Total synthesis of spirotryprostatin a, leading to the discovery of some biologically promising analogues

Article abstract of DOI:10.1021/ja983788i

The total synthesis of the title compound has been accomplished. A key step involves the oxidative rearrangement of the β-carboline derivative to an oxindole via the action of N-bromosuccinimide. From this point, a diketopiperazine was introduced. A thiophenyl group served as a precursor of the isopropylidene function. Implementation of the same sort of chemistry starting with a methoxytryptophan derivative led to the parent structures. Furthermore, it was shown that the difficultly accessible isopropylidene side chain of spirotryprostatin A is not necessary for biological activity. Moreover, three analogues lacking the diketopiperazine system were shown to be quite active as cell cycle inhibitors.

Full text of DOI:10.1021/ja983788i

J. Am. Chem. Soc. 1999, 121, 2147-2155
2147
Total Synthesis of Spirotryprostatin A, Leading to the Discovery of
Some Biologically Promising Analogues
Scott Edmondson,† Samuel J. Danishefsky,*,†,‡ Laura Sepp-Lorenzino,§ and Neal Rosen§
Contribution from the Department of Chemistry, Columbia UniVersity, HaVemeyer Hall,
New York, New York 10027, and Laboratories for Bioorganic Chemistry and for Molecular Oncogenesis,
Sloan-Kettering Institute for Cancer Research, 1275 York AVenue, Box 106, New York, New York 10021
ReceiVed October 30, 1998
Abstract: The total synthesis of the title compound has been accomplished. A key step involves the oxidative
rearrangement of the â-carboline derivative to an oxindole via the action of N-bromosuccinimide. From this
point, a diketopiperazine was introduced. A thiophenyl group served as a precursor of the isopropylidene
function. Implementation of the same sort of chemistry starting with a methoxytryptophan derivative led to
the parent structures. Furthermore, it was shown that the difficultly accessible isopropylidene side chain of
spirotryprostatin A is not necessary for biological activity. Moreover, three analogues lacking the diketopiperazine
system were shown to be quite active as cell cycle inhibitors.
Introduction
A growing number of alkaloids, probably derived from
L-tryptophan, which also bear a pyrrolo ring in the context of a
diketopiperazine system (or another heterocyclic array), are
being discovered. Adding to their interest is the fact that they
display a range of biological profiles effecting cell cycle pro-
gression.1 One of these molecules, tryprostatin A, has recently
been shown to be a novel inhibitor of microtubule assembly.1c
Our laboratory has particularly focused on those members of
this class that also carry prenyl or “reverse-prenyl” substituents.
As a prelude to multidisciplinary investigations addressed to
structure-activity relationship and mode of action issues, we
have concerned ourselves with the goal of total synthesis. To
date, we have described the total syntheses of amauramine, the
ardeemins, gypsetin, and tryprostatin B.2 The ardeemins are
currently being pursued in our program as potential MDR
reversal agents.
Recently, spirotryprostatins A and B were isolated from the
fermentation broth of Aspergillus fumigatus.1 Besides possessing
synthetically challenging structural features, these spirooxindoles
were shown to inhibit the cell cycle in the G2/M phase with
IC50’s of 197.5 (1) and 14.0 µm (4). Cell cycle inhibitors not
only possess the potential to act as antineoplastic agents but
could also serve as possible probes to gain information about
cell signaling pathways. The difference between the activities
in these two cell cycle inhibitors is striking, with 4 being more
than an order of magnitude more potent than 1. Studies in related
natural products indicate that the aromatic methoxy group
present in 1 and 3 can weaken their activities significantly. When
this effect is quantified, however, these related examples
underestimate the difference in activity between 1 and 4.1b
Analogues 2 and 3 would allow a complete assessment of the
importance of the methoxy group relative to the importance of
unsaturation at C8/C9. Since 400 L of fermentation broth yielded
only 1 mg of 1 and 11 mg of 4, a total chemical synthesis of
these molecules seems at least a competitive way to obtain the
compounds in quantities that are ample for launching a thorough
biological investigation.
The overall synthesis strategy which we came to favor for
reaching the spirotryprostatin targets is illustrated in Scheme
1.3 Initial formation of the cis-substituted tetrahydro-â-carboline
5 would be accomplished using a Pictet-Spengler reaction
between a tryptophan derivative (cf. 8, vide infra) and a synthetic
equivalent of prenyl aldehyde. Spirorearrangement of an indole
so derived (cf. 5) to an oxindole 7 (perhaps via an intermediate
of the type 6) was viewed as the central step in the enterprise,
in that it would accomplish installation of the quaternary center
at C3 and could provide control over the relative stereochemistry
† Department of Chemistry, Columbia University.
‡ Laboratory for Bioorganic Chemistry, Sloan-Kettering Institute for
Cancer Research.
§ Laboratory for Molecular Oncogenesis, Sloan-Kettering Institute for
Cancer Research.
(1) (a) Cui, C.-B.; Kakeya, H.; Okada, G.; Onose, R.; Osada, H. J.
Antibiot. 1996, 49, 527. (b) Cui, C.-B.; Kakeya, H.; Osada, H. Tetrahedron
1997, 53, 59. (c) Usui, T.; Kondoh, M.; Cui, C.-B.; Mayumi, T.; Osada, H.
Biochem. J. 1998, 333, 543.
(2) (a) Marsden, S. P.; Depew, K. M.; Danishefsky, S. J. J. Am. Chem.
Soc. 1994, 116, 11143. (b) Schkeryantz, J.; Woo, J.; Danishefsky, S. J. J.
Am. Chem. Soc. 1995, 117, 7025. (c) Depew, K. M.; Danishefsky, S. J.;
Rosen, N.; Sepp-Lorenzino, L. J. Am. Chem. Soc. 1996, 118, 12463.
(3) For an earlier communication of this synthesis, see: Edmondson, S.
D.; Danishefsky, S. J. Angew. Chem., Int. Ed. 1998, 37, 1138.
10.1021/ja983788i CCC: $18.00 © 1999 American Chemical Society
Published on Web 02/26/1999

2148 J. Am. Chem. Soc., Vol. 121, No. 10, 1999
Edmondson et al.
Scheme 1
Scheme 3
Scheme 2
thermodynamic equilibration. Unfortunately, we required in-
termediates in the cis “family.”
Although the separation of 12a from 12b was readily
achieved, comparable purification of cis 11a in the face of trans
11b proved to be quite difficult. Fortunately, these diastereomers
could be more readily separated after suitable protection of the
basic nitrogen. Conversion of the sterically crowded secondary
amines to their corresponding tert-butylcarbamate (Boc) deriva-
tives was sluggish but furnished reasonable yields (based on
recovered starting material) of 13a and 14a. Deprotection of
the Boc group under standard conditions then afforded pure
samples of 11a (cis) and 11b (trans), which were initially
identified using Cook’s 13C NMR method and later confirmed
by NOE methods.6
Given this less than ideal situation, additional effort was
directed toward improving the synthesis of the desired cis
compound. The plan involved use of the Bischler-Napieralski
reaction to generate dihydro-â-carbolines (cf. 16) which might
be reduced in the desired sense. A model experiment involved
heating amide 15 with phosphorus oxychloride in benzene,
followed by treatment of the intermediate imine 16 with sodium
borohydride (Scheme 3). This protocol did, indeed, produce the
clearly desired cis product 17. Unfortunately, 17 thus obtained
was racemic. It is not clear whether racemization at the “tryp-
tophan” chiral center had occurred on a mechanistic intermediate
derived from 15 en route to cyclization or at the stage of 16.
Given this result, we were unable to exploit the fact that simple
reduction of the crude intermediate following cyclization (cf.
16) did, indeed, produce the desired diastereomer 17. Further-
more, exposure of amide 18 to the above conditions produced
the racemic product 12a in modest yield (21%), with side prod-
ucts resulting from replacement of the thiophenyl group with a
chlorine atom. In light of these findings in the context of the
Bischler-Napieralski route, the Pictet-Spengler sequence,
albeit far from ideal, seemed to be the preferred method for
producing the desired cis adducts in enantiomerically homoge-
neous form.
at carbons 3 and 18 in the eventual target 1. The precise timing
of installation of the isopropylidene group and the diketopip-
erazine ring were issues which would surely merit close
attention. However, our primary focus was on the all-critical
spirorearrangement step. It was believed that a â-oriented R
group at C18 of 5 would direct functionalization of the indole
ring to the R-face. It was further anticipated that the rearrange-
ment step would occur with inversion at C3, thereby producing
the C3, C18, and C9 stereochemical connectivities shown in 7.
Synthetic Results
Previous reports concerning attempted Pictet-Spengler reac-
tions between commercially available tryptophan methyl ester
(8) and prenyl aldehyde per se have been quite discouraging.4
Moreover, early investigations suggested that the isopropylidene
group would be likely to interfere with the maneuvers we had
in mind to achieve the overall transformation of 5 f 7. We
thus came to faVor installation of this moiety after the oxidatiVe
rearrangement of the indole had been accomplished. Com-
mercially available benzyloxyacetaldehyde (9) or readily avail-
able thioaldehyde 10 were evaluated as potential Pictet-
Spengler substrates whose functionalities might lend themselves
to the eventual incorporation of the isopropylidene linkage. In
the event, reaction of these aldehydes with 8 under anhydrous
acid conditions provided the desired cis-related tetrahydrocar-
bolines 11a and 12a in excellent yields in the expected marginal
selectivities with respect to their trans counterparts, 11b and
12b (Scheme 2).5
Assembly of a diketopiperazine starting from 11a,b was
achieved. The first step involved acylation of the mixture with
the proline-derived acid chloride 19. The crude seco compound
was subjected to the action of zinc metal. This treatment
accomplished the desired deprotection of the carbamate, thereby
setting into motion the required cyclization (see 20, in 54%
overall yield) (Scheme 4).7
Compound 20 was subjected to the action of N-bromosuc-
cinimide (NBS) in aqueous acetic acid.8 This exposure sufficed
to bring about oxidative rearrangement as originally planned.
Surprisingly extensive NMR analysis of the resultant product,
particularly its NOESY spectrum, revealed it to be oxindole
23. Thus, the stereosense of the formation of the spirorear-
rangement product had occurred opposite to our expectation.
Our results followed the pattern established in the long-term
and scholarly studies of Cook and associates6 as regards the
kinetic outcome of the Pictet-Spengler reactions of various
tryptophan derivatives. The kinetic outcome favors cis products
(cf. 11a) but only by modest selectivities. By contrast, the trans
compounds (cf. 11b) can often be obtained in high margins by
(4) (a) Harrison, D. M. Tetrahedron Lett. 1981, 22, 2501. (b) O’Malley,
G. J.; Cava, M. P. Tetrahedron Lett. 1987, 28, 1131.
(5) The Pictet-Spengler reaction of 8 and 38 with 10 has been
reported: (a) Harrison, D. M.; Sharma, R. B. Tetrahedron Lett. 1986, 27,
521. (b) Kodato, S.; Nakagawa, M.; Hongu, M.; Kawate, T.; Hino, T.
