The stereocontrolled total synthesis of altohyrtin A/spongistatin 1: Fragment couplings, completion of the synthesis, analogue generation and biological evaluation

Article abstract of DOI:10.1039/b504151a

The antimitotic marine macrolide altohyrtin A/spongistatin 1 (1) has been synthesised in a highly convergent and stereocontrolled manner, thus contributing to the replenishment of the largely exhausted material from the initial isolation work. Coupling of

Full text of DOI:10.1039/b504151a

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A R T I C L E
The stereocontrolled total synthesis of altohyrtin A/spongistatin 1:
fragment couplings, completion of the synthesis, analogue generation
and biological evaluation†‡
Ian Paterson,* David Y.-K. Chen, Mark J. Coster,§ Jose´ L. Acen˜a, Jordi Bach and
Debra J. Wallace
University Chemical Laboratory, Lensfield Road, University of Cambridge, Cambridge,
UK CB2 1EW. E-mail: ip100@cam.ac.uk; Fax: +44 (0)1223 336 362
Received 22nd March 2005, Accepted 3rd May 2005
First published as an Advance Article on the web 24th May 2005
The antimitotic marine macrolide altohyrtin A/spongistatin 1 (1) has been synthesised in a highly convergent and
stereocontrolled manner, thus contributing to the replenishment of the largely exhausted material from the initial
isolation work. Coupling of the AB- and CD-spiroacetal subunits by a stereoselective aldol reaction was achieved by
using either a lithium (67 : 33 dr) or boron enolate (90 : 10 dr). A highly (Z)-selective Wittig coupling was used to
unite the northern hemisphere aldehyde 2 with the southern hemisphere phosphonium salt 3. Deprotection and
subsequent regioselective macrolactonisation on a triol seco-acid completed the synthesis of altohyrtin A. Two
structural analogues were also prepared and evaluated as growth inhibitory agents against a range of human tumour
cell lines, including Taxol-resistant strains, alongside altohyrtin A and paclitaxel (Taxol), revealing that dehydration
in the E-ring is tolerated and results in enhanced cytotoxicity (at the low picomolar level), whereas the presence of the
full C44–C51 side-chain appears to be crucial for biological activity.
natural marine sponge sources.1–3 Our highly flexible, convergent
Introduction
synthetic approach1,4 to the spongipyrans was designed to allow
Altohyrtin A/spongistatin 1 (1, Scheme 1) is a remarkably
the generation of useful quantities of 1 for the resumption of
cytotoxic macrolide that is in extremely limited supply from its
biological studies, in addition to facilitating the synthesis of
various altohyrtin congeners and wholly synthetic analogues
† Part 4 of a series of four papers.1
for implementing structure–activity relationship (SAR) work.
‡ Electronic supplementary information (ESI) available: general exper-
Furthermore, the endgame for our synthesis required careful
imental information and procedures for the synthesis of compounds
planning and judicious choice of reagents and conditions in
not detailed in the Experimental section of this paper. See http://
order to preserve the sensitive functionality present within
www.rsc.org/suppdata/ob/b5/b504151a/
late-stage compounds, e.g., the acid-sensitive CD-spiroacetal
§ Current address: School of Chemistry, University of Sydney, NSW
and chlorotriene side-chain. The final stages of our synthetic
strategy for altohyrtin A involve three key bond-forming steps
2006, Australia. Email: m.coster@chem.usyd.edu.au; Fax: +61 2 9351
3329.
Scheme 1 Fragment couplings for the synthesis of altohyrtin A/spongistatin 1 (1).
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5 O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 4 3 1 – 2 4 4 0
T h i s j o u r n a l i s
2 4 3 1
©

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Scheme 2 Reagents and conditions: for M = Li: (a) LiTMP–LiBr, THF, −78 ◦C, 15 min; (b) 4, −78 ◦C, 3 min; for M = B(Chx)2: (a) Chx2BCl, Et3N,
Et2O, −78 → 0 ◦C, 20 min; (b) 4, −78 → −20 ◦C, 17 h, then SiO2, rt, 40 min; (c) Ac2O, DMAP, pyr, rt, 2 h; (d) DDQ (portionwise), CH2Cl2–pH 7
buffer (10 : 1), 0 ◦C, 2 h; (e) cat. TPAP, NMO, 4 A mol. sieves, CH2Cl2, rt, 15 min.
˚
(Scheme 1). Macrocycle formation would be achieved by
Yamaguchi macrolactonisation of a fully functionalised seco-
acid, engaging the C41 alcohol selectively, as initially reported
by Evans2c,d and Kishi2f on related systems. This advanced
intermediate, in turn, would be derived, in the forward sense, by
(Z)-selective Wittig coupling of the ABCD northern hemisphere
aldehyde 2 and the EF southern hemisphere phosphonium salt
3. An anti-aldol reaction between the AB-spiroacetal aldehyde
4 and the CD-spiroacetal ketone 5, under Felkin–Anh control,
would assemble the C1–C28 ABCD subunit. Herein, we provide
a full account of the final fragment-coupling stages of our
total synthesis of altohyrtin A, and the synthesis and biological
evaluation {alongside 1 and paclitaxel (Taxol)} of two synthetic
analogues of the natural product.
A/spongistatin 1 (1), allowed for the confident assignment of
the major isomer as the desired species. While this lithium
aldol procedure was successful at providing sufficient quantities
of 7 to progress the synthesis, the boron aldol (as used with
great effect by the Evans group2c,d )¶ was re-investigated, in an
effort to improve the scalability of the process. In the event,
enolisation of 5 to give dicyclohexylboron enolate 6b, in situ,
and subsequent reaction with aldehyde 4, was followed by a
non-oxidative workup protocol, involving breakdown of the
intermediate boron aldolate on silica gel, to afford 7 with
improved diastereoselectivity (90 : 10 dr) in 89% yield. This
boron aldol procedure proved to be highly scalable, providing
>400 mg of 7 in a single reaction. Acetylation of the C15
hydroxyl (Ac2O, DMAP, pyridine), provided 8 in 98% yield.
Completion of the northern hemisphere aldehyde 2 was achieved
in 78% yield from 8, by removal of the C28 p-methoxybenzyl
(PMB) ether under carefully controlled conditions (portionwise
Results and discussion
◦
Aldol coupling of the AB- and CD-spiroacetal subunits
addition of excess of DDQ, 10 : 1 CH2Cl2–pH 7 buffer, 0 C)
and oxidation of the resultant primary alcohol (TPAP, NMO).9
Early attempts to effect the boron aldol5 coupling of the
AB- and CD-spiroacetal subunits by regio- and (E)-selective
enolisation under standard conditions (Chx2BCl, Et3N, Et2O)6
of 5,1b exposure to aldehyde 41a and oxidative workup (H2O2,
MeOH, pH 7 buffer) afforded only trace quantities of the
desired aldol adduct. Furthermore, none of the valuable starting
materials were recovered. Given this initial set-back, efforts
were directed to the lithium-mediated aldol reaction (Scheme 2).
To this end, (E)-selective enolisation of 5 with lithium 2,2,6,6-
tetramethylpiperidide–lithium bromide (LiTMP–LiBr)7 to give
enolate 6a, and reaction with aldehyde 4 provided the desired
aldol adduct 7 as the major diastereomer (67 : 33 dr) in 84% yield,
where presumably the Felkin–Anh transition state is favoured
(i.e., stereoinduction from C14 as shown). At this point, it did
not prove possible to form MTPA esters8 of 7, however, analysis
of 1H NMR coupling constants, extensive model studies4c,e
and the excellent NMR spectroscopic agreement of the derived
acetate 8, vide infra, with the corresponding region for altohyrtin
Wittig coupling of the northern (ABCD) and southern (EF)
hemisphere subunits and completion of the total synthesis of
altohyrtin A/spongistatin 1
The crucial Wittig coupling to unite the northern hemisphere
aldehyde 2 with the southern hemisphere phosphonium salt
31c was the final carbon–carbon bond-forming process in our
synthesis, was also used in the Evans2c,d and Kishi2f routes, and
represents one of the more challenging Wittig reactions to be
performed in natural products synthesis. As such, significant
effort was expended to study the Wittig coupling of model
systems, such as E-ring phosphonium salts and a side-chain
truncated C29–C46 EF phosphonium salt. Through these model
¶ Subsequently the Smith,2i Crimmins2n and Heathcock2o groups used
boron aldol reactions to form the C15–C16 bond in a similar manner.
