1464 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 8
Pettit et al.
of psi-scans).22 Structure determination was readily accom-
plished with the direct-methods program SIR92.23 All non-
hydrogen atom coordinates were located in a routine run using
default values in that program. The remaining H atom
coordinates were calculated at optimum positions. All non-
hydrogen atoms were refined anistropically in a full-matrix
least-squares refinement using SHELXL-97.24 The H atoms
were included; their Uiso thermal parameters were fixed at 1.5
the Uiso of the atom to which they were attached and forced to
ride that atom. The final standard residual R1 value for 4e
was 0.0634 for observed data and 0.0642 for all data. The
goodness-of-fit on F2 was 1.036. The corresponding Sheldrick
R values were wR2 of 0.1726 and 0.1732, respectively. A final
difference Fourier map showed minimal residual electron
density; the largest difference peak and hole being 0.280 and
-0.163 e/Å3, respectively. The absolute structure of 4e could
be assigned with certainty based on the value of the Flack
parameter (0.06, esd 0.03) for the enantiomer shown in Figure
3.25 Consequently, the absolute stereochemistry of structure
of the silyl-protected diacetate derivative 4d can be assigned
the S configuration at both chiral carbons, C1A and C1′A. Final
bond distances and angles were all within acceptable limits.
concentrated, yielding a white solid. This was recrystallized
from carbon disulfide to give a white powder: yield, 0.60 g;
1H NMR δ (300 MHz, CDCl3) 3.70 (6H, s), 3.72 (3H, s), 3.75
(3H, s), 4.54 (2H, s (coalesced doublet)), 6.29 (2H, s), 6.78 (1H,
d, J 8 Hz), 6.83 (1H, dd, J 2, 8 Hz), 7.03 (1H, d, J 2 Hz), 7.61
(2H, d, J 8 Hz), 8.00 (2H, d, J 8 Hz); EIMS m/z 532 (1%, M+),
517 (5%, M+ - CH3), 514 (5%, M+ - H2O), 335 (5%, M+ - OCH
- C6H3(OCH3)3), 198 (100%, M+ - HOCH - C6H3(OCH3)-
(O2C6H4Br)), 183 (45%, [OCC6H4Br]+).
(1R,2R)-1,2-Diacetoxy-1-(3-[p-br om oben zoyloxy]-4-m eth -
oxyp h en yl)-2-(3′,4′,5′-tr im eth oxyp h en yl)eth a n e (4l). Ace-
tic anhydride (84 µL, 0.89 mmol, 2.5 equiv) was added to a
solution of the diol 4k (0.19 g, 0.36 mmol, 1.0 equiv) with
DMAP (8.8 mg, 0.071 mmol, 0.2 equiv) and triethylamine (0.15
mL, 1.07 mmol, 3.0 equiv) in DCM (1 mL) under Ar at room
temperature. The contents were stirred for 3 h, and TLC (1:1
hexanes-EtOAc) showed no residual starting material. Metha-
nol (5 mL) was added and the reaction mixture concentrated
to a yellow oil that was washed with ether, which was removed
by evaporation. The oily residue was partitioned with ether
(15 mL) and 1 N HCl (15 mL). The organic layer was further
washed with 10% aqueous sodium bicarbonate (15 mL). The
combined aqueous layers were back-extracted with DCM (5
mL), and the organic layers were combined and dried. Filtra-
tion and evaporation of solvents gave an off-white solid that
was subjected to flash chromatography (eluant 1:1 hexanes-
EtOAc). The desired fractions were collected and concentrated,
(1S,2S)-1,2-Di(p-b r om ob en zoyloxy)-1-(3-[ter t-b u t yld i-
m eth ylsilyloxy]-4-m eth oxyp h en yl)-2-(3′,4′,5′-tr im eth oxy-
p h en yl)eth a n e (4i). The resultant diol from AD mix-R 4a
(0.75 g, 1.61 mmol, 1.0 equiv) was dissolved in DMF (15 mL),
and pyridine (15 mL, 1:1 DMF-pyridine) was added at room
temperature. The reaction was stirred until homogeneous, and
4-bromobenzoyl chloride (0.89 g, 4.04 mmol, 2.5 equiv) was
added all at once. The yellow mixture was stirred under Ar at
room temperature. A white precipitate formed within 30 min,
and after 2 h the temperature was raised to 45 °C; 16 h later,
the temperature was raised to 85 °C, and another 2.5 equiv of
4-bromobenzoyl chloride was added. No starting material was
visualized following TLC. Ice (30 g) and ether (25 mL) were
added. The ethereal layer was successively washed with 1 M
HCl (25 mL), 10% sodium bicarbonate (25 mL), and water (25
mL). The organic phase was dried and filtered, and solvent
was removed to give a yellow oil that was subjected to flash
chromatography (9:1 hexanes-EtOAc). The desired product
(Rf ) 0.33, 4:1 hexanes-EtOAc) was isolated as an off-white
solid that was recrystallized from EtOAc-hexane to afford
small needles: yield, 0.70 g; 1H NMR δ (300 MHz, CDCl3)
-0.02 (3H, s), 0.04 (3H, s), 0.92 (9H, s), 3.70 (6H, s), 3.73 (3H,
s), 3.76 (3H, s), 6.23 (1H, d, J 9 Hz), 6.29 (1H, d, J 9 Hz), 6.41
(2H, s), 6.70 (1H, d, J 8 Hz), 6.78 (1H, s), 6.79 (1H, d, J 8 Hz),
7.52 (4H, d, J 8 Hz), 7.84 (4H, d, J 8 Hz); EIMS m/z 830 (2%,
M+2), 828 (1%, M+), 774 (15%, M+ - t-Bu + H), 183 (100%,
[OCC6H4Br]+).