Tetrahedron 1988, 44, 359.
(6) For lead references of the Pictet-Spengler reaction to synthesize cis
and trans tetrahydrocarbolines, see: (a) Cox, E. D.; Hamaker, L. K.; Li, J.;
Yu, P.; Czerwinski, K. M.; Deng., L.; Bennett, D. W.; Cook, J. M.; Watson,
W. H.; Krawlec, M. J. Org. Chem. 1997, 62, 44. (b) Cox, E. D.; Cook, J.
M. Chem. ReV. 1995, 95, 1797.
(7) Boyd, S. A.; Thompson, W. J. J. Org. Chem. 1987, 52, 1790.
(8) VanTamelen, E. E.; Yardley, J. P.; Miyano, M.; Hinshaw, W. B. J.
Am. Chem. Soc. 1969, 91, 7333.

Total Synthesis of Spirotryprostatin A
J. Am. Chem. Soc., Vol. 121, No. 10, 1999 2149
Scheme 4
Scheme 6
Scheme 7
Scheme 5
showed that the desired stereochemistry had now been obtained
following the spirorearrangement step. Irradiation of H4 typi-
cally showed NOE enhancements at H8â and H19, while
irradiation of H18 showed enhancements at H8R, H9, and H19.
The reverse enhancements were also observed.
Rearrangements of this type had been studied extensively by
Borschberg et al., and a detailed conformational analysis can
be found in that work.15 Also to be noted is the resistance of
the phenyl sulfide to oxidation under the spirorearrangement
conditions. Care must be taken to employ appropriate amounts
of NBS since excess reagent induces electrophilic aromatic
bromination of the oxindole products.
Amine 27 was next converted to the corresponding dike-
topiperazine 29, under conditions similar to those employed
above (Scheme 6). However, deprotection of the benzyl group
from 29 proved to be problematic, affording low yields of the
corresponding alcohol. Furthermore, oxidation of the resulting
alcohol to the corresponding aldehyde was a low-yielding and
incomplete process.16
In a model system, oxindole 32 was generated by spirorear-
rangement of the cis N-tosyl derivative of 11a (Scheme 7).
Deprotection of the benzyl group was easily accomplished by
hydrogenolysis. Although oxidation of this alcohol proved to
be difficult, the pure aldehyde was finally obtained only after
repeated exposure of partially oxidized mixtures to Dess-
Martin’s periodinane. Proton and carbon NMR analysis of this
aldehyde indicated that it was actually a 1:1 mixture of two
products. This suggested the occurrence of a rapid enolization
and epimerization of the “R-chiral aldehyde”. In any case, the
mixture of 33 was resistant to olefination procedures, however,
and this route was abandoned.
Attention was next directed to sulfide 26. Oxidation of this
compound to a mixture of sulfoxides was followed by thermal
elimination and nitrogen deprotection to give a 1:1.5 mixture
of external olefin 34 and enamine 35, respectively (Scheme 8).
When sulfoxide elimination was induced after carbamate
deprotection, 34 was obtained. Apparently, the acidic conditions
required to achieve Boc deprotection also had induced isomer-
ization of the trisubstituted double bond to form the stable
enamine 35. By contrast, the undesired alternate elimination
product, 34, is stable to the reaction conditions. Presumably,
35 benefits from nitrogen resonance with the double bond.
The use of some alternative oxidants such as osmium tetraoxide
or BuOCl resulted in diminished yields of 23 (19% and 42%,
t
respectively).10 The use of other agents such as dimethyl
dioxirane11 or lead tetraacetate12 led to complicated mixtures
which did not lend themselves to separation. Replacement of
the benzyl group with a tert-butyldimethylsilyl group also failed
to correct the problem.13 Apparently, the diketopiperazine ring
enforces a poorly understood conformational preference on the
fused pyrrolo ring which faVors electrophilic attack at the â-face
of the indole syn to the benzyloxymethylene group. The
intermediate bromoindolenine 21 is then solvolyzed to form
hemiaminal 22. The latter proceeds to rearrange to 23.14
Since the precise factors which favored attack of the oxidant
syn to the benzyloxymethyl group remain somewhat mysterious,
we were obliged to survey other substrates without the benefit
of a guiding rationale, hoping to find one where attack of the
oxidant anti to the resident C3 group was favored. An obvious
possibility was to conduct spirorearrangement before diketopip-
erazene formation.
With this subgoal in mind, indoles 13a and 14a were exposed
to the aforementioned NBS-mediated rearrangement conditions
to afford oxindoles 25 and 26 (Scheme 5). Since the proton
NMR spectra of these molecules were complicated by carbamate
rotamers, deprotection of the Boc groups was necessary before
the stereochemistry of these products could be confirmed. The
appropriate NOE enhancements of amines 27 and 28 indeed
(9) (a) Takayama, H.; Kitajima, M.; Okata, K.; Sakai, S. J. Org. Chem.
1992, 57, 4583. (b) Peterson, A. C.; Cook, J. M. Tetrahedron Lett. 1994,
35, 2651.
(10) (a) Takayama, H.; Masubuchi, K.; Kitajima, M.; Aimi, N.; Sakai,
S.-i. Tetrahedron 1989, 45, 1327. (b) Hollinshead, S. P.; Grubisha, D. S.;
Bennett, D. W.; Cook, J. M. Heterocycles 1989, 29, 529.
(11) (a) Zhang, X.; Foote, C. S. J. Am. Chem. Soc. 1993, 115, 8867. (b)
Adam, W.; Ahrweiler, M.; Peters, K.; Schmeideskamp, B. J. Org. Chem.
1994, 59, 2733.
(12) Finch, N.; Gemenden, C. W.; Hsu, I. H.-C.; Kerr, A.; Simm, G. A.;
Tayer, W. I. J. Am. Chem. Soc. 1965, 87, 2229.
(13) The synthesis of the TBS analogue of 20 is achieved easily in two
steps: TMSI, CH3CN/CH2Cl2; then TBSCl, imid, DMF. Attempts to
oxidatively rearrange this molecule resulted in complicated mixtures and
loss of silicon.
(14) An observation of molecular models reveals that the corresponding
trans ring fusion, resulting from attack of water on the R-face of 21, would
be a highly strained molecule and, thus, less likely to form.
(15) (a) Pelligrini, C.; Strassler, C.; Weber, M.; Borschberg, H.-J.
Tetrahedron: Asymmetry 1994, 5, 1979. (b) Pelligrini, C.; Weber, M.;
Borschberg, H.-J. HelV. Chim. Acta 1996, 79, 151.
(16) In part, the difficulty in oxidizing of 30 is due to the poor solubility
of this molecule in organic solvents. Advantage was taken in the model
system (Scheme 7) of the more desirable solubility properties that these
molecules possess prior to diketopiperazine formation.

2150 J. Am. Chem. Soc., Vol. 121, No. 10, 1999
Edmondson et al.
Scheme 8
spirorearrangement was observed, apparently due to the in-
creased susceptibility of the methoxy-bearing oxindole to
electrophilic aromatic bromination.
Conversion of 42 to the diketopiperazine was followed by
sulfide oxidation and sulfoxide elimination to afford a 2.5:1
mixture of 1 and 43, respectively. HPLC separation of these
isomers afforded pure natural product. External olefin 43 could
then be converted to spirotryprostatin A by treatment with
1
rhodium chloride in refluxing ethanol. The H and 13C NMR
spectra and mass spectrum of 1 matched those of the naturally
Scheme 9
occurring material in all respects.17 The optical rotation of
synthetic 1 ([R]21.4 -116.2°), however, was significantly dif-
D
ferent from that of naturally occurring 1 ([R]26D -34.0°). Since,
in principle, every chiral center of 1 is susceptible to epimer-
ization, it is conceivable that, during its isolation, naturally
occurring 1 had undergone substantial racemization. Alterna-
tively, and more likely, the discrepancy reflects the fact that
only small, inhomogeneous samples of 1 were isolated from
natural sources. By contrast, chemical synthesis, even in the
face of some difficulties described above, provides ample
amounts of optically pure material.
In summary, the total synthesis of spirotryprostatin A (1) and
its demethoxy congener (2) were each achieved in a total of
eight steps in 10% and 14% yields, respectively. Highlighted
in this synthesis is the ability to control the stereochemical
relationship between C3 and C18 during the stereodefining
spirorearrangement step. The late-stage regioselective sulfoxide
elimination that favors formation of the internal olefin over the
external olefin (despite a 3:1 statistical bias) also merits attention.
Scheme 10
Biological Results
We now describe the biological evaluation of spirotryprostatin
and some of its analogues available by total synthesis. We started
with the fully synthetic spirotryprostatin A. Cell cycle inhibition
of mouse tsFT210 cell lines in the G2/M phase had been
reported for 1 (IC50 ) 197.5 µM) and 3 (IC50 ) 14.0 µM) by
Osada et al.1 With access to substantial quantities of 1 and
selected analogues of 1 at our disposal, we explored the activity
of six molecules (1, 2, 23, 25, 29, and 43) on MCF-7 and MDA
MB-468 human breast cancer cells (Figure 1).2c
Given the low activity of 1 with the tsFT210 cell line, it was
not surprising that it shows little activity in the anchorage-
dependent growth assay. MCF7 cells were not inhibited in terms
of growth with concentrations as high as 300 µM (Figure 1
and Table 1), and high micromolar concentrations were neces-
sary to inhibit the growth of MDA MB-468 cells (IC50 ) 110
µM). Similar values were obtained for demethoxyspirotrypro-
statin A (2) and isospirotryprostatin A (43). These compounds
showed no significant activity in MCF7 cells, whereas micro-
molar concentrations of both compounds inhibited MDA MB-
468 cell growth (Figure 1 and Table 1).
By contrast, 23, 25, and 29 were active in both cells lines
(Figure 1 and Table 1). As seen most remarkably for MDA
MB-468 cells, 23, 25, and 29 were 3-4 orders of magnitude
more potent than the natural product in inhibiting cancer cell
growth (Figure 1 and Table 1). It should be noted that one of
these active compounds, 25, is also the simplest of the
molecules, since it lacks the proline-containing diketopiperazine
ring. Oxindole 25 had been easily synthesized in only three steps
from commercially available starting materials. Moreover, the
synthesis of 23 is also both shorter and higher yielding (four
steps, 43% yield) than is the synthesis of the natural product
itself.