2 4 3 2
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 4 3 1 – 2 4 4 0

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Scheme 3 Reagents and conditions: (a) LiHMDS, CaH2, THF–HMPA (10 : 1), −78 ◦C, 10 min; then 2, −78 ◦C → rt, 40 min; (b) DDQ (portionwise),
CH2Cl2–pH 7 buffer (10 : 1), 0 ◦C, 1.5 h; (c) Zn, THF–1 M aq. NH4OAc (10 : 1), rt, 0.5 h; (d) 2,4,6-trichlorobenzoyl chloride, Et3N, THF, rt, 3 h;
then DMAP, PhMe, 110 ◦C, 16 h; (e) HF, MeCN, H2O, 0 ◦C, 4 h.
studies, the deleterious role of adventitious water and oxygen
on the outcome of the Wittig reaction were demonstrated.
While oxygen levels could be conveniently minimised by careful
experimental setup, adventitious moisture was best removed by
the use of in situ CaH2. By stirring a 10 : 1 THF–HMPA solution
of phosphonium salt 3 with CaH2 prior to deprotonation with
lithium hexamethyldisilazide (LiHMDS), subsequent Wittig
reaction with aldehyde 2 reproducibly provided the desired (Z)-
alkene 9 (Z/E > 97 : 3 by 800 MHz 1H NMR) in 64–65% yield
(Scheme 3).
With the fully functionalised, protected seco-acid of 1 in
hand, the closing stages of our synthesis were explored. It was
considered that oxidative removal of the three PMB protecting
groups in 9 could be accompanied by oxidation of the potentially
labile unsaturated side-chain, since our group had previously
shown that allylic dienol silyl ethers can be oxidised in good
yields to the corresponding dienones with DDQ.10 However,
we were also guided by the successful PMB ether deprotections
performed at a late stage in Kishi’s synthesis of altohyrtin A.2f In
the event, treatment of 9 with an excess of DDQ under carefully
controlled conditions, afforded the tris-deprotected triol in 61%
yield, with no indication of side-chain oxidation. However,
partial hydrolysis of the C37 methyl acetal was unavoidable,
resulting in formation of an ca. 1.1 : 1 inseparable mixture of the
methyl acetal and the corresponding hemiacetal hydrolysis prod-
uct, respectively.11 Interestingly, Heathcock et al. subsequently
reported that PMB deprotection of related compounds, with
DDQ, en route to altohyrtin C/spongistatin 2 (lacking the C50
chlorine) led to competing oxidation of the diene segment to
a dienone, attributing the difference in reactivity patterns to a
retarding influence of the electron-withdrawing C50 halogen on
the rate of side-chain oxidation.2p
In preparation for macrolactonisation, removal of the 2,2,2-
trichloroethyl (TCE) ester protecting group with zinc dust in
10 : 1 THF–1 M NH4OAc12 provided seco-acid 10 in 58%
yield, still as a methyl acetal–hemiacetal mixture. Surprisingly,
significant quantities of partially dechlorinated compounds, the
2,2-dichloroethyl and 2-chloroethyl esters of 10 (24% combined
yield), accompanied the formation of 10.
Regioselective macrolactonisation of 10 under modified Ya-
maguchi conditions,13 engaging the C41 hydroxy group in
preference to those at C42 and C38, provided the 42-membered
macrolide 11 in 50% yield. Finally, treatment of this compound
with aqueous HF in MeCN effected deprotection of the four
silyl ethers and hydrolysis of the remaining methyl acetal to
provide (+)-altohyrtin A/spongistatin 1 (1) in an unoptimised
22% yield, after reverse-phase HPLC purification, along with
an E-ring dehydrated analogue 12 in 13% yield, vide infra.*
The spectroscopic data for synthetic 1 [1H NMR (CD3CN and
CD3OD, 500 and 800 MHz), 13C NMR (CD3CN), IR, HRMS],14
along with specific rotation [a]2D0 = +21.0 (c = 0.44, MeOH);
c.f. Kobayashi15 [a]D20 = +21.7 (c = 1.20, MeOH) and Pettit16
* This final deprotection has been optimised subsequently by the
Heathcock group, both to enhance the yield of altohyrtin C/spongistatin
2 (92%) and circumvent the competing dehydration in the E-ring.2p
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 4 3 1 – 2 4 4 0
2 4 3 3

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[a]2D0 = +26.2 (c = 0.32, MeOH)] were in excellent agreement
with that reported (and by comparison with the NMR spectra
kindly provided by Professors Pettit and Kishi).17 Moreover,
our synthetic material was identical to natural spongistatin 1 in
cytotoxicity bioassays performed by Professor Pettit’s group.
Altogether, we prepared 13 mg of altohyrtin A/spongistatin
1, which corresponds almost exactly to the amount of natural
spongistatin isolated by the Pettit group from some 400 kg of
the marine sponge Spongia sp.16
Synthesis and biological evaluation of analogues
Due to the extremely limited natural supply of the spongipyran
natural products, lack of material has halted the preclinical
development of these compounds in cancer chemotherapy.
Despite the considerable synthetic interest that these compounds
have garnered, relatively little is known regarding SAR for these
architecturally complex natural products.18–20 Smith et al. have
described two simplified spongipyran analogues bearing a model
F-ring and retaining the C44–C51 triene side-chain, both of
which displayed growth inhibitory activity against several cancer
cell lines, albeit only at the micromolar level.18a In contrast,
the design, synthesis and surprisingly high level of biological
activity of a greatly simplified analogue, based solely on the AB-
spiroacetal motif, has been reported by Uckun and co-workers.19
This claim has been questioned, as the Smith group prepared the
same analogue, as well as another AB-spiroacetal analogue, and
determined that neither had significant cytotoxic or anti-tubulin
activity.18b With these contradictory results in mind, we decided
to explore less extreme simplifications of 1, in order to gather
SAR data and help identify the spongipyran pharmacophore.
The deprotection of 11 with aqueous HF–MeCN to afford
1, as outlined above, was accompanied by the formation of a
minor component in 13% yield. This byproduct was purified
by reverse-phase HPLC and was readily identified as a close
Scheme
4
Reagents and conditions: (a) PPh3, NaI, i-Pr2NEt,
MeCN–MeOH (9 : 1), D, 20 h; (b) LiHMDS, CaH2, THF–HMPA (10 :
1), −78 ◦C, 10 min; then 2, −78 ◦C → rt, 40 min; (c) DDQ (portionwise),
CH2Cl2–pH 7 buffer (10 : 1), 0 ◦C, 1.5 h; (d) Zn, THF–1 M aq. NH4OAc
(10 : 1), rt, 0.5 h; (e) 2,4,6-trichlorobenzoyl chloride, Et3N, THF, rt, 3 h;
then DMAP, PhMe, 110 ◦C, 16 h; (f) HF, MeCN, H2O, 0 ◦C, 4 h.
1
analogue of 1 by its H NMR spectra, with differences only
in the regions corresponding to resonances for the E-ring
protons. The structure of this analogue was determined as 12,
corresponding to an E-ring dehydrated version of 1, following
mass spectrometry and 1H NMR analysis (500 MHz, COSY).
A further analogue of 1 was synthesised in order to ascertain
the importance of the C47–C51 chlorodienol side-chain for
biological activity. Thus, side-chain truncated EF segment 131c
was converted into the corresponding phosphonium salt 14 by
exposure to PPh3 in the presence of NaI (Scheme 4). Wittig
coupling of this compound with northern hemisphere aldehyde
2, under the optimised conditions (LiHMDS, CaH2, 10 : 1 THF–
HMPA), provided the side-chain truncated, protected seco-acid
15 in 71% yield (>97 : 3 Z : E). Removal of the PMB protecting
groups with DDQ provided 16 in 69% yield, once again with
partial hydrolysis of the C37 methyl acetal. Removal of the
TCE protecting group (Zn, 10 : 1 THF–1 M NH4OAc) gave
the seco-acid 17 in 62% yield. Finally, macrolactonisation under
modified Yamaguchi conditions,13 and global deprotection (aq.
HF–MeCN) provided the side-chain truncated spongipyran
analogue 18 in 14% yield from 17.
With analogues 12 and 18 in hand, the effects of E-ring
dehydration and removal of the C47–C51 chlorodienol segment
on cytotoxicity were now investigated. The results of growth
inhibition experiments21 for paclitaxel/Taxol (19), altohyrtin
A/spongistatin 1 (1), E-ring dehydrated analogue 12 and side-
chain truncated analogue 18, against a set of five different human
cancer cell lines are listed in Table 1.
