupling of the known aldehyde 2024 with
Brown’s (E)-crotyldiisopinocampheylborane (21),25 pre-
pared from (+)-diisopinocampheyl(methoxy)borane, yielded
the anti homoallylic alcohol 22 with no visible trace of
the syn stereoisomer (dr > 50:1). The enantiomeric excess
of 22, as measured on its Mosher ester,26 was 93%. After
conversion of 22 to bis silyl ether 23, the terminal alkene
was cleaved by ozonolysis to furnish aldehyde 24. Wads-
worth-Emmons olefination of 24 with diethylbenzylphos-
phonate27 gave alkene 25 as the E stereoisomer exclu-
sively. The primary silyl ether of 25 was cleaved selec-
tively and in quantitative yield with HF-pyridine complex,
and the resulting primary alcohol 26 was oxidized to
aldehyde 27 with Dess-Martin periodinane. Wittig ole-
fination of 27 with phosphorane 1220 produced 18,
identical with the substance obtained from 7. This route
afforded hydroxy ester 19 in an overall yield of 20% from
20.
(22) Takai, K.; Nitta, K.; Utimoto, K. J . Am. Chem. Soc. 1986, 108,
7408.
(23) Stille, J . K.; Groh, B. L. J . Am. Chem. Soc. 1987, 109, 813.
(24) Kozikowski, A. P.; Stein, P. D. J . Org. Chem. 1984, 49, 2301.
(25) J adhar, P. K.; Bhat, K. S.; Perumal, P. T.; Brown, H. C. J . Org.
Chem. 1986, 57, 432.
methyl-D-tyrosine (35), prepared by chlorination of N-
acetyl-O-methyl-D-tyrosine with sulfuryl chloride5 fol-
lowed by protection with Boc anhydride, gave 36, from
which the benzyl ester was removed by hydrogenolysis.
(26) Sullivan, G. R.; Dale, J . A.; Mosher, H. S. J . Org. Chem. 1973,
38, 2143.
(27) J ohns, A.; Murphy, J . A.; Sherburn, M. S.; Tetrahedron 1989,
45, 7835.
(28) Fredrick, D.; Bengt, F.; Leif, G.; Ulf, R. J . Chem. Soc., Perkin
Trans. 1 1993, 11.

Total Synthesis of Cryptophycins
J . Org. Chem., Vol. 64, No. 17, 1999 6209
The resultant carboxylic acid 37 represents the peptidic
moiety of 6.
The connection of A and B subunits was made through
esterification of hydroxy ester 19 successively with car-
boxylic acids 34, 37, 45, and 47. This afforded amino ester
derivatives 48-51, respectively, in high yield and set the
stage for final ring closure via macrolactamization. The
Boc protecting group and tert-butyl ester of each coupled
product were cleaved in a single step with CF3CO2H, and
the resultant amino acids were immediately activated as
their acyl azides.30 Spontaneous cyclization occurred to
give desepoxyarenastatin A (52), cryptophycin-3 (3),
cryptophycin-4 (4), and cryptophycin-29 (6) from 48, 51,
50, and 49, respectively. Spectral data (IR, 1H NMR, and
13C NMR) for 3, 4, and 6, were in excellent agreement
with those recorded for the natural materials.3,11
For the synthesis of the peptidic segment correspond-
ing to cryptophycins-1-4 (1-4), it was necessary to insert
a (2R)-3-amino-2-methylpropionate subunit in place of
â-alanine. Synthesis of the requisite N-protected amino
acid 38 was accomplished from (2S)-3-bromo-2-methyl-
propanol (39) by displacement with sodium azide10 fol-
lowed by hydrogenation of the azido alcohol 40 in the
presence of Boc anhydride.29 This furnished the protected
amino alcohol 41, which was then oxidized to 38. Esteri-
fication of 38 with alcohol 28 afforded diester 42, from
which the Boc protection was removed to yield amine 43.
Coupling of 43 to D-tyrosine derivative 32 gave the
dipeptide 44, and hydrogenolysis of this benzyl ester
produced carboxylic acid 45. Analogous coupling of 43
Epoxidation of 52 to arenastatin A (5) and its stereo-
isomer 53 with dimethyldioxirane has been previously
reported by Kitagawa to yield a 2.2:1 ratio of 5:53.7b
with the chlorinated tyrosine 35 yielded peptide 46,
which was converted to 47 upon hydrogenolysis.
Lowering the temperature of this reaction to -30 °C was
found to slightly improve this ratio to 3:1 in favor of 5.
(30) Shioiri, T.; Ninomiya, K.; Yamada, S. J . Am. Chem. Soc. 1972,
94, 6203.
(29) Pearson, A. J .; Shin, H. J . Org. Chem. 1994, 59, 2314.

6210 J . Org. Chem., Vol. 64, No. 17, 1999
White et al.
δ 159.2, 135.2, 129.9, 129.2, 117.1, 113.8, 75.0, 74.4, 73.0, 55.2,
39.3, 37.79, 13.78; HRMS (CI, m/z) calcd for C15H22O3 (M+)
250.1569, found 250.1565.
The mixture of arenastatin (5) and epiarenastatin (53)
was separated by HPLC, and the major component was
shown to be identical spectroscopically with natural
arenastatin A.3 Analogous epoxidation of cryptophycin-3
(3) at -30 °C gave cryptophycin-1 (1) and its epimer 54,
also in a 3:1 ratio, respectively. After separation, 1 was
found to be identical with natural cryptophycin-1 by
comparison of spectral data with those published by Sih.11
ter t-Bu tyld im eth ylsilyl Eth er 10. To a solution of 9 (1.25
g, 5.00 mmol) in dry DMF (16.7 mL) were added imidazole
(852 mg, 12.5 mmol) and tert-butyldimethylsilyl chloride (1.13
g, 7.51 mmol). The mixture was stirred at room temperature
for 18 h, and H2O was added to quench the reaction. The
aqueous layer was extracted with Et2O, and the organic extract
was washed with H2O and saturated aqueous NaCl solution,
dried (MgSO4), filtered, and concentrated in vacuo. The residue
was purified by flash chromatography (silica gel, elution with
9% Et2O in hexanes) to give 1.74 g (4.77 mmol, 95%) of 10 as
a colorless oil: Rf 0.61 (50% Et2O in hexanes, PMA); [R]22
D
+14.5 (c 1.50, CHCl3); IR (film) 2955, 2928, 2854, 1513, 1248,
1
1074, 835, 774 cm-1; H NMR (CDCl3, 300 MHz) δ 7.28 (AA′
of AA′BB′, 2H), 6.90 (BB′ of AA′BB′, 2H), 5.85 (m, 1H), 5.05
(m, 2H), 4.43 (ABq, 2H, J AB ) 11.6 Hz, ∆υAB ) 20.8 Hz), 3.82
(s, 3H), 3.74 (m, 1H), 3.48 (m, 1H), 3.31 (m, 2H), 2.22 (m, 2H),
1.98 (m, 1H), 0.95 (d, 3H, J ) 7.1 Hz), 0.90 (s, 9H), 0.08 (s,
3H), 0.06 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 159.0, 135.5,
130.9, 129.0, 116.6, 113.7, 73.4, 72.6, 72.1, 55.2, 38.4, 38.2, 25.9,
18.1, 13.3, -4.2, -4.7; HRMS (FAB, m/z) calcd for C21H37O3Si
(M+ + H) 365.2513, found 365.2512.
In summary, a modular synthesis of cryptophycins has
been demonstrated that allows access to a variety of
structures in this class. Interest in these macrocyclic
depsipeptides as possible agents for treatment of certain
cancers is likely to continue, and versatile synthetic
routes to members of this group will play an important
role in this area of drug development.
(3S,4R)-3-ter t-Bu tyld im eth ylsila n yloxy-5-(4-m eth oxy-
ben zyloxy)-4-m eth ylp en ta n a l (11). To a solution of 10 (235
mg, 0.646 mmol) in THF (17.2 mL) and H2O (8.6 mL) was
added a solution of OsO4 in t-BuOH (2.5 wt %, 0.66 mL, 0.646
mmol). After 15 min, NaIO4 (552 mg, 2.58 mmol) was added,
and the mixture was stirred at room temperature for 20 h.
The resulting white suspension was filtered and washed with
Et2O, and the filtrate was diluted with 20% Na2S2O3 solution.
After being stirred for 10 min, the solution was extracted with
Et2O, and the ethereal extract was dried (MgSO4), filtered, and
concentrated in vacuo. The residue was purified by flash
chromatography (silica gel, elution with 11% Et2O in hexanes)
to give 182 mg (0.496 mmol, 77%) of 11 as a pale yellow oil:
Exp er im en ta l Section
Gen er a l Meth od s. All moisture-sensitive reactions were
performed in flame-dried glassware under a dry argon atmo-
sphere. Tetrahydrofuran (THF), diethyl ether (Et2O), and
toluene (PhCH3) were distilled from sodium-benzophenone
ketyl. Dichloromethane (CH2Cl2), triethylamine (Et3N), di-
methyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF)
were distilled from calcium hydride. All other commercial
reagents were purchased and used as received unless other-
wise specified. Melting points (mp) are uncorrected. Optical
rotations are reported in g/100 mL. Infrared spectra (IR) are
reported in wavenumbers (cm-1) with broad signals denoted
by (br). High-resolution mass spectra were obtained using
chemical ionization (CI) or fast atom bombardment (FAB).
Analytical thin-layer chromatography (TLC) was performed
using TLC plates precoated with silica gel 60 F-254 (0.25 mm
layer thickness). TLC visualization was accomplished using
either a UV lamp, iodine adsorbed on silica gel, or phospho-
molybdic acid (PMA) solution. Flash chromatography was
performed on 320-400-mesh silica gel. Solvent mixtures used
Rf 0.55 (50% Et2O in hexanes, PMA); [R]22 -4.43 (c 1.31,
D
CHCl3); IR (film) 2954, 2928, 2854, 1726, 1613, 1513, 1463,
1
1249, 1085, 1036, 837, 776 cm-1; H NMR (CDCl3, 300 MHz)
δ 9.76 (t, 1H, J ) 2.3 Hz), 7.23 (AA′ of AA′BB′, 2H), 6.87 (BB′
of AA′BB′, 2H), 4.50 (ABq, 2H, J AB ) 11.7 Hz, ∆υAB ) 21.7
Hz), 4.33 (m, 1H), 3.78 (s, 3H), 3.31 (m, 2H), 2.46 (m, 2H),
2.05 (m, 1H), 0.90 (d, 3H, J ) 7.0 Hz), 0.87 (s, 9H), 0.074 (s,
3H), 0.051 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 202.2, 159.1,
130.3, 129.0, 113.6, 72.6, 71.6, 68.9, 55.1, 47.0, 39.3, 25.7, 17.9,
12.0, -4.7, -4.7; HRMS (CI, m/z) calcd for C20H33O4Si (M+
H) 365.2148, found 365.2141.
-
ter t-Bu tyl (5S,6R)-5-ter t-Bu tyld im eth ylsila n yloxy-7-(4-
m eth oxyben zyloxy)-6-m eth ylh ep t-2(E)-en oa te (13). To a
solution of 11 (521 mg, 1.42 mmol) in CH2Cl2 (4.0 mL) was
added (tert-butoxycarbonylmethylene)triphenylphosphorane
(12, 1.07 g, 2.85 mmol). The mixture was stirred at room
temperature for 20 h, after which time the solvent was
removed in vacuo. The residue was purified by flash chroma-
tography (silica gel, elution with 9% Et2O in hexanes) to give
627 mg (1.35 mmol, 95%) of 13 as a pale yellow oil: Rf 0.67
for TLC and flash chromatography are reported in V/Vtotal
×
100. Reversed-phase preparative HPLC was carried out using
an ODS-AQ (S-5 µm, 120 A, 250 × 10 mm i.d.) silica column.
