Synthesis of 10b(R)-hydroxypancratistatin, 10b(S)-hydroxy-1-epipancratistatin, 10b(S)-hydroxy-1,2-diepipancratistatin and related isocarbostyrils

Article abstract of DOI:10.3987/com-01-s(k)7

Narciclasine (2) was transformed by a series of reactions where Sharpless asymmetric hydroxylations served as the stereochemical controlling step to 10b(R)-hydroxypancratistatin (3), 10b(S)-hydroxy-1-epipancratistatin (13) and 10b(S)-hydroxy-1,2-diepipancratistatin (16). Synthesis of 10b(S)-hydroxy-1,2-diepipancratistatin (16) proceeded from α-triol (11) via cyclic sulfate (14) and inversion of C-2 with cesium benzoate followed by saponification and treatment with a catalytic amount of acid. Compared to pancratistatin (1), these structural modifications led to decreased cancer cell growth inhibition against a minipanel of human cancer cell lines. Narciclasine (2) inhibited the pathogenic yeast Cryptococcus neoformans, and modifications (4, 14 and 15) inhibited growth of the pathogenic bacterium Neisseria gonorrhoeae.

Full text of DOI:10.3987/com-01-s(k)7

HETEROCYCLES, Vol. 56, 2002, pp. 139 - 155, Received, 19th March, 2001
SYNTHESIS OF 10b(R)-HYDROXYPANCRATISTATIN, 10b(S)-HYDROXY-1-
EPIPANCRATISTATIN, 10b(S)-HYDROXY-1,2-DIEPIPANCRATISTATIN AND
RELATED ISOCARBOSTYRILS1
George R. Pettit,* Noeleen Melody, Delbert L. Herald, Jean M.
Schmidt, Robin K. Pettit, and Jean-Charles Chapuis
Cancer Research Institute and Department of Chemistry and
Biochemistry, Arizona State University, P.O. Box 872404, Tempe,
Arizona, 85287-2404, USA
Abstract - Narciclasine (2) was transformed by a series of
reactionswhereSharplessasymmetrichydroxylationsservedasthe
stereochemical controlling step to 10b(R)-hydroxypancratistatin
(3), 10b(S)-hydroxy-1-epipancratistatin (13) and 10b(S)-hydroxy-
1,2-diepipancratistatin (16). Synthesis of 10b(S)-hydroxy-1,2-
diepipancratistatin (16) proceeded from ·-triol (11) via cyclic
sulfate (14)andinversionofC-2withcesiumbenzoatefollowedby
saponification and treatment with a catalytic amount of acid.
Compared to pancratistatin (1), these structural modifications
led to decreased cancer cell growth inhibition against a mini-
panel ofhuman cancercelllines. Narciclasine (2)inhibitedthe
pathogenic yeast Cryptococcus neoformans, and modifications (4,
14 and15) inhibitedgrowth ofthe pathogenicbacteriumNeisseria
gonorrhoeae.
The terrestrial flora continues to be an exceptionally productive, albeit still
largely unexplored, sourceof newandpotentially usefulantineoplasticsubstances.
Recent examples of such biologically active constituents from plants include new
combretastatins,2 other stilbenes,3 flavonoids,3 podophyllotoxin-type lignans,4
quinones,5,6 tetrahydrofurans,7 steroidal glycosides,8 pentacyclic triterpenes,9
ambewelamides A and B1 0 from a lichen and the new anticancer drug
hydroxymethylacylfulvene, a derivative of the mushroom constituent illudinS.11 Our
early research12 directed at discovery of useful plant constituents for improving
human cancer treatment has resulted in on-going clinical development of
combretastatin A-4 prodrug13 and phyllanthostatin 1/phyllanthoside,14 and (+)-
pancratistatin (1)15 in advanced preclinical development.
In anticipation of meeting clinical supply requirements for pancratistatin (1), we
developed a practical horticultural procedure16 for producing this anticancer and
antiviral isocarbostyril while in parallel investigating synthetic17,18 approaches
with narciclasine (2) as relay19 that became successful.20,21 In some Narcissus spp.
(Amaryllidaceae),22 narciclasine (2) is reasonably abundant,16 and we have employed

(following isolation) this plant constituent as a very useful intermediate for
synthetic conversion20 to (+)-pancratistatin (1) and to conduct a series of SAR
studies. The present investigation was concerned with further defining structural
requirements for maintaining or enhancing the anticancer activity of (+)-
pancratistatin (1).
As we reported in a preliminary communication,19 10b(R)-hydroxypancratistatin (3)
and 10b(R)-hydroxy-2,3,4,7-tetra-O-acetylpancratistatin (5) were synthesized from
narciclasine (2) and 2,3,4,7-tetra-O-acetylnarciclasine (4), respectively, using
osmium tetroxideandthechiral directingligandhydroquinine4-chlorobenzoate(HQ)23
(Scheme1). Interestingly,10b(S)-hydroxy-1-epipancratistatinwasnotobtainedwhen
HQ was replaced with its diastereoisomer, hydroquinidine 4-chlorobenzoate (HQD).
Presumably, the stereochemistry of the C-2 allylic hydroxyl group of narciclasine
(2) and its peracetate derivative was causing the osmium tetroxide to approach the
olefinic bond from the opposite facial side.24
Scheme 1
OH
OH
H
OH
OH
HO
OH
OH
O
O
O
O
a
H
NH
H
NH
HO
OH
HO
OH
OH
O
O
OH
OH
O
O
2
3
H
NH
H
O
b
c
OH
OCOCH3
OCOCH3
OCOCH3
1
H
HO
OCOCH3
O
O
O
OCOCH3
a
OCOCH3
H
NH
H
NH
HO
O
O
O
CH3CO2
CH3CO2
4
5
o
(a) OsO4 (cat.), NMO, HQ 4-chlorobenzoate, DMF-H2O (9:1), 0 - 24 C;
(b) Ac2O, py, 24 h; (c) CH2Cl2, 2M NH3 in CH3OH
Accordingly, we proceeded to investigate the possibility of obtaining the 10b(S)-
hydroxy-1-epipancratistatin by preparing narciclasine derivatives which might
reverse this β-approach of the osmium tetroxide to the olefinic bond. We found that
the narciclasine derivative N-methyl-2-O-acetylnarciclasine-3,4-acetonide (8),upon
treatment with a catalytic amount of osmium tetroxide and the chiral directing
ligand HQD, afforded N-methyl-2-O-acetyl-10b(S)-hydroxy-1-epipancratistatin-3,4-
acetonide (9) in a 2:1 ratio with its 10b-(R)-diastereoisomer (10) (Scheme 2). When