The paclitaxel-resistant strains, MIP101 colon and
1A9PTX22 ovarian cancer, are included in the cell lines that
these compounds were tested against. In all cases examined, 1
was found to be significantly more active (6- to 2000-fold) than
paclitaxel, and was particularly effective against the MIP101
colon cancer cell line, indicating that it is a poor substrate for
the P-glycoprotein (Pgp) drug efflux pump. Given the already
exceptional cytotoxicity displayed by 1, we were surprised and
delighted to observe that the E-ring dehydrated analogue 12
2 4 3 4
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 4 3 1 – 2 4 4 0

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Table 1 Growth inhibition against human cancer cell linesa
IC50 values (nM)
19
1
12
18
587
407
>632
>632
>632
MIP101 colon (Pgp-1 overexpressing)
HCT116 colon
1A9PTX22 ovarian (mutation in b-tubulin)
1A9 ovarian (parental)
200
0.3
47
1
6
0.1
0.08
0.02
0.007
0.007
0.04
0.05
0.03
0.03
0.07
A549 non-small cell lung
a Cells were plated in 96 well plates at 4 × 103 cells per well for MIP 101, HCT 116 and A549 cell lines, and at 2 × 104 cells per well for
1A9 and 1A9/PTX22 cell lines. Compounds dissolved in DMSO were added to the wells at 5 fold serial dilutions starting from 1 lg ml−1. No
compound was added to control wells. After 72 h incubation, the number of viable cells was assessed using an MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-
diphenyl-tetrazolium bromide) assay.22 After processing, the plates were read in a Molecular Devices 96-well plate reader at 540 nm and IC50 values
(concentrations of compounds in nM causing 50% inhibition of cell growth) were calculated.
was generally (2- to 4-fold) more potent than the parent natural
product. Analogue 12 had low picomolar IC50 values, in the
range 0.007–0.08 nM, against this set of cancer cell lines. This
indicates that the C35 hydroxyl of 1 is unnecessary for biological
activity, and that its removal leads to an increase in potency.†† In
contrast, the dramatic attenuation of cytotoxicity for analogue
18, against all cell lines employed in these assays (e.g., 0.587 and
0.407 lM against the MIP101 and HCT116 colon carcinoma
cell lines), reveals that the C47–C51 chlorodiene allylic alcohol
moiety is an essential structural feature. These results suggest
that the full C44–C51 triene side-chain is a crucial part of the
spongipyran pharmacophore, which concurs with the findings
of the Smith group18 but differs from the SAR work of Uckun.19
exhausted natural material from the initial isolation work.
Furthermore, two analogues of the altohyrtins/spongstatins,
i.e., 12 and 18, have been synthesised and evaluated for their
growth inhibitory activity against a panel of human cancer
cell lines. The evaluation of these analogues has confirmed the
crucial role of the full C44–C51 triene side-chain for biological
activity and has also revealed an increase in potency can be
achieved by dehydration in the E-ring. While E-ring modification
can be tolerated but not side chain truncation, the design
of simplified synthetic analogues of the spongipyrans, while
retaining the exceptional antimitotic potency, constitutes an
important goal and clearly requires a great deal more SAR work.
Experimental
Conclusions
ABCD aldol adduct (7)
Overall, this highly stereocontrolled total synthesis of altohyrtin
A/spongistatin 1 (1) proceeds in 33 steps and ca. 0.5% over-
all yield for the longest linear sequence (based on the AB-
spiroacetal subunit). This synthesis has served to demonstrate
the power of boron-mediated aldol methodology for construct-
ing structurally complex polyketides, having been used in 10
separate instances (Fig. 1), examples of which, such as the union
of the AB- and CD-spiroacetal subunits and C47–C51 side-chain
installation, constitute some of the most testing applications
of this versatile carbon-carbon bond forming reaction in total
synthesis.5 To date, this total synthesis has provided useful quan-
tities of altohyrtin A/spongistatin 1 (1) for further preclinical
studies and has thus contributed to replenishing the largely
◦
To a cold (−78 C) solution of ketone 5 (470 mg, 0.88 mmol,
2 eq.) in Et2O (5.0 mL) was added Et3N (195 lL, 1.40 mmol,
3.2 eq.) followed by Chx2BCl (211 lL, 0.96 mmol, 2.2 eq.). The
reaction mixture was stirred at −78 ◦C for 10 min and allowed to
warm to 0 ◦C over a period of 10 min. The reaction mixture was
then cooled to −78 ◦C and a solution of aldehyde 4 (281 mg, 0.44
mmol) in Et2O (0.5 mL + 2 × 0.25 mL washings) was added via
cannula. The reaction was stirred at −78 ◦C for 1 h and then at
−20 ◦C for 16 h. The reaction was quenched by addition of silica
gel (Merck Kieselgel 60, 230–400 mesh, ca. 2 g) and allowed to
warm to rt and stirred for a further 40 min. The resultant slurry
was filtered, eluting with EtOAc (30 mL) and concentrated in
vacuo. Flash chromatography (5 : 95 → 60 : 40 EtOAc–light
petroleum) afforded major aldol isomer 7 (415 mg, 80%), minor
aldol isomers (45 mg, 9%) and recovered ketone 5 (231 mg, 98%
recovery) as colourless oils.
Major diastereomer 7: Rf: 0.17 (40 : 60 EtOAc–hexanes); [a]D20
−31.8 (c 0.20, CHCl3); IR (liquid film): 3500 (m, OH), 1758,
1
=
=
=
1729 (s, C O), 1612 (w, C C), 1513 (w, ArC C); H NMR: d
(500 MHz, CDCl3) 7.26 (2H, d, J = 8.5 Hz, ArH), 6.86 (2H,
=
d, J = 8.5 Hz, ArH), 5.17 (1H, s, C CHaHb), 5.05 (1H, m,
=
5-CH), 4.95 (1H, s, C CHaHb), 4.82 (1H, d, J = 12.0 Hz,
OCHaHbCCl3), 4.64 (1H, d, J = 12.0 Hz, OCHaHbCCl3), 4.52
(3H, m, 27-CH + OCH2Ar), 4.41 (1H, m, 3-CH), 4.30 (1H,
m, 11-CH), 4.11 (1H, m, 25-CH), 3.97 (1H, m, 19-CH), 3.80
(3H, s, ArOCH3), 3.63 (1H, m, 15-CH), 3.50–3.48 (3H, m, 21-
CH + 28-CH2), 3.32 (3H, s, OCH3), 2.95 (1H, dd, J = 18.0,
3.9 Hz, 18-CHaHb), 2.86 (1H, dd, J = 18.0, 8.8 Hz, 18-CHaHb),
2.68 (1H, br quin., J = 7.4 Hz, 16-CH), 2.73 (1H, dd, J =
16.3, 5.9 Hz, 2-CHaHb), 2.52 (1H, dd, J = 16.3, 7.3 Hz, 2-
CHaHb), 2.44 (1H, m, 14-CH), 2.29 (1H, dd, J = 14.4, 8.7 Hz,
12-CHaHb), 2.24 (1H, m, 20-CHaHb), 2.16 (1H, dd, J = 14.4,
3.5 Hz, 24-CHaHb), 2.01–2.08 (6H, m, 12-CHaHb + 22-CHaHb +
OH + COCH3), 1.86–1.88 (2H, m, 4-CHaHb + 6-CHaHb), 1.77
(1H, d, J = 13.1 Hz, 8-CHaHb), 1.70 (1H, m, 26-CHaHb), 1.58–
1.63 (4H, m, 4-CHaHb + 6-CHaHb + 10-CHaHb + 26-CHaHb),
1.51 (1H, dd, J = 14.4, 4.0 Hz, 24-CHaHb), 1.38 (1H, m, 22-
CHaHb), 1.40 (1H, d, J = 13.1 Hz, 8-CHaHb), 1.21 (4H, m,
Fig. 1 Summary of aldol reactions employed in the total synthesis of
altohyrtin A/spongistatin 1 (1), including boron Lewis acid reagents
utilised and diastereoselectivities obtained.
†† A similar observation for the altohyrtin C/spongistatin 2 series has
subsequently been made by Heathcock et al.2p
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 4 3 1 – 2 4 4 0
2 4 3 5

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10-CHaHb + 9-CCH3), 1.10 (1H, m, 20-CHaHb), 1.00–1.01 (6H,
m, 14-CHCH3 + 16-CHCH3), 0.93 (9H, m, Si(CH2CH3)3), 0.84
(9H, s, SiC(CH3)3), 0.54 (6H, m, Si(CH2CH3)3), 0.03 (3H, s,
SiCH3), 0.02 (3H, s, SiCH3); 13C NMR: d (100.6 MHz, CDCl3)
213.0, 170.9, 169.0, 159.1, 148.0, 130.6, 129.3, 113.9, 113.7, 98.4,
97.1, 94.9, 74.0, 73.9, 73.3, 72.9, 70.3, 66.7, 66.4, 65.1, 64.5, 64.4,
60.7, 55.5, 55.3, 49.7, 48.4, 47.7, 45.2, 43.2, 41.4, 40.7, 40.0, 38.4,
36.9, 35.6, 35.2, 32.0, 25.9, 21.5, 18.1, 13.2, 11.3, 7.2, 6.8, −4.8,
−4.9; HRMS: (+FAB) Calc. for C57H93O15Cl3Si2Na [M + Na]+:
1201.5016, found: 1201.5030. m/z: (+FAB) 1204 ([M + Na]+,
100), 587 (30).