(2R,3S)-1-(4-Met h oxyb en zyloxy)-2-m et h ylh ex-5-en -3-
ol (9). To a cooled (-100 °C) solution of tri-n-butylallylstan-
nane (1.95 g, 5.89 mmol) in dry CH2Cl2 (12.0 mL) was added
dropwise a solution of tin tetrachloride in CH2Cl2 (5.89 mL,
1.0 M, 5.89 mmol) at -100 °C. After addition was complete,
the solution was stirred for 15 min, and a solution of 7 (754
mg, 3.93 mmol) in CH2Cl2 (3.6 mL) was added dropwise via
cannula. The mixture was stirred at -100 °C for 1 h and then
was quenched by addition of saturated aqueous NaHCO3
solution and was allowed to warm to room temperature. The
aqueous layer was extracted with Et2O, and the combined
organic layers were dried (MgSO4), filtered, and concentrated
in vacuo. The residue was purified by flash chromatography
(silica gel, elution with 20% Et2O in hexanes) to give 0.747 g
(2.99 mmol, 76%) of 9 and its 3R stereoisomer (20:1) as a
colorless oil: Rf 0.32 (50% Et2O in hexanes, PMA); [R]22D -6.46
(c 1.30, CHCl3); IR (film) 3463 (br), 2959, 1612, 1513, 1248,
1089, 1036, 820 cm-1; 1H NMR (CDCl3, 300 MHz) δ 7.25 (AA′
of AA′BB′, 2H), 6.87 (BB′ of AA′BB′, 2H), 5.88 (m, 1H), 5.10
(m, 2H), 4.45 (s, 2H), 3.80 (s, 3H), 3.57 (m, 2H), 3.44 (dd, 1H,
J ) 7.1, 9.2 Hz), 3.30 (s, 1H), 2.32 (m, 1H), 2.18 (m, 1H), 1.86
(m, 1H), 0.90 (d, 3H, J ) 7.1 Hz); 13C NMR (CDCl3, 75 MHz)
(50% Et2O in hexanes, PMA); [R]22 +10.2 (c 2.0, CHCl3); IR
D
(film) 2955, 2928, 2855, 1714, 1513, 1249, 1153, 1078, 836, 775
1
cm-1; H NMR (CDCl3, 300 MHz) δ 7.24 (AA′ of AA′BB′, 2H),
6.86 (m, 3H), 5.73 (d, 1H, J ) 15.5 Hz), 4.40 (ABq, 2H, J AB
)
11.6 Hz, ∆υAB ) 20.1 Hz), 3.82 (m, 1H), 3.80 (s, 3H), 3.42 (dd,
1H, J ) 6.3, 9.3 Hz), 3.28 (dd, 1H, J ) 6.3, 9.3 Hz), 2.27 (m,
2H), 1.95 (m, 1H), 1.48 (s, 9H), 0.90 (d, 3H, J ) 6.9 Hz), 0.88
(s, 9H), 0.036 (s, 3H), 0.03 (s, 3H); 13C NMR (CDCl3, 75 MHz)
δ 165.7, 159.1, 145.1, 130.7, 129.1, 125.0, 113.7, 79.9, 72.6, 71.9,
55.2, 39.0, 36.1, 29.7, 28.1, 25.8, 18.0, 12.8, -4.4, -4.7; HRMS
(FAB, m/z) calcd for C26H44O5Si (M+) 464.2958, found 464.2958.
ter t-Bu t yl (5S,6R)-5-ter t-Bu t yld im et h ylsila n yloxy-7-
h yd r oxy-6-m eth ylh ep t-2(E)-en oa te (14). To a cooled (0 °C)
solution of 13 (1.24 g, 2.67 mmol) in CH2Cl2 (37.9 mL) and
H2O (3.8 mL) was added DDQ (1.21 g, 5.35 mmol) in one
portion. The mixture was stirred at 0 °C for 0.5 h and then
was allowed to warm to room temperature during 0.5 h. The
reaction was quenched with saturated aqueous NaHCO3

Total Synthesis of Cryptophycins
J . Org. Chem., Vol. 64, No. 17, 1999 6211
solution, and the aqueous layer was extracted with CH2Cl2.
The organic extract was dried (MgSO4), filtered, and concen-
trated in vacuo, and the residue was purified by flash chro-
matography (silica gel, gradient elution with 17% and 25%
Et2O in hexanes) to give 849 mg (2.47 mmol, 92%) of 14 as a
colorless oil: Rf 0.31 (50% Et2O in hexanes, PMA); [R]22D +20.2
(c 1.08, CHCl3); IR (film) 3453 (br), 2956, 2929, 2856, 1715,
1367, 1255, 1157, 1076, 1039, 837, 775 cm-1; 1H NMR (CDCl3,
300 MHz) δ 6.76 (dt, 1H, J ) 7.6, 15.6 Hz), 5.70 (d, 1H, J )
15.5 Hz), 3.76 (dt, 1H, J ) 5.1, 5.8 Hz), 3.60 (dd, 1H, J ) 4.8,
10.9 Hz), 3.48 (dd, 1H, J ) 5.7, 10.9 Hz), 2.73 (s, 1H), 2.34 (m,
2H), 1.70 (m, 1H), 1.40 (s, 9H), 0.89 (d, 3H, J ) 7.0 Hz), 0.83
(s, 9H), 0.018 (s, 3H), 0.009 (s, 3H); 13C NMR (CDCl3, 75 MHz)
δ 165.5, 143.9, 125.2, 80.0, 74.8, 64.7, 39.3, 37.1, 28.0, 25.7,
17.8, 13.6, -4.5, -4.8; HRMS (CI, m/z) calcd for C18H37O4Si
(M+ + H) 345.2461, found 345.2458.
(dt, 1H, J ) 7.6, 15.5 Hz), 6.40 (d, 1H, J ) 16.0 Hz), 6.18 (dd,
1H, J ) 8.1, 16.0 Hz), 5.75 (d, 1H, J ) 15.5 Hz), 3.76 (dt, 1H,
J ) 4.0, 6.3 Hz), 2.48 (m, 1H), 2.34 (m, 2H), 1.49 (s, 9H), 1.12
(d, 3H, J ) 6.9 Hz), 0.93 (s, 3H), 0.081 (s, 3H); 13C NMR
(CDCl3, 75 MHz) δ 165.7, 144.8, 137.6, 132.0, 130.4, 128.4,
127.0, 126.0, 125.1, 80.0, 75.1, 42.8, 37.2, 28.1, 25.8, 18.1, 16.0,
-4.4, -4.5; HRMS (CI, m/z) calcd for C25H39O3Si (M+ - H)
415.2668, found 415.2667; calcd for C25H41O3Si (M+ + H)
417.2825, found 417.2793.
ter t-Bu tyl (5S,6R)-5-Hyd r oxy-6-m eth yl-8-p h en ylocta -
2(E),7(E)-d ien oa te (19). To a solution of 18 (54.0 mg, 0.130
mmol) in THF (1.85 mL) was added tetra-n-butylammonium
fluoride hydrate (TBAF, 102 mg, 0.389 mmol), and the mixture
was stirred at room temperature for 4.5 h. The solvent was
removed in vacuo, and the residue was purified by flash
chromatography (silica gel, gradient elution with 17% and 25%
Et2O in hexanes) to give 28.9 mg (0.0957 mmol, 75%) of 19 as
ter t-Bu tyl (5S, 6S)-5-ter t-Bu tyld im eth ylsila n yloxy-6-
m eth yl-7-oxoh ep t-2(E)-en oa te (15). To a cooled (0 °C)
solution of 14 (198 mg, 0.576 mmol) in CH2Cl2 (5.76 mL) was
added Dess-Martin periodinane (488 mg, 1.15 mmol) in one
portion, and the mixture was stirred at room temperature for
3 h. The solvent was removed in vacuo, and the residue was
diluted with Et2O and saturated aqueous NaHCO3 solution.
The aqueous layer was extracted with Et2O, and the organic
extract was dried (MgSO4), filtered, and concentrated in vacuo.
The residue was purified by flash chromatography (silica gel,
elution with 13% Et2O in hexanes) to give 181 mg (0.528 mmol,
92%) of 15 as a colorless oil: Rf 0.55 (50% Et2O in hexanes,
PMA); [R]22D +45.3 (c 1.62, CHCl3); IR (film) 2955, 2930, 2857,
a colorless oil: Rf 0.28 (50% Et2O in hexanes, PMA); [R]22
D
+62.2 (c 0.83, CHCl3); IR (film) 3453 (br), 2974, 2929, 2856,
1712, 1651, 1367, 1154, 980 cm-1; 1H NMR (CDCl3, 300 MHz)
δ 7.20-7.40 (m, 5H), 6.93 (dt, 1H, J ) 7.2, 15.8 Hz), 6.47 (d,
1H, J ) 15.9 Hz), 6.14 (dd, 1H, J ) 8.6, 15.9 Hz), 5.84 (d, 1H,
J ) 15.8 Hz), 3.65 (dt, 1H, J ) 2.5, 4.1 Hz), 2.30-2.48 (m,
3H), 1.86 (br, 1H), 1.48 (s, 9H), 1.15 (d, 3H, J ) 6.8 Hz); 13C
NMR (CDCl3, 75 MHz) δ 165.7, 144.0, 137.0, 131.5, 131.0,
128.5, 127.6, 126.2, 125.4, 80.2, 73.8, 43.2, 37.2, 28.1, 16.7;
HRMS (CI, m/z) calcd for C19H25O3 (M+ - H) 301.1804, found
301.1799.
(3S,4R)-1-ter t-Bu t yld im et h ylsila n yloxy-4-m et h ylh ex-
5-en -3-ol (22). To a cooled (-78 °C) suspension of potassium
tert-butoxide (4.20 g, 37.4 mmol) in dry THF (40 mL) under
Ar was added trans-2-butene (6.70 mL, 74.2 mmol) via
cannula, followed by n-butyllithium (1.60 M in hexanes, 25.0
mL, 40.0 mmol). The resulting yellow mixture was stirred at
-45 °C for 0.5 h and then was cooled to -78 °C. A solution of
(+)-B-methoxydiisopinocampheylborane (12.0 g, 37.97 mmol)
in THF (40.0 mL) was added via cannula, and the mixture
was stirred for 1 h. BF3‚Et2O (5.10 mL, 40.0 mmol) was
introduced slowly, and the solution was stirred for 0.5 h, after
which time a solution of 20 (5.10 g, 27.1 mmol) in THF (40.0
mL) was added via cannula. The mixture was stirred at -78
°C for 4 h, quenched with 3 N NaOH (50.0 mL) at -78 °C
followed by a 30% solution of H2O2 (50.0 mL), and was allowed
to warm to room temperature. The aqueous layer was ex-
tracted with Et2O, and the organic extract was washed with
brine, dried (MgSO4), filtered, concentrated, and purified by
flash chromatography (silica gel, elution with 12% Et2O in
hexanes) to give 4.70 g (19.3 mmol, 71%) of 22 as a colorless
1
1717, 1665, 1256, 1156, 837, 777 cm-1; H NMR (CDCl3, 300
MHz) δ 9.74 (d, 1H, J ) 2.2 Hz), 6.83 (dt, 1H, J ) 7.5, 15.6
Hz), 5.78 (d, 1H, J ) 15.6 Hz), 4.03 (q, 1H, J ) 5.6 Hz), 2.53
(m, 1H), 2.40 (m, 2H), 1.48 (s, 9H), 1.09 (d, 3H, J ) 7.1 Hz),
0.88 (s, 9H), 0.072 (s, 3H), 0.057 (s, 3H); 13C NMR (CDCl3, 75
MHz) δ 204.3, 165.4, 142.8, 126.1, 80.3, 72.5, 51.1, 37.6, 28.1,
25.7, 18.0, 10.4, -4.3, -5.8; HRMS (CI, m/z) calcd for C18H33O4-
Si (M+ - H) 341.2148, found 341.2141.
ter t-Bu t yl (5S,6R)-5-ter t-Bu t yld im et h ylsila n yloxy-8-
iod o-6-m eth ylocta -2(E),7(E)-d ien oa te (16). To a stirred
suspension of anhydrous CrCl2 (388 mg, 3.16 mmol) in dry
THF (5.26 mL) under Ar at 0 °C were added dropwise a
solution of 15 (180 mg, 0.526 mmol) and iodoform (415 mg,
1.05 mmol) in THF (2.63 mL). After being stirred at 0 °C for
3 h, the reaction was quenched with H2O, and the aqueous
layer was extracted with Et2O. The organic extract was dried
(MgSO4), filtered, and concentrated in vacuo, and the residue
was purified by flash chromatography (silica gel, elution with
2% Et2O in hexanes) to give 152 mg (0.326 mmol, 62%) of 16
as a colorless oil: Rf 0.46 (9% Et2O in hexanes, PMA); [R]22
oil: Rf 0.49 (15% Et2O in hexanes, PMA); [R]22 +7.74 (c 1.55,
D
D
+58.6 (c 1.66, CHCl3); IR (film) 2955, 2928, 2856, 1714, 1665,
CHCl3); IR (film) 3453, 3076, 2955, 2928, 2856, 1471, 1255
cm-1; 1H NMR (CDCl3, 300 MHz) δ 5.82 (m, 1H), 5.0-5.1 (m,
2H), 3.92-3.75 (m, 2H), 3.68 (m, 1H), 3.20 (s, 1H), 2.23 (m,
1H), 1.62 (m, 1H), 1.04 (d, 3H, J ) 6.6 Hz), 0.89 (s, 9H), 0.06
(s, 6H); 13C NMR (CDCl3, 75 MHz) δ 140.7, 115.1, 75.0, 62.7,
43.9, 35.5, 25.8, 18.1, 15.7, -5.6, -5.5; HRMS (CI, m/z) calcd
for C13H29O2Si (M+ + H) 245.1937, found 245.1934.