the osmylation reaction was repeated under the same conditions using the HQ chiral
directing ligand, the ratio of 9:10 was found to be 1:6. These results agree with
the prediction that olefin (8) is positioned as suggested by the Sharpless and
coworkers25 mnemonic device with the smallest substituent (the hydrogen) in the
southeast quadrant which is considered the most hindered space, and the aromatic
group occupying the southwest quadrant. Osmium tetroxide is more likely to attack
from the β-face in the case of hydroquinidine (HQD) derivatives, or from the α-face
in the case of hydroquinine (HQ) derived ligands.
Scheme 2
OH
OH
H
H
O
O
O
O
O
O
O
O
a
b
H
NH
H
2
N
CH3
O
O
OH
OH
6
7
OCOCH3
O
HO
O
O
O
H
HO
N
OCOCH3
O
CH3
H
O
OH
9
O
O
O
H
d
c
OCOCH3
O
N
CH3
HO
O
OH
8
O
O
O
H
HO
N
CH3
O
OH
10
(a) PTSA, DMP, DMF, 24 h; (b) CH3 I, K 2CO3; (c) Ac2O (1 equiv), py;
(d) OsO4 (cat.), NMO, HQD 4-chlorobenzoate, acetone-H2O (9:1)
The diols were separated by column chromatography and examined by NMR. Crystals
grown from acetone-hexane and examined by X-Ray crystallography confirmed the
structure and stereochemistry (Figure 1) of α-diol (9), and, as a consequence, β-
diol (10) as well. Encouraged by the preceding results, synthesis of the 10b(S)-
hydroxy-1-epipancratistatin (13) (Scheme 3) was undertaken. The 10b(S)-hydroxy-1-
epipancratistatin-3,4-acetonide (11) was obtained in a 2:1 ratio with 10b(R)-
hydroxypancratistatin-3,4-acetonide (12) when narciclasine-3,4-acetonide (6) was
allowed to react with osmium tetroxide and either the chiral directing ligand

Figure 1. The crystal structure of α-diol (9) (50% thermal ellipsoid probability
plot).
Scheme 3
OH
OH
HO
HO
O
O
O
O
O
O
O
O
a
H
NH
+
H
NH
6
HO
HO
O
O
OH
OH
11
12
b
b
OH
OH
HO
OH
OH
HO
OH
OH
O
O
O
O
H
NH
H
NH
HO
HO
O
O
OH
OH
13
3
(a) OsO4 (cat.), NMO, (DHQD )2PHAL, DMF-H2O (9:1), 0 - 15 oC;
(b) THF, H2SO4, H2O, 24 h
hydroquinidine 4-chlorobenzoate (HQD) or dihydroquinidine phthalazine (DHQD)2PHAL26
in DMF-H2O (overall yield of 79%).

It should be noted that we were unsuccessful in obtaining either diol using the AD-
mix formulation.26 The acetonide protecting group was removed from each isomer by
treating with sulfuric acid in THF-H2O to give 10b(S)-hydroxy-1-epipancratistatin
(13) and 10b(R)-hydroxypancratistatin (3). In an effort to synthesize the 10b(S)-
hydroxypancratistatin, thecyclic sulfate(14) wassynthesized byreactingacetonide
(11) with thionyl chloride. Here it was considered probable that the10b(S)-hydroxy
cyclic sulfate (14) would undergo inversion at C-1 when allowed to react with cesium
benzoate.18,20 Subsequent treatment with acid would give the desired 10b(S)-
hydroxypancratistatin. However, the SN2substitution occurred atC-2 withinversion
of configuration, to give only the C-2 benzoate (15) (Scheme 4).
Scheme 4
O
O S
O
O
OCOPh
OH
HO
O
O
O
O
O
O
a
b
OH
H
H
11
HO
HO
NH
NH
O
O
OH
OH
14
15
OH
HO
OH
OH
O
O
c
H
NH
HO
O
OH
16
(a)(i) SOCl2, (C2H5)3 N, THF; (ii) RuCl3 3H2O/NaIO4, CH3CN-CCl4-H2O; (b)(i) Cs2 CO3,
.
C6H5CO2H, DMF; (ii) THF-H2O/H2SO4 (cat.), 60 oC; (c) K2CO3, CH3 OH, rt
Presumably, the presence of the 10b(S)-hydroxyl group made substitution at the C-2
position more favorable electronically. Presence of the benzoate group at the C-2
carbon was discovered by careful examination of the 1H NMR, COSY, and ROESY spectra.
The signal assigned to the H-2 proton was down field (δ 5.02 ppm) relative to the
H-1 signal (δ 4.29 ppm). A large coupling constant was observed between the two
protons (J = 9 Hz), which confirmed the trans relationship. The small coupling
constant between H-2 and H-3 (J = 2.5 Hz) implied that those protons were on the
same side of the molecule in a cis relationship. The ROESY spectrum showed very
clear correlation peaks between the H-1 signal and the H-4a signal indicating their
positions on the same side of the molecule. Strong correlation peaks were also
observed between H-3 and H-4, and between H-2 and the hydroxyl groups 1 and 10b, as
expected. The C-2 benzoyl group was removed by saponification with potassium

carbonate to give pentaol (16). A crystal of alcohol (16) was grown from methanol
and the structure deduced by X-Ray crystallography, which confirmed the structure
(16) as shown in Figure 2.
Figure 2. The crystal structure (50% thermal probability ellipsoids) of 10b(S)-
hydroxy-1,2-diepipancratistatin(16), includingthetwoassociatedsolvatemolecules
of methanol.
Isocarbostyrils (3-5) and (7-16) were tested for potential activity against a mini-
panel of human cancer lines and the P388 murine leukemia cell line (Table 1). The
compounds all showed decreased cancer cell growth inhibitory activity.
Interestingly, the presence of the C-2 benzoate group caused a considerable
improvement in the activity of 15 compared with 16. In broth microdilution assays
(National Committee for Clinical Laboratory Standards, Documents M27-A and M7-A4,
1997), narciclasine (2) exhibited antifungal activity (MIC=8-16 µg/mL,Cryptococcus
neoformans), and pancratistatin structural modifications 4, 14 and 15 exhibited
marginal antibacterial activity (MIC=32-64 µg/mL, Neisseria gonorrhoeae).
EXPERIMENTAL
Solvents were purified by redistillation and in addition tetrahydrofuran was
distilled from sodium benzophenone, dimethyformamide from phosphorouspentoxide and
triethylamine from potassium hydroxide. TLC was performed on Merck kieselgel 60F
254 plates eluting with the solvents indicated. Visualization was provided using
a 254 mm UV lamp and development with a ceric sulfate spray with heat. Flash column
chromatography was performed with Merck silica gel 60 slurry packed in flash columns
using the initiating solvent. Melting points are uncorrected and were observed
using a Fisher-Johns melting point apparatus. NMR spectra were acquired at either
300 MHz, 400 or 500 MHz for 1H and for 13C employing Varian Gemini 300 and Inova-500