Although, in principle, 34 could be converted to the desired
target, a late-stage sulfoxide elimination was investigated with
the hope that introduction of the diketopiperazine ring might
modulate regioselectivity in the desired sense. Formation of the
diketopiperazine from 28 proceeded without event to give 36
(Scheme 9). Careful oxidation of 36 with 1 equiv of sodium
periodate afforded a 1:1 mixture of the two diastereomeric
sulfoxides in nearly quantitative yield (97%). A reaction
designed to achieve elimination of the sulfoxides in refluxing
toluene then afforded a mixture of the external and internal
olefins in 93% yield and 2.6:1 selectivity, favoring the internal
olefin. HPLC separation of the double bond isomers then
1
afforded pure samples of 37 and 2. A comparison of H and
13C NMR spectral data between 2 and naturally occurring 1
revealed striking similarities in all respects except the aromatic
regions (which was to be expected). An extensive series of NOE
enhancements further supported the relative stereochemistry of
C3, C9, C12, and C18. We were pleased to find that we could
further increase the efficiency of our route by transforming 37
to 2 using rhodium chloride catalysis. The first total synthesis
of spirotryprostatin 2 was now complete.
With a workable route to spirotryprostatin A accomplished,
we set about to apply this chemistry to the real system (Scheme
10). Pictet-Spengler reaction of 38 with 9 was followed by
protection of the amine as its Boc derivative to give 40.
Spirorearrangement of 40 to the oxindole 41 was followed by
deprotection of the carbamate under standard conditions to
afford amine 42. A detrimental effect on the yield of the
(17) Spectral data of naturally occurring 1 were kindly provided by
Professor Osada.

Total Synthesis of Spirotryprostatin A
J. Am. Chem. Soc., Vol. 121, No. 10, 1999 2151
3.68 (t, J ) 9.3 Hz, 1 H), 3.18 (dd, J ) 16.0, 12.0 Hz, 1 H), 2.86 (m,
1 H), 2.22 (s, 1 H); 13C NMR (75 MHz, CDCl3) δ ) 173.4, 137.5,
135.8, 134.5, 128.6 (2 C), 128.1, 128.0 (2 C), 126.7, 121.7, 119.3,
118.0, 110.9, 107.5, 73.8, 73.5, 56.3, 52.2, 52.1, 25.6.
For 11b: 13C NMR (75 MHz, CDCl3) δ ) 174.0, 137.8, 135.9,
133.5, 128.6 (2 C), 128.0, 127.9 (2 C), 126.7, 121.7, 119.3, 118.0,
110.9, 107.0, 73.6, 73.6, 56.3, 53.3, 49.5, 24.8.
cis-Benzyloxycarbamate 13. To the mixture 11a,b (4.72 g, 13.5
mmol) in 60 mL of 5:1 MeOH/Et3N was added the Boc2O (8.84 g,
40.5 mmol), and the mixture was stirred at 50 °C for 14 h and then
cooled to room temperature. The crude mixture was concentrated and
chromatographed (SiO2, 10% EtOAc/hexanes) to afford 1.07 g of 13a,
0.571 g of 13b (27% yield, 1.9:1 cis/trans), and 3.42 g of recovered
starting material (97% adjusted yield). For 13a: [R]21.0D +141.9° (c )
1.812, CHCl3); IR (CHCl3) 3420, 2986, 2960, 2932, 2908, 2840, 1730,
1678, 1618, 1448, 1390 cm-1; HRMS (FAB) m/z (M+) calcd 450.2156,
obsd 450.2142.
Carbamate Sulfide 14. To the amine 12a5 (2.49 g, 6.3 mmol) in
100 mL of 9:1 CH3CN/Et3N was added the Boc2O (4.10 g, 18.9 mmol),
and the mixture was stirred at 50 °C for 14 h and then cooled to room
temperature. The crude mixture was concentrated and chromatographed
(SiO2, 15% EtOAc/hexanes) to afford 1.02 g of the desired product
14a (33%) and 1.59 g of recovered starting material (90% adjusted
yield). For 14a: [R]21.6D -14.6° (c ) 2.17, CDCl3); IR (CDCl3) 3434,
3292, 3057, 2981, 2934, 2858, 1741, 1684, 1623, 1391, 1368, 1165
cm-1; 1H NMR (500 MHz, CDCl3) δ ) 8.94-8.84 (br s, 1 H), 7.56-
7.13 (series of m, 9 H), 5.75-4.98 (m, 2 H), 3.68-3.62 (m, 3 H),
3.40-3.10 (m, 2 H), 2.35-2.11 (m, 2 H), 1.62-1.23 (m, 15 H); HRMS
m/z (M+) calcd 494.2241, obsd 494.2239.
Bischler-Napieralski Reaction of 15. Amide 1518 (303 mg, 1.10
mmol) in 5 mL of benzene and 1 mL of POCl3 was heated to reflux
for 40 min, cooled to room temperature, and then concentrated. After
the orange viscous oil was taken up in 10 mL of methanol, NaBH4
(285 mg, 7.54 mmol) was added to the mixture at room temperature,
and the yellow slurry was stirred for an additional 30 min, quenched
with 5 mL of 5% HCl, diluted with 100 mL of saturated NaHCO3, and
extracted with CH2Cl2 (3 × 50 mL). The organic layers were then
washed with saturated NaHCO3 (2 × 20 mL), dried over MgSO4,
filtered, concentrated, and chromatographed (SiO2, 30% EtOAc/
hexanes) to afford 282 mg (99%) of the racemic product 17.19
Figure 1. Effect of spirotryprostatin A and derivatives on anchorage-
dependent tumor cell growth. MCF7 (A) and MDA MB-468 (B) human
breast cancer cells were plated at 10 000 cells/well on six-well plates
and treated with increasing concentrations of spirotryprostatin A and
analogues. Drugs were added from 1000× stock solutions dissolved
in dimethyl sulfoxide. Control cultures received an equivalent volume
of dimethyl sulfoxide. Cultures were refed with drug-containing medium
at day 3, and cultures were trypsinized and cell number determined at
day 6. Results are the averages of two independent experiments.
Table 1. IC50 for Inhibition of Anchorage-Dependent Growth of
MDA MB-468 and MCF7 Human Breast Cancer Cells
IC50 (M)
compound
MDA MB-468
MCF7
spirotryprostatin A (1)
demethoxyspirotryprostatin A (2)
isospirotryprostatin A (43)
benzyl spiroisomer (23)
benzyl analogue (29)
1.1 × 10-4
.3 × 10-4
.3 × 10-4
.3 × 10-4
1 × 10-4
1 × 10-4
8.5 × 10-5
2.5 × 10-8
2 × 10-8
Amide 18. Readily available 3-methyl-3-phenylsulfonylbutyric acid20
(4.70 g, 22.4 mmol) in 50 mL of benzene and 10 mL of SOCl2 was
heated to reflux for 90 min and then concentrated to form the
corresponding acid chloride. To tryprophan methyl ester hydrochloride
(4.58 g, 18 mmol) and Et3N (5.0 mL, 36 mmol) in 100 mL of
CH2Cl2 at 0 °C was added the acid chloride (dropwise in 60 mL of
CH2Cl2) over 30 min. The reaction mixture was then allowed to stir
for 60 min at 0 °C and for 60 min at room temperature before being
quenched with 50 mL of water and extracted with CH2Cl2 (3 × 200
mL). The organic layers were then washed with 5% HCl (3 × 100
mL), saturated NaHCO3 (2 × 200 mL), and brine (100 mL), dried over
MgSO4, filtered, concentrated, and chromatographed (SiO2, 30%
EtOAc/hexanes f 70% EtOAc/hexanes) to afford 6.91 g (94%) of
8 × 10-5
spirooxindole (25)
2 × 10-8
4 × 10-5
In conclusion, the synthetic studies directed at spirotrypro-
statin A haVe yielded three analogues which show much greater
actiVity than the natural product itself. It appears that the
structure-activity relationships among spirotryprostatins are
multifaceted and go beyond the presence or absence of a
methoxy group on the aromatic ring in the fully developed
structure. Further studies concerning the nature of these
structure-activity relationships, as well as a search for more
optimal development candidates, are currently underway.
amide 18: [R]20.0 +33.9° (c ) 1.42, CHCl3); IR (CHCl3) 3458,
D
3407, 3285, 2996, 2950, 2908, 1730, 1656, 1502, 1430 cm-1; 1H NMR
(400 MHz, CDCl3) δ ) 8.82 (s, 1 H), 7.58 (d, J ) 7.9 Hz, 1 H), 7.38-
7.07 (m, 7 H), 7.02 (d, J ) 2.2 Hz, 1 H), 5.01 (dd, J ) 12.9, 6.7 Hz,
1 H), 3.68 (s, 3 H), 3.39 (dd, J ) 14.9, 5.4 Hz, 1 H), 3.32 (dd, J )
14.9, 6.7 Hz, 1 H), 2.36 (s, 2 H), 1.35 (s, 3 H), 0.93 (s, 3 H); 13C NMR
(75 MHz, CDCl3) δ ) 172.4, 170.1, 137.2 (2 C), 136.1, 130.6, 129.0,
Experimental Section
Benzyloxytetrahydro-â-carbolines 11. To L-tryptophan methyl ester
(4.417 g, 20.2 mmol), powdered 4-Å molecular sieves (300 mg), and
benzyloxyacetaldehyde (3.75 g, 25 mmol) in 50 mL of CH2Cl2 at 0 °C
was added 1.7 mL (22 mmol) of trifluroroacetic acid, and the reaction
mixture was stirred at 0 °C for 1 h. Then, an additional 3.0 mL (60.6
mmol total) of trifluoroacetic acid was added to the reaction mixture,
and the solution was stirred at 0 °C for an additional 4 h before the
mixture was filtered, dissolved into 500 mL of CH2Cl2, washed with
saturate NaHCO3 (2 × 200 mL) and brine (100 mL), dried over MgSO4,
filtered, concentrated, and chromatographed (SiO2, 20% EtOAc/
hexanes) to afford 6.155 g (87%) of the cis/trans diastereomers 11 (2.3:
1). For 11a: 1H NMR (400 MHz, CDCl3) δ ) 8.52 (s, 1 H), 7.52 (d,
J ) 8.3 Hz, 1 H), 7.18 (t, J ) 7.8 Hz, 1 H), 7.12 (t, J ) 7.5 Hz, 1 H),
4.66 (s, 2 H), 4.42-4.41 (m, 1 H), 3.84 (s, 3 H), 3.86-3.81 (m, 3 H),
(18) Yoshioka, T.; Mohri, K.; Oikawa, Y.; Yonemitsu, O. J. Chem. Res.
1981, 7, 2252.
(19) Ungemach, F.; Soerens, D.; Weber, R.; DiPierro, M.; Campos, O.;
Mokry, P.; Cook, J. M.; Silverton, J. V. J. Am. Chem. Soc. 1980, 102,
6976.