1
1366, 1255, 1154, 1092, 837, 775 cm-1; H NMR (CDCl3, 300
MHz) δ 6.77 (dt, 1H, J ) 7.4, 15.7 Hz), 6.46 (dd, 1H, J ) 8.6,
14.6 Hz), 6.02 (d, 1H, J ) 4.1 Hz), 5.73 (d, 1H, J ) 5.5 Hz),
3.61 (dt, 1H, J ) 4.4, 6.0 Hz), 2.27 (m, 3H), 1.47 (s, 9H), 0.98
(d, 3H, J ) 6.9 Hz), 0.88 (s, 9H), 0.036 (s, 3H), 0.030 (s, 3H);
13C NMR (CDCl3, 75 MHz) δ 165.5, 147.9, 143.9, 125.3, 80.1,
75.7, 74.1, 45.924, 37.4, 28.1, 25.8, 18.0, 15.6, -4.4, -4.5;
HRMS (CI, m/z) calcd for C19H34O3SiI (M+ - H) 465.1322,
found 465.1303.
(3S,4R)-1-ter t-Bu t yld im et h ylsila n yloxy-3-m et h ylh ex-
1-en e (23). To a rapidly stirred solution of 22 (3.60 g, 14.8
mmol) in DMF (30.0 mL) was added imidazole (2.01 g, 29.5
mmol) followed by tert-butyldimethylsilyl choloride (2.89 g,
19.2 mmol). The resulting mixture was stirred at room
temperature until TLC showed complete comsumption of
starting material, and the reaction was quenched by the
addition of water (30 mL). The aqueous layer was extracted
with Et2O, and the organic extract was washed with brine.
The organic solution was dried (MgSO4), filtered, and concen-
trated in vacuo, and the residue was purified by chromatog-
raphy (silica gel, elution with 7% EtOAc in hexanes) to give
4.91 g (13.7 mmol, 97%) of 23: Rf 0.35 (7% EtOAc in hexanes,
PMA); [R]22D +7.74 (c 1.55, CHCl3); IR (film) 2953, 2926, 2855,
ter t-Bu tyl (5S,6R)-tr a n s-5-ter t-Bu tyldim eth ylsilan yloxy-
6-m eth yl-8-p h en ylocta -2(E),7(E)-d ien oa te (18). To a mix-
ture of 16 (40.0 mg, 0.0858 mmol) and bis(acetonitrile)-
dichloropalladium(II) (1.2 mg, 0.00215 mmol) in dry DMF
(degassed, 0.80 mL) was added phenyltrimethyltin (17, 31 mg,
0.129 mmol). The mixture was stirred in the dark at room
temperature for 20 h, and the reaction was quenched with 10%
NaHCO3 solution. The aqueous layer was extracted with Et2O,
and the organic extract was washed with H2O and saturated
aqueous NaCl solution, dried (MgSO4), filtered, and concen-
trated in vacuo. The residue was purified by flash chromatog-
raphy (silica gel, elution with 2.5% Et2O in hexanes) to give
23.9 mg (0.0575 mmol, 67%) of 18 as a colorless oil: Rf 0.34
1
1472, 1255, 1099, 836, 774 cm-1; H NMR (CDCl3, 300 MHz)
δ 5.78 (ddd, 1H, J ) 7.4, 9.6, 17.4 Hz), 5.02 (m, 1H), 4.97 (m,
1H), 3.74 (dt, 1H, J ) 3.7, 6.1 Hz), 3.63 (q, 2H, J ) 6.5 Hz),
2.30 (m, 1H), 1.58 (q, 2H, J ) 6.4 Hz), 1.00 (d, 3H, J ) 6.8
(9% Et2O in hexanes, PMA); [R]22 +79.9 (c 1.66, CHCl3); IR
D
(film) 2956, 2928, 2856, 1714, 1655, 1256, 1155, 1097, 836, 775
1
cm-1; H NMR (CDCl3, 300 MHz) δ 7.20-7.38 (m, 5H), 6.86
Hz), 0.89 (s, 9H), 0.88 (s, 9H), 0.051 (s, 6H), 0.035 (s, 6H); 13
C

6212 J . Org. Chem., Vol. 64, No. 17, 1999
White et al.
NMR (CDCl3, 75 MHz) δ 140.8, 114.3, 72.3, 60.1, 43.3, 36.3,
25.9, 25.7, 18.2, 18.1, 14.7, -4.5, -5.3; HRMS (CI, m/z) calcd
for C19H41O2Si2 (M+ - H) 357.2645, found 357.2649.
Na2S2O3 solution. The aqueous layer was extracted with Et2O,
and the organic extract was washed with brine, dried (MgSO4),
filtered, and concentrated in vacuo. The residue was purified
by flash chromatography (silica gel, elution with 15% EtOAc
in hexanes) to give 189 mg (0.59 mmol, 98%) of 27 as a
(2S,3S)-3,5-Bis(ter t-bu tyld im eth ylsila n yloxy)-2-m eth -
ylp en ta n a l (24). Ozone was bubbled through a stirred solu-
tion of 23 (500 mg, 1.40 mmol) in CH2Cl2 (47 mL) at -78 °C
until a light blue color persisted. After the reaction was
complete, Ar was bubbled through the solution until it became
colorless. Dimethyl sulfide (2.60 mL, 34.9 mmol) was added
via syringe at -78 °C, and the mixture was allowed to slowly
warm to room temperature. The solvent was removed in vacuo,
and the residue was purified by flash chromatography (silica
gel, elution with 5% Et2O in hexanes) to give 302 mg (0.840
mmol, 62%) of 24 as a colorless oil: Rf 0.29 (5% Et2O in
colorless oil: Rf 0.41 (15% EtOAc in hexanes, PMA); [R]22
D
+43.4 (c 1.99 CHCl3); IR (film) 2954, 2927, 1724, 1253, 1096
cm-1 1H NMR (CDCl3, 300 MHz) δ 9.80 (t, 1H), 7.26-7.39
;
(m, 4H), 7.20 (m, 1H), 6.40 (d, 1H, J ) 16.0 Hz), 6.13 (dd, 2H,
J ) 7.7, 16.0 Hz), 4.26 (m, 1H), 2.6-2.5 (m, 3H), 1.14 (d, 3H,
J ) 7.0 Hz), 0.91 (s, 9H), 0.13 (s, 3H), 0.08 (s, 3H); 13C NMR
(CDCl3, 75 MHz) δ 201.9, 137.3, 131.3, 130.9, 128.5, 127.2,
126.1, 71.3, 48.1, 43.3, 25.8, 18.0, 15.2, -4.5, -4.6; HRMS (CI,
m/z) calcd for C19H29O2Si (M+ - H) 317.1935, found 317.1937.
ter t-Bu t yl (5S,6R)-5-ter t-Bu t yld im et h ylsila n yloxy-6-
m eth yl-8-p h en ylocta -2(E),7(E)-d ien -oa te (18). To a solu-
tion of 27 (48.5 mg, 0.153 mmol) in dry CH2Cl2 (3.0 mL) was
added (tert-butoxycarbonylmethylene)triphenylphosphorane
(12, 287 mg, 0.763 mmol). The mixture was stirred at room
temperature for 18 h and was concentrated in vacuo. The
residue was purified by flash chromatography (silica gel,
elution with 15% EtOAc in hexanes) to give 54.1 mg (130
mmol, 85%) of 18, identical with material prepared from 16.
Ben zyl (2S)-2-(3-ter t-Bu toxyca r bon ya m in op r op ion yl-
oxy)-4-m eth ylp en ta n oa te (30). To a cooled (0 °C) solution
of benzyl (-)-2-hydroxyisocaproate (28, 111 mg, 0.50 mmol)
and N-Boc-â-alanine (29, 142 mg, 0.75 mmol) in CH2Cl2 (2.5
mL) were added 4-(dimethylamino)pyridine (DMAP, 92.0 mg,
0.75 mmol) and 1-(3-dimethylaminopropyl)-3-ethylcarbodi-
imide hydrochloride (EDCI, 144 mg, 0.75 mmol), and the
mixture was stirred at room temperature for 18 h. The solvent
was removed in vacuo, and the residue was purified by flash
chromatography (silica gel, elution with 20% Et2O in hexanes)
to give 195 mg (0.496 mmol, 99%) of 30 as a colorless oil: Rf
0.43 (50% Et2O in hexanes, PMA); [R]22D -28.1 (c 1.34, CHCl3);
hexanes, PMA); [R]22 +22.9 (c 1.77, CHCl3); IR (film) 2955,
D
2929, 2857, 1727, 1471, 1256, 1099 cm-1; 1H NMR (CDCl3, 300
MHz) δ 9.73 (d, 1H, J ) 2.0 Hz), 4.14 (q, 1H), 3.69 (t, 2H, J )
6.2 Hz), 2.54 (m, 1H), 1.82-1.56 (m, 2H), 1.10 (d, 3H, J ) 7.1
Hz), 0.88 (s, 18H), 0.76 (s, 3H), 0.63 (s, 3H), 0.04 (s, 6H); 13C
NMR (CDCl3, 75 MHz) δ 204.8, 70.4, 59.1, 51.5, 37.6, 25.9,
25.8, 18.2, 18.0, 10.2, -4.4, -4.8, -5.4; HRMS (CI, m/z) calcd
for C18H40O3Si2 (M+ - H) 359.2436, found 359.2438.
(3R,4S)-[4,6-Bis(ter t-bu tyld im eth ylsila n yloxy)-3-m eth -
ylh ex-1(E)-en yl]ben zen e (25). To a cooled (-78 °C) solution
of diethyl benzylphosphonate (0.253 mL, 1.22 mmol) in dry
THF (4.0 mL) under Ar was added n-BuLi, (1.60 M in hexane,
0.607 mL, 0.972 mmol). After 15 min, a solution of 24 (219
mg, 0.610 mmol) in THF (1.5 mL) was added via cannula, and
the mixture was stirred at -78 °C for 2 h. The mixture was
allowed to warm to room temperature, and the reaction was
quenched with H2O. After dilution with Et2O, the mixture was
extracted with Et2O, and the organic extract was washed with
brine, dried (MgSO4), filtered, and concentrated in vacuo. The
residue was purified by flash chromatography (silica gel,
elution with 5% Et2O in hexanes) to give 212 mg (0.490 mmol,
79%) of 25 as a colorless oil: Rf 0.63 (5% Et2O in hexanes,
PMA); [R]22D +24.6 (c 1.84, CHCl3); IR (film) 2954, 2927, 2855,
IR (film) 3394 (br), 2974, 2960, 1742, 1714, 1250, 1169 cm-1
;
1H NMR (CDCl3, 300 MHz) δ 7.35 (m, 5H), 5.14 (m, 4H), 3.41
(m, 2H), 2.57 (t, 2H, J ) 6.4 Hz), 1.60-1.72 (m, 3H), 1.42 (s,
9H), 0.93 (d, 3H, J ) 5.6 Hz), 0.90 (d, 3H, J ) 5.7 Hz); 13C
NMR (CDCl3, 75 MHz) δ 171.9, 170.5, 155.7, 135.1, 128.5,
128.4, 128.1, 79.2, 71.1, 67.0, 39.5, 36.2, 34.5, 28.3, 24.5, 22.9,
21.4; HRMS (CI, m/z) calcd for C21H36NO6 (M+ + H) 394.2230,
found 394.2218.