instruments. The EIMS spectra were determined using a Finnigan-MAT spectrometer
(model 312) instrument. Analytical combustion analyses were performed by Galbraith
Laboratories, Inc., Knoxville, Tennessee.
10b(R)-Hydroxypancratistatin (3).
Before adding narciclasine (2), (0.7 g, 2.28 mmol), a solution of DMF-water (9:1 mL)
and hydroquinidine 4-chlorobenzoate (0.1 g, 0.21 mmol, 10.8 eq.), N-methyl-
morpholine-N-oxide (NMO) (0.6 mL, 50% in water) and osmium tetroxide (0.1 mL, 4
mol%) was stirred at 0°C for 1 h. The reaction mixture was allowed to warm to rt
and stirred for 24 h. Sodium metabisulfite (2 g) was added followed by an equal
volume of acetone and sodium sulfate (2 g). The mixture was stirred at rt for a
further 2 h. The solid was collected and the solvent concentrated (under vacuum).
The crude product was separated by column chromatography on silica gel using
dichloromethane-methanol (1:9) as eluent to give a white solid, (0.3 g, 40%): mp
269°C, [α]D22 +70° (c 0.58, CH3OH); EIMS m/z (%) 341 (M+, 27), 250(15), 233(16),
222(100), 165(11, 135(6), 107(3), 73(26Z), 60(9); 1H NMR (300 MHz, DMSO-d6) δ 12.75
(s, 1H), 8.40 (s, 1H), 6.61 (s, 1H), 6.02 (m, 2H), 5.48 (d, J = 5.7 Hz, 1H), 5.40
(s, 1H), 4.75 (d, J = 6 Hz, 1H), 4.62 (d, J = 4.8 Hz, 1H), 4.55 (d, J = 7.2 Hz, 1H),
4.02 (m, 1H), 3.74 (d, J = 3 Hz, 1H), 3.6-3.5 (m, 2H), 3.15 (t, J = 8.0 Hz, 1H) ppm.
13C NMR (300 MHz, DMSO-d6) δ 169.9, 152.3, 145.0, 140.9, 132.8, 104.7, 102.5, 99.9,
75.6, 74.4, 71.8, 71.6, 71.3, 58.2 ppm. Anal. Calcd for C14H15NO9. 1H2O; C, 46.83;
H, 4.77; N, 3.90. Found: C, 46.95; H, 4.79; N, 3.96.
2,3,4,7-Tetra-O-acetylnarciclasine (4).27
To a solution of pyridine (5 mL) and acetic anhydride (5 mL) was added narciclasine
(0.9 g, 3.25 mmol) and the mixture stirred at rt for 16 h. Iced water was added and
the white precipitate was collected by filtration and recrystallized from
dichloromethane: methanol to give a colorless crystalline compound (0.85 g, 61%),
mp 249°C, [α]D24 +229° (c 0.33, CHCl3), EIMS m/z (%) 475 (M+, 5) 433(33), 373(6),
1
313(29), 271(100), 242(11), 169(2), 140(3), 83(8), 60(3). H NMR (500 MHz, CDCl3)
δ 6.92 (s, 1H), 6.15 (m, 1H), 6.10 (d, J = 1 Hz, 1H), 6.09 (d, J = 1 Hz, 1H), 5.86
(s, 1H), 5.43 (m, 1H), 5.34 (m, 1H), 5.2 (ddd, J = 1.2, 2.4, 9 Hz, 1H), 4.57 (br d,
13
J = 9 Hz, 1H), 2.37 (s, 3H), 2.12 (s, 3H), 2.1 (s, 3H), 2.08 (s, 3H) ppm. C NMR
(500 MHz, CDCl3) δ 170.5, 169.7, 169.5, 169.0, 162.2, 152.5, 141.6, 134.2, 133.8,
131.6, 118.2, 114.7, 103.1, 101.9, 71.4, 68.3, 68.04, 50.2, 20.8, 20.9, 20.7 ppm.
10b(R)-Hydroxy-2,3,4,7-tetra-O-acetylpancratistatin (5).
Dimethylformamide (9 mL) and water (1 mL) were stirred together in a round-bottomed
flask. Hydroquinine 4-chlorobenzoate (0.1 g, 0.2 mmol, 17 mol%) was added followed
by osmium tetroxide (0.1 mL, 0.1 mmol, 8 mol%) and the reaction mixture was stirred
and cooled to 0°C for 1 h before adding 3 (0.6 g. 1.26 mmol). The reaction mixture
was allowed to warm to rt and stirred for a further 40 h. Sodium metabisulfite (2
g) was added followed by an equal volume of acetone. Sodium sulfate (2 g) was added
and the reaction mixture stirred for 4 h. The solids were collected by filtration
and the filtrate concentrated to a crude solid which crystallized from methanol at

0°C in a colorless crystalline solid (0.425 g, 66%). Further recrystallization from
methanol gave crystals which were suitable for X-Ray crystallography. mp 266°C,
[α]D25 = +165° (c 0.55, DMSO), EIMS m/z (%) 509 (M+, 9), 467(16), 371(12), 329(18),
1
287(100), 258(21), 222(63), 201(5), 165(5), 115(5), 60(98). H NMR (300 MHz, DMSO-
d6) δ 8.14 (s, 1H), 7.12 (s, 1H), 6.13 (s, 1H), 6.11 (s, 1H), 5.72 (s, 1H), 5.44 (t,
J = 10.5 Hz, 1H), 5.29-5.20 (m, 3H), 3.80 (d, J = 1.8 Hz, 1H), 3.50 (t, J = 8.5 Hz,
13
1H), 2.22 (s, 3H), 2.04 (s, 3H), 1.60 (s, 3H), 1.93 (s, 3H) ppm. C NMR (500 MHz,
DMSO-d6) δ 169.8, 169.6, 169.2, 168.4, 161.9, 150.8, 140.9, 139.2, 132.1, 112.9,
105.3, 102.8, 72.8, 71.9, 70.9, 69.4, 68.2, 55.9, 20.9, 20.7, 20.6, 20.4, ppm.
Anal. Calcd for C22H23NO13.CH3OH: C, 51.06; H, 5.03; N, 2.59. Found: C, 51.27; H, 4.69;
N, 2.61.
Narciclasine-3,4-acetonide (6).
2,2-Dimethoxypropane (25 mL) was added to a solution of narciclasine (2, 5 g, 16.3
mmol) in DMF (25 mL). p-Toluenesulfonic acid (0.83 g) was added to the solution and
the reaction stirred at rt for 16 h. Pyridine (8.5 mL) followed by water (150 mL)
was added to the suspension and the mixture stirred for 1 h at rt. The precipitated
product was collected using vacuum filtration, washed with water and dried at 64°C
over P2O5 under highvacuum to give anamorphous powder ofnarciclasine-3,4-acetonide
(5.49 g, 97%), mp 270-273°C (lit.28 mp 275°C), IR (KBr) 3497, 3184, 1676, 1599, 1467,
1
1373, 1294, 1111, 1039 cm-1. H NMR (300 MHz, DMSO-d6) δ 13.70 (s, 1H), 8.80 (s,
1H), 7.01 (s, 1H), 6.47 (br s, 1H), 6.06 (m, 2H), 5.73 (br s, 1H), 4.2-3.90 (m, 4H),
13
1.45 (s, 3H), 1.31 (s, 1H) ppm. C NMR (300 MHz, DMSO-d6) δ 167.6, 152.5, 145.2,
133.3, 128.8, 128.3, 125.98, 109.8, 104.3, 102.0, 94.2, 79.0 ppm. EIMS m/z (%) 347
(M+, 28); 332(1), 289(2), 273(6), 260(8), 247(100), 242(22), 218(10), 85(2),73(10).
N-Methylnarciclasine-3,4-acetonide (7).
Compound (6) (1.3 g, 2.88 mmol) was dissolved in dry acetone (50 mL) and DMF (56
mL), and stirred under argon at rt. Potassium carbonate (1.0 g, 5.06 mmol) was
added followed by methyl iodide (1 mL, 16 mmol) and the reaction mixture was heated
at reflux for 18 h to give one product by TLC (chloroform:acetone 4:1). The mixture
was cooled and chloroform (100 mL) was added. The organic layer was washed with
water (2 x 100 mL) followed by brine and dried over sodium sulfate. The solvent was
removed by concentration under vacuum to give a residue (1.10 g). Column
chromatography on silica gel (eluent; chloroform) yielded compound (7, 1 g, 96%)
following recrystallization from chloroform:acetone: mp 245-247°C, Rf 0.78,
(CH2Cl2:MeOH 4%). EIMS m/z (%) 361 (M+, 28), 343(1), 303(4), 286(6), 274(5),
1
260(100), 256(40), 232(14), 204(3), 174(3), 118(3), 85(5), 77(5). H NMR (500 MHz,
CDCl3) δ 13.42 (s, 1H), 6.65 (s, 1H), 6.35 (t, J = 3 Hz, 1H), 6.03 (d, J = 1 Hz,
1H), 6.02 (d, J = 1 Hz, 1H), 4.31-4.29 (m, 1H), 4.25 (t, J = 7.75, Hz, 1H), 4.13 (m,
13
1H), 3.97 (t, J = 7.75 Hz, 1H), 3.26 (s, 3H), 1.55 (s, 3H), 1.37 (s, 3H). C NMR
(500 MHz, CDCl3) δ 166.7, 152.6, 145.8, 134.5, 127.7, 127.6, 125.1, 11.7, 105.4,
102.3, 93.4, 79.6, 79.3, 72.6, 61.9, 33.3, 27.1, 24.7 ppm. HRMS (FAB+): calcd for
C18H20NO7 (M+H+) 362.3579. Found: 362.1242. Anal. Calcd for C18H19NO7: C, 59.83; H,