(20) Tercio, J.; Ferreira, B.; Catani, V.; Comasseto, J. V. Synthesis 1987,
149.
(21) (a) Taniguchi, M.; Hino, T. Tetrahedron 1981, 37, 1487. (b)
Taniguchi, M.; Anjiki, T.; Nakagawa, M.; Hino, T. Chem. Pharm. Bull.
1984, 32, 2544. (c) Irie, K.; Ishida, A.; Nakamura, T.; Oh-ishi, T. Chem.
Pharm. Bull. 1984, 32, 2126.

2152 J. Am. Chem. Soc., Vol. 121, No. 10, 1999
Edmondson et al.
128.6 (2 C), 127.3, 122.9, 121.9, 119.3, 118.2, 111.3, 109.4, 52.9, 52.1,
48.0, 47.0, 28.8, 28.2, 27.4; HRMS m/z (M+ + 1) calcd 411.17, obsd
411.18.
1390 cm-1; 1H NMR (500 MHz, CDCl3) δ ) 8.13 (s, 1 H), 7.59 (d, J
) 7.7 Hz, 1 H), 7.36 (d, J ) 7.9 Hz, 1 H), 7.20 (t, J ) 7.5 Hz, 1 H),
7.15 (t, J ) 7.4 Hz, 1 H), 5.33 (dd, J ) 8.3, 4.0 Hz, 1 H), 4.17-4.12
(m, 2 H), 4.05 (dd, J ) 8.0, 4.0 Hz, 1 H), 3.66-3.63 (m, 2 H), 3.53
(dd, J ) 15.8, 5.0 Hz, 1 H), 3.45 (t, J ) 8.5 Hz, 1 H), 3.10 (dd, J )
15.8, 11.7 Hz, 1 H), 2.48-1.93 (series of m, 4 H), 0.82 (s, 9 H), -0.07
(s, 3 H), -0.14 (s, 3 H); 13C NMR (75 MHz, CDCl3) δ ) 170.4, 165.6,
136.1, 132.6, 126.1, 122.0, 119.8, 118.3, 111.1, 106.8, 65.4, 59.2, 56.5,
53.7, 45.4, 28.6, 25.8 (3 C), 23.1, 21.8, 18.2, -5.7 (2 C); HRMS m/z
(M+ + K) calcd 478.1928, obsd 478.1939.
Oxindole 23. To the indole 20 (167 mg, 0.401 mmol) in 30 mL of
1:1:1 THF/AcOH/H2O at 0 °C was added NBS (93 mg, 0.52 mmol),
and the resulting mixture was stirred at room temperature for 8 h. The
mixture was then carefully quenched with 200 mL of saturated Na2-
CO3 and extracted with CH2Cl2 (3 × 100 mL). The organic layers were
then washed with saturated NaHCO3 (2 × 80 mL) and brine (80 mL),
dried over MgSO4, filtered, concentrated, and chromatographed (SiO2,
EtOAc f 5% MeOH/CH2Cl2) to afford 155 mg (90%) of oxindole
23: [R]20.4D -33.5° (c ) 0.822, CH2Cl2); IR (CHCl3) 3404, 3310, 2957,
2926, 2843, 1736, 1664, 1524, 1420, 1233 cm-1; 1H NMR (500 MHz,
CDCl3) δ ) 10.11 (s, 1 H), 7.81 (d, J ) 8.2 Hz, 1 H), 7.43-7.29 (m,
7 H), 7.17 (t, J ) 7.4 Hz, 1 H), 6.60 (s, 1 H), 4.72 (s, 2 H), 4.56 (d,
J ) 1.9 Hz, 2 H), 4.47-4.40 (m, 1 H), 3.98-3.95 (m, 2 H), 3.62-
3.44 (m, 3 H), 2.24-1.80 (series of m, 4 H); 13C NMR (75 MHz,
CDCl3) δ ) 190.8, 169.4, 165.6, 136.3, 131.2, 129.1, 128.8 (2 C), 128.6,
128.3 (2 C), 127.3, 121.3, 121.2, 120.8, 112.4, 74.2, 59.0, 56.6, 45.8,
45.4, 29.4, 28.1, 25.6, 22.5.; HRMS m/z (M+ + 1) calcd 432.1923,
obsd 432.1935.
Oxindole Amine 27. To the indole 13 (750 mg, 1.60 mmol) in 45
mL of 1:1:1 THF/AcOH/H2O at 0 °C was added NBS (322 mg, 1.80
mmol) portionwise over 20 min, and then the resulting mixture was
stirred for an additional 90 min at 0 °C. The mixture was then care-
fully quenched with 100 mL of saturated Na2CO3 and extracted with
CH2Cl2 (3 × 100 mL). The organic layers were then washed with
saturated NaHCO3 (2 × 80 mL) and brine (80 mL), dried over MgSO4,
filtered, concentrated, and chromatographed (SiO2, 25% EtOAc/
hexanes) to afford 473 mg (63%) of oxindole 25: [R]20.6D +2.1° (c )
0.908, CHCl3); IR (CHCl3) 3400, 2995, 2953, 2930, 2835, 1745, 1702,
1684, 1608, 1460, 1380, 1357 cm-1; HRMS (CI) m/z (M+ + K) calcd
505.1741, obsd 505.1751.
The carbamate 25 (58 mg, 0.123 mmol) was stirred with 10 mL of
1:1 CH2Cl2/TFA at room temperature for 30 min and then concentrated,
dissolved into 50 mL of CH2Cl2, washed with saturated NaHCO3 (50
mL), dried over MgSO4, filtered, concentrated, and filtered through a
plug of SiO2 (25% EtOAc/hexanes) to afford 40 mg (89%) of amine
27: [R]20.9D +11.2° (c ) 2.32, CHCl3); IR (CHCl3) 3630, 3400, 3000,
2980, 2832, 1712, 1700, 1600, 1455 cm-1; 1H NMR (500 MHz, CDCl3)
δ ) 7.85 (s, 1 H), 7.32 (d, J ) 7.5 Hz, 1 H), 7.24-7.20 (m, 5 H),
7.07-7.00 (m, 2 H), 6.85 (d, J ) 7.7 Hz, 1 H), 4.26-4.22 (m, 1 H),
4.24 (d, J ) 11.9 Hz, 1 H), 4.10 (d, J ) 11.6 Hz, 1 H), 3.81-3.78 (m,
1 H), 3.77 (s, 3 H), 3.41 (dd, J ) 9.4, 5.7 Hz, 1 H), 3.17 (dd, J ) 9.4,
6.8 Hz, 1 H), 2.84 (dd, J ) 13.7, 10.1 Hz, 1 H), 2.24 (dd, J ) 13.7,
6.3 Hz, 1 H); 13C NMR (75 MHz, CDCl3) δ ) 180.6, 173.9, 140.6,
137.7, 131.4, 128.2 (2 C), 128.0, 127.4 (2 C), 127.2, 124.8, 122.4,
109.7, 73.2, 69.7, 67.2, 58.8, 56.2, 52.3, 41.8; HRMS m/z (M+ + 1)
calcd 367.1658, obsd 367.1653; NOE data, irradiated proton (enhance-
ments), H4 (H5, H19 (2 H), H8b), H8a (H8b, H9, H18), H8b (H4,
H8a), H19 (H4, H18, H19), H19′ (H4, H18, H19).
Bischler-Napieralski Reaction of 18. Amide 18 (210 mg, 0.513
mmol) in 5 mL of benzene and 4 mL of POCl3 was heated to reflux
for 2.5 h, cooled to room temperature, and then concentrated. After
the orange viscous oil was then taken up in 15 mL of methanol, NaBH4
(700 mg, 18.5 mmol) was added to the mixture at 0 °C, and the yellow
slurry was stirred for an additional 30 min at this temperature, quenched
with 3 mL of 10% HCl, diluted with 50 mL of saturated NaHCO3, and
extracted with CH2Cl2 (3 × 50 mL). The organic layers were then
washed with saturated NaHCO3 (20 mL), dried over MgSO4, filtered,
concentrated, and chromatographed (SiO2, 20% EtOAc/hexanes) to
afford 43.4 mg (21%) of the racemic product 12a,5 12.0 mg of the
chloride, and 63.7 mg of recovered starting material.
Diketopiperazine 20. To the amine mixture 11 (386 mg, 1.10 mmol)
and Et3N (0.307 mL, 2.20 mmol) in 4 mL of CH2Cl2 at 0 °C was added
acid chloride 197 (583 mg, 1.88 mmol) in 10 mL of CH2Cl2 dropwise.
After the addition, the reaction mixture was allowed to warm to room
temperature and stirred for 5 h before being quenched with 10 mL of
water. Extraction of the aqueous layer with CH2Cl2 (3 × 40 mL) was
followed by washing with 10% HCl and saturated NaHCO3 (50 mL
each), drying over MgSO4, filtration, concentration, and chromatography
(SiO2, 30% EtOAc/hexanes) to afford 434 mg of the desired cis
diastereomer and 167 mg of the trans diastereomer (87% total yield,
2.6:1).
To the above cis amide (343 mg, 0.549 mmol) in 35 mL of 2:2:1
THF/MeOH/saturated NH4Cl was added zinc dust (3 g), and the gray
slurry was stirred at reflux for 6 h. After cooling to room temperature,
the slurry was filtered, concentrated, dissolved into 20 mL of water,
and then washed with saturated NaHCO3 and brine (50 mL each), dried
over MgSO4, filtered, concentrated, and chromatographed (SiO2, 80%
EtOAc, hexanes) to afford 198 mg (86%) of diketopiperazine 20:
[R]21.7D -5.3° (c ) 2.35, CH2Cl2); IR (CHCl3) 3679, 3453, 3011, 2863,
1
1663, 1520, 1420, 1212 cm-1; H NMR (500 MHz, CDCl3) δ ) 8.19
(s, 1 H), 7.60 (d, J ) 7.7 Hz, 1 H), 7.36 (d, J ) 7.9 Hz, 1 H), 7.28-
7.15 (m, 7 H), 5.47 (dd, J ) 9.8, 4.0 Hz, 1 H), 4.47 (d, J ) 9.9 Hz, 1
H), 4.39 (d, J ) 9.9 Hz, 1 H), 4.18-4.11 (m, 2 H), 3.94 (dd, J ) 9.2,
3.9 Hz, 1 H), 3.66-3.63 (m, 2 H), 3.56 (dd, J ) 15.9, 4.9 Hz, 1 H),
3.33 (t, J ) 8.5 Hz, 1 H), 3.08 (dd, J ) 15.8, 11.8 Hz, 1 H), 2.48-
1.94 (series of m, 4 H); 13C NMR (75 MHz, CDCl3) δ ) 170.4, 165.5,
137.8, 136.1, 132.5, 128.4 (2 C), 127.7, 127.0 (2 C), 126.0, 122.1,
119.1, 118.3, 111.3, 106.8, 73.3, 72.4, 59.2, 58.5, 51.8, 45.4, 28.0, 23.1,
21.8; HRMS m/z (M+ + 1) calcd 416.1976, obsd 416.1981.