1
1471, 1255, 1098 cm-1; H NMR (CDCl3, 300 MHz) δ 7.265-
7.39 (m, 4H), 7.20 (m, 1H), 6.35 (d, 1H, J ) 16.1 Hz), 6.19 (dd,
2H, J ) 7.7, 16.0 Hz), 3.86 (m, 1H), 3.68 (m, 2H), 2.48 (m,
1H), 1.65 (q, 2H, J ) 6.5 Hz), 1.11 (d, 3H, J ) 6.8 Hz), 0.92 (s,
9H), 0.89 (s, 9H), 0.08 (s, 6H), 0.044 (s, 3H), 0.041 (s, 3H); 13
C
NMR (CDCl3, 75 MHz) δ 137.8, 132.8, 129.8, 128.4, 126.8,
126.0, 72.7, 60.1, 42.7, 36.7, 25.9, 18.3, 18.1, 15.5, -4.5, -5.3;
HRMS (CI, m/z) calcd for C25H46O2Si2 (M+ - H) 433.2956,
found 433.2958.
Ben zyl (2S)-2-[3-[(2R)-2-ter t-Bu toxyca r bon yla m in o-3-
(4-m et h oxyp h en yl)p r op ion yla m in o]-p r op ion yloxy]-4-
m eth ylp en ta n oa te (33). A solution of 30 (100 mg, 0.255
mmol) in CH2Cl2 (1.25 mL) at 0 °C was treated with CF3CO2H
(1.20 mL), and the mixture was stirred at 0 °C for 1 h. The
solvent was removed in vacuo, and the residue (123 mg) was
dried by azeotropic removal of H2O with toluene. The crude
material was subjected to the next reaction without further
purification.
(3S,4R)-3-ter t-Bu tyldim eth ylsilan yloxy-4-m eth yl-6-ph en -
ylh ex-5(E)-en -1-ol (26). A solution of HF-pyridine was
prepared by addition of 13.0 g of HF-pyridine to pyridine (31
mL) and THF (100 mL). This solution (3.82 mL) was added to
a solution of 25 (272 mg, 0.627 mmol) in THF (11.4 mL) via
syringe, and the mixture was stirred for 18 h at room
temperature. The reaction was quenched by addition of
saturated of NaHCO3 solution, and the aqueous layer was
extracted with Et2O. The organic extract was washed with
brine, dried (MgSO4), filtered, and concentrated in vacuo, and
the residue was purified by flash chromatography (silica gel,
elution with 15% EtOAc in hexanes) to give 194 mg (0.61
mmol, 97%) of 26 as a colorless oil: Rf 0.22 (15% EtOAc in
To a cooled (0 °C) solution of the crude amine-TFA salt (123
mg, 0.255 mmol) and N-Boc-O-methyl-D-tyrosine (32, 123 mg,
0.331 mmol) in THF (2.5 mL) and CH2Cl2 (0.5 mL) were added
1-hydroxybenzotriazole (HOBT, 34.5 mg, 0.255 mmol), Et3N
(62.0 mg, 0.0850 mL, 0.611 mmol), and 1-(3-dimethylamino-
propyl)-3-ethylcarbodiimide hydrochloride (EDCI, 63.4 mg,
0.331 mmol). The mixture was stirred at 0 °C for 0.5 h and
then was allowed to warm to room temperature and was
stirred for 18 h. The solvent was removed in vacuo, and the
residue was purified by flash chromatography (silica gel,
elution with 25% EtOAc in hexanes) to give 144 mg (0.252
mmol, 99%) of 33 as a colorless oil: Rf 0.29 (50% EtOAc in
hexanes, PMA); [R]22 +28.8 (c 2.59, CHCl3); IR (film) 3360
D
(br), 2954, 2927, 2855, 1471, 1255, 1098 cm-1; 1H NMR (CDCl3,
300 MHz) δ 7.26-7.39 (m, 4H), 7.20 (m, 1H), 6.38 (d, 1H, J )
16.0 Hz), 6.19 (dd, 2H, J ) 7.7, 16.0 Hz), 3.90 (m, 1H), 3.75
(m, 2H), 2.56 (m, 1H), 1.97 (s, 1H), 1.73 (q, 2H, J ) 5.7, 12.3
Hz), 1.10 (d, 3H, J ) 6.7 Hz), 0.92 (s, 9H), 0.11 (s, 6H); 13C
NMR (CDCl3, 75 MHz) δ 137.5, 132.6, 130.0, 128.5, 127.0,
126.0, 74.6, 60.5, 42.7, 35.0, 25.9, 18.0, 14.8, -4.3, -4.6; HRMS
(CI, m/z) calcd for C19H32O2Si (M+ - H) 319.2092, found
319.2093.
hexanes, PMA); [R]22 -26.3 (c 1.03, CHCl3); IR (film) 3321
D
(br), 2955, 2930, 1740, 1659, 1513, 1247, 1170 cm-1; 1H NMR
(CDCl3, 300 MHz) δ 7.32 (m, 5H), 7.07 (d, 2H, J ) 8.1 Hz),
6.77 (d, 2H, J ) 8.4 Hz), 6.72 (br. 1H), 5.12 (m, 4H), 4.31 (s,
3H), 3.72 (s, 3H), 3.67-3.46 (m, 2H), 2.95 (m, 2H), 2.52 (m,
2H), 1.70 (m, 3H), 1.37 (s, 9H), 0.90 (d, 3H, J ) 5.6 Hz), 0.88
(d, 3H, J ) 5.7 Hz); 13C NMR (CDCl3, 75 MHz) δ 171.2, 170.6,
158.3, 155.1, 134.9, 130.1, 128.5, 128.3, 128.0, 113.7, 79.5, 71.0,
67.0, 55.6, 55.0, 39.3, 37.8, 34.9, 33.9, 28.1, 24.4, 22.7, 21.4;
HRMS (CI, m/z) calcd for C31H43N2O8 (M+ + H) 571.3019, found
571.3007.
(3S,4R)-3-ter t-Bu tyldim eth ylsilan yloxy-4-m eth yl-6-ph en -
ylh ex-5(E)-en a l (27). To a cooled (0 °C) solution of 26 (193
mg, 0.604 mmol) in dry CH2Cl2 (6.04 mL) was added Dess-
Martin periodinane (536 mg, 1.21 mmol). The mixture was
stirred at room temperature for 1 h and was treated with 10
mL of saturated NaHCO3 solution and 10 mL of 20% aqueous

Total Synthesis of Cryptophycins
J . Org. Chem., Vol. 64, No. 17, 1999 6213
(2S)-2-[3-[(2R)-2-ter t-Bu toxyca r bon yla m in o-3-(4-m eth -
oxyp h en yl)p r op ion yla m in o]p r op ion yloxy]-4-m eth ylp en -
ta n oic Acid (34). To a solution of 33 (20.0 mg, 0.0351 mmol)
in EtOAc (0.5 mL) was added Pd(OH)2 (20% on carbon, 2.5
mg, 0.00351 mmol), and the mixture was stirred vigorously
at room temperature under a H2 atmosphere for 2 h. The
mixture was filtered, and the filtrate was concentrated in
vacuo. The residue (17.0 mg) was dried by azeotropic removal
of H2O with toluene to leave crude 34, which was subjected to
the next reaction without further purification: [R]22D -0.89 (c
1.81, CHCl3); IR (film) 3316 (br), 2959, 2925, 1733, 1714, 1514,
14.3 Hz), 3.04 (dd, 1H, J ) 7.4, 14.3 Hz), 2.35-2.55 (m, 4H),
1.60-1.75 (m, 3H), 1.33 (m, 1H), 1.13 (d, 3H, J ) 6.7 Hz), 0.74
(d, 3H, J ) 6.4 Hz), 0.71 (d, 3H, J ) 6.4 Hz); 13C NMR (CDCl3,
75 MHz) δ 172.8, 170.7, 165.5, 158.5, 141.5, 136.7, 131.8, 130.2,
128.6, 127.5, 126.1, 125.1, 114.1, 77.2, 71.5, 55.2, 54.1, 42.3,
39.7, 36.4, 35.2, 34.2, 34.4, 29.7, 24.3, 22.6, 21.2, 17.3; HRMS
(FAB, m/z) calcd for C34H43N2O7 (M+ + H) 591.3070, found
591.3065.
Ar en a sta tin A (5). To a cooled (-30 °C) solution of 52 (20.0
mg, 0.0339 mmol) in CH2Cl2 (1.18 mL) was added a solution
of dimethyldioxirane in acetone (1.0 mL, 0.06 M, 0.060 mmol)
dropwise at -30 °C. The mixture was stirred at -30 °C for 6
h, after which time an additional quantity (1.0 mL, 0.06M,
0.060 mmol) of dimethyldioxirane-acetone solution was added.
The mixture was stirred at -30 °C for a further 18 h and then
was allowed to warm to room temperature. The solvent was
removed in vacuo, and the residue (20 mg) was dissolved in
CH2Cl2 (0.2 mL) and MeOH (0.3 mL) and was purified by
reversed-phase HPLC (YMC-Pack ODS-AQ, S-5 µm, 120 A,
250 × 10 mm i.d.; UV dectection at 254 nm, MeOH/H2O )
1248, 1176 cm-1 1H NMR (CDCl3, 300 MHz, mixture of
;
rotamers) δ 8.90 (bs, 1H), 7.07 (d, 2H, J ) 7.2 Hz), 6.77 (d,
2H, J ) 8.6 Hz), 5.45 (m, 1H), 5.05 (m, 1H), 4.26 (m, 1H), 3.73
(s, 3H), 3.62 (m, 1H), 3.45 (m, 2H), 2.92 (m, 2H), 2.48 (m, 2H),
1.72 (m, 3H), 1.36 (s, 9H), 0.91 (d, 3H, J ) 5.9 Hz), 0.88 (d,
3H, J ) 5.9 Hz); 13C NMR (CDCl3, 75 MHz) δ 171.8, 171.6,
158.4, 155.7, 130.2, 128.5, 113.8, 80.3, 77.2, 71.6, 55.7, 55.1,
39.6, 37.7, 35.2, 34.0, 29.6, 28.2, 24.7, 23.0, 21.4; HRMS (FAB,
m/z) calcd for C24H37N2O8 (M+ + H) 481.2550, found 481.2555.
ter t-Bu tyl (5S,6R)-5-[(2S)-2-[3-[(2R)-2-ter t-Bu toxyca r -
bon yla m in o-3-(4-m eth oxyp h en yl)- p r op ion yla m in o]p r o-
pion yloxy]-4-m eth ylpen tan oyloxy]-6-m eth yl-8-ph en ylocta-
2(E),7(E)-d ien oa te (48). To a solution of 19 (28.9 mg, 0.0957
mmol) and 34 (77.0 mg, 0.144 mmol) in CH2Cl2 (0.8 mL) was
added 4-(dimethylamino)pyridine (DMAP, 17.6 mg, 0.144
mmol). To this solution was slowly added 1,3-diisopropylcar-
bodiimide (DIC, 18.1 mg, 0.0225 mL, 0.144 mmol), and the
mixture was stirred at room temperature for 18 h. The solvent
was removed in vacuo, and the residue was purified by flash
chromatography (silica gel, gradient elution with 20% and 50%
Et2O in hexanes) to give 68.2 mg (0.0849 mmol, 93%) of 48 as
75:25, flow rate 3.5 mL/min) to afford arenastatin A (5, tR
)
17.92 min) and its epimer (53, tR ) 19.77 min) in MeOH-
H2O. Removal of MeOH from each fraction in vacuo gave 5
(12.3 mg, 0.0202 mmol, 60%) and 53 (4.0 mg, 0.00658 mmol,
20%) as colorless solids. Data for 5: Rf 0.29 (50% acetone in
hexanes, PMA); [R]22 +48.7 (c 0.87, CHCl3) (lit.3 [R]22 +48.8
D
D
(c 0.63, CHCl3)); IR (film) 3404, 3282, 2964, 2930, 1738, 1670,
1514, 1240, 1176, 756 cm-1; 1H NMR (CDCl3, 300 MHz) δ 7.36
(m, 3H), 7.26 (m, 2H), 7.10 (d, 2H, J ) 8.6 Hz), 6.99 (t, 1H, J
) 6.0 Hz), 6.80 (d, 2H, J ) 8.7 Hz), 6.70 (ddd, 1H, J ) 4.8,
10.3, 15.1 Hz), 5.70 (dd, 1H, J ) 1.2, 15.2 Hz), 5.63 (d, 1H, J
) 8.1 Hz), 5.20 (m, 1H), 4.90 (dd, 1H, J ) 3.6, 9.9 Hz), 4.70
(m, 1H), 3.77 (s, 3H), 3.68 (d, 1H, J ) 2.0 Hz), 3.40-3.50 (m,
2H), 3.14 (dd, 1H, J ) 4.7, 14.4 Hz), 3.02 (dd, 1H, J ) 7.6,
14.4 Hz), 2.92 (dd, 1H, J ) 1.8, 7.4 Hz), 2.20-2.55 (m, 4H),
1.70 (m, 3H), 1.14 (d, 3H, J ) 7.0 Hz), 0.84 (d, 3H, J ) 6.4
Hz), 0.83 (d, 3H, J ) 6.4 Hz); 13C NMR (CDCl3, 75 MHz) δ
172.8, 170.6, 165.3, 158.5, 141.1, 136.7, 130.2, 128.7, 128.5,
128.4, 125.6, 125.2, 114.1, 77.2, 75.8, 71.2, 63.0, 59.0, 55.2, 54.1,
40.6, 39.5, 36.7, 35.2, 34.2, 32.4, 24.4, 22.8, 21.2, 13.5; HRMS
(FAB, m/z) calcd for C34H43N2O8 (M+ + H) 607.3019, found
607.3022.