5.30; N, 3.88. Found: C, 59.66; H, 5.40; N, 3.86.
2-O-Acetyl-N-methylnarciclasine-3,4-acetonide (8).
To a solution of 7 (1 g, 2.77 mmol) in pyridine (6 mL) was added acetic anhydride
(0.3 mL, 3.17 mmol). The reaction mixture was stirred and monitored by TLC
(hexane:acetone 6:4). The reaction was stopped after 24 h with the addition of iced
water (100 mL). A white crystalline compound precipitated from solution. The
compound was filtered and recrystallized from hot ethanol to yield 8 (0.95 g, 85%)
mp 95°C, Rf 0.86 (CH2Cl2:MeOH 2%) [α]D23 = +75° (c 0.48, CHCl3) EIMS m/z (%) 403 (M+,
46), 345(24), 303(50), 285(27), 274(53), 261(100), 257(64), 232(1), 191(6), 149(6),
115(5), 85(8), 60(4). 1H NMR (500 MHz, CDCl3) δ 13.39 (s, 1H), 6.61 (s, 1H), 6.03
(d, J = 1.5 Hz, 1H), 6.01 (d, J = 1.5 Hz, 1H), 5.28 (m, 1H), 4.26-4.17 (m, 3H), 3.26
13
(s, 3H), 3.20 (s, 3H), 1.55 (s, 3H), 1.36 (s, 3H) ppm. C NMR (500 MHz, CDCl3) δ
170.5, 166.7, 152.6, 145.8, 134.8, 128.7, 127.4, 122.4, 111.8, 105.4, 102.3, 93.6,
79.02, 75.9, 73.9, 61.7, 33.4, 26.9, 24.7, 21.1 ppm. Anal. Calcd for C20H21NO8: C,
59.55; H, 5.25; N, 3.47. Found: C, 59.18; H, 5.41; N, 3.47.
2-O-Acetyl-N-methyl-10b(S)-hydroxy-1-epipancratistatin 3,4-acetonide (9) and 2-O-
acetyl-N-methyl-10b(R)-hydroxypancratistatin-3,4-acetonide (10).
A 100 ml round-bottomed flask was charged with acetone (7 mL) and water (2 mL), NMO
(60% aq soln, 0.59 mL, 3.3 mmol), and dihydroquinidine 4-chlorobenzoate (0.59 g,
0.11 mmol). The mixture was cooled in an ice-salt bath over a cold plate stirrer
and OsO4 (50 mL of a 1 M soln in toluene, 12.5 mmol) was added. The solution was
stirred at 0°C for 1 h before adding 8 (0.9 g, 0.22 mmol). The reaction mixture was
then stirred at 15°C for 20 h. Sodium metabisulfite (2 g) was added and the mixture
was stirred for 1 h. Dichloromethane (equal volume) was next added and the mixture
was stirred for a further 30 min. Sodium sulfate (2 g) was added and the mixture
was stirred for 30 min. The pink solids were collected by filtration through a bed
of celite and washed several times with dichloromethane. The filtrate and washings
were concentrated to a yellow solid which was dissolved in ethyl acetate (350 mL)
and washed with 2 N HC1 (3 x 50 mL) and water (100 mL), dried over Na2SO4, and
concentrated to a yellow solid 0.7 g. Column chromatography on silica gel (eluent;
chloroform:acetone 14%) gave 9 (0.275 g, 28%). It was recrystallized from
acetone:hexane to give crystals which were examined by X-Ray crystallography. Rf
0.28 (CHCl3:CH3COCH3 8:1), mp 255°C, [α]D +95.8° (c 0.26, CHCl3), EIMS m/z (%), 437 (M+,
1
62), 377(4), 302(4), 252(87), 235(100), 206(9), 149(8), 85(13), 59(13). H NMR (400
MHz, CDCl3) δ 12.9 (s, 1H), 6.83 (s, 1H), 5.94 (s, 2H), 4.85 (dd, J = 6.2, 11 Hz,
1H), 4.62-4.47 (m, 3H), 3.68 (d, J = 6.8 Hz, 1H), 3.63 (s,s 1H), 3.20 (m, 4H), 2.15
13
(s, 3H), 1.43 (s, 3H), 1.35 (s, 3H) ppm. C NMR (400 MHz, CDCl3) δ 170.3, 167.9,
152.5, 145.5, 135.4, 134.4, 110.4, 106.2, 102.4, 97.6, 75.7, 72.6, 71.3, 70.4, 68.9,
61.4, 30.1, 27.7, 25.6, 20.9 ppm. Anal. Calcd for C20H23NO10: C, 54.92; H, 5.30; N,
3.20. Found: C, 54.80; H, 5.40; N, 3.19.
Continuing elution gave 10 (0.139 g, 14%), which upon recrystallization
(acetone:hexane) gave crystals which were examined by X-Ray crystallography, Rf 0.18