Deprotection of 20. To the ether 20 (222 mg, 0.535 mmol) in 150
mL of CH3CN/CH2Cl2 (1.5:1) was added TMSI (0.304 mL, 2.14 mmol)
at 0 °C, the reaction mixture was stirred at 0 °C for 90 min, and then
MeOH (5 mL) was added and the resulting mixture was stirred for an
additional 30 min. This mixture was then quenched with saturated
NaHSO3 (10 mL) and extracted with CH2Cl2 (3 × 80 mL). The
combined organic layers were washed with saturated NaHCO3 and brine
(50 mL each), dried over MgSO4, filtered, concentrated, and chro-
matographed (SiO2, EtOAc f 5% MeOH in CH2Cl2) to afford 134
mg (77%) of the pure alcohol as a colorless solid: [R]20.6 -76.2° (c
D
) 0.803, MeOH); IR (CHCl3) 3457, 3050, 2986, 1676, 1452, 1401,
1261 cm-1; 1H NMR (400 MHz, CDCl3) δ ) 8.77 (s, 1 H), 7.59 (d, J
) 7.7 Hz, 1 H), 7.35 (d, J ) 7.7 Hz, 1 H), 7.21-7.14 (m, 2 H), 5.51
(t, J ) 5.8 Hz, 1 H), 4.16-4.09 (m, 2 H), 3.91 (m, 1 H), 3.70-3.55
(m, 4 H), 3.15-3.05 (m, 2 H), 2.47-1.94 (series of m, 4 H); 13C NMR
(75 MHz, CDCl3) δ ) 174.4, 165.2, 136.3, 131.0, 125.9, 122.3, 120.0,
118.4, 111.4, 107.4, 68.9, 59.2, 58.9, 54.9, 54.8, 45.4, 28.8, 23.0; HRMS
m/z (M+ + 1) calcd 326.1505, obsd 326.1491.
Oxindole Amine 28. To indole 14 (970 mg, 1.96 mmol) in 60 mL
of 1:1:1 THF/AcOH/H2O at 0 °C was added NBS (454 mg, 2.50 mmol)
in 20 mL of THF dropwise over 10 min, and the resulting mixture was
stirred for 90 min at 0 °C and for 3 h at room temperature. The mixture
was then carefully quenched with 100 mL of saturated Na2CO3 and
extracted with CH2Cl2 (3 × 100 mL). The organic layers were then
washed with saturated NaHCO3 (2 × 80 mL) and brine (80 mL), dried
over MgSO4, filtered, concentrated, and chromatographed (SiO2, 20%
EtOAc/hexanes) to afford 429 mg (43%) of oxindole 26 and 283 mg
tert-Butyldimethylsilyl Analogue of 20. To the above alcohol (81
mg, 0.249 mmol) in 2 mL of DMF were added the TBSCl (301 mg,
2.0 mmol) and imidazole (170 mg, 2.5 mmol), and the reaction mixture
was stirred at room temperature for 12 h. This solution was quenched
with 10 mL of water and extracted with CH2Cl2 (3 × 50 mL), and the
organic layers were washed with brine (5 × 20 mL), dried over MgSO4,
filtered, concentrated, and chromatographed (SiO2, EtOAc) to afford
of recovered starting material (61% adjusted yield): [R]26.3 -47.3°
D
(c ) 2.38, CDCl3); IR (CDCl3) 3436, 3191, 3075, 2979, 1710, 1617,
1474, 1382, 1368, 1176 cm-1; 1H NMR (500 MHz, CDCl3) δ ) 9.26-
8.95 (two br s, 1 H), 7.54-7.14 (m, 6 H), 7.02 (d, J ) 7.4 Hz, 1 H),
89 mg (82%) of the desired silyl ether: [R]21.6 -17.6° (c ) 0.944,
D
CHCl3); IR (CH2Cl2) 3432, 3030, 2963, 2938, 2910, 2840, 1659, 1440,

Total Synthesis of Spirotryprostatin A
J. Am. Chem. Soc., Vol. 121, No. 10, 1999 2153
6.92 (t, J ) 7.1 Hz, 1 H), 6.86 (d, J ) 7.7 Hz, 1 H), 5.03-4.85 (br m,
1 H), 4.54 (br s, 1 H), 3.75 (s, 3 H), 2.50-2.38 (m, 2 H), 2.05-1.81
(m, 2 H), 1.49 (s, 9 H), 1.36-1.23 (m, 6 H); HRMS m/z (M+ + 1)
calcd 511.2269, obsd 511.2267.
J ) 10.3, 8.8 Hz, 1 H), 3.60 (s, 3 H), 3.35 (d, J ) 15.7 Hz, 1 H), 2.62
(m, 1 H), 2.37 (s, 3 H); 13C NMR (75 MHz, CDCl3) δ ) 171.4, 143.9,
137.8, 137.0, 135.9, 131.2, 130.0 (2 C), 128.7 (2 C), 128.1, 128.0 (2
C), 126.8 (2 C), 125.9, 122.1, 119.4, 118.2, 111.0, 104.7, 74.6, 73.7,
54.1, 52.6, 51.3, 22.4, 21.5; HRMS (CI) m/z (M+ + K) calcd 543.1356,
obsd 543.1352.
The carbamate 26 (61 mg, 0.119 mmol) was stirred with 9 mL of
2:1 CH2Cl2/TFA at room temperature for 45 min and then concentrated,
dissolved into 50 mL of CH2Cl2, washed with saturated NaHCO3 (20
mL), dried over MgSO4, filtered, concentrated, and filtered through a
plug of SiO2 (50% EtOAc/hexanes) to afford 46 mg (94%) of amine
28: [R]25.3D -35.4° (c ) 1.22, CHCl3); IR (CHCl3) 3426, 3298, 3192,
For the trans tosylate: [R]21.3 -26.4° (c ) 0.652, CHCl3); IR
D
(CHCl3) 3410, 3040, 2966, 2930, 2840, 1742, 1443, 1323, 1150 cm-1
;
1H NMR (400 MHz, CDCl3) δ ) 8.32 (s, 1 H), 7.74 (d, J ) 8.4 Hz,
2 H), 7.46 (d, J ) 7.8 Hz, 1 H), 7.44-7.07 (m, 11 H), 5.23 (dd, J )
8.4, 4.5 Hz, 1 H), 4.68 (dd, J ) 8.7, 4.8 Hz, 1 H), 4.47 (s, 2 H), 4.00
(dd, J ) 9.0, 4.5 Hz, 1 H), 3.74 (s, 3 H), 3.55 (t, J ) 8.8 Hz, 1 H),
3.31 (m, 1 H), 3.10 (dd, J ) 15.1, 4.5 Hz, 1 H), 2.35 (s, 3 H); 13C
NMR (75 MHz, CDCl3) δ ) 170.8, 143.7, 138.0, 137.4, 136.2, 132.1,
129.4 (2 C), 128.5 (2 C), 128.0, 127.8 (2 C), 127.2 (2 C), 126.3, 122.1,
119.5, 118.2, 111.0, 107.2, 73.5, 72.1, 57.5, 53.8, 52.5, 24.0, 21.5;
HRMS (CI) m/z (M+ + K) calcd 543.1356, obsd 543.1344.
3064, 3011, 2958, 2928, 2853, 1728, 1709, 1619, 1471, 1222 cm-1
;
1H NMR (500 MHz, CDCl3) δ ) 8.77 (s, 1 H), 7.39-7.19 (m, 7 H),
7.02 (t, J ) 7.2 Hz, 1 H), 6.89 (d, J ) 7.7 Hz, 1 H), 4.21 (dd, J )
10.5, 5.8 Hz, 1 H), 3.79 (s, 3 H), 3.71 (d, J ) 9.0 Hz, 1 H), 3.00-2.40
(br s, 1 H), 2.85 (dd, J ) 13.7, 10.5 Hz, 1 H), 1.26-1.09 (m, 2 H),
1.20 (s, 3 H), 1.17 (s, 3 H); 13C NMR (75 MHz, CDCl3) δ ) 180.2,
174.2, 140.0, 137.6 (2 C), 132.1, 131.5, 128.7, 128.4 (2 C), 127.9,
124.4, 122.8, 109.8, 66.3, 59.1, 59.0, 52.4, 48.0, 43.0, 41.1, 29.1, 29.0;
HRMS m/z (M+ + 1) calcd 411.1744, obsd 411.1748.
Spiro Tosylate 32. To the above cis tosylate (2.35 g, 4.66 mmol)
in 60 mL of 1:1:1 THF/AcOH/H2O at 0 °C was added NBS (1.08 g,
6.1 mmol) portionwise over 20 min, and and then the resulting mixture
was allowed to warm to room temperature and stirred for an additional
90 min. The mixture was then carefully quenched with 200 mL of
saturated Na2CO3 and extracted with CH2Cl2 (3 × 200 mL). The organic
layers were then washed with saturated NaHCO3 (2 × 200 mL) and
brine (100 mL), dried over MgSO4, filtered, concentrated, and chro-
matographed (SiO2, 25% EtOAc/hexanes) to afford 1.58 g (65%) of
oxindole 32 and 230 mg of recovered starting material (72% adjusted
yield). For 32: [R]20.9D +31.9° (c ) 1.376, CHCl3); IR (CHCl3) 3400,
3000, 2928, 2905, 2830, 2800, 1718, 1710, 1608, 1583, 1347, 1150
cm-1; 1H NMR (400 MHz, CDCl3) δ ) 8.31 (s, 1 H), 7.83 (d, J ) 8.3
Hz, 2 H), 7.53 (d, J ) 7.7 Hz, 1 H), 7.31 (d, J ) 8.3 Hz, 2 H), 7.26-
6.99 (m, 7 H), 6.80 (d, J ) 7.9 Hz, 1 H), 4.71 (dd, J ) 8.3, 7.0 Hz, 1
H), 4.27-4.09 (m, 4 H), 3.95 (m, 1 H), 3.81-3.74 (m, 1 H), 3.76 (s,
3 H), 3.55 (dd, J ) 10.0, 8.0 Hz, 1 H), 2.40 (s, 3 H); 13C NMR (75
MHz, CDCl3) δ ) 179.3, 171.9, 144.0, 140.9, 137.7, 134.3, 129.6 (2
C), 128.6, 128.3 (2 C), 128.1 (2 C), 128.0, 127.5, 127.3 (2 C), 125.6,
122.4, 109.9, 73.3, 70.0, 65.0, 60.8, 55.9, 52.5, 38.8, 21.6; HRMS (CI)
m/z (M+ + K) calcd 559.1305, obsd 559.1324.