a colorless oil: Rf 0.26 (50% EtOAc in hexanes, PMA); [R]22
D
+2.24 (c 1.70, CHCl3); IR (film) 3355 (br), 2960, 2867, 1741,
1711, 1666, 1513, 1248, 1167, 756 cm-1; 1H NMR (CDCl3, 300
MHz) δ 7.20-7.30 (m, 5H), 7.12 (d, 2H, J ) 8.6 Hz), 6.80 (d,
2H, J ) 8.6 Hz), 6.74 (br, 1H), 6.42 (d, 1H, J ) 15.9 Hz), 6.02
(dd, 1H, J ) 8.6, 15.8 Hz), 5.83 (d, 1H, J ) 15.6 Hz), 5.42 (br,
1H), 5.04 (m, 1H), 4.96 (dd, 1H, J ) 4.0, 9.8 Hz), 4.34 (m, 1H),
3.75 (s, 3H), 3.52 (m, 2H), 3.13 (dd, 1H, J ) 5.4, 13.8 Hz), 2.93
(m, 1H), 2.43-2.62 (m, 5H), 1.65 (m, 3H), 1.48 (s, 9H), 1.35 (s,
9H), 1.10 (d, 3H, J ) 6.8 Hz), 0.84 (d, 3H, J ) 6.5 Hz), 0.79 (d,
3H, J ) 6.5 Hz); 13C NMR (CDCl3, 75 MHz) δ 171.5, 171.3,
170.7, 165.7, 158.4, 155.4, 141.7, 136.8, 131.7, 130.3, 130.0,
129.1, 128.5, 127.4, 126.1, 113.8, 80.4, 79.5, 76.6, 76.4, 71.2,
55.8, 40.9, 39.6, 37.8, 35.1, 34.7, 34.2, 29.6, 28.2, 28.1, 24.5,
22.8, 21.3, 16.9; HRMS (FAB, m/z) calcd for C43H61N2O10 (M+
+ H) 765.4326, found 765.4319.
Data for 53: Rf 0.29 (50% acetone in hexanes, PMA); [R]22
D
+34.5 (c 0.40, CHCl3); IR (film) 3394, 3282, 2960, 2925, 1738,
1679, 1250, 1176, 756 cm-1; 1H NMR (CDCl3, 400 MHz) δ 7.33
(m, 3H), 7.23 (m, 2H), 7.12 (d, 2H, J ) 8.4 Hz), 7.03 (m, 1H),
6.80 (d, 2H, J ) 8.4 Hz), 6.70 (m, 1H), 5.77 (m, 2H), 5.18 (m,
1H), 4.98 (m, 1H), 4.73 (m, 1H), 3.78 (s, 3H), 3.59 (d, 1H, J )
1.3 Hz), 3.48 (m, 2H), 3.16 (dd, 1H, J ) 5.5, 14.4 Hz), 3.04
(dd, 1H, J ) 7.4, 14.2 Hz), 2.90 (dd, 1H, J ) 6.3, 7.5 Hz), 2.55-
2.65 (m, 4H), 1.76 (m, 3H), 1.05 (d, 3H, J ) 6.9 Hz), 0.89 (d,
3H, J ) 6.4 Hz), 0.87 (d, 3H, J ) 6.4 Hz); 13C NMR (CDCl3,
100 MHz) δ 172.8, 170.8, 165.6, 158.6, 141.4, 137.1, 130.2,
128.6, 128.3, 125.4, 125.2, 114.1, 76.7, 75.5, 71.4, 65.8, 63.2,
56.3, 55.2, 54.2, 40.9, 39.5, 36.6, 35.2, 34.2, 32.5, 24.6, 23.0,
21.4, 15.2, 13.4; HRMS (FAB, m/z) calcd for C34H43N2O8 (M+
+ H) 607.3019, found 607.3026.
Desep oxya r en a sta tin A (52). To a solution of 48 (68.0 mg,
0.0891 mmol) in CH2Cl2 (1.27 mL) at 0 °C was slowly added
CF3CO2H (5.09 mL), and the mixture was allowed to warm to
room temperature and was stirred for 2 h. The solvent was
removed in vacuo, and the residue (84.9 mg) was dried by
azeotropic removal of H2O with toluene. This material was
subjected to the next reaction without further purification.
To a cooled (0 °C) solution of the crude amine-TFA salt
(84.9 mg, 0.0891 mmol) in dry DMF (11.1 mL) were added
NaHCO3 (45.0 mg, 0.535 mmol) and diphenyl phosphorazidate
(DPPA, 36.8 mg, 0.029 mL, 0.134 mmol), and the mixture was
stirred at 0 °C for 72 h. The reaction was quenched by addition
of H2O, and the aqueous layer was extracted with EtOAc,
CH2Cl2, and EtOAc. The combined organic extract was washed
with H2O, dried (MgSO4), filtered, and concentrated in vacuo,
and the residue was purified by flash chromatography (silica
gel, gradient elution with 50% EtOAc in hexanes, 17% and
25% acetone in hexanes) to give 30.0 mg (0.051 mmol, 57%) of
52 as a colorless oil: Rf 0.33 (50% acetone in hexanes, PMA);
ter t-Bu tyl (2R)-(3-Hyd r oxy-2-m eth ylp r op yl)ca r ba m a te
(41). A solution of 39 (500 mg, 3.26 mmol) and NaN3 (426 mg,
6.55 mmol) in DMF (3.4 mL) was heated at 100 °C for 4 h.
After being cooled to room temperature, the mixture was
filtered, and the solids were washed with Et2O. The filtrate
was washed with H2O and saturated aqueous NaCl solution,
dried (MgSO4), filtered, and concentrated in vacuo to give crude
40 as a colorless oil (307 mg, 2.67 mmol, 82%).
To a solution of 40 (100 mg, 0.870 mmol) and Boc2O (285
mg, 1.31 mmol) in THF (4.3 mL) was added 10% Pd on carbon
(99.0 mg), and the mixture was stirred at room temperature
for 36 h under a H2 atmosphere. The mixture was filtered
through a pad of silica gel that was thoroughly washed with
EtOAc, and the filtrate was concentrated in vacuo. The residue
was purified by flash chromatography (silica gel, elution with
50% Et2O in hexanes) to give 98.5 mg (0.521 mmol, 60%) of
41 as a colorless oil: Rf 0.27 (50% EtOAc in hexanes, PMA);
[R]22 +34.0 (c 1.36, CH2Cl2); mp 250-251 °C; IR (film) 3282
D
(br), 2957, 2926, 1741, 1731, 1674, 1513, 1247, 1176, 971 cm-1
;
1H NMR (CDCl3, 300 MHz) δ 7.18-7.35 (m, 5H), 7.12 (d, 2H,
J ) 8.5 Hz), 7.00 (br, 1H), 6.80 (d, 1H, J ) 8.5 Hz), 6.71 (ddd,
1H, J ) 4.5, 10.2, 15.3 Hz), 6.40 (d, 1H, J ) 15.8 Hz), 6.02
(dd, 1H, J ) 8.8, 15.8 Hz), 5.74 (d, 1H, J ) 15.3 Hz), 5.67 (d,
1H, J ) 8.2 Hz), 5.04 (m, 1H), 4.90 (dd, 1H, J ) 3.5, 9.5 Hz),
4.74 (m, 1H), 3.77 (s, 3H), 3.46 (m, 2H), 3.15 (dd, 1H, J ) 5.6,
[R]22 -12.9 (c 1.93, CHCl3); IR (film) 3349 (br), 2974, 2930,
D

6214 J . Org. Chem., Vol. 64, No. 17, 1999
2881, 1687, 1525, 1173 cm-1 1H NMR (CDCl3, 300 MHz) δ
5.12 (br, 1H), 3.66 (br. 1H), 3.48 (m, 1H), 3.30 (m, 1H), 3.13
(m, 1H), 2.97 (dt, 1 H, J ) 6.5, 13.2 Hz), 1.72 (m, 1H), 1.37 (s,
9H), 0.81 (d, 3H, J ) 7.0); 13C NMR (CDCl3, 75 MHz) δ 157.3,
79.4, 64.3, 42.6, 36.1, 28.2, 14.3; HRMS (CI, m/z) calcd for
C9H20NO3 (M+ + H) 190.1443, found 190.1442.
Ben zyl (2S)-2-((2R)-3-ter t-Bu toxycar bon ylam in o-2-m eth -
ylp r op ion yloxy)-4-m eth ylp en ta n oa te (42). To a solution
of 41 (97.0 mg, 0.513 mmol) and NaIO4 (328 mg, 1.53 mmol)
in CCl4 (1.06 mL), CH3CN (1.06 mL), and H2O (1.64 mL) was
added ruthenium(III) chloride trihydrate (13.4 mg, 0.0511
mmol). The mixture was stirred at room temperature for 2.5
h, diluted with CH2Cl2, dried (MgSO4), filtered, and concen-
trated in vacuo. The resulting crude 38 (103 mg, 0.510 mmol,
99%) was used for the next reaction without further purifica-
tion.
White et al.