(CHCl3:CH3COCH3), mp 253°C, [α]D23 -65.4° (c 0.46, CHCl3) EIMS m/z (%) 437 (M+, 62),
1
377(4), 302(4), 252(16), 234(87), 235(100), 206(9), 149(8), 85(13), 59(13). H NMR
(400 MHz, CDCl3) δ 12.60 (s, 1H), 6.78 (s, 1H), 6.04 (m, 2H), 5.32 (dd, J = 7, 10
Hz, 1H), 4.18 (t, J = 7.2 Hz, 1H), 4.12-3.97 (m, 3H), 3.67 (d, J = 10 Hz, 1H), 3.59
(d, J = 8.8 Hz, 1H), 3.26 (s, 3H), 2.17 (s, 3H), 1.55 (s, 3H), 1.28 (s, 3H) ppm.
13C NMR (400 MHz, CDCl3) δ 171.3, 166.2, 152.7, 145.5, 134.4, 110.7, 106.6, 102.5,
98.3, 75.8, 75.5, 72.4, 71.9, 68.4, 66.5, 36.8, 27.1, 24.6, 21.1 ppm. Anal. Calcd
for C20H23NO10: C, 54.92; H, 5.30; N, 3.20. Found: C, 55.00; H, 5.71; N, 3.08.
The X-Ray crystal structure determination of 2-O-acetyl-N-methyl-10b(S)-hydroxy-1-
epipancratistatin-3,4-acetonide (9).
A small, block-shaped crystal (~0.24 x 0.20 x 0.20 mm), grown from CH3COCH3:hexane
solution, was mounted on the tip of a glass fiber. Cell parameter measurements and
data collection were performed at 296 ± 1°K. Accurate cell dimensions were
determined by least-squares fitting of 25 carefully centered reflections in the
range of 35°<θ<40° using Cu Kα radiation. Crystal Data: C20H23N1O10, FW=437.39,
orthorhombic, P212121,a=11.443(2), b=12.354(3),c=14.356(3)Å, V=2029.5(7))Å3,Z=4,
ρc=1.432 Mg/m3, µ(CuKα)=0.991 mm-1, λ=1.54178 Å.
All reflections corresponding to a complete octant (0<=h<=11, 0<=k<=13, 0<=1<=16)
were collected over the range of 0<2θ<130° using the ω/2θ scan technique. Friedel
reflections were also collected (whenever possible) immediately after each
reflection. Three intensity control reflections were also measured for every 60
minutes of X-Ray exposure time and showed a maximum variation of -1.2% over the
course of the collection. A total of 1599 reflections were collected. Subsequent
statistical analysis of the complete reflection data set using the XPREP29 program,
verified that the space group as P212121. A total of 1499 reflections were
considered observed (Io >2σ(Io)) and used in the subsequent structure determination
and refinement. Linear and anisotropic decay corrections were applied to the
intensity data as well as an empirical absorption correction (based on a series of
psi-scans).30 Structure determination and refinement was readily accomplished with
the direct-methods program in SHELXTL-pc.31 All non-hydrogen atom coordinates were
located in a routine run using default values for that program. The remaining H
atom coordinates were calculated at optimum positions. All non-hydrogen atoms were
refined anisotropically in a full-matrix least-squares refinement procedure. The
H atoms were included, their Uiso thermal parameters fixed at either 1.2 or 1.5
(depending on atom type) the value of the Uiso of the atom to which they were
attached and forced to ride that atom. The final standard residual R1 value for 9
was 0.0511 for observed data and 0.0550 for all data. The goodness-of-fit on F2 was
1.076. The corresponding Sheldrick R values were wR2 of 0.1410 and 0.1455,
respectively. A final difference Fourier map showed minimal residual electron
density; the largest difference peak and hole being 0.234 and -0.277 e/Å3,
respectively. Final bond distances and angles were all within expected and
acceptable limits. The absolute stereochemical structure of 9, as shown in Figure

1, was assigned by relaying the known absolute stereochemistry of the unaffected
chiral centers at C3 and C4 in the starting material (narciclasine). Thus, using
the numbering shown in Figure 1, the chiral centers of 9 can be assigned as follows:
1R, 2S, 3S, 4S, 4aS, 10bS.
10b(S)-Hydroxy-1-epipancratistatin-3,4-acetonide (11) and 10b(R)-hydroxy-
pancratistatin-3,4-acetonide (12).
A solution of DMF (4.5 mL) and H2O (0.5 mL) was stirred at 15°C on a cold plate
stirrer; NMO (60% by wt/H2O) (0.3 mL) was added followed by (DHQD)2 PHAL (0.045 g,
0.053 mmol) and OsO4 [100 µL of a 0.65 M biphasic solution toluene (4 mL) and H2O
(2 mL). The solution turned orange upon addition of the OsO4 and was stirred for
1 h before adding 6 (0.7 g, 2.02 mmol). The reaction mixture was stirred at 17°C
for 24 h. Sodium metabisulfite (2 g) was added followed by acetone (5 mL), and the
mixture was stirred for 30 min before adding Na2SO4(2 g). The mixture was stirred
for a further 2 h before collecting the salts by filtration. The filtrate was
concentrated under vacuum followed by high vacuum to remove the DMF. The brown
residue was separated using flash chromatography on silica gel and a gradient
elution of CH2Cl2:CH3OH 2%-CH2Cl2:CH3OH 5% to give diol (11) (0.38 g, 54%) and diol
(12) (0.17 g, 24%). Diol (11) was recrystallized from CH2Cl2:CH3OH 1:1 (minimum
volume with heating), needlelike crystals were obtained Rf 0.28 (CH2Cl2:CH3OH 4%),
mp 225°C, [α]D25 +15.1° (c 0.93, DMSO), EIMS m/z (%) 381 (M+), 366, 323, 306, 288,
263, 234, 221, 73, 60. IR (thin film) 3381, 3055, 2945, 2833, 1674, 1643, 1602,
1
1348, 1267, 1028, 738 cm-1. H NMR (500 MHz DMSO-d6)δ 13.30 (br s, 1H), 8.63 (s,
1H), 7.20 (s, 1H), 6.06 (s, 1H), 6.02 (s, 1H), 5.30 (br s, 1H), 5.23 (s, 1H), 5.10
(s, 1H), 4.30 (t, J = 7.2 Hz, 1H), 4.10 (m, 1H), 3.80 (m, 1H), 3.50 (d, J = 8.5 Hz,
13
1H), 1.31 (s, 3H), 1.39 (s, 1H) ppm. C NMR (500 MHz DMSO-d6) δ 168.6, 151.5,
145.0, 138.8, 132.7, 108.6, 106.4, 101.8, 98.3, 76.0, 74.9, 69.7, 69.4, 69.3, 56.3,
27.9, 25.5 ppm. Anal Calcd for C17H19NO9• 1/2 H2O: C, 52.35; ;H, 5.12; N, 3.59.
Found: C, 52.39; H, 5.02; N, 3.67.
Diol (12) Rf 0.20 (CH2Cl2:CH3OH 4%) mp 229-230°C, [α]D25 = + 31.3° (c 0.81, DMSO), EIMS
m/z (%) 381 (M+) 366, 323, 234, 221, 165, 85, 73, 60, 44. IR (thin film) 3396, 2918,
1
1672, 1624, 1467, 1354, 1221, 1078, 1016 cm-1. H NMR (500 MHz, CD3OD) δ 6.85 (s,
1H), 6.00 (s, 2H), 4.25 (dd, J = 6, 4 Hz, 1H), 4.13 (t, J = 6.7 Hz, 1H), 4.05 (d,
J = 4 Hz, 1H), 3.97 (dd, J = 8, 10 Hz, 1H), 3.55 (d, J = 10 Hz, 1H), 1.53 (s, 1H),
13
1.35 (s, 3H) ppm. C NMR (500 MHz, CD3OD) δ 170.8, 154.2, 146.4, 141.0, 134.7,
110.7, 106.1, 76.9, 73.8, 73.7, 73.1, 58.2, 28.3, 26.1 ppm. Anal Calcd for C17H19NO9:
C, 53.55; H, 5.02; N, 3.67. Found: C, 53.23; H, 5.23; N, 3.38.
10b(S)-Hydroxy-1-epipancratistatin (13).
To a solution of THF (2 mL) was added 7 (0.086 g, 0.225 mmol). The solution was
stirred at rt, water (3 drops from a pipette) and conc. H2SO4 (2 drops from a
pipette) was added, and the mixture was stirred for 22 h at rt. THF (10 mL) was
added and ethyl acetate (5 mL) was added. The solution was neutralized by washing
with 5% NaHCO3. The organic layer was separated and washed with water (10 mL) dried