Diketopiperazine 29 (Representative Procedure for Diketopip-
erazine Formation). To the amine 27 (171 mg, 0.470 mmol) and Et3N
(0.40 mL, 2.76 mmol) in 5 mL of CH2Cl2 at 0 °C was added the acid
chloride 19 (492 mg, 1.69 mmol) in 20 mL of CH2Cl2 dropwise. After
the addition, the reaction mixture was allowed to warm to room
temperature and stirred for 12 h before being quenched with 10 mL of
water. Extraction of the aqueous layer with CH2Cl2 (3 × 80 mL) was
followed by washing with 10% HCl and saturated NaHCO3 (50 mL
each), drying over MgSO4, filtration, concentration, and chromatography
(SiO2, 30% EtOAc/hexanes) to afford 384 mg of the crude amide.
To the crude amide in 30 mL of 1:1:1 THF/MeOH/saturated NH4Cl
was added zinc dust (2 g), and the gray slurry was stirred at room
temperature for 12 h. The slurry was then filtered, concentrated,
dissolved into 200 mL of CH2Cl2, and then washed with 10% HCl,
saturated NaHCO3, and brine (50 mL each), dried over MgSO4, filtered,
concentrated, and chromatographed (SiO2, 80% EtOAc, hexanes f
EtOAc) to afford 175 mg (87%) of diketopiperazine 29: [R]20.5D -27.1°
(c ) 1.594, CH2Cl2); IR (CDCl3) 3398, 3168, 3052, 3032, 3000, 2923,
2892, 2850, 1690, 1650, 1608, 1590, 1456, 1408 cm-1; 1H NMR (400
MHz, CDCl3) δ ) 9.14 (s, 1 H), 7.41 (d, J ) 7.4 Hz, 1 H), 7.33-7.18
(m, 6 H), 6.97 (t, J ) 7.7 Hz, 1 H), 6.87 (d, J ) 7.7 Hz, 1 H), 4.94
(dd, J ) 9.6, 7.7 Hz, 1 H), 4.54 (d, J ) 12.1 Hz, 1 H), 4.37 (d, J )
12.1 Hz, 1 H), 4.27 (t, J ) 8.1 Hz, 1 H), 4.16 (m, 2 H), 3.74 (t, J )
6.7 Hz, 1 H), 3.59-3.49 (m, 2 H), 3.40 (d, J ) 9.4 Hz, 1 H), 2.99 (dd,
J ) 13.5, 10.6 Hz, 1 H), 2.33-1.82 (series of m, 4 H); 13C NMR (75
MHz, CDCl3) δ ) 181.3, 167.3, 166.9, 141.5, 137.6, 129.0, 128.3 (2
C), 127.6, 127.2 (2 C), 126.8, 125.9, 122.7, 110.0, 73.1, 66.2, 61.1,
60.9, 58.7, 55.3, 45.0, 35.3, 27.5, 23.6; HRMS m/z (M+ + 1) calcd
432.1923, obsd 432.1935.
Aldehydes 33. The benzyl ether 32 (700 mg, 1.34 mmol) in 50 mL
of EtOH and 3 mL of AcOH was carefully added to a flask containing
10% Pd/C (50 mg) under hydrogen gas. After the addition, the reaction
mixture was stirred under a hydrogen atmosphere for 24 h and then
filtered through Celite and taken up in 200 mL of CH2Cl2. The organic
layer was then washed with saturated NaHCO3 (2 × 60 mL) and brine
(60 mL), dried over MgSO4, filtered, and concentrated to afford 575
mg (99%) of the desired alcohol: [R]20.3 +12.6° (c ) 1.10, CHCl3);
D
IR (CHCl3) 3420, 2992, 2930, 1710, 1609, 1586, 1345, 1150 cm-1; 1H
NMR (400 MHz, CDCl3) δ ) 8.07 (s, 1 H), 7.80 (d, J ) 8.2 Hz, 2 H),
7.77 (d, J ) 7.7 Hz, 1 H), 7.34 (d, J ) 8.1 Hz, 2 H), 7.27 (dt, J ) 7.7,
0.9 Hz, 1 H), 7.09 (dt, J ) 7.6, 0.5 Hz, 1 H), 6.82 (d, J ) 7.7 Hz, 1
H), 4.75 (dd, J ) 9.6, 7.8 Hz, 1 H), 4.11 (dd, J ) 12.4, 2.7 Hz, 1 H),
3.97 (br s, 1 H), 3.90 (s, 3 H), 3.82 (d, J ) 2.0 Hz, 1 H), 3.64 (d, J )
12.3 Hz, 1 H), 2.73 (dd, J ) 12.7, 9.8 Hz, 1 H), 2.41 (dd, J ) 12.8,
7.8 Hz, 1 H), 2.38 (s, 3 H); 13C NMR (75 MHz, CDCl3) δ ) 180.1,
174.7, 143.9, 141.0, 134.7, 129.4 (2 C), 129.2, 128.2 (2 C), 126.8,
125.9, 123.1, 109.7, 65.7, 63.6, 59.5, 55.7, 53.2, 39.5, 21.6; HRMS
(CI) m/z (M+ + K) calcd 469.0836, obsd 469.0816.
Alcohol 30. To the ether 29 (60 mg, 0.139 mmol) in 6 mL of 1:1
CH3CN/CH2Cl2 was added the TMSI (0.5 mL, 1.27 mmol), and the
mixture was stirred at room temperature for 7 h and then diluted with
MeOH and saturated NaHSO3 (4 mL each). The reaction mixture was
then diluted with NaHCO3 (30 mL), extracted with CH2Cl2 (3 × 40
mL), then washed with saturated NaHCO3 and brine (20 mL each),
dried over MgSO4, filtered, concentrated, and chromatographed (SiO2,
EtOAc f 3% MeOH/CH2Cl2) to afford 33 mg of 29 and 22 mg (34%
adjusted) of 30.
Tosylation of 11. To the amine mixture 11 (1.08 g, 3.08 mmol) in
30 mL of pyridine was added TsCl (5.88 g, 30.8 mmol), and the reaction
mixture was stirred at room temperature for 20 h, diluted with 10%
HCl (100 mL), and extracted with CH2Cl2 (3 × 100 mL). The organic
layers were then washed with 5% HCl (2 × 200 mL) and brine (100
mL), dried over MgSO4, filtered, concentrated, and chromatographed
(SiO2, 15% EtOAc/hexanes) to afford 790 mg of the desired cis
diastereomer and 327 mg of the trans diastereomer (77% yield, 2.4:1
To this alcohol (106 mg, 0.246 mmol) in 10 mL of CH2Cl2 was
added Dess-Martin’s periodinane (1.06 g, 2.5 mmol), and the resulting
mixture was stirred at room temperature for 3 h, quenched with saturated
NaHCO3 (50 mL), extracted with CH2Cl2 (3 × 50 mL), dried over
MgSO4, filtered, and concentrated. Crude NMR showed a 1:1.5 mixture
of product:starting material, so the crude product was reexposed to the
reaction conditions and worked up in the same manner. After chro-
matography (SiO2, 40% EtOAc/hexanes), 49.5 mg (48%) was obtained
of the pure aldehyde mixture 33: 1H NMR (500 MHz, CDCl3) δ )
9.57 (d, J ) 3.6 Hz, 1 H), 7.74 (d, J ) 8.3 Hz, 2 H), 7.57 (d, J ) 7.7
Hz, 1 H), 7.40 (d, J ) 8.0 Hz, 2 H), 7.24 (dt, J ) 7.7, 0.9 Hz, 1 H),
7.06 (dt, J ) 7.7, 0.8 Hz, 1 H), 6.83 (d, J ) 7.8 Hz, 1 H), 4.46 (dd, J
) 9.9, 5.4 Hz, 1 H), 3.94 (d, J ) 3.6 Hz, 1 H), 3.88 (s, 3 H), 2.62 (dd,
J ) 13.6, 9.9 Hz, 1 H), 2.47 (s, 3 H), 2.37 (dd, J ) 13.6, 5.4 Hz, 1 H);
ratio). For the cis tosylate: [R]20.7 +109.4° (c ) 0.622, CHCl3); IR
D
(CHCl3) 3410, 3005, 2932, 2900, 2820, 1737, 1730, 1585, 1340, 1160
cm-1; 1H NMR (400 MHz, CDCl3) δ ) 8.64 (s, 1 H), 7.71 (d, J ) 8.4
Hz, 2 H), 7.42-7.23 (m, 9 H), 7.16 (t, J ) 7.0 Hz, 1 H), 7.08 (t, J )
7.0 Hz, 1 H), 5.14 (d, J ) 6.6 Hz, 1 H), 4.74 (d, J ) 11.3 Hz, 1 H),
4.65 (d, J ) 11.3 Hz, 1 H), 4.25 (dd, J ) 8.5, 3.7 Hz, 1 H), 4.01 (dd,

2154 J. Am. Chem. Soc., Vol. 121, No. 10, 1999
Edmondson et al.
13C NMR (75 MHz, CDCl3) δ ) 197.5 (0.5 C), 197.4 (0.5 C), 176.7,
171.2, 145.2, 140.3, 131.8, 130.1 (2 C), 129.7, 128.5 (0.5 C), 128.4
(0.5 C), 126.2, 125.8, 123.2, 110.5, 72.0 (0.5 C), 71.9 (0.5 C), 60.9
(0.5 C), 60.8 (0.5 C), 60.5, 55.6, 52.8, 39.7, 21.7.
Conversion of 26 to Olefins 34 and 35. To the carbamate 26 (165
mg, 0.323 mmol) in 15 mL MeOH and 2 mL of water was added NaIO4
(77 mg, 0.36 mmol), and the resulting white slurry was stirred at room
temperature for 18 h, diluted with 50 mL of water, and extracted with
CH2Cl2 (3 × 50 mL). The organic layers were then dried over MgSO4,
filtered, concentrated, and chromatographed (SiO2, 40% EtOAc/
hexanes) to afford 117 mg (69%) of sulfoxide mixture.
MgSO4, filtered, concentrated, and chromatographed (SiO2, CH2Cl2 f
3% MeOH/CH2Cl2) to afford 50.2 mg (97%) of the 1:1 sulfoxide
mixture: 1H NMR (400 MHz, CDCl3) δ ) 8.94 (s, 1 H), 8.86 (s, 1 H),
7.52-7.42 (m, 10 H), 7.19-7.14 (m, 2 H), 6.90-6.77 (m, 6 H), 4.92-
4.84 (m, 2 H), 4.29-4.18 (m, 4 H), 3.59-3.56 (m, 4 H), 2.63-2.56
(m, 2 H), 2.38-1.90 (m, 14 H), 1.25 (s, 3 H), 1.24 (s, 3 H), 0.30 (s, 3
H), 0.27 (s, 3 H).