;
a m in o]-2-m eth ylp r op ion yloxy]-4-m eth ylp en ta n oyloxy]-
6-m eth yl-8-p h en ylocta -2(E),7(E)-d ien oa te (51). To a solu-
tion of 46 (87.5 mg, 0.142 mmol) in EtOAc (2.0 mL) was added
Pd(OH)2 (20% on carbon, 10 mg, 0.0142 mmol), and the
mixture was stirred vigorously at room temperature under a
H2 atmosphere for 2 h. The mixture was filtered, and the
filtrate was concentrated in vacuo. The residue of crude 19
(80.2 mg) was dried by azeotropic removal of H2O with toluene
and was subjected to the next reaction without further
purification.To a solution of crude 19 (30.2 mg, 0.106 mmol)
and 47 (80.2 mg, 0.142 mmol) in CH2Cl2 (0.88 mL) was added
DMAP (19.4 mg, 0.159 mmol), followed slowly by 1,3-diiso-
propylcarbodiimide (DIC, 20.0 mg, 0.025 mL, 0.159 mmol), and
the mixture was stirred at room temperature for 18 h. The
solvent was removed in vacuo, and the residue was purified
by flash chromatography (silica gel, gradient elution with 17%
and 25% EtOAc in hexanes) to give 76.8 mg (0.0946 mmol,
89%) of 51 as a colorless oil: Rf 0.37 (50% EtOAc in hexanes,
To a cooled (0 °C) solution of 28 (75.6 mg, 0.340 mmol) and
38 (103 mg, 0.510 mmol) in CH2Cl2 (1.70 mL) were added
4-(dimethylamino)pyridine (DMAP, 62.3 mg, 0.510 mmol) and
1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride
(EDCI, 97.8 mg, 0.510 mmol), and the mixture was stirred at
room temperature for 18 h. The solvent was removed in vacuo,
and the residue was diluted with Et2O, washed with H2O and
saturated aqueous NaCl solution, dried (MgSO4), filtered, and
concentrated in vacuo. The residue was purified by flash
chromatography (silica gel, elution with 14% Et2O in hexanes)
to give 133 mg (0.327 mmol, 96%) of 42 as a colorless oil: Rf
0.44 (50% Et2O in hexanes, PMA); [R]22D -49.7 (c 1.50, CHCl3);
PMA); [R]22 -4.7 (c 4.50, CHCl3); IR (film) 3336 (br), 2976,
D
2935, 1738, 1732, 1714, 1670, 1504, 1372, 1258, 1168, 756
cm-1; H NMR (CDCl3, 300 MHz) δ 7.18-7.32 (m, 6H), 7.10
1
(dd, 1H, J ) 2.1, 8.4 Hz), 7.05 (m, 1H), 6.82 (d, 1H, J ) 8.4
Hz), 6.80 (m, 1H), 6.40 (d, 1H, J ) 15.8 Hz), 6.00 (dd, 1H, J )
8.7, 15.8 Hz), 5.82 (d, 1H, J ) 15.6 Hz), 5.76 (m, 1H), 5.05 (m,
1H), 4.97 (dd, 1H, J ) 3.6, 9.8 Hz), 4.36 (m, 1H), 3.83 (s, 3H),
3.70 (m, 1H), 3.20 (m, 2H), 2.85 (m, 1H), 2.38-2.68 (m, 4H),
1.50-1.70 (m, 3H), 1.47 (s, 9H), 1.34 (s, 9H), 1.13 (d, 3H, J )
7.9 Hz), 1.11 (d, 3H, J ) 6.9 Hz), 0.83 (d, 3H, J ) 6.3 Hz),
0.77 (d, 3H, J ) 6.3 Hz); 13C NMR (CDCl3, 75 MHz) δ 173.5,
171.8, 171.0, 165.8, 155.7, 153.6, 141.7, 136.7, 131.8, 131.1,
130.6, 129.9, 128.5, 127.4, 126.1, 122.0, 112.1, 80.4, 79.7, 76.6,
70.7, 63.8, 56.0, 42.1, 41.0, 40.6, 39.5, 37.4, 34.9, 29.6, 28.2,
28.1, 24.7, 22.8, 21.2, 16.9, 14.5; HRMS (FAB, m/z) calcd for
IR (film) 3394 (br), 2960, 1740, 1717, 1509, 1251, 1172 cm-1
;
1H NMR (CDCl3, 300 MHz) δ 7.32 (m, 5H), 5.16 (m, 4H), 3.37
(m, 1H), 3.20 (m, 1H), 2.74 (m, 1H), 1.62-1.84 (m, 3H), 1.41
(s, 9H), 1.15 (d, 3H, J ) 8.2 Hz), 0.91 (d, 3H, J ) 6.2 Hz), 0.89
(d, 3H, J ) 6.2 Hz); 13C NMR (CDCl3, 75 MHz) δ 174.6, 170.5,
155.9, 135.1, 128.5, 128.3, 128.2, 79.1, 70.8, 67.0, 43.0, 40.2,
39.6, 28.2, 24.6, 22.9, 21.4, 14.4; HRMS (CI, m/z) calcd for
C
44H62N2O1035Cl (M+ + H) 813.4093, found 813.4104.
Cr yp top h ycin 3 (3). To a solution of 51 (76.0 mg, 0.0936
C
C
22H34NO6 (M+ + H) 408.2386, found 408.2377; calcd for
mmol) in CH2Cl2 (1.33 mL) at 0 °C was slowly added CF3CO2H
(5.35 mL), and the mixture was allowed to warm to room
temperature. After the mixture was stirred for 2 h, the solvent
was removed in vacuo and the residue (75.1 mg) was dried by
azeotropic removal of H2O with toluene. To a solution of the
crude amine-TFA salt (75.1 mg, 0.0936 mmol) in dry DMF
(11.7 mL) at 0 °C were added NaHCO3 (47.2 mg, 0.562 mmol)
and diphenyl phosphorazidate (DPPA, 38.7 mg, 0.0303 mL,
0.141 mmol), and the mixture was stirred at 0 °C for 72 h.
The reaction was quenched with H2O, and the aqueous layer
was extracted with EtOAc, CH2Cl2, and EtOAc again. The
combined organic extract was washed with H2O, dried (Mg-
SO4), filtered, and concentrated in vacuo, and the residue was
purified by flash chromatography (silica gel, gradient elution
with 50% EtOAc in hexanes, 17% and 25% acetone in hexanes)
to give 31.0 mg (0.0486 mmol, 52%) of 3 as a colorless oil: Rf
22H32NO6 (M+ - H) 406.2230, found 406.2227.
Ben zyl (2S)-2-[(2R)-3-[(2R)-2-ter t-Bu toxycar bon ylam in o-
3-(3-ch lor o-4-m eth oxyp h en yl) p r op ion yla m in o]-2-m eth -
ylp r op ion yloxy]-4-m eth ylp en ta n oa te (46). To a solution
of 42 (133 mg, 0.327 mmol) in CH2Cl2 (1.63 mL) at 0 °C was
added CF3CO2H (1.63 mL), and the mixture was stirred at 0
°C for 1 h. The solvent was removed in vacuo, and the residue
(169 mg) was dried by azeotropic removal of H2O with toluene.
Crude 43 was subjected to the next reaction without further
purification.To a cooled (0 °C) solution of crude 43 (169 mg,
0.327 mmol) and N-Boc-O-methyl-D-3-chlorotyrosine (52.7 mg,
0.160 mmol) in THF (1.28 mL) and CH2Cl2 (0.32 mL) were
added 1-hydroxybenzotriazole (HOBT, 32.4 mg, 0.240 mmol),
Et3N (40.5 mg, 0.0560 mL, 0.400 mmol), and 1-(3-dimethyl-
aminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI, 61.4
mg, 0.320 mmol). The mixture was stirred at 0 °C for 0.5 h
and then was allowed to warm to room temperature and was
stirred for a further 18 h. The solvent was removed in vacuo,
and the residue was diluted with Et2O. The ethereal solution
was washed with H2O, and the organic layer was dried
(MgSO4), filtered, and concentrated in vacuo. The residue was
purified by flash chromatography (silica gel, elution with 50%
Et2O in hexanes) to give 87.5 mg (0.142 mmol, 88%) of 46 as
0.39 (50% acetone in hexanes, PMA); [R]22 +29.5 (c 2.0,
D
CHCl3) (lit.9 [R]22 +28.8 (c 0.65, CHCl3)); IR (film) 3409 (br),
D
3287 (br), 2964, 2925, 1745, 1730, 1674, 1503, 1181, 1064, 750
cm-1; H NMR (CDCl3, 300 MHz) δ 7.20-7.35 (m, 6H), 7.06
1
(dd, 1H, J ) 2.0, 8.5 Hz), 7.00 (m, 1H), 6.82 (d, 1H, J ) 8.4
Hz), 6.68 (ddd, 1H, J ) 5.2, 9.7, 15.2 Hz), 6.40 (d, 1H, J )
15.8 Hz), 6.00 (dd, 1H, J ) 8.8, 15.9 Hz), 5.86 (d, 1H, J ) 8.4
Hz), 5.78 (d, 1H, J ) 15.4 Hz), 5.02 (m, 1H), 4.82 (m, 2H),
3.85 (s, 3H), 3.46 (m, 1H), 3.31 (m, 1H), 3.13 (dd, 1H, J ) 5.6,
14.5 Hz), 3.00 (dd, 1H, J ) 7.6, 14.5 Hz), 2.70 (m, 1H), 2.54
(m, 2H), 2.37 (m, 1H), 1.57-1.68 (m, 3H), 1.32 (m, 1H), 1.21
(d, 3H, J ) 7.2 Hz), 1.12 (d, 3H, J ) 6.8 Hz), 0.75 (d, 3H, J )
6.4 Hz), 0.71 (d, 3H, J ) 6.3 Hz); 13C NMR (CDCl3, 75 MHz)
δ 175.6, 171.0, 170.9, 165.5, 153.9, 141.4, 136.7, 131.8, 131.0,
130.1, 129.9, 128.6, 128.4, 127.6, 126.1, 125.2, 122.4, 112.2,
77.4, 71.5, 56.1, 53.7, 42.2, 41.1, 39.5, 38.2, 36.4, 35.1, 24.5,
21.2, 17.3, 14.1; HRMS (FAB, m/z) calcd for C35H44N2O735Cl
(M+ + H) 639.2837, found 639.2840.
a colorless oil: Rf 0.41 (50% EtOAc in hexanes, PMA); [R]22
D
-32.0 (c 1.22, CHCl3); IR (film) 3306 (br), 2955, 2935, 1739,
1655, 1503, 1257, 1172 cm-1 1H NMR (CDCl3, 300 MHz) δ
;
7.32 (m, 5H), 7.18 (d, 1H, J ) 1.7 Hz), 7.01 (dd, 1H, J ) 1.9,
8.3 Hz), 6.91 (br. 1H), 6.78 (d, 1H, J ) 8.5 Hz), 5.16 (m, 4H),
4.32 (m, 1H), 3.82 (s, 3H), 3.63 (m, 1H), 3.16 (ddd, 1H, J )
5.0, 9.3, 13.9 Hz), 3.00 (dd, 1H, J ) 6.4, 13.9 Hz), 2.93 (m,
1H), 2.74 (m, 1H), 1.60-1.80 (m, 3H), 1.37 (s, 9H), 1.13 (d,
3H, J ) 7.1 Hz), 0.90 (d, 3H, J ) 6.8 Hz), 0.88 (d, 3H, J ) 6.8
Hz); 13C NMR (CDCl3, 75 MHz) δ 173.7, 171.1, 155.1, 153.7,
134.8, 131.0, 129.9, 128.5, 128.5, 128.1, 122.0, 112.0, 79.7, 70.7,
67.4, 56.0, 55.6, 41.6, 40.2, 39.2, 37.8, 28.1, 24.6, 22.8, 21.4,
14.5; HRMS (CI, m/z) calcd for C31H43N2O8 (M+ + H) 619.2786,
found 619.2776.
Cr yp top h ycin -1 (1) a n d Ep icr yp top h ycin -1 (54). To a
cooled (-30 °C) solution of cryptophycin-3 (3, 30.0 mg, 0.0486
mmol) in CH2Cl2 (1.62 mL) was added a solution of dimeth-
yldioxirane in acetone (1.44 mL, 0.06 M, 0.0864 mmol) at -30
°C. The mixture was stirred at -30 °C for 6 h, and an
additional 1.44 mL (0.06 M, 0.0864 mmol) of dimethyldioxi-
ter t-Bu tyl (5S,6R)-5-[(2S)-2-[(2R)-3-[(2R)-2-ter t-Bu toxy-
ca r bon yla m in o-3-(3-ch lor o-4-m eth oxyp h en yl)p r op ion yl-

Total Synthesis of Cryptophycins
J . Org. Chem., Vol. 64, No. 17, 1999 6215
rane-acetone solution was added. The mixture was stirred
at -30 °C for a further 18 h and was allowed to warm to room
temperature. The solvent was removed in vacuo, the residue
(38 mg) was dissolved in CH2Cl2, and the mixture of 1 and 54
was separated by reversed-phase HPLC (YMC-Pack ODS-AQ,
S-5 µm, 120 A, 250 × 10 mm i.d.; UV dectection at 254 nm,
2.70 (m, 1H), 1.60-1.77 (m, 3H), 1.36 (s, 9H), 1.11 (d, 3H, J )
7.0 Hz), 0.89 (d, 3H, J ) 6.4 Hz), 0.87 (d, 3H, J ) 6.3 Hz); 13
C
NMR (CDCl3, 75 MHz) δ 173.9, 171.5, 170.9, 158.4, 155.1,
134.9, 130.2, 128.6, 128.5, 128.5, 128.2, 113.8, 79.5, 70.7, 67.2,
55.8, 55.0, 41.6, 40.0, 39.3, 38.0, 28.2, 24.6, 22.8, 21.4, 14.5;
HRMS (CI, m/z) calcd for C32H45N2O8 (M+ + H) 585.3176, found
585.3166.