97.0, 95.1, 74.0, 73.5, 73.1, 72.4, 70.5, 66.8, 66.3, 64.8, 64.4, 63.9,
60.6, 54.9, 54.6, 49.2, 47.6, 47.4, 45.0, 43.3, 42.4, 39.7, 38.1,
37.4, 36.9, 34.9, 34.8, 33.5, 31.3, 25.4, 20.8, 20.1, 18.7, 17.8,
13.0, 11.2, 10.7, 6.8, 6.5, −5.6, −5.7; HRMS: (+FAB) Calc. for
C59H95O16Cl3Si2Na [M + Na]+: 1243.5134, found: 1243.5122.
PMB deprotection of 8 – ABCD 1◦ alcohol
To a cold (0 ◦C) solution of p-methoxybenzyl ether 8 (877 mg,
0.72 mmol) in CH2Cl2–pH7 buffer (10 : 1, 20 mL) was added
DDQ (1.96 g, 8.62 mmol, 12 eq.) over a period of 2 h (1 eq.
every 10 min). The reaction was quenched by pouring into
sat. aq. NaHCO3 (100 mL) and the layers were separated. The
aqueous phase was extracted with Et2O (3 × 100 mL), combined
organics were washed with sat. aq. NaHCO3 (50 mL) and
brine (50 mL), dried (MgSO4) and concentrated in vacuo. Flash
chromatography (50 : 50 → 100 : 0 EtOAc–light petroleum)
afforded the 1◦ alcohol (743 mg, 94%) as a colourless oil: Rf: 0.31
Acetylated ABCD aldol adduct (8)
To a solution of aldol product 7 (179 mg, 0.15 mmol) in pyridine
(3.2 mL) was added DMAP (cat.) and Ac2O (0.97 mL). The
reaction mixture was stirred at rt for 2 h then quenched by
slow addition to a stirred solution of sat. aq. NaHCO3 (50
mL). EtOAc (30 mL) was added and the layers were separated.
The aqueous phase was extracted with EtOAc (3 × 50 mL),
combined organics were washed with sat. aq. NaHCO3 (30 mL)
and brine (30 mL), dried (MgSO4) and concentrated in vacuo.
Flash chromatography (5 : 95 → 60 : 40 EtOAc–light petroleum)
afforded acetate 8 (180 mg, 98%) as a colourless oil: Rf: 0.25 (40
(50 : 50 EtOAc–hexanes); [a]2D0 −6.2 (c 1.20, CHCl3); IR (liquid
1
=
film): 3503, 1758, 1732 (C O), 1612; H NMR: d (400 MHz,
CDCl3) 5.23 (1H, dd, J = 10.0, 2.8 Hz, 15-CH), 5.04 (1H, m,
=
=
5-CH), 5.01 (1H, s, C CHaHb), 4.83 (1H, s, C CHaHb), 4.82
(1H, d, J = 12.0 Hz, OCHaHbCCl3), 4.62 (1H, d, J = 12.0 Hz,
OCHaHbCCl3), 4.42 (1H, m, 27-CH), 4.34 (1H, m, 3-CH), 4.23
(1H, m, 11-CH), 4.10 (1H, m, 25-CH), 3.93 (1H, m, 19-CH),
3.68 (1H, m, 28-CHaHb), 3.51 (1H, m, 28-CHaHb), 3.46 (1H, m,
21-CH), 3.30 (3H, s, 21-OCH3), 2.92 (1H, dq, J = 10.0, 7.1 Hz,
16-CH), 2.88 (1H, dd, J = 17.6, 3.7 Hz, 18-CHaHb), 2.73 (1H,
dd, J = 17.6, 6.9 Hz, 18-CHaHb), 2.68 (1H, dd, J = 16.4, 5.9 Hz,
2-CHaHb), 2.57 (1H, m, 14-CH), 2.53 (1H, dd, J = 16.4, 7.5 Hz,
2-CHaHb), 2.27 (2H, m, 12-CH2), 2.13 (2H, m, 20-CHaHb + 24-
CHaHb), 2.02 (3H, s, COCH3), 2.00 (1H, m, 22-CHaHb), 1.92
(3H, s, COCH3), 1.84 (2H, m, 6-CHaHb + 4-CHaHb), 1.74 (1H,
dd, J = 14.2, 1.7 Hz, 8-CHaHb), 1.66 (1H, m, 26-CHaHb), 1.60–
1.53 (3H, m, 10-CHaHb + 4-CHaHb + 6-CHaHb), 1.48 (1H, dd,
J = 14.2, 3.3 Hz, 26-CHaHb), 1.38–1.20 (4H, m, 22-CHaHb +
8-CHaHb + 24-CHaHb + 10-CHaHb), 1.22 (3H, s, 9-CCH3), 1.06
(6H, m, 16-CHCH3 + 14-CHCH3), 0.94 (9H, m, Si(CH2CH3)3),
0.88 (1H, m, 20-CHaHb), 0.85 (9H, s, SiC(CH3)3), 0.54 (6H,
1
: 60 EtOAc–hexanes); [a]2D0 −15.0 (c 1.60, CHCl3); H NMR:
d (400 MHz, CD3CN) 7.26 (2H, d, J = 8.4 Hz, ArH), 6.86
(2H, d, J = 8.4 Hz, ArH), 5.15 (1H, dd, J = 10.0, 2.5 Hz, 15-
=
CH), 4.95 (1H, s, C CHaHb), 4.93 (1H, m, 5-CH), 4.86 (1H, s,
C CHaHb), 4.84 (1H, d, J = 12.2 Hz, OCHaHbCCl3), 4.74 (1H,
=
d, J = 12.2 Hz, OCHaHbCCl3), 4.38–4.48 (3H, m, 27-CH +
OCH2Ar), 4.31 (1H, m, 3-CH), 4.23 (1H, m, 11-CH), 4.14 (1H,
m, 25-CH), 3.88 (1H, m, 19-CH), 3.78 (3H, s, ArOCH3), 3.46
(1H, br tt, J = 11.3, 4.4 Hz, 21-CH), 3.38 (2H, m, 28-CH2), 3.24
(3H, s, OCH3), 3.00 (1H, dq, J = 10.0, 7.1 Hz, 16-CH), 2.80 (1H,
dd, J = 17.5, 3.8 Hz, 18-CHaHb), 2.72 (1H, dd, J = 16.6, 5.5 Hz,
2-CHaHb), 2.71 (1H, dd, J = 17.5, 8.8 Hz, 18-CHaHb), 2.54 (1H,
dd, J = 16.6, 7.9 Hz, 2-CHaHb), 2.57 (1H, m, 14-CH), 2.28 (1H,
dd, J = 14.4, 3.7 Hz, 12-CHaHb), 2.10–2.18 (3H, m, 12-CHaHb +
20-CHaHb + 24-CHaHb), 2.00 (1H, m, 22-CHaHb), 1.96 (3H, s,
COCH3), 1.86 (3H, s, COCH3), 1.85 (1H, m, 6-CHaHb), 1.71–
1.76 (2H, m, 4-CHaHb + 6-CHaHb), 1.44–1.63 (6H, m, 4-
CHaHb + 8-CHaHb + 10-CHaHb + 24-CHaHb + 26-CH2), 1.34
(1H, d, J = 14.2 Hz, 8-CHaHb), 1.20–1.24 (4H, m, 9-CCH3 + 10-
CHaHb), 1.12 (1H, br t, J = 11.8 Hz, 22-CHaHb), 1.06 (3H, d, J =
7.0 Hz, 16-CHCH3), 1.03 (3H, d, J = 7.1 Hz, 14-CHCH3), 0.93
(9H, m, Si(CH2CH3)3), 0.88 (1H, m, 20-CHaHb), 0.86 (9H, s,
SiC(CH3)3), 0.58 (6H, m, Si(CH2CH3)3), 0.03 (3H, s, SiCH3),
0.02 (3H, s, SiCH3); 1H NMR: d (800 MHz, CDCl3) 7.26 (2H,
d, J = 8.5 Hz, ArH), 6.86 (2H, d, J = 8.5 Hz, ArH), 5.22 (1H,
dd, J = 9.7, 2.6 Hz, 15-CH), 5.04 (1H, m, 5-CH), 5.01 (1H, s,
m, Si(CH2CH3)3), 0.03 (3H, s, SiCH3), 0.01 (3H, s, SiCH3); 13
C
NMR: d (62.5 MHz, CDCl3) 209.8, 171.0, 169.4, 169.0, 147.0,
113.7, 98.3, 97.0, 94.9, 74.1, 73.9, 73.8, 70.4, 66.6, 66.3, 66.3,
65.9, 64.3, 64.3, 60.6, 55.6, 49.4, 47.9, 47.7, 45.3, 43.2, 42.1,
40.1, 38.5, 37.9, 36.8, 35.7, 34.2, 33.9, 32.0, 25.9, 21.5, 20.8,
18.1, 13.3, 12.0, 7.3, 6.8, −4.9, −4.9; m/z: (+ESI) 1123 ([M +
Na]+, 100).