Alkenes 37 and 2 (Representative Procedure). The above sulfox-
ides (56 mg, 0.114 mmol) were dissolved into 5 mL of toluene and
heated to reflux for 60 min. After cooling to room temperature, the
reaction mixture was concentrated and chromatographed (SiO2,
CH2Cl2 f 5% MeOH/CH2Cl2) to afford 38.8 mg (93%) of the olefin
mixture (2.5:1, 2:37). This mixture was further purified by HPLC (90%
This mixture was then heated to reflux in 10 mL of toluene for 45
min, cooled to room temperature, and chromatographed (SiO2, 30%
EtOAc/hexanes) to afford 78.9 mg (96%) of pure product. The material
was stirred with 15 mL of 2:1 CH2Cl2/TFA at room temperature for
30 min and then concentrated, dissolved into 50 mL of CH2Cl2, washed
with saturated NaHCO3 (50 mL), dried over MgSO4, filtered, concen-
trated, and then chromatographed (SiO2, 40% EtOAc/hexanes) to afford
21.9 mg of the less polar 34 and 34.0 mg of 35 (1:1.5, 58% from 26).
EtOAc/hexanes) to afford 28 mg of 2 and 10 mg of 37. For 37: [R]22.4
D
-72.1° (c ) 0.117, CHCl3); IR (CH2Cl2) 3225, 3000, 2979, 2942, 2900,
2885, 1740, 1674, 1625, 1425 cm-1; 1H NMR (500 MHz, CDCl3) δ )
8.58 (s, 1 H), 7.22 (td, J ) 7.7, 0.8 Hz, 1 H), 7.16 (d, J ) 7.5 Hz, 1
H), 6.99 (t, J ) 7.3 Hz, 1 H), 6.86 (d, J ) 7.7 Hz, 1 H), 4.86 (t, J )
9.2 Hz, 1 H), 4.46 (d, J ) 8.5 Hz, 1 H), 4.45 (d, J ) 1.5 Hz, 1 H),
4.26 (t, J ) 8.0 Hz, 1 H), 4.21 (s, 1 H), 3.61-3.56 (m, 2 H) 2.77-
2.69 (m, 2 H), 2.42-1.93 (series of m, 7 H), 1.59 (s, 3 H); 13C NMR
(75 MHz, CDCl3) δ ) 180.4, 168.4, 166.9, 141.4, 140.8, 129.0, 127.4,
125.5, 122.4, 112.0, 109.8, 61.5, 60.0, 58.4, 55.1, 45.1, 39.8, 33.7, 28.0,
23.7, 22.6; HRMS m/z (M+) calcd 365.1739, obsd 365.1627.
For 34: [R]20.9 -42.3° (c ) 0.438, CHCl3); IR (CHCl3) 3436, 2958,
D
2935, 2898, 2855, 1725, 1621, 1468 cm-1; 1H NMR (400 MHz, CDCl3)
δ ) 8.67 (s, 1 H), 7.30 (dd, J ) 7.5, 0.5 Hz, 1 H), 7.22 (td, J ) 7.7,
1.2 Hz, 1 H), 7.05 (td, J ) 7.6, 1.0 Hz, 2 H), 6.89 (dd, J ) 7.5, 0.3
Hz, 1 H), 4.60 (s, 1 H), 4.39 (d, J ) 1.2 Hz, 1 H), 4.18 (dd, J ) 10.4,
5.8 Hz, 1 H), 3.78 (s, 3 H), 3.66 (dd, J ) 8.3, 5.7 Hz, 1 H), 2.89 (dd,
J ) 13.7, 10.5 Hz, 1 H), 2.60-2.20 (br s, 1 H), 2.20 (dd, J ) 13.7, 5.8
Hz, 1 H), 1.91 (dd, J ) 14.0, 8.3 Hz, 1 H), 1.77 (dd, J ) 14.1, 5.5 Hz,
1 H), 1.63 (d, J ) 0.3 Hz, 3 H); 13C NMR (75 MHz, CDCl3) δ )
180.6, 174.2, 141.7, 140.4, 131.8, 128.0, 124.6, 122.7, 112.7, 109.8,
66.3, 58.6, 57.7, 52.4, 42.6, 38.7, 22.2; HRMS m/z (M+) calcd 300.1474,
obsd 300.1469.
For 2: [R]20.1D -79.2° (c ) 0.171, CHCl3); IR (CHCl3) 3424, 2996,
2954, 2937, 2886, 1722, 1670, 1653, 1623, 1469, 1414 cm-1; 1H NMR
(500 MHz, CDCl3) δ ) 8.44 (s, 1 H), 7.20 (t, J ) 7.5 Hz, 1 H), 7.03
(d, J ) 7.4 Hz, 1 H), 6.96 (t, J ) 7.5 Hz, 1 H), 6.85 (d, J ) 7.7 Hz,
1 H), 5.06-5.02 (m, 2 H), 4.82 (d, J ) 9.1 Hz, 1 H), 4.30 (t, J ) 8.0
Hz, 1 H), 3.65-3.54 (m, 2 H), 2.65 (dd, J ) 13.4, 10.8 Hz, 1 H), 2.42
(dd, J ) 13.4, 7.0 Hz, 1 H), 2.36-1.92 (series of m, 4 H), 1.62 (s, 3
H), 1.11 (s, 3 H); 13C NMR (75 MHz, CDCl3) δ ) 180.5, 167.03,
166.95, 140.8, 138.3, 128.6, 127.1, 126.5, 122.0, 121.4, 109.4, 61.1,
For 35: [R]20.9D -42.3° (c ) 0.438, CHCl3); IR (CHCl3) 3390, 3160,
2958, 2923, 1690, 1672, 1603 cm-1; 1H NMR (400 MHz, CDCl3) δ )
8.01 (s, 1 H), 7.86 (d, J ) 7.7 Hz, 1 H), 7.27 (t, J ) 7.7 Hz, 1 H), 7.12
(t, J ) 7.7 Hz, 1 H), 6.93 (d, J ) 7.7 Hz, 1 H), 4.66 (dd, J ) 11.2, 2.9
Hz, 1 H), 4.15 (dd, J ) 12.0, 3.7 Hz, 1 H), 3.80 (s, 3 H), 3.00 (dd, J
) 14.0, 11.3 Hz, 1 H), 2.23 (dd, J ) 14.0, 3.0 Hz, 1 H), 1.55-1.39
(m, 2 H), 1.37 (d, J ) 13.0 Hz, 6 H); 13C NMR (75 MHz, CDCl3) δ
) 177.9, 170.8, 151.8, 140.3, 129.1, 128.8, 126.5, 123.2, 110.3, 80.4,
60.7, 58.2, 56.7, 52.5, 38.5, 29.7, 27.2; HRMS m/z (M+) calcd 300.1474,
obsd 300.1464.
Conversion of 26 to 34. To the thioether 26 (165 mg, 0.402 mg) in
10 mL of CH2Cl2 were added NaHCO3 (168 mg, 2.0 mmol) and
m-CPBA (65 mg, 0.402 mmol) at -78 °C. The mixture was then stirred
at 0 °C for 40 min and at room temperature for 10 min, quenched with
20 mL of water, extracted with CH2Cl2 (2 × 25 mL), washed with
saturated NaHCO3 (20 mL), dried over MgSO4, filtered, concentrated,
and then chromatographed (SiO2, 40% EtOAc/hexanes) to afford 54
mg of 26 and 91 mg of the sulfoxides (79%).
60.4, 58.6, 56.0, 45.2, 34.3, 27.5, 25.4, 23.7, 17.9; HRMS m/z (M+
+
1) calcd 366.1812, obsd 366.1819; NOE data H4 (H8b, H19, H20, H21),
H8a (H8b, H9), H8b (H4, H8a, H19), H12 (H9, H13, H13), H20 (H4,
H19, H21), H21 (H19, H20).
Rearrangement of 37 to 2 (Representative Procedure). To the
external olefin 37 (10.0 mg, 0.027 mmol) in 4 mL of EtOH was added
RhCl3‚3H2O (17.0 mg, 0.081 mmol) under Ar, and the reaction mixture
was heated to reflux for 3 h, cooled to room temperature, filtered
through a pipet column (SiO2, CH2Cl2), concentrated, and then chro-
matographed (SiO2, EtOAc f 5% MeOH/CH2Cl2) to give 4.5 mg (45%)
of pure 2.
Methoxycarbamate Sulfide 40. To the amine 395 (1.54 g, 3.6 mmol)
in 50 mL of 4:1 CH3CN/Et3N was added the Boc2O (3.17 g, 14.5
mmol), and the mixture was stirred at 50 °C for 10 h and then cooled
to room temperature. The crude mixture was concentrated and chro-
matographed (SiO2, 15% EtOAc/hexanes) to afford 590 mg of the
desired product 40 (31%) and 970 mg of recovered starting material
This sulfoxide mixture was then heated to reflux in 5 mL of toluene
for 30 min, cooled to room temperature, and chromatographed (SiO2,
50% EtOAc/hexanes) to afford 24 mg (34%) of pure 34.
(84% adjusted yield). For 40: [R]20.9 -26.9° (c ) 1.25, CHCl3); IR
D
(CHCl3) 3450, 3430, 3307, 3004, 2975, 2947, 2852, 1739, 1735, 1683,
1630, 1501, 1473, 1393, 1369 cm-1; 1H NMR (400 MHz, CDCl3) δ )
8.85 (s, 1 H), 7.71-7.28 (m, 6 H), 6.84-6.77 (m, 2 H), 5.67-4.95
(m, 2 H), 3.83 (s, 3 H), 3.64-3.59 (m, 3 H), 3.28-3.00 (m, 2 H),
2.25-2.03 (m, 2 H), 1.66-0.89 (m, 15 H); HRMS m/z (M+) calcd
524.2347, obsd 524.2345.
Methoxyoxindole Amine 41. To indole 40 (166 mg, 0.316 mmol)
in 25 mL of 2:2:1 AcOH/H2O/THF at 0 °C was added NBS (68 mg,
0.380 mmol) in 5 mL of THF dropwise over 5 min, and the resulting
mixture was stirred for 10 min at 0 °C and 90 min at room temperature.