Na2SO4, and concentrated to a white solid (0.04 g, 52%), which was recrystallized
1
from CH2Cl2 CH3OH (1:1), mp 185° [α]D= -54.5° (c 0.2, DMSO-d6). H NMR (500 MHz, DMSO-
d6) δ 13.03 (s, 1H), 7.48 (s, 1H), 7.44 (s, 1H), 6.06 (s, 1H), 6.02 (s, 1H), 5.44
(br s, 1H), 5.03-4.99 (m, 3H), 3.98-3.92 (m, 2H), 3.83 (br s, 2H), 3.49 (d, J = 10.8
13
Hz, 1H) ppm. C (500 MHz, DMSO-d6) δ 169.1, 151.2, 144.9, 138.9, 132.6, 107, 101.8,
98.6, 74.9, 71.9, 71.5, 67.4, 64.9, 55.9 ppm. Anal. Calcd for C14H15NO9⋅CH3OH; C,
48.26; H, 5.13; N, 3.75. Found: C, 48.9; H, 5.31; N, 3.38.
Cyclic sulfate (14).
Diol (7) (0.13 g, 0.34 mmol) was dissolved in dry THF (3.5 mL), triethylamine (0.19
mL, 1.36 mmol) was added and the reaction mixture cooled to 0°C using an ice bath
before adding SOCl2 (0.027 mL, 0.4 mmol). The reaction mixture was stirred at 0°C
for 10 min and TLC (CH2Cl2:CH3OH 4%) showed complete conversion to product. The
reaction was stopped after 15 min by the addition of ethyl acetate (20 mL). The
organic layer was washed with water (2 x 10 mL) followed by brine (10 mL), dried
(MgSO4), filtered and concentrated to a glassy solid. The solid was purified by
passing it through a silica gel column using flash chromatography and ethyl acetate
as the eluent before proceeding to the next step. The clear oil (0.12 g) was taken
up in CCl4:CH3CN 1.2:1.5, and stirred at rt until dissolved. RuCl3.3H2O (0.0054 g,
0.027 mmol) and NaIO4 (0.096 g, 0.447 mmol) were added together to the reaction
solution quickly followed by H2O (1.2 mL). The black-green mixture was stirred for
50 min before adding ethyl acetate (20 mL). The organic layer was washed with water
(3 x 5 mL), brine (1 x 5 mL) and dried (MgSO4), filtered through a pad of silica
gel, and concentrated to a crystalline solid (0.079 g, 63% yield), Rf 0.8 (DCM:MeOH
4%), mp 169-170°C, [α]D25 = -3.04° (c 0.82, CH3CN), EIMS m/z (%) 443(31), 355(16),
287(26), 267(14), 249(16), 221(15), 207(100), 191(21), 133(37), 96(17), 73(19),
64(66), 59(37), 49(32), 44(91). IR (thin film) 3213, 2976, 2872, 1676, 1464, 1400,
1
1356, 1213, 1068, 898, 856 cm-1. H NMR (500 MHz, DMSO-d6) δ 13.24 (s, 1H), 9.12 (s,
1H), 6.72 (s, 1H), 6.55 (s, 1H), 6.14 (s, 1H), 6.10 (s, 1H), 5.59 (d, J = 10 Hz,
1H), 5.19 (t, J = 8.25 Hz, 1H), 4.73 (t, J = 7.75 Hz, 1H), 4.50 (t, J = 7.5 Hz, 1H),
13
3.74 (d, J = 7 Hz, 1H), 1.46 (s, 3H), 1.35 (s, 3H) ppm. C NMR (500 MHz, DMSO-d6)
δ 167.8, 152.0, 145.2, 134.4, 133.8, 110.5, 105.9, 102.4, 98.0, 84.4, 82.2, 75.8,
73.9, 54.9, 27.3, 24.9 ppm. Anal. Calcd for C17H17NO11S; C, 46.05; H, 3.86; N, 3.16.
Found: C, 45.76; H, 4.50; N, 3.07.
2-Benzoyl-10b(S)-1,2-diepipancratistatin (15).
A DMF (4 mL) solution of 10 (0.35 g, 0.79 mmol) was stirred at 65°C under reflux and
a drying tube. Benzoic acid (0.145 g, 1.06 mmol) was added, followed by Cs2CO3 (0.41
g, 1.26 mmol). The reaction mixture was stirred for 23 h at 65°C, and all the
product was on the base line by TLC (CH2Cl2:CH3OH 4%). The reaction mixture was
concentrated under high vacuum to remove the DMF. The brown residue was taken up
in THF (10 mL) and water (12 drops from a pipette) was added to the suspension
followed by H2SO4 (8 drops from a pipette). The reaction mixture was heated under
reflux to 65-75°C for 2 h. The crude reaction mixture was purified on a column of