ABCD aldehyde (2)
To a solution of ABCD 1◦ alcohol from the above procedure
(229 mg, 0.21 mmol) in CH2Cl2 (2.0 mL) was added activated
˚
=
=
C CHaHb), 4.83 (1H, s, C CHaHb), 4.82 (1H, d, J = 12.0 Hz,
OCHaHbCCl3), 4.63 (1H, d, J = 12.0 Hz, OCHaHbCCl3), 4.51
(3H, m, 27-CH + OCH2Ar), 4.34 (1H, m, 3-CH), 4.21 (1H,
m, 11-CH), 4.10 (1H, m, 25-CH), 3.93 (1H, m, 19-CH), 3.80
(3H, s, ArOCH3), 3.44–3.51 (3H, m, 21-CH + 28-CH2), 3.30
(3H, s, OCH3), 2.86–2.91 (2H, m, 16-CH + 18-CHaHb), 2.75
(1H, dd, J = 16.4, 9.3 Hz, 2-CHaHb), 2.71 (1H, m, 18-CHaHb),
2.56 (1H, m, 14-CH), 2.51 (1H, dd, J = 16.4, 7.5 Hz, 2-CHaHb),
2.27 (2H, m, 12-CH2), 2.14 (2H, m, 20-CHaHb + 24-CHaHb),
2.06 (1H, m, 22-CHaHb), 2.03 (3H, s, COCH3), 1.91 (3H, s,
COCH3), 1.85–1.88 (2H, m, 4-CHaHb + 6-CHaHb), 1.76 (1H, d,
J = 14.1 Hz, 8-CHaHb), 1.70 (1H, m, 26-CHaHb), 1.62–1.53 (3H,
m, 4-CHaHb + 6-CHaHb + 10-CHaHb), 1.58 (1H, br dd, J = 14.4,
3.6 Hz, 26-CHaHb), 1.34 (1H, br t, J = 12.0 Hz, 22-CHaHb),
1.29 (1H, d, J = 14.1 Hz, 8-CHaHb), 1.19–1.25 (5H, m, 9-
CCH3 + 10-CHaHb + 24-CHaHb), 1.08 (6H, m, 14-CHCH3 + 16-
CHCH3), 0.93 (9H, m, Si(CH2CH3)3), 0.88 (1H, m, 20-CHaHb),
0.85 (9H, s, SiC(CH3)3), 0.54 (6H, m, Si(CH2CH3)3), 0.02 (3H, s,
SiCH3), 0.01 (3H, s, SiCH3); 13C NMR: d (100.6 MHz, CD3CN)
210.1, 170.5, 169.1, 169.0, 147.3, 130.7, 129.4, 113.6, 113.3, 98.2,
(heated under vacuum) powdered 4 A molecular sieves (200
mg), NMO (73 mg, 0.63 mmol, 3.0 eq.) and TPAP (15 mg,
0.042 mmol, 20 mol%). The reaction mixture was stirred at rt
for 15 min, and loaded directly onto a silica column. Flash
chromatography (50 : 50 EtOAc–light petroleum) afforded
aldehyde 2 (190 mg, 83%) as a colourless oil: Rf: 0.24 (50
: 50 EtOAc–hexanes); [a]D20 −8.3 (c 0.60, CHCl3); IR (liquid
1
=
film): 1734 (C O), 1647; H NMR: d (400 MHz, CDCl3) 9.72
(1H, s, CHO), 5.22 (1H, dd, J = 9.7, 2.8 Hz, 15-CH), 5.04
=
(1H, m, 5-CH), 5.01 (1H, s, C CHaHb), 4.80–4.88 (3H, m,
=
C CHaHb + OCHaHbCCl3 + 27-CH), 4.62 (1H, d, J = 12.0 Hz,
OCHaHbCCl3), 4.35 (1H, m, 3-CH), 4.25 (1H, m, 11-CH), 4.17
(1H, m, 25-CH), 3.93 (1H, m, 19-CH), 3.49 (1H, m, 21-CH),
3.31 (3H, s, 21-OCH3), 2.95–2.87 (2H, m, 16-CH + 18-CHaHb),
2.76 (1H, dd, J = 18.2, 9.5 Hz, 18-CHaHb), 2.74 (1H, dd, J =
16.1, 6.0 Hz, 2-CHaHb), 2.59 (1H, m, 14-CH), 2.53 (1H, dd,
J = 16.1, 7.5 Hz, 2-CHaHb), 2.26 (2H, m, 12-CH2), 2.20 (2H,
m, 20-CHaHb + 24-CHaHb), 2.09 (1H, dd, J = 12.2, 3.1 Hz,
22-CHaHb), 2.02 (3H, s, COCH3), 1.92 (3H, s, COCH3), 1.86–
1.83 (3H, m, 6-CHaHb + 4-CHaHb + 26-CHaHb), 1.73 (1H, dd,
2 4 3 6
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 4 3 1 – 2 4 4 0

View Article Online
J = 14.2, 1.76 Hz, 8-CHaHb), 1.66–1.49 (5H, m, 10-CHaHb +
4-CHaHb, + 6-CHaHb + 26-CHaHb + 24-CHaHb), 1.44 (1H,
br t, J = 12.0 Hz, 22-CHaHb), 1.28 (2H, m, 8-CHaHb + 10-
CHaHb), 1.20 (3H, s, 9-CCH3), 1.07 (6H, m, 16-CHCH3 + 14-
CHCH3), 0.93 (9H, m, Si(CH2CH3)3), 0.88 (1H, m, 20-CHaHb),
0.85 (9H, s, SiC(CH3)3), 0.54 (6H, m, Si(CH2CH3)3), 0.05 (3H, s,
SiCH3), 0.03 (3H, s, SiCH3); 13C NMR: d (100.6 MHz, CDCl3);
209.6, 202.6, 171.0, 169.3, 169.0, 147.0, 113.8, 110.1, 98.6, 96.9,
94.9, 74.1, 73.9, 73.5, 71.1, 70.3, 66.6, 64.3, 63.6, 60.6, 55.6,
49.4, 47.8, 47.6, 45.3, 43.3, 42.1, 40.1, 38.5, 37.8, 36.9, 35.2,
33.9, 33.1, 32.0, 25.9, 21.5, 20.8, 18.1, 13.3, 11.9, 7.3, 6.8, −4.9,
−5.0; HRMS: (+FAB) Calc. for C51H85O15Si2Cl3Na [M + Na]+:
1121.4385, found: 1121.4319.