The mixture was then carefully quenched with 100 mL of saturated
Na2CO3 and extracted with CH2Cl2 (3 × 80 mL). The organic layers
were then washed with saturated NaHCO3 (2 × 50 mL) and brine (50
mL), dried over MgSO4, filtered, concentrated, and chromatographed
(SiO2, 20% EtOAc/hexanes) to afford 53 mg (31%) of oxindole and
55 mg of recovered starting material (46% adjusted yield). For the
oxindole: [R]24.0D -13.1° (c ) 0.788, CHCl3); IR (CHCl3) 3433, 2993,
2930, 2861, 1724, 1710, 1637, 1628, 1368 cm-1; 1H NMR (500 MHz,
CDCl3) δ ) 9.17-8.74 (m, 1 H), 7.53-7.16 (m, 5 H), 6.88 (d, J )
8.3 Hz, 1 H), 6.46 (d, J ) 1.7 Hz, 1 H), 6.43 (dd, J ) 8.3, 1.9 Hz, 1
Diketopiperazine 36. See the above representative procedure for
diketopiperazine 29. After chromatographic purification, amine 28 (98
mg, 0.238 mmol) afforded 77.7 mg (69%) of diketopiperazine 36:
[R]25.2 -147.7° (c ) 1.06, CHCl3); IR (CHCl3) 3435, 3196, 3009,
D
2884, 1711, 1675, 1617, 1467, 1415, 1218 cm-1; 1H NMR (500 MHz,
CDCl3) δ ) 8.56 (s, 1 H), 7.43-7.31 (m, 5 H), 7.12 (t, J ) 7.7 Hz, 1
H), 6.79 (d, J ) 7.8 Hz, 1 H), 6.69 (d, J ) 7.8 Hz, 1 H), 6.64 (t, J )
7.5 Hz, 1 H), 4.87 (dd, J ) 10.8, 7.0 Hz, 1 H), 4.27 (t, J ) 8.1 Hz, 1
H), 4.15 (d, J ) 6.8 Hz, 1 H), 3.60-3.55 (m, 2 H), 2.55 (dd, J ) 13.3,
10.9 Hz, 1 H), 2.38-1.93 (series of m, 7 H), 1.31 (s, 3 H), 0.43 (s, 3
H); 13C NMR (75 MHz, CDCl3) δ ) 181.1, 167.5, 166.8, 141.1, 138.1
(2 C), 131.5, 128.8 (2 C), 128.6 (2 C), 127.4, 125.9, 122.3, 109.9,
61.4, 58.8, 58.1, 55.4, 48.2, 45.1, 42.6, 34.5, 28.0, 27.8, 26.4, 23.7;
HRMS m/z (M+) calcd 476.2010, obsd 476.1989.
Oxidation of 36 (Representative Procedure). To the sulfide 36
(50.0 mg, 0.105 mmol) in 3 mL of MeOH were added the NaIO4 (25
mg, 0.115 mmol) and 0.1 mL of water. After being stirred at room
temperature for 12 h, the reaction mixture was diluted with 60 mL of
CH2Cl2 and then washed with saturated NaHCO3 (10 mL), dried over

Total Synthesis of Spirotryprostatin A
J. Am. Chem. Soc., Vol. 121, No. 10, 1999 2155
H), 5.09-4.49 (m, 2 H), 3.80 (s, 3 H), 3.74 (s, 3 H), 2.47-1.89 (m, 4
H), 1.48 (s, 9 H), 1.35-1.25 (m, 6 H); HRMS m/z (M+ + 1) calcd
541.2374, obsd 541.2373.
Alkenes 43 and 1. See the representative procedure for 37 and 2
above. The above sulfoxides (83 mg, 0.159 mmol) afforded 61.6 mg
(98%) of the olefin mixture (2.5:1, 1:43). This mixture was further
purified by HPLC (90% EtOAc/hexanes) to afford 31.2 mg of 1, 15.9
The above carbamate (45 mg, 0.083 mmol) was stirred with 5 mL
of 3:2 CH2Cl2/TFA and a few drops of 1,3-dimethoxybenzene at room
temperature for 30 min and then concentrated, dissolved into 50 mL
of CH2Cl2, washed with saturated NaHCO3 (20 mL), dried over MgSO4,
filtered, concentrated, and filtered through a plug of SiO2 (50% EtOAc/
mg of 43, and 14.6 mg of the mixture enriched in 1. For 43: [R]22.0
D
-67.0° (c ) 0.100, CHCl3); IR (CDCl3) 3436, 3207, 3072, 2958, 2886,
1722, 1711, 1670, 1597, 1504, 1410 cm-1; 1H NMR (500 MHz, CDCl3)
δ ) 8.20 (s, 1 H), 7.05 (d, J ) 8.4 Hz, 1 H), 6.51 (dd, J ) 8.4, 2.3 Hz,
1 H), 6.44 (d, J ) 2.3 Hz, 1 H), 4.84 (t, J ) 8.2 Hz, 1 H), 4.49 (s, 1
H), 4.42 (t, J ) 7.2 Hz, 1 H), 4.26 (m, 1 H), 4.25 (s, 1 H), 3.79 (s, 3
H), 3.61-3.55 (m, 2 H), 2.72 (dd, J ) 13.5, 10.1 Hz, 1 H), 2.68 (dd,
J ) 14.7, 6.2 Hz, 1 H), 2.39-1.93 (series of m, 6 H), 1.61 (s, 3 H);
13C NMR (75 MHz, CDCl3) δ ) 181.0, 168.4, 167.0, 160.7, 142.1,
141.5, 126.3, 119.2, 112.1, 107.0, 97.3, 61.5, 59.7, 58.3, 55.5, 54.9,
45.2, 40.0, 33.8, 28.0, 23.7, 22.5; HRMS m/z (M+) calcd 434.1482,
obsd 434.1487.
hexanes) to afford 34 mg (93%) of amine 41: [R]21.5 -41.4° (c )
D
0.269, CHCl3); IR (CDCl3) 3438, 3189, 3065, 2961, 2908, 1728, 1707,
1
1629, 1598, 1505 cm-1; H NMR (500 MHz, CDCl3) δ ) 8.54 (s, 1
H), 7.40 (d, J ) 2.3 Hz, 1 H), 7.31-7.16 (m, 5 H), 6.54 (dd, J ) 8.3,
2.3 Hz, 1 H), 6.47 (d, J ) 2.3 Hz, 1 H), 4.18 (dd, J ) 10.6, 5.6 Hz, 1
H), 3.78 (s, 3 H), 3.78 (s, 3 H), 3.64 (d, J ) 9.5 Hz, 1 H), 2.83 (dd, J
) 13.7, 10.6 Hz, 1 H), 2.68 (br s, 1 H), 2.11 (dd, J ) 13.7, 5.6 Hz, 1
H), 1.27-1.09 (m, 2 H), 1.21 (s, 3 H), 1.18 (s, 3 H); 13C NMR (75
MHz, CDCl3) δ ) 180.8, 174.4, 159.9, 141.2, 137.6 (2 C), 131.7, 128.7,
128.3 (2 C), 125.1, 124.2, 107.4, 97.2, 66.2, 59.1, 58.6, 55.5, 52.3,
48.0, 43.3, 41.3, 29.2, 29.1; HRMS m/z (M+ + 1) calcd 441.1848,
obsd 441.1832; NOE data, irradiated proton (enhancements), H4 (H8b,
H19), H8a (H8b, H9, H18), H8b (H4, H8a, H19), H9 (H8a, H8b, H18),
H18 (H8a, H9), H19 (H4, H5, H18).
For 1: [R]21.4D -111.3° (c ) 0.088, CHCl3); [R]19.0D -117.0° (c )
0.314, CH2Cl2).
Rearrangement of 43 to 1. See the representative procedure for
rearrangement of 37. The external olefin 43 (8.3 mg, 0.021 mmol) gave
3.4 mg (41%) of pure 1.
Cell Proliferation Assay. To investigate the effect of spirotrypro-
statin A and analogues on the proliferation of MDA MB-468 and MCF7
human tumor cells, six-well plates were seeded at 10 000 cells/well,
and duplicate wells were treated with increasing drug concentrations.
Drugs were dissolved in dimethyl sulfoxide, and 1000× stock solutions
were made for each concentration to be tested. Control cultures received
an equivalent volume of dimethyl sulfoxide. Cultures were fed medium
and drug at days 1 and 3, and cell number was determined on day 6.
Attached cells were trypsinized, and samples were counted on a Coulter
counter.
Methoxydiketopiperazine 42. See the above representative proce-
dure for diketopiperazine 29. After chromatographic purification, amine
41 (59.5 mg, 0.135 mmol) afforded 46.3 mg (68%) of diketopiperazine
42: [R]20.9 -109.5° (c ) 0.731, CH2Cl2); IR (CH2Cl2) 3421, 3055,
D
2985, 2890, 1723, 1675, 1631, 1597, 1418 cm-1; 1H NMR (500 MHz,
CDCl3) δ ) 9.02 (s, 1 H), 7.41-7.30 (m, 5 H), 6.53 (d, J ) 8.4 Hz,
1 H), 6.36 (d, J ) 2.3 Hz, 1 H), 6.08 (dd, J ) 8.4, 2.3 Hz, 1 H), 4.84
(dd, J ) 10.7, 5.7 Hz, 1 H), 4.25 (dd, J ) 8.0, 8.0 Hz, 1 H), 4.09 (dd,
J ) 6.7, 6.3 Hz, 1 H), 3.72 (s, 3 H), 3.55 (m, 1 H), 2.49 (dd, J ) 13.4,
11.1 Hz, 1 H), 2.36-1.92 (m, 8 H), 1.31 (s, 3 H), 0.45 (s, 3 H); 13C
NMR (75 MHz, CDCl3) δ ) 181.7, 167.5, 166.8, 160.4, 142.4, 138.1
(2 C), 131.7, 128.7, 128.5 (2 C), 126.5, 119.2, 106.6, 97.6, 61.3, 58.7,
58.0, 55.4, 55.1, 48.3, 45.0, 42.8, 34.5, 27.9, 27.7, 26.5, 23.6; HRMS
m/z (M+) calcd 506.2116, obsd 506.2102.
Oxidation of 42. See the representative procedure for oxidation of
36. Sulfide 42 (68.0 mg, 0.134 mmol) afforded 57.7 mg (82%) of the
corresponding 1:1 sulfoxide mixture: 1H NMR (500 MHz, CDCl3) δ
) 9.20 (s, 1 H), 9.11 (s, 1 H), 7.49-7.41 (m, 10 H), 6.74-6.69 (m, 2
H), 6.38-6.24 (m, 4 H), 4.84-4.82 (m, 2 H), 4.25-4.11 (m, 4 H),
3.71 (s, 6 H), 3.54 (br s, 4 H), 2.52-1.85 (m, 16 H), 1.25 (s, 6 H),
0.31 (6 H).
Acknowledgment. This work was supported by the National
Institutes of Health [Grants HL-25848 (S.J.D.) and CA-08748
(S.K.I.)]. S.E. gratefully acknowledges the NIH for postdoctoral
fellowship support (Grant GM18335-02). N.R. and L.S.-L. are
supported by CaPCure and by an NCI Breast SPORE Program
P50CA68425-02 grant and career development award, respec-
tively. We are grateful to Vinka Parmakovich and Barbara
Sporer of the Columbia University Mass Spectral Facility.
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