silica gel using flash chromatography and CH2Cl2:CH3OH 10% as the eluent. The C-
1-benzoyl product was isolated as a crystalline solid (0.215 g, 61.2%) Rf 0.41
(CH2Cl2:CH3OH 10%), mp 185°C, [α]D21 +39.5° (c 0.56, EtOH); IR (thin film) 3367, 2362,
1703, 1670, 1620, 1465, 1342, 1280, 1122, 1085, 1028, 9378 cm-1. EIMS m/z (%), 445
(M+, 34), 341(11), 287(5), 263(10), 233(18), 221(16), 205(7), 122(45), 105(100),
1
77(53), 45(62). H NMR (500 MHz, DMSO-d6) δ 13.08 (br s, 1H), 8.06 (d, J = 7.5 Hz,
2H), 7.66 (t, J = 7.5 Hz, 1H), 7.54 (t, J = 7.5 Hz, 2H), 7.47 (s, 1H), 7.41 (s, 1H),
6.06 (s, 1H), 6.04 (s, 1H), 5.43 (s, 1H), 5.39 (d, J = 7.5 Hz, 1H), 5.28 (d, J = 4
Hz, 1H), 5.15 (d, J = 5.5 Hz, 1H), 5.02 (dd, J = 10.0, 2.5 Hz, 1H), 4.29 (t, J = 8.5
13
Hz, 1H), 4.08 (br s, 1H), 3.80 (m, 1H), 3.60 (d, J = 10.5 Hz, 1H) ppm. C NMR (500
MHz, DMSO-d6) δ 169.2, 165.8, 151.2, 145.1, 139.0, 133.2, 132.7, 130.3, 129.5(2C),
128.5(2C), 107.4, 101.9, 98.8, 75.6, 69.5, 68.8, 68.9, 66.7, 55.7 ppm. HRMS (FAB):
calcd for C21H19NO10 (M+) 445.1009. Found: 445.0992.
10b(S)-Hydroxy-1,2-diepipancratistatin (16).
Compound (15) (0.172 g, 0.386 mmol) was dissolved in CH3OH (5 mL) and stirred at rt,
and K2CO3 (0.01 g, 0.06 mmol) was added. A white precipitate developed. TLC
(CH2Cl2:CH3OH 10%) showed that no starting material remained after 7 h stirring. The
reaction mixture was concentrated to a white solid which was dissolved in THF and
the insoluble salts were filtered off. The solution was concentrated to a white
solid (0.07 g, 53%), which crystallized from hot methanol in crystals that were
examined by X-Ray crystallography, Rf 0.07 (CH2Cl2:CH3OH 10%), mp 199.4-200°C, [α]D25
= -30.2° (c 0.57, MeOH), EIMS m/z (%), 341 (M+, 78), 287(3), 247(11), 233(64),
1
221(35), 205(21), 175(18), 165(16), 122(20), 105(32), 91(16), 77(26), 45(100). H
NMR (500 MHz, DMSO-d6) δ 13.07 (s, 1H), 7.41 (s, 1H), 7.35 (s, 1H), 6.05 (d, J = 0.5
Hz, 1H), 6.01 (d, J = 0.5 Hz, 1H), 5.03 (s, 1H), 4.90 (d, J = 7.0 Hz, 1H), 4.86 (d,
J = 6.5 Hz, 1H), 4.80 (d, J = 3.5 Hz, 1H), 4.64 (d, J = 6.5 Hz, 1H), 3.84 (m, 2H),
13
3.68 (m, 1H), 3.50 (m, 2H) ppm. C NMR (500 MHz, DMSO-d6) δ 169.2, 151.2, 145.0,
139.7, 132.5, 107.2, 101.8, 98.9, 71.9, 71.6, 71.3, 68.9, 67.1, 55.9 ppm. Anal.
Calcd for C14H15NO9⋅CH3OH. C, 48.26; H, 5.13; N, 3.75. Found: C, 48.02; H, 4.50; N,
3.90.
X-Ray crystal structure determination of 16.
A thin plate (~0.04 x 0.20 x 0.24 mm), grown from hot methanol solution, was mounted
on the tip of a glass fiber. Cell parameter measurements and data collection were
performed at 298 ± 1°K with a Bruker SMART 6000 diffractometer system using CuKα
radiation. A sphere of reciprocal space was covered using the multirun technique.31
Thus, six sets of frames of data were collected with 0.40° steps in ω, and a last
set of frames with 0.40° steps in ω such that 97.5% coverage of all unique
reflections to a resolution of 0.84Å was accomplished. Crystal Data: C16H23NO11 • 2
CH3OH (methanol solvate), FW=405.35 monoclinic, P21, a=7.8697(4), b=7.4195(4),
c=14.9035(8) Å, β=95.131(3)°,V=866.72(8) Å3,Z=2, ρc=1.553Mg/m3, µ(CuKα)=1.147mm-1,
λ=1.54178 Å.
A total of 6046 reflections were collected, of which 2366 reflections were

independent reflections (R(int)=0.0870). Subsequent statistical analysis of the
data set with the XPREP29 program indicated the spacegroup was P21. Final cell
constants were determined from the set of the 2094 observed (>2σ (I)) reflections
which were used in structure solution and refinement. An absorption correction was
applied to the datawith SADBS.33 Structure determinationand refinement wasreadily
accomplished with the direct-methods program SHELXTL.31 All non-hydrogen atom
coordinates were located in a routine run using default values for that program.
The remaining H atom coordinates were calculated at optimum positions. All non-
hydrogen atoms were refined anisotropically in a full-matrix least-squares
refinement procedure. The H atoms were included, their Uiso thermal parameters
fixed at either 1.2 or 1.5 (depending on atom type) the value of the Uiso of the
atom to which they were attached and forced to ride that atom. The final standard
residual R1 value for 16 was 0.0594 for observed data and 0.0632 for all data. The
goodness-of-fit on F2 was 1.025. The corresponding Sheldrick R values were wR2 of
0.1451 and 0.1475, respectively. A final difference Fourier map showed minimal
residual electron density; the largest difference peak and hole being 0.307 and –
0.322 e/Å3, respectively. Final bond distances and angles were all within expected
and acceptable limits. The Flack absolute structure parameter ¯ for the model shown
in Figure 2 is 0.0(4), indicating that the absolute stereochemical structure shown
for 16 is correct. Consequently, the stereochemistry at the chiral centers in 16
can be assigned as follows: 1R, 2S, 3S, 4S, 4aS, 10bS.
ACKNOWLEDGEMENTS
The very necessary financial support for this investigation was provided by
Outstanding Investigator Grant CA-44344-O1A1-O1-12 from the Division of Cancer
Treatment and Diagnosis, National Cancer Institute, DHHS; the Arizona Disease
Control Research Commission; the Fannie E. Rippel Foundation; Robert B. Dalton
Endowment Fund; Gary L. and Diane R. Tooker; Sally Schloegel; Billie Jean Baguley;
the Fraternal Order of Eagles Art Ehrmann Cancer Fund; and the Ladies Auxiliary to
the Veterans of Foreign Wars. We are also very pleased to thank for other
assistance: Professor Barry M. Trost (Stanford University), Drs. Ralph A. Backhaus,
Gordon M. Cragg, Dennis L. Doubek, Cherry L. Herald, Fiona Hogan, Sheo Bux Singh and
Rui Tan; Joy Bell, Heather Herald, George R. Pettit III, Sandy Pon and Lee Williams;
and the U. S. National Science Foundation (Grant No. CHE-9808678).
REFERENCES
1.
Dedicated to Professor James P. Kutney on the occasion of his 70th birthday;
Antineoplastic Agents series part 467: for part 466 consult S. M. Nabha, N.
R. Wall, R. M. Mohammad, G. R. Pettit, and A. M. Al-Katib, Anti-Cancer Drugs,
2000, 11, 385.
2.
3.
S. Schwikkard, B.-N. Zhou, T. E. Glass, J. L. Sharp, M. R. Mattern, R. K.
Johnson, and D. G. I. Kingston, J. Nat. Prod., 2000, 63, 457.
N. Fang and J. E. Casida, J. Nat. Prod., 1999, 62, 205.