7.0 Hz, 30-CH2), 2.31–2.33 (1H, m, 44-CHaHb), 2.30 (1H, dd,
J = 16.6, 6.7 Hz, 2-CHaHb), 2.20 (1H, m, 40-CH), 2.15 (1H,
br d, J = 12.1 Hz, 22-CHaHb), 2.10 (1H, d, J = 14.0 Hz, 24-
CHaHb), 2.01 (1H, d, J = 15.5 Hz, 36-CHaHb), 1.95 (3H, s,
COCH3), 1.92 (1H, d, J = 14.7 Hz, 6-CHaHb), 1.82–1.86 (1H,
m, 32-CHaHb), 1.79 (3H, s, COCH3), 1.77–1.80 (1H, m, 31-
CHaHb), 1.76 (1H, app t, J = 12.1 Hz, 22-CHaHb), 1.71 (1H, d,
J = 13.4 Hz, 4-CHaHb), 1.67 (1H, d, J = 13.7 Hz, 26-CHaHb),
1.61–1.63 (1H, m, 8-CHaHb), 1.60 (1H, m, 26-CHaHb), 1.57–
1.60 (1H, m, 34-CH), 1.49–1.53 (1H, m, 31-CHaHb), 1.48–1.52
(1H, m, 32-CHaHb), 1.41 (1H, d, J = 12.9 Hz, 10-CHaHb), 1.23
(3H, d, J = 7.0 Hz, 14-CHCH3), 1.22–1.24 (1H, m, 6-CHaHb),
1.18 (3H, d, J = 6.9 Hz, 16-CHCH3), 1.17 (1H, m, 4-CHaHb),
1.13 (9H, s, SiC(CH3)3), 1.12–1.14 (1H, m, 24-CHaHb), 1.02–
1.06 (1H, m, 20-CHaHb), 1.02 (18H, s, 2 × SiC(CH3)3), 1.01–1.04
(9H, m, Si(CH2CH3)3), 1.00–1.03 (1H, m, 8-CHaHb), 0.99 (3H, s,
9-CCH3), 0.97–1.00 (1H, m, 10-CHaHb), 0.97–0.99 (3H, m, 34-
CHCH3), 0.81 (3H, d, J = 6.4 Hz, 40-CHCH3), 0.57–0.60 (6H,
m, Si(CH2CH3)3), 0.25 (3H, m, SiCH3), 0.16 (3H, m, SiCH3),
0.14 (3H, m, SiCH3), 0.10 (3H, m, SiCH3), 0.08 (6H, m, 2 ×
SiCH3); 13C NMR: d (100.6 MHz, C6D6) 209.6, 170.2, 169.2,
168.8, 159.9, 159.8, 148.0, 143.3, 138.9, 138.7, 132.3, 131.7,
131.6, 131.5, 131.0, 130.8, 129.5, 129.4, 128.7, 126.5, 115.7,
115.1, 114.2, 114.1, 113.8, 103.0, 98.4, 97.2, 95.6, 87.2, 83.4, 80.0,
78.7, 76.2, 74.9, 74.8, 74.7, 74.6, 74.1, 73.9, 71.4, 71.1, 70.7, 67.6,
66.9, 66.7, 65.3, 64.6, 62.3, 60.9, 55.2, 54.8, 54.8, 54.8, 51.2, 48.0,
47.9, 47.3, 46.2, 45.5, 44.6, 43.0, 40.4, 39.5, 39.2, 39.0, 38.7, 38.6,
38.0, 34.9, 34.2, 33.3, 32.2, 31.7, 28.8, 26.9, 26.2, 26.2, 21.4, 20.6,
18.5, 18.4, 18.4, 13.7, 13.4, 12.3, 10.6, 7.6, 7.2, −4.1, −4.2, −4.4,
−4.7, −4.8; HRMS: (+ESI) Calc. for C114H180O25Cl4Si4Na [M +
Na]+: 2224.0537, found: 2224.0346.
The protected seco-acid of spongistatin 1 (9)
CaH2 (spatula tip) was added to phosphonium salt 3 (195 mg,
0.129 mmol) in a glove box and the system was evacuated and
recharged with Ar. O2-free THF (1.5 mL) was added, followed
by HMPA (150 lL) and the mixture was stirred at rt for
2 h. The phosphonium salt–CaH2 suspension was cooled to
−78 ◦C and a freshly prepared solution of LiHMDS (0.253 M
in THF, 816 lL, 0.206 lmol, 1.6 eq.) was added, upon which
the solution developed an intense yellow–orange colour. The
reaction mixture was stirred at −78 ◦C for a further 10 min. A
500 lL gas-tight syringe was flushed with a solution of aldehyde
2 (190 mg, 0.173 mmol, 1.3 eq.) in THF (0.5 mL) and then the
aldehyde solution was added to the ylide solution via this syringe.
The resultant mixture was removed from the cooling bath and
allowed to warm to rt. The mixture was stirred at rt for 40 min by
which time a deep red coloration had developed. The reaction
was quenched by transferring it, by pipette, to a cold (0 ◦C),
vigorously stirred mixture of sat. aq. NH4Cl–20% aq. Na2S2O3
(2 : 1, 30 mL), and washing the flask with Et2O (3 × 10 mL). The
layers were separated and the aqueous phase was extracted with
Et2O (3 × 30 mL), the combined organic extracts were dried
(Na2SO4) and concentrated in vacuo. Flash chromatography (10
: 90 → 60 : 40 EtOAc–hexanes) afforded the desired Wittig
product 9 (181 mg, 64%) as a white amorphous solid: Rf: 0.18
(40 : 60 EtOAc–hexanes); [a]2D0 −8.7 (c 0.60, CHCl3); IR (liquid
film): 2932, 1732, 1514 cm−1; 1H NMR: d (800 MHz, C6D6) 7.44
(2H, d, J = 8.5 Hz, ArH), 7.36 (2H, d, J = 8.4 Hz, ArH), 7.29
(2H, d, J = 8.4 Hz, ArH), 6.84–6.85 (4H, m, ArH), 6.83 (2H,
d, J = 8.5 Hz, ArH), 6.46 (1H, dd, J = 14.9, 5.2 Hz, 48-CH),
6.39 (1H, d, J = 14.9 Hz, 49-CH), 5.76 (1H, br t, J = 9.7 Hz,
28-CH), 5.65 (1H, br t, J = 10.3 Hz, 27-CH), 5.63 (1H, dd,
J = 11.6, 2.3 Hz, 15-CH), 5.55 (1H, br dt, J = 10.8, 7.3 Hz,
tris-PMB removal of 9
To a cooled (0 ◦C) solution of tris-PMB ether 9 (188 mg,
0.085 mmol) in CH2Cl2–pH7 buffer (10 : 1, 11 mL) was added
DDQ (1.74 g, 7.67 mmol, 90 eq.) over a period of 1.5 h (10
eq. every 10 min). The reaction was quenched by pouring into
sat. aq. NaHCO3 (50 mL) and the layers were separated. The
aqueous phase was extracted with Et2O (3 × 100 mL), combined
organics were dried (Na2SO4) and concentrated in vacuo. Flash
chromatography (20 : 80 → 100 : 0 EtOAc–hexanes) afforded
the desired tris-PMB deprotected material (96 mg, 61%) as a
white amorphous solid, consisting of an inseparable ca. 1.1 : 1
mixture of methyl acetal and hemiacetal at C37: Rf: 0.67 (80 :
=
20 EtOAc–hexanes); IR (liquid film): 3448, 2952, 1734 (C O),
1
1459 cm−1; H NMR: d (500 MHz, C6D6) 6.44–6.51 (2H, m,
=
29-CH), 5.22 (1H, s, 13-C CHaHb), 5.15 (1H, s, 51-CHaHb),
48-CH + 49-CH), 5.81 (1H, m, 28-CH), 5.71 (1H, br d, J =
=
=
5.15 (1H, s, 45-C CHaHb), 5.13 (1H, s, 45-C CHaHb), 5.04
(1H, d, J = 11.2 Hz, OCHaHbAr), 5.03 (1H, s, 51-CHaHb), 5.02
9.6 Hz, 15-CH), 5.68 (1H, m, 27-CH), 5.60 (1H, m, 29-CH),
=
5.38 (0.5H, s, 37-COH), 5.31 (1H, s, 13-C CHaHb), 5.28, 5.27,
=
=
(1H, br s, 5-CH), 4.98 (1H, s, 13-C CHaHb), 4.98 (1H, d, J =
5.20, 5.15, 5.13 (4H, 5 × s, 45-C CH2 + 51-CH2), 5.10 (1H, m,
=
10.7 Hz, OCHaHbAr), 4.94 (1H, d, J = 11.1 Hz, OCHaHbAr),
4.77 (1H, d, J = 12.0 Hz, OCHaHbCCl3), 4.76 (1H, d, J =
11.2 Hz, OCHaHbAr), 4.63 (1H, d, J = 10.7 Hz, OCHaHbAr),
4.57 (1H, d, J = 11.1 Hz, OCHaHbAr), 4.48–4.52 (2H, m, 3-
CH + 47-CH), 4.47 (1H, d, J = 12.0 Hz, OCHaHbCCl3), 4.35–