MeOH/H2O ) 75:25, flow rate 3.5 mL/min) to afford 1 (tR
)
17.72 min) and its epimeric epoxide 54 (tR ) 19.51 min) as
separate solutions in MeOH-H2O. Solvents were removed in
vacuo to give pure 1 (17.5 mg, 0.0268 mmol, 55%) and 54 (6.0
mg, 0.00917 mmol, 19%) as colorless films. Data for crypto-
ter t-Bu tyl (5S,6R)-5-[(2S)-2-[(2R)-3-[(2R)-2-ter t-Bu toxy-
ca r bon yla m in o-3-(4-m eth oxyp h e-n yl)-p r op ion yla m in o]-
2-m eth ylpr opion yloxy]-4-m eth ylpen tan oyloxy]-6-m eth yl-
8-h en yloct a -2-(E),7(E)-d ien oa t e (50). To a solution of 44
(178.3 mg, 0.305 mmol) in EtOAc (4.36 mL) was added
Pd(OH)2 (20% on carbon, 21.4 mg, 0.0305 mmol), and the
mixture was stirred vigorously at room temperature under a
H2 atmosphere for 2 h. The solution was filtered, and the
filtrate was concentrated in vacuo. The resulting crude acid
45 (162.4 mg) was dried by azeotropic removal of H2O with
toluene and was used for the next reaction without further
purification. To a solution of 19 (30.2 mg, 0.100 mmol) and
crude 45 (80.0 mg, 0.150 mmol) in CH2Cl2 (0.83 mL) at room
temperature was added 4-(dimethylamino)pyridine (DMAP,
18.3 mg, 0.150 mmol) followed slowly by 1,3-diisopropylcar-
bodiimide (DIC, 19.0 mg, 0.024 mL, 0.150 mmol). The mixture
was stirred at room temperature for 18 h, and the solvent was
removed in vacuo. The residue was purified by flash chroma-
tography (silica gel, gradient elution with 25% and 50% Et2O
in hexanes) to give 65.0 mg (0.0837 mmol, 84%) of 50 as a
colorless oil: Rf 0.55 (50% EtOAc in hexanes, PMA); [R]22D -5.4
(c 1.33, CHCl3); IR (film) 3332 (br), 2978, 2937, 1740, 1718,
phycin-1 (1): Rf 0.38 (50% acetone in hexanes, PMA); [R]22
D
+31.5 (c 1.75, MeOH); [R]22 +24.5 (c 1.50, CHCl3) (lit.9 [R]22
D
D
+33.8 (c 1.83, MeOH)); IR (film) 3409 (br), 3282 (br), 2959,
2925, 1748, 1728, 1679, 1504, 1176, 1069, 756 cm-1; 1H NMR
(CDCl3, 300 MHz) δ 7.36 (m, 3H), 7.23 (m, 2H), 7.21 (dd, 1H,
J ) 2.1, 8.7 Hz), 7.05 (dd, 1H, J ) 2.1, 8.4 Hz), 6.97 (br, 1H),
6.82 (d, 1H, J ) 8.5 Hz), 6.68 (ddd, 1H, J ) 5.4, 9.6, 15.1 Hz),
5.73 (d, 1H, J ) 12.0 Hz), 5.70 (d, 1H, J ) 4.6 Hz), 5.14 (m,
1H), 4.80 (m, 2H), 3.86 (s, 3H), 3.68 (d, 1H, J ) 1.9 Hz), 3.46
(m, 1H), 3.30 (m, 1H), 3.14 (dd, 1H, J ) 5.5, 14.5 Hz), 3.02
(dd, 1H, J ) 7.3, 14.5 Hz), 2.92 (dd, 1H, J ) 1.9, 7.4 Hz), 2.70
(m, 1H), 2.40-2.58 (m, 2H), 1.56-1.82 (m, 3H), 1.37 (m, 1H),
1.22 (d, 3H, J ) 7.3 Hz), 1.14 (d, 3H, J ) 7.0 Hz), 0.86 (d, 3H,
J ) 6.9 Hz), 0.84 (d, 3H, J ) 6.3 Hz); 13C NMR (CDCl3, 75
MHz) δ 175.6, 170.9, 170.7, 165.3, 153.9, 141.0, 136.7, 129.7,
128.7, 128.5, 128.3, 125.6, 125.2, 122.4, 112.2, 76.1, 71.3, 63.0,
59.0, 56.1, 53.7, 41.0, 40.6, 39.4, 38.2, 36.7, 35.0, 24.5, 22.9,
21.3, 14.1, 13.5; HRMS (FAB, m/z) calcd for C35H44N2O835Cl
(M+ + H) 655.2786, found 655.2786.
1658, 1510, 1247, 1169 cm-1 1H NMR (CDCl3, 300 MHz) δ
;
Data for epicryptophycin-1 (54): Rf 0.38 (50% acetone in
7.18-7.30 (m, 5H), 7.14 (d, 2H, J ) 8.4 Hz), 6.86 (br, 1H), 6.80
(d, 2H, J ) 8.6 Hz), 6.40 (d, 1H, J ) 15.8 Hz), 6.00 (dd, 1H, J
) 8.7, 15.9 Hz), 5.82 (d, 1H, J ) 15.7 Hz), 5.57 (m, 1H), 5.06
(m, 1H), 4.96 (dd, 1H, J ) 3.8, 9.7 Hz), 3.74 (s, 3H), 3.60 (m,
1H), 3.15 (m, 2H), 2.92 (m, 1H), 2.40-2.68 (m, 4H), 1.50-1.70
(m, 3H), 1.48 (s, 9H), 1.34 (s, 9H), 1.14 (d, 3H, J ) 8.9 Hz),
1.12 (d, 3H, J ) 6.9 Hz), 0.84 (d, 3H, J ) 6.3 Hz), 0.79 (d, 3H,
J ) 6.3 Hz); 13C NMR (CDCl3, 75 MHz) δ 173.6, 171.7, 170.8,
165.6, 158.3, 155.5, 141.6, 136.7, 131.8, 130.2, 129.9, 129.3,
128.5, 127.4, 126.1, 113.8, 106.0, 80.3, 79.4, 76.6, 70.6, 56.1,
55.1, 41.9, 40.8, 40.5, 39.5, 37.7, 34.7, 29.6, 28.2, 28.1, 24.6,
22.8, 21.3, 16.9, 14.5; HRMS (FAB, m/z) calcd for C44H63N2O10
(M+ + H) 779.4482, found 779.4494.
hexanes, PMA); [R]22 +10.3 (c 0.60, CHCl3); IR (film) 3409
D
(br), 3277 (br), 2964, 2925, 1748, 1733, 1666, 1504, 1469, 1264,
1
1181, 1070, 760 cm-1; H NMR (CDCl3, 300 MHz) δ 7.35 (m,
3H), 7.25 (m, 3H), 7.10 (dd, 1H, J ) 2.2, 8.5 Hz), 6.97 (br, 1H),
6.84 (d, 1H, J ) 8.3 Hz), 6.70 (ddd, 1H, J ) 5.5, 9.6, 15.2 Hz),
5.82 (d, 1H, J ) 15.4 Hz), 5.70 (d, 1H, J ) 8.4 Hz), 5.15 (m,
1H), 4.92 (m, 1H), 4.82 (m, 1H), 3.88 (s, 3H), 3.60 (d, 1H, J )
1.9 Hz), 3.50 (m, 1H), 3.32 (m, 1H), 3.16 (dd, 1H, J ) 5.5, 14.4
Hz), 3.05 (dd, 1H, J ) 7.3, 14.4 Hz), 2.90 (m, 1H), 2.40-2.78
(m, 3H), 1.76 (m, 3H), 1.50 (m, 1H), 1.24 (d, 3H, J ) 7.4 Hz),
1.05 (d, 3H, J ) 7.0 Hz), 0.91 (d, 3H, J ) 6.5 Hz), 0.88 (d, 3H,
J ) 6.3 Hz); 13C NMR (CDCl3, 75 MHz) δ 175.6, 171.0, 170.8,
165.4, 154.0, 141.4, 137.1, 131.0, 129.8, 128.6, 128.4, 128.3,
125.4, 125.2, 122.4, 112.2, 77.2, 71.5, 63.2, 56.3, 56.1, 53.6, 41.1,
40.0, 39.3, 38.3, 36.7, 35.1, 24.7, 23.1, 21.3, 14.1, 13.5; HRMS
(FAB, m/z) calcd for C35H44N2O835Cl (M+ + H) 655.2786, found
655.2787.
Cr yp top h ycin 4 (4). To a solution of 50 (65.0 mg, 0.0837
mmol) in CH2Cl2 (1.19 mL) at 0 °C was slowly added CF3CO2H
(4.78 mL), and the mixture was allowed to warm to room
temperature and was stirred for 2 h. The solvent was removed
in vacuo, and the residue (81.0 mg) was dried by azeotropic
removal of H2O with toluene. To a cooled (0 °C) solution of
the crude amine-TFA salt (81.0 mg, 0.0837 mmol) in dry DMF
(10.5 mL) were added NaHCO3 (42.3 mg, 0.504 mmol) and
diphenyl phosphorazidate (DPPA, 34.5 mg, 0.0270 mL, 0.126
mmol), and the mixture was stirred at 0 °C for 72 h. The
reaction was quenched by addition of H2O, and the aqueous
layer was extracted with EtOAc, CH2Cl2, and EtOAc again.
The combined organic extract was washed with H2O, dried
(MgSO4), filtered, and concentrated in vacuo, and the residue
was purified by flash chromatography (silica gel, gradient
elution with 50% EtOAc in hexanes, 17% and 25% acetone in
hexanes) to give 30.6 mg (0.0507 mmol, 61%) of cryptophycin-4
(4) as a colorless oil: Rf 0.33 (50% acetone in hexanes, PMA);
[R]22 +29.1 (c 2.1, CHCl3) (lit.9 [R]22 +22.8 (c 0.2, CHCl3));
Ben zyl (2S)-2-[(2R)-3-[(2R)-2-ter t-Bu toxycar bon ylam in o-
3-(4-m e t h o x y p h e n y l)p r o p io n y la m in o ]-2-m e t h y lp r o -
p ion yloxy]-4-m eth ylp en ta n oa te (44). To a solution of 42
(133 mg, 0.327 mmol) in CH2Cl2 (1.63 mL) at 0 °C was added
CF3CO2H (1.63 mL), and the mixture was stirred at 0 °C for
1 h. The solvent was removed in vacuo, and the residual crude
43 (172 mg) was dried by azeotropic removal of H2O with
toluene. To a cooled (0 °C) solution of crude 43 (172 mg, 0.327
mmol) and N-Boc-O-methyl-D-3-chlorotyrosine (125.4 mg, 0.425
mmol) in THF (2.64 mL) and CH2Cl2 (0.66 mL) were added
1-hydroxybenzotriazole (HOBT, 44.2 mg, 0.327 mmol), Et3N
(79.4 mg, 0.110 mL, 0.785 mmol), and 1-(3-dimethylamino-
propyl)-3-ethylcarbodiimide hydrochloride (EDCI, 81.5 mg,
0.425 mmol). The mixture was stirred at 0 °C for 0.5 h and
then was allowed to warm to room temperature and was
stirred for a further 18 h. The solvent was removed in vacuo,
and the residue was taken up in Et2O. The ethereal solution
was washed with H2O, and the organic layer was dried
(MgSO4), filtered, and concentrated in vacuo. The residue was
purified by flash chromatography (silica gel, elution with 50%
Et2O in hexanes) to give 178.3 mg (0.305 mmol, 93%) of 44 as
D
D
IR (film) 3414 (br), 3287 (br), 2957, 2930, 1745, 1726, 1655,
1513, 1247, 1177, 751 cm-1 1H NMR (CDCl3, 300 MHz) δ
;
7.18-7.34 (m, 5H), 7.11 (d, 2H, J ) 8.6 Hz), 7.08 (m, 1H), 6.80
(d, 2H, J ) 8.5 Hz), 6.71 (ddd, 1H, J ) 5.8, 10.8, 15.8 Hz),
6.40 (d, 1H, J ) 15.8 Hz), 6.02 (dd, 1H, J ) 8.8, 15.8 Hz), 5.75
(d, 1H, J ) 10.7 Hz), 5.71 (d, 1H, J ) 3.4 Hz), 5.03 (m, 1H),
4.85 (dd, 1H, J ) 3.4, 9.7 Hz), 4.78 (m, 1H), 3.77 (s, 3H), 3.39
(m, 2H), 3.14 (dd, 1H, J ) 5.5, 14.4 Hz), 3.06 (dd, 1H, J ) 7.2,
14.5 Hz), 2.68 (m, 1H), 2.52 (m, 2H), 2.35 (m, 1H), 1.64 (m,
2H), 1.45 (m, 1H), 1.22 (d, 3H, J ) 7.2 Hz), 1.12 (d, 3H, J )
a colorless oil: Rf 0.42 (50% EtOAc in hexanes, PMA); [R]22
D
-36.2 (c 1.21, CHCl3); IR (film) 3302 (br), 2959, 2934, 1738,
1660, 1513, 1247, 1175 cm-1 1H NMR (CDCl3, 300 MHz) δ
;
7.32 (m, 5H), 7.05 (d, 2H, J ) 8.5 Hz), 6.82 (br, 1H), 6.75 (d,
2H, J ) 8.4 Hz), 5.12 (m, 4H), 4.30 (m, 1H), 3.70 (s, 3H), 3.54
(m, 1H), 3.17 (ddd, 1H, J ) 5.1, 8.8, 13.8 Hz), 2.96 (m, 2H),
6.9 Hz), 0.75 (d, 3H, J ) 6.4 Hz), 0.72 (d, 3H, J ) 6.4 Hz); 13
C
NMR (CDCl3, 75 MHz) δ 175.9, 171.2, 170.8, 165.3, 158.5,
141.5, 136.7, 131.7, 130.2, 128.6, 128.5, 127.5, 126.1, 125.0,

6216 J . Org. Chem., Vol. 64, No. 17, 1999
White et al.