(1S ,2S )-1,2-Di(p -b r om ob e n zoyloxy)-1-(3-h yd r oxy-4-
m eth oxyp h en yl)-2-(3′,4′,5′-tr im eth oxyp h en yl)eth a n e (4j).
4i (1.24 g, 1.49 mmol) was converted to 4j in an identical
fashion to the deprotection procedure of 4c. After flash
chromatography (2:1 hexanes-EtOAc), the desired fractions
were concentrated to give a fine woolly solid (4j): yield, 0.79
g; 1H NMR δ (400 MHz, CDCl3) 3.72 (6H, s), 3.78 (3H, s), 3.84
(3H, s), 5.56 (1H, s), 6.29 (1H, d, J 9 Hz), 6.29 (1H, d, J 9 Hz),
6.43 (2H, s), 6.67 (1H, dd, J 2, 8 Hz), 6.68 (1H, d, J 8 Hz), 6.97
(1H, d, J 2 Hz), 7.54 (4H, m), 7.87 (4H, m); EIMS m/z 716
(10%, M+), 516 (5%, M+ - HO2CC6H4Br), 183 (100%, [OCC6H4-
Br]+).
1
producing a white solid: yield, 0.20 g; H NMR δ (300 MHz,
CDCl3) 2.10 (3H, s), 2.12 (3H, s), 3.75 (3H, s), 3.76 (6H, s),
3.78 (3H, s), 5.93 (1H, d, J 9 Hz), 5.97 (1H, d, J 9 Hz), 6.34
(2H, s), 6.80 (1H, d, J 8 Hz), 6.89 (1H, dd, J 2, 8 Hz), 7.08 (1H,
d, J 2 Hz), 7.65 (2H, d, J 8 Hz), 8.03 (2H, d, J 8 Hz); EIMS
m/z 616 (15%, M+), 559 (1%, M+ - O2CCH3), 498 (5%, M+
-
(O2CCH3)2), 434 (6%, M + H - OCC6H4Br), 197 (100%,
[HOCHC6H2(OCH3)3]+), 183 (55%, [OCC6H4Br]+).
An tim icr obia l Su scep tibility Testin g. Compounds were
screened against the bacteria Stenotrophomonas maltophilia,
Micrococcus luteus, Staphylococcus aureus, Escherichia coli,
Enterobacter cloacae, Enterococcus faecalis, Streptococcus pneu-
moniae, and Neisseria gonorrhoeae and the fungi Candida
albicans and Cryptococcus neoformans, according to estab-
lished disk susceptibility testing protocols.27
Ack n ow led gm en t. Appreciation and thanks for
support of this research are extended to Outstanding
Investigator Grant CA 44344-05-9 with the Division of
Cancer Treatment and Diagnosis, NCI, DHHS, the
Arizona Disease Control Research Commission, Virginia
Piper, Diane Cummings Halle, Gary L. and Diane R.
Tooker, Polly Trautman, J ohn and Edith Reyno, the
Caitlin Robb Foundation, and the Robert B. Dalton
Endowment. We also thank Drs. Cherry L. Herald,
Fiona Hogan, J ean M. Schmidt, and Michael D. Wil-
liams, as well as David M. Carnell, Laura Crews, and
Lee Williams, the National Science Foundation for
equipment Grant CHE-8409644, and the NSF Regional
Instrumentation Facility in Nebraska (Grant CHE-
8620177).
Su p p or tin g In for m a tion Ava ila ble: Expanded Table 2
containing the murine P388 and human cancer cell line results
for the less active and inactive compounds 4a , 4b, and 4g-4l;
X-ray crystallographic tables of experimental detail, atomic
coordinates, bond lengths and angles, and anisotropic thermal
parameters for 3c, 4d , and 4e. This information is available
(1R,2R)-1,2-Dih yd r oxy-1-(3-[p -b r om ob e n zoyloxy]-4-
m eth oxyph en yl)-2-(3′,4′,5′-tr im eth oxyph en yl)eth an e (4k).
The chiral phenol 4d (0.5 g, 1.43 mmol, 1.0 equiv) was
dissolved in DMF (20 mL), and triethylamine (0.40 mL, 2.85
mmol, 2.0 equiv) was added. After 10 min, addition of p-
bromobenzoyl chloride (0.31 g, 1.43 mmol, 1.0 equiv) resulted
in
a yellow solution as the reaction proceeded at room
temperature under Ar. Starting material could no longer be
visualized by TLC after 2 h. Ice was added, and a precipitate
formed that was removed by filtration. The aqueous filtrate
was washed with ethyl acetate (25 mL), and the concentrated
residue was added to the filtered solid and flash chromato-
graphed (1:1 hexanes-EtOAc). The desired fraction were
Refer en ces
(1) For contribution 409, refer to: Pettit, G. R.; Tan, R.; Melody,
N.; Kielty, J . M.; Pettit, R. K.; Herald, D. L.; Tucker, B.; Mallavia,
L. P.; Doubek, D. L.; Schmidt, J . M. Antineoplastic Agents 409.
Isolation and Structure of Montanastatin from a Terrestrial
Actinomycete. Bioorg. Med. Chem., in press.