4.38 (1H, m, 33-CH), 4.34 (1H, m, 11-CH), 4.19 (1H, br t, J =
10.6 Hz, 19-CH), 3.96 (1H, m, 35-CH), 3.91 (1H, br s, 25-CH),
3.71 (1H, s, 38-CH), 3.58 (1H, app t, J = 9.0 Hz, 43-CH), 3.38
(1H, m, 42-CH), 3.37 (1H, d, J = 10.0 Hz, 39-CH), 3.32 (3H, s,
ArOCH3), 3.32 (3H, s, ArOCH3), 3.32 (3H, s, ArOCH3), 3.25
(1H, tt, J = 10.9, 4.6 Hz, 21-CH), 3.23 (3H, s, 37-COCH3), 3.19
(1H, dd, J = 10.4, 9.8 Hz, 41-CH), 3.10 (1H, dd, J = 17.7,
2.5 Hz, 18-CHaHb), 3.05 (3H, s, 21-COCH3), 2.91 (1H, dq, J =
9.7, 6.9 Hz, 16-CH), 2.77 (1H, br t, J = 9.7 Hz, 44-CHaHb),
2.74–2.79 (2H, m, 14-CH + 18-CHaHb), 2.68 (1H, dd, J = 13.6,
6.4 Hz, 46-CHaHb), 2.66 (1H, dd, J = 16.6, 6.4 Hz, 2-CHaHb),
2.57 (1H, dd, J = 15.5, 3.7 Hz, 36-CHaHb), 2.53 (1H, dd, J =
13.4, 6.7 Hz, 46-CHaHb), 2.48 (2H, app d, J = 6.6 Hz, 12-CH2),
2.40 (1H, br d, J = 12.5 Hz, 20-CHaHb), 2.37 (2H, dt, J = 7.3,
5-CH), 5.09 (1H, 13-C CHaHb), 4.87 (0.5H, d, J = 12.0 Hz,
CHaHbCCl3), 4.87 (0.5H, J = 12.0 Hz, CHaHbCCl3), 4.58 (1H,
d, J = 12.0 Hz, CHaHbCCl3), 4.58 (2H, m, 3-CH + 47-CH),
4.41 (2H, m, 33-CH + 11-CH), 4.26 (1H, m, 19-CH), 4.01, (2H,
br s, 25-CH + 35-CH), 3.89 (0.5H, d, J = 6.2 Hz), 3.85 (0.5H,
d, J = 10.3 Hz), 3.76 (0.5H, d, J = 8.0 Hz), 3.56 (0.5H, br
t, J = 9.0 Hz, 43-CH), 3.44 (0.5H, br t, J = 9.0 Hz, 43-CH),
3.28–3.41 (1.5H, m), 3.26 (1.5 H, s, 37-OCH3), 3.04–3.22 (3H,
m), 3.15 (3H, 2 × s, 21-OCH3), 2.97 (0.5H, m), 2.84–2.92 (3.5H,
m), 2.76 (1H, dd, J = 16.4, 6.5 Hz), 2.60–2.67 (2H, m), 2.57
(2H, m), 2.49–2.53 (2H, m), 2.41 (2H, m), 2.33 (2H, m), 2.11–
2.21 (3H, m), 2.05 (3H, 2 × s, COCH3), 2.02 (2H, m), 1.92 (3H,
2 × s, COCH3), 1.81–1.88 (3H, m), 1.70 (5H, m), 1.50 (3H,
m), 1.08–1.22 (51H, m), 1.02 (3H, m, 34-CHCH3), 0.96 (3H,
m, 40-CHCH3), 0.68 (6H, q, J = 7.6 Hz, Si(CH2CH3)3), 0.13–
0.32 (18H, m, 3 × Si(CH3)2); HRMS: (+ESI) Calc. for desired
methyl acetal, C90H156O22Cl4Si4Na [M + Na]+: 1863.8812, found:
1863.8779, Calc. for desired hemiacetal, C89H154O22Cl4Si4Na
[M + Na]+: 1849.8655, found: 1849.8575.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 4 3 1 – 2 4 4 0
2 4 3 7

View Article Online
Spongistatin 1 seco-acid (10)
(1.5H, m), 2.58–2.82 (4.5H, m), 2.44 (1H, br d, J = 13.8 Hz),
2.24–2.38 (4H, m), 1.99–2.18 (6H, m), 1.95 (3H, m, COCH3),
1.87, 1.87 (3H, 2 × s, COCH3), 1.82–1.87 (2H, m), 1.71–1.76
(2H, m), 1.29–1.65 (10H, m), 1.05–1.21 (13H, m), 0.87–0.98
(43H, m), 0.60 (6H, m, Si(CH2CH3)3), 0.02–0.11 (18H, m, 3 ×
Si(CH3)2). The appearance of double-doublet signal at d 4.68
(J = 10.6, 9.0 Hz) indicated the formation of the macrolactones;
m/z: (+ESI) 1684 (55), 1151 (17), 907 (23), 862 (100), 734 (49).
To a solution of the PMB deprotected material from the above
procedure (30.6 mg, max. 0.017 mmol) in THF (1.0 mL) was
added Zn dust (1.0 g, excess). The resultant suspension was
stirred at rt for 2 min and aq. NH4OAc (1 M, 100 lL) was added.
The reaction mixture was stirred at rt for 30 min and then diluted
with EtOAc (10 mL). The supernatant was separated with a
pipette and the resultant Zn residue was washed with EtOAc
(3 × 10 mL). The combined organics were dried (Na2SO4),
filtered through sinter, and concentrated in vacuo. Flash column
chromatography (30 : 70 → 100 : 0 EtOAc–hexanes, then 1
: 99 AcOH–EtOAc) afforded seco-acid 10 (16.5 mg, 58%) and
partially dechlorinated products (7.1 mg, 24%) as an amorphous
solid and a colourless oil respectively.
Spongistatin 1 (1)14
◦
To a cold (0 C) solution of macrolactones 11 (27.5 mg, max.
0.016 mmol) in MeCN (4.9 mL) was added a freshly prepared
HF solution (40% HF(aq)–H2O–MeCN, 0.5 : 0.9 : 8.6, 405 lL)
and the reaction mixture was stirred at 0 ◦C for 4 h before being
quenched with sat. aq. NaHCO3 (20 mL). The resultant mixture
was diluted with CH2Cl2 (20 mL) and the layers were separated.
The aqueous phase was extracted with CH2Cl2 (3 × 30 mL),
combined organics were dried (Na2SO4) and concentrated in
vacuo. Flash chromatography (5 : 95 → 10 : 90 MeOH–CH2Cl2)
afforded spongistatin 1 (1) and dehydrated product 12 as an
inseparable mixture (11.1 mg, 55%). Further purification by
reverse phase HPLC (Prodigy C18 4.6 × 250 mm, 5 lm analytical
column; 27.5% H2O–MeOH; 1 mL min−1) afforded spongistatin
1 (1) (4.4 mg, 22%) and dehydrated product 12 (2.7 mg, 13%) as
white solids.
seco-Acid 10: Rf: 0.48 (80 : 20 EtOAc–hexanes); IR (liquid
film): 3583, 2952, 1734 (C O), 1459 cm ; 1H NMR: d
−1
=
(500 MHz, C6D6) 6.50–6.55 (2H, m, 48-CH + 49-CH), 5.80
(2H, m, 15-CH +28-CH), 5.69 (1H, m, 27-CH), 5.56 (1H, m,
=
29-CH), 5.09–5.28 (7.5H, m, 37-OH + 5-CH + 13-C CH2,
=
=
45-C CH2 + 51-C CH2), 4.53–4.62, 4.30–4.38 (5H, 2 × m, 3-
CH + 11-CH + 19-CH + 33-CH + 47-CH), 3.85–4.01 (4H, m,
25-CH + 35-CH + 38-CH +39-CH), 3.39–3.60 (1.5H, m), 3.27–
3.36 (1.5H, m), 3.27 (1.5H, s, 37-OCH3), 3.15 (3H, s, 21-OCH3),
2.99–3.13 (3H, m), 2.76–2.97 (4H, m), 2.67 (2H, m), 2.50 (6H,
m), 2.33 (2H, m), 2.20 (3H, m), 2.07, 2.05 (3H, 2 × s, COCH3),
1.99–2.12 (2H, m), 1.97, 1.95 (3H, 2 × s, COCH3), 1.88–2.02
(3H, m), 1.83 (3H, m), 1.68 (5H, m), 1.01–1.51 (57H, m), 0.71
(6H, m, Si(CH2CH3)3), 0.09–0.38 (18H, m, 3 × Si(CH3)2). The
absence of doublet peaks at 4.58 and 4.87 indicated the loss of
the 2,2,2-trichloroethyl ester moiety; HRMS: (+ESI) Calc. for
methyl acetal 10Me, C88H155O22ClSi4Na [M + Na]+: 1733.9668,
found: 1733.9790, Calc. for hemiacetal 10H, C87H153O22ClSi4Na
[M + Na]+: 1719.9511, found: 1719.9625.