114.1, 77.2, 71.5, 55.2, 53.9, 42.2, 40.7, 39.5, 38.1, 36.4, 35.3,
6H), 7.07 (dd, 1H, J ) 2.1, 8.3 Hz), 6.96 (br, 1H), 6.83 (d, 1H,
J ) 8.5 Hz), 6.81 (m, 1H), 6.40 (d, 1H, J ) 15.8 Hz), 6.00 (dd,
1H, J ) 8.7, 15.9 Hz), 5.83 (d, 1H, J ) 15.6 Hz), 5.55 (m, 1H),
5.05 (m, 1H), 4.95 (dd, 1H, J ) 3.9, 9.9 Hz), 4.36 (m, 1H), 3.83
(s, 3H), 3.52 (m, 2H), 3.15 (dd, 1H, J ) 5.2, 14.0 Hz), 2.88 (m,
1H), 2.40-2.53 (m, 5H), 1.63 (m, 3H), 1.47 (s, 9H), 1.35 (s, 9H),
1.10 (d, 3H, J ) 6.7 Hz), 0.82 (d, 3H, J ) 6.4 Hz), 0.76 (d, 3H,
J ) 6.4 Hz); 13C NMR (CDCl3, 75 MHz) δ 171.3, 170.8, 165.8,
155.4, 141.8, 136.7, 131.7, 131.1, 130.5, 130.0, 128.5, 127.4,
126.1, 121.9, 112.0, 80.4, 79.5, 76.4, 71.2, 56.0, 55.6, 41.0, 39.5,
37.4, 35.1, 34.8, 34.2, 28.2, 28.1, 24.5, 22.7, 21.2, 16.9; HRMS
(FAB, m/z) calcd for C43H60N2O1035Cl (M+ + H) 799.3937, found
799.3947.
Cr yp top h ycin -29 (6). To a solution of 49 (69.5 mg, 0.0872
mmol) in CH2Cl2 (1.24 mL) at 0 °C was slowly added CF3CO2H
(4.98 mL), and the mixture was allowed to warm to room
temperature and was stirred for a further 2 h. The solvent
was removed in vacuo, and the residue (86.9 mg) was dried
by azeotropic removal of H2O with toluene and used for the
next reaction without further purification.
24.4, 22.6, 21.2, 17.3, 14.1; HRMS (FAB,m/z) calcd for
C
35H45N2O7 (M+ + H) 605.3227, found 605.3222.
Ben zyl (2S)-2-[3-[(2R)-2-ter t-Bu toxyca r bon yla m in o-3-
(3-c h lo r o -4-m e t h o x y p h e n y l)p r o p i o n y la m i n o ]p r o -
p ion yloxy]-4-m eth ylp en ta n oa te (36). A solution of 30 (129
mg, 0.327 mmol) in CH2Cl2 (1.63 mL) at 0 °C was added
CF3CO2H (1.63 mL), and the mixture was stirred at 0 °C for
1 h. The solvent was removed in vacuo, the residue (148 mg)
was dried by azeotropic removal of H2O with toluene, and the
resultant crude 31 was subjected to the next reaction without
further purification.
To a cooled (0 °C) solution of crude 31 (148 mg, 0.327 mmol)
and N-Boc-O-methyl-D-3-chlorotyrosine (61.5 mg, 0.160 mmol)
in THF (1.28 mL) and CH2Cl2 (0.32 mL) were added 1-hy-
droxybenzotriazole (HOBT, 32.4 mg, 0.240 mmol), Et3N (40.5
mg, 0.560 mL, 0.400 mmol), and 1-(3-dimethylaminopropyl)-
3-ethylcarbodiimide hydrochloride (EDCI, 61.4 mg, 0.320
mmol). The mixture was stirred at 0 °C for 0.5 h and then
was allowed to warm to room temperature and was stirred
for a further 18 h. The solvent was removed in vacuo, and the
residue was taken up in Et2O. The ethereal solution was
washed with H2O, and the organic layer was dried (MgSO4),
filtered, and concentrated in vacuo. The residue was purified
by flash chromatography (silica gel, gradient elution with 33%
and 50% Et2O in hexanes) to give 92.7 mg (0.153 mmol, 96%)
of 36 as a colorless oil: Rf 0.41 (50% EtOAc in hexanes, PMA);
To a cooled (0 °C) solution of the crude amine-TFA salt
(86.9 mg, 0.0872 mmol) in dry DMF (10.9 mL) were added
NaHCO3 (44.0 mg, 0.523 mmol) and diphenyl phosphorazidate
(DPPA, 36.0 mg, 0.028 mL, 0.131 mmol), and the mixture was
stirred at 0 °C for 72 h. The reaction was quenched by addition
of H2O, and the aqueous layer was extracted with EtOAc,
CH2Cl2, and EtOAc again. The combined organic extract was
washed with H2O, dried (MgSO4), filtered, and concentrated
in vacuo, and the residue was purified by flash chromatogra-
phy (silica gel, gradient elution with 20% and 33% acetone in
hexanes) to give 31.6 mg (0.0506 mmol, 58% for two steps) of
cryptophycin-29 (6) as a colorless oil: Rf 0.28 (50% acetone in
hexanes, PMA); [R]22 +32.5 (c 1.17, CHCl3) (li.3 [R]22 +22.2
[R]22 -21.9 (c 1.32, CHCl3); IR (film) 3316 (br), 2964, 2930,
D
1743, 1659, 1504, 1257, 1170 cm-1; 1H NMR (CDCl3, 300 MHz)
δ 7.33 (m, 5H), 7.18 (d, 1H, J ) 2.0 Hz), 7.02 (dd, 1H, J ) 2.0,
8.4 Hz), 6.81 (br. 1H), 6.80 (d, 1H, J ) 8.4 Hz), 5.15 (m, 4H),
4.30 (m, 1H), 3.82 (s, 3H), 3.58 (m, 1H), 3.49 (m, 1H), 3.02
(dd, 1H, J ) 6.2, 12.9 Hz), 2.90 (m, 1H), 2.54 (t, 2H, J ) 6.4
Hz), 1.60-1.80 (m, 3H), 1.37 (s, 9H), 0.90 (d, 3H, J ) 5.8 Hz),
0.88 (d, 3H, J ) 5.8 Hz), 0.88 (d, 3H, J ) 5.9 Hz); 13C NMR
(CDCl3, 75 MHz) δ 171.3, 171.0, 170.9, 155.1, 153.7, 134.9,
131.0, 129.8, 128.6, 128.4, 128.1, 122.0, 112.0, 79.8, 71.0, 67.3,
56.0, 55.5, 39.3, 37.6, 35.0, 34.1, 28.1, 24.5, 22.8, 21.4; HRMS
(CI, m/z) calcd for C31H42N2O835Cl (M+ + H) 605.2629, found
605.2616.
D
D
(c 1.13, CHCl3)); IR (film) 3409, 3277 (br), 2958, 2928, 1742,
1673, 1503, 1258, 1173, 750 cm-1; 1H NMR (CDCl3, 300 MHz)
δ 7.18-7.32 (m, 6H), 7.06 (dd, 1H, J ) 2.1, 8.5 Hz), 6.99 (br,
1H), 6.82 (d, 1H, J ) 8.5 Hz), 6.69 (ddd, 1H, J ) 5.0, 10.2,
15.2 Hz), 6.40 (d, 1H, J ) 15.8 Hz), 6.03 (d, 1H, J ) 8.8 Hz),
5.98 (d, 1H, J ) 8.7 Hz), 5.78 (d, 1H, J ) 15.8 Hz), 5.03 (m,
1H), 4.89 (dd, 1H, J ) 3.5, 9.8 Hz), 4.74 (m, 1H), 3.85 (s, 3H),
3.49 (m, 2H), 3.15 (dd, 1H, J ) 5.8, 14.4 Hz), 2.97 (dd, 1H, J
) 7.7, 14.4 Hz), 2.34-2.60 (m, 4H), 1.55-1.65 (m, 3H), 1.33
(m, 1H), 1.13 (d, 3H, J ) 6.8 Hz), 0.74 (d, 3H, J ) 6.3 Hz),
0.70 (d, 3H, J ) 6.4 Hz); 13C NMR (CDCl3, 75 MHz) δ 172.6,
170.8, 170.6, 165.7, 153.8, 141.4, 136.7, 131.8, 130.9, 130.2,
130.0, 128.6, 128.4, 127.5, 126.1, 125.2, 122.3, 112.2, 77.0, 71.4,
56.1, 54.0, 42.3, 39.7, 36.4, 34.9, 34.4, 32.4, 24.3, 22.6, 21.2,
17.2; HRMS (FAB, m/z) calcd for C34H42N2O735Cl (M+ + H)
625.2681, found 625.2675.
ter t-Bu tyl (5S,6R)-5-[(2S)-2-[3-[(2R)-2-(ter t-Bu toxyca r -
bon ylam in o)-3-(3-ch lor o-4-m eth oxyph en yl)pr opion ylam i-
no]propionyloxy]-4-methylpentanoyloxy]-6-methyl-8-phen-
ylocta -2(E),-7(E)-d ien oa te (49). To a solution of 36 (85.7 mg,
0.142 mmol) in EtOAc (2.0 mL) was added Pd(OH)2 (20% on
carbon, 10.0 mg, 0.0142 mmol), and the mixture was stirred
vigorously at room temperature under a H2 atmosphere for 2
h. The mixture was filtered, and the filtrate was concentrated
in vacuo. The crude acid 37 (78.0 mg) was dried by azeotropic
removal of H2O with toluene and was subjected to the next
reaction without further purification.
Ack n ow led gm en t. We are indebted to Professors
Marc A. Tius and Richard E. Moore, University of
Hawaii, for providing 1H and 13C NMR spectra of
natural 5 and to R. Thomas Williamson for assistance
with the HPLC separation. Financial support was
provided by the National Institutes of Health (GM50574).
To a solution of 19 (31.0 mg, 0.103 mmol) and crude 37 (78.0
mg, 0.142 mmol) in CH2Cl2 (0.86 mL) at room temperature
was added 4-(dimethylamino)pyridine (DMAP, 19.0 mg, 0.155
mmol), followed slowly by 1,3-diisopropylcarbodiimide (DIC,
19.5 mg, 0.024 mL, 0.155 mmol). The mixture was stirred at
room temperature for 18 h, and the solvent was removed in
vacuo. The residue was purified by flash chromatography
(silica gel, gradient elution with 20% and 50% Et2O in hexanes)
to give 69.5 mg (0.0872 mmol, 85%) of 49 as a colorless oil: Rf
Su p p or tin g In for m a tion Ava ila ble: NMR spectra of
synthesized compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
0.49 (50% EtOAc in hexanes, PMA); [R]22 +1.66 (c 1.39,
D
CHCl3); IR (film) 3350, 29656, 2931, 1741, 1713, 1658, 1504,
1257, 1168 cm-1; 1H NMR (CDCl3, 300 MHz) δ 7.18-7.32 (m,
J O9907585