4.
L. Udino, J. Abaul, P. Bourgeois, L. Gorrichon, H. Duran, and C. Zedde, Planta
Med., 1999, 65, 279.
5.
6.
R. M. Khan and S. M. Mlungwana, Phytochemistry, 1999, 50, 439.
S. Kosela, S.-G. Cao, X.-H. Wu, J. J. Vittal, T. Sukri, Masdianto, S.-H. Goh,
and K.-Y. Sim, Tetrahedron Lett., 1999, 40, 157.
7.
8.
J.-H. Woo, S.-H. Kim, and J. L. McLaughlin, Phytochemistry, 1999, 50, 1033.
M. Kuroda, Y. Mimaki, Y. Sashida, T. Yamori, and T. Tsuruo, Tetrahedron Lett.,
2000, 41, 251.
9.
Y. Deng, T.-Y. Jiang, S. Sheng, M. Tianasoa-Ramamonjy, and J. K. Snyder, J.
Nat. Prod., 1999, 62, 471.
10. D. E. Williams, K. Bombuwala, E. Lobkovsky, E. D. de Silva, V. Karunaratne,
T. M. Allen, J. Clardy, and R. J. Andersen, Tetrahedron Lett., 1998, 39, 9579.
11. T. C. McMorris, Bioorganic & Med. Chem., 1999, 7, 881.
12. G. R. Pettit, J. Nat. Prod. 1996, 59, 812.
13. G. R. Pettit, M. R. Rhodes, and R. Tan, J. Nat. Prod., 1999, 62, 409; D. J.
Chaplin, G. R. Pettit, and S. A. Hill, Anticancer Research, 1999, 19, 189; G.
R. Pettit, M. R. Rhodes, D. L. Herald, D. J. Chaplin, M. R. L. Stratford, E.
Hamel, R. K. Pettit, J.-C. Chapuis, and D. Oliva, Anti-Cancer Drug Design,
1998, 13, 981.
14. G. R. Pettit, G. M. Cragg, and M. Suffness, J. Org. Chem., 1985, 50, 5060.
15. G. R. Pettit, V. Gaddamidi, G. M. Cragg, D. L. Herald, and Y. Sagawa, J. Chem.
Soc., Chem. Commun., 1984, 1693; G. R. Pettit, V. Gaddamidi, and G. M. Cragg,
J. Nat. Prod., 1984, 47, 1018; G. R. Pettit, V. Gaddamidi, D. L. Herald, S.
B. Singh, G. M. Cragg, J. M. Schmidt, F. E. Boettner, M. Williams, and Y.
Sagawa, J. Nat. Prod., 1986, 49, 995; B. Gabrielsen, T. P. Monath, J. W.
Huggins, D. F. Kefauver, G. R. Pettit, G. Groszek, M. Hollingshead, J. J.
Kirsi, W. M. Shannon, E. M. Schubert, J. DaRe, B. Ugarkar, M. A. Ussery, and
M. J. Phelan, J. Nat. Prod., 1992, 55, 1569; B. Gabrielsen, T. P. Monath, J.
W. Huggins, J. J. Kirsi, M. Hollingshead, W. M. Shannon, and G. R. Pettit,
"Natural Products as Antiviral Agents", ed. by C. K. Chu and H. Cutler,
Plenum, New York, 1992, pp. 121-135.
16. G. R. Pettit, G. R. Pettit III, G. Groszek, R. A. Backhaus, D. L. Doubek, J.
R. Barr, and A. W. Meerow, J. Nat. Prod., 1995, 58, 756; G. R. Pettit, G. R.
Pettit III, R. A. Backhaus, and F. E. Boettner, J. Nat. Prod., 1995, 58, 37;
G. R. Pettit, G. R. Pettit III, G. Groszek, R. A. Backhaus, M. R. Boyd, and
A. W. Meerow, J. Nat. Prod., 1993, 56, 1682.
17. S. Danishefsky and J. Y. Lee, J. Am. Chem. Soc., 1989, 111, 4829; X. Tian, T.
Hudlicky, and K. Koingsberger, J. Am. Chem. Soc., 1995, 117, 3643; T.
Hudlicky, X. Tian, K. Königsberger, R. Maurya, J. Rouden, and B. J. Fan, J.
Am. Chem. Soc., 1996, 118, 10752; T. J. Doyle, M. Hendrix, D. VanDerveer, S.
Javanmard, and J. Haseltine, Tetrahedron, 1997, 53, 11153; P. Magnus and I.
K. Sebhat, J. Am. Chem. Soc., 1998, 120, 5341; S. Ohta and S. Kimoto, Chem.

Pharm. Bull., 1976, 24, 2977; H. Paulsen and M. Stubbe, Liebigs Ann. Chem.,
1983, 535; X. Tian, R. Maurya, K. Königsberger, and T. Hudlicky, Synlett,
1995, 1125; N. Chida, M. Iitsuoka, Y. Yamamoto, M. Ohrauk, and S. Ogawa,
Heterocycles, 1996, 43, 1385; R. Polt," Organic Synthesis: Theory and
Application", Vol. 3, ed. by T. Hudlicky, JAI Press, Greenwich, 1996, p. 109;
O. Hoshino. "The Alkaloids", Vol. 51, ed. by G. A. Cordell, Academic Press,
San Diego, 1998, p. 328; L. M. Grubb, A. L. Dowdy, H. S. Blanchette, G. K.
Friestad, and B. P. Branchaud, Tetrahedron Lett., 1999, 40, 2691; J. L. Aceña,
O. Arjona, F. Iradier, and J. Plumet, Tetrahedron Lett., 1996, 37, 105; D. R.
Gauthier and S. L. Bender, Tetrahedron Lett., 1996, 37, 13.
18. B. M. Trost and S. R. Pulley, J. Am. Chem. Soc., 1995, 117, 10143.
19. G. R. Pettit, N. Melody, M. O'Sullivan, M. A. Thompson, D. L. Herald, and B.
Coates, J. Chem. Soc., Chem. Commun., 1994, 2725.
20. G. R. Pettit, N. Melody, and D. L. Herald, J. Org. Chem., 2001, 66, 2583.
21. J. H. Rigby, U. S. M. Maharoof, and M. E. Mateo, J. Am. Chem. Soc., 2000, 122,
6624; J. H. Rigby and M. E. Mateo, J. Am. Chem. Soc., 1997, 119, 12655.
22. J. Labraña, G. Choy, X. Solans, M. Font-Bardia, G. de la Fuente, F. Viladomat,
C. Codina, and J. Bastida, Phytochemistry, 1999, 50, 183.
23. H. C. Kolb, M. S. Van Nieuwenhze, and K. B. Sharpless, Chem. Rev., 1994, 94,
2483.
24. W. J. Christ, J. K. Cha, and Y. Kishi, Tetrahedron Lett., 1983, 24, 3947.
25. H. C. Kolb, P. G. Andersson, and K. B. Sharpless, J. Am. Chem. Soc., 1994,
116, 1278.
26. K. B. Sharpless, W. Amberg, Y. Bennani, G. A. Crispino, J. Hartung, K.-S
Jeong, H.-L Kwong, K. Morikawa, Z.-M Wang, D. Xu, and X.-L Zhang, J. Org.
Chem., 1992, 57, 2768.
27. A. Mondon and K. Krohn, Chem. Ber., 1970, 103, 2729. A. Immirzi and C.
Fugarti, Chem. Commun. 1972, 240.
28. A. Mondon and K. Krohn, Chem. Ber., 1975, 108, 445.
29. XPREP-The automatic space group determination program in the SHELXTL. (see
ref. 19).
30. A. C. North, D. C. Phillips, and F. S. Mathews, Acta. Cryst., 1968, A2, 351.
31. SHELXTL-PC Version 5.1, 1997, an integrated software system for the
determination of crystal structures from diffraction data, Bruker Analytical
X-ray Systems, Inc., Madison, WI 53719. This package includes, among others:
XPREP, an automatic space group determination program; XS, the Bruker SHELXS
module for the solution of X-ray crystal structures from diffraction data;
XL, the Bruker SHELXL module for structure refinement; and XP, the Bruker
interactive graphics display module for crystal structures.
32. SMART for Windows NT and Irix Software Reference Manual, Version 5.0, 1998,
pp 2-9.
33. Blessing, R. Acta Crystallogr., 1995, A51, 33.