Spongistatin 1 (1): Rf: 0.20 (5 : 95 MeOH–CH2Cl2); Reverse
phase HPLC: Rt 12.5 min (27.5 : 72.5 H2O–MeOH); [a]2D0 +21.0
(c 0.44, MeOH); IR (liquid film): 3430, 2940, 1733, 1386, 1259,
1176, 1086, 893 cm−1; 1H NMR: d (500 MHz, CD3CN) 6.41 (1H,
dd, J = 15.0, 1.1 Hz, 49-CH), 6.11 (1H, dd, J = 15.0, 5.7 Hz,
48-CH), 5.48 (1H, ddd, J = 10.6, 9.9, 9.9 Hz, 29-CH), 5.45 (1H,
br s, 51-CHaHb), 5.35 (1H, br s, 51-CHaHb), 5.32 (1H, br t, J =
10.8 Hz, 28-CH), 5.11 (1H, dd, J = 10.7, 1.8 Hz, 15-CH), 5.00
(1H, ddd, J = 9.9, 9.9, 3.8 Hz, 27-CH), 4.92 (1H, br s, 5-CH),
Protected macrocycle of spongistatin 1 (11)
=
=
4.89 (1H, br s, 45-C CHaHb), 4.86 (1H, br s, 45-C CHaHb),
4.83 (2H, br s, 13-C CH2), 4.75 (1H, dd, J = 11.0, 9.2 Hz, 41-
=
To a solution of seco-acid 10 (28.4 mg, max. 0.017 mmol) in THF
(200 lL) was added a freshly prepared solution of Et3N (0.5 M
in THF, 100 lL, 0.050 mmol, 3 eq.) and a solution of 2,4,6-
trichlorobenzoyl chloride (0.5 M in THF, 166 lL, 0.083 mmol,
5 eq.). The resultant solution was left to stir at rt for 1 h before
a further aliquot of reagents (Et3N and 2,4,6-trichlorobenzoyl
chloride, same stoichiometry as above) were added. This process
was repeated for a third time such that a total of Et3N (15
eq.) and 2,4,6-trichlorobenzoyl chloride (9 eq.) were added in
three portions over a period of 3 h. The reaction mixture was
diluted with PhMe (2 mL) and this solution was then added to a
refluxing solution of DMAP (41 mg, 0.33 mmol, 20 eq.) in PhMe
(12 mL) over a period of 3 min. The anhydride flask was rinsed
with PhMe (2 × 1 mL) and added to the refluxing reaction.
The resultant cloudy white suspension was heated at reflux for
16 h and then cooled to rt before being quenched with sat.
NaHCO3 (30 mL). The layers were separated and the aqueous
phase was extracted with EtOAc (3 × 30 mL). The combined
organic extracts were washed with brine (30 mL), dried (Na2SO4)
and concentrated in vacuo. Flash chromatography (20 : 80 → 80
: 20 EtOAc–hexanes) afforded macrolactone 11 (14.1 mg, 50%)
as a colourless oil consisting of an inseparable mixture of methyl
acetal and hemiacetal at C37: Rf: 0.45 (40 : 60 EtOAc–hexanes);
CH), 4.72 (1H, d, J = 2.5 Hz, 37-OH), 4.39 (1H, d, J = 10.0 Hz,
25-OH), 4.36 (1H, m, 47-CH), 4.35 (1H, br d, J = 5.3 Hz, 42-
OH), 4.31 (1H, br s, 9-OH), 4.24 (2H, br t, J = 10,7 Hz, 3-CH,
11-CH), 4.13 (1H, dt, J = 9.0, 3.0 Hz, 33-CH), 3.99 (1H, br t,
J = 11.1 Hz, 19-CH), 3.94 (1H, br m, 25-CH), 3.82 (1H, d, J =
9.4 Hz, 35-OH), 3.72 (1H, br d, J = 10.2 Hz, 39-CH), 3.65 (1H,
m, 35-CH), 3.51 (1H, d, J = 2.5 Hz, 47-OH), 3.46 (1H, tt, J =
11.6, 4.2 Hz, 21-CH), 3.38 (1H, td, J = 8.6, 2.2 Hz, 43-CH),
3.34 (1H, d, J = 10.7 Hz, 38-CH), 3.24 (3H, s, 21-OCH3), 3.11
(1H, td, J = 9.1, 5.4 Hz, 42-CH), 3.04 (1H, dq, J = 10.7, 6.9 Hz,
16-CH), 2.86 (1H, dd, J = 19.4, 10.1 Hz, 18-CHaHb), 2.86 (1H,
br d, J = 10.1 Hz, 38-OH), 2.78 (1H, m, 14-CH), 2.75 (1H, br
d, J = 13.9 Hz, 44-CHaHb), 2.61 (1H, br d, J = 18.2 Hz, 18-
CHaHb), 2.52 (1H, dd, J = 16.2, 1.8 Hz, 2-CHaHb), 2.45 (1H,
dd, J = 16.2, 10.5 Hz, 2-CHaHb), 2.33 (1H, br dd, J = 13.6,
6.3 Hz, 46-CHaHb), 2.27 (1H, m, 24-CHaHb), 2.26 (1H, br d,
J = 14.0 Hz, 12-CHaHb), 2.18 (2H, m, 30-CHaHb + 46-CHaHb),
2.08 (1H, m, 44-CHaHb), 2.00 (1H, m, 30-CHaHb), 1.99 (2H, m,
12-CHaHb + 22-CHaHb), 1.98 (1H, m, 20-CHaHb), 1.94 (3H, s,
COCH3), 1.91 (1H, m, 40-CH), 1.89 (1H, m, 36-CHaHb), 1.84
(3H, s, COCH3), 1.78 (1H, d, J = 15.1 Hz, 6-CHaHb), 1.68
(1H, m, 4-CHaHb), 1.66 (1H, dd, J = 15.2, 4.4 Hz, 6-CHaHb),
1.61 (1H, m, 36-CHaHb), 1.60 (2H, m, 8-CHaHb + 31-CHaHb),
1.57 (3H, m, 26-CH2 + 34-CH), 1.55 (3H, m, 4-CHaHb + 10-
CHaHb + 24-CHaHb), 1.46 (1H, d, J = 14.0 Hz, 8-CHaHb),
1.42 (1H, m, 32-CHaHb), 1.30 (1H, m, 32-CHaHb), 1.28 (1H, m,
10-CHaHb), 1.23 (1H, m, 31-CHaHb), 1.15 (3H, d, J = 6.9 Hz,
16-CHCH3), 1.08 (1H, t, J = 12.1 Hz, 22-CHaHb), 1.06 (3H, s,
9-CCH3), 1.04 (3H, d, J = 6.9 Hz, 14-CHCH3), 0.96 (1H, ddd,
J = 12.0, 12.0, 12.0 Hz, 20-CHaHb), 0.81 (3H, d, J = 7.2 Hz,
34-CHCH3), 0.74 (3H, d, J = 6.6 Hz, 40-CHCH3); 13C NMR:
d (125 MHz, CD3CN) 213.5, 173.1, 171.6, 170.2, 148.0, 144.0,
139.2, 139.2, 133.4, 131.2, 127.0, 116.6, 116.5, 114.9, 99.9, 99.4,
−1
1
=
IR (liquid film): 2926, 1734 (C O), 1458 cm ; H NMR: d
(500 MHz, CD3CN) 6.37 (1H, d, J = 14.8 Hz, 49-CH), 6.11 (1H,
=
m, 48-CH), 4.44 (1H, s, 51-C CHaHb), 5.40 (1H, m, 28-CH),
=
5.38 (1H, s, 51-C CHaHb), 5.36 (1H, m, 29-CH), 5.10–5.20 (2H,
=
m, 15-CH + 27-CH), 4.85–4.92 (5H, m, 5-CH + 13-C CH2 +
=
45-C CH2), 4.72, 4.68 (1H, m, dd, J = 10.6, 9.0 Hz, 41-CH),
4.45 (1H, m, 47-CH), 4.30 (2H, m, 3-CH + 11-CH), 4.13 (2H,
m), 4.06 (1H, m), 3.98 (0.5H, m), 3.89 (1.5H, m), 3.79 (1H, m),
3.60–3.63 (1H, m), 3.48 (1H, m, 21-CH), 3.30–3.43 (2H, m, 38-
CH + 43-CH), 3.24, 3.24 (3H, 2 × s, 21-OCH3), 3.16 (1.5H, s,
37-OCH3), 3.14 (1H, m, 42-CH), 3.06 (1H, m, 16-CH), 2.89
2 4 3 8
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 4 3 1 – 2 4 4 0

View Article Online
99.3, 81.3, 80.6, 78.7, 75.3, 74.0, 73.1, 73.1, 71.5, 70.1, 69.6,
67.2, 67.1, 66.2, 64.7, 64.4, 63.6, 61.2, 55.7, 52.0, 47.6, 46.8, 45.0,
44.2, 44.2, 43.9, 40.9, 40.2, 39.3, 39.1, 38.2, 37.7, 37.3, 36.6, 34.9,
34.7, 33.8, 32.8, 30.2, 28.1, 27.8, 27.0, 21.0, 13.7, 12.7, 12.1, 11.6;
HRMS: (+ESI) Calc. for C63H95O21ClNa [M + Na]+: 1245.5946,
found: 1245.5895.
Dehydrated product 12: Rf: 0.20 (5 : 95 MeOH–CH2Cl2);
Reverse phase HPLC: Rt 19.4 min (27.5 : 72.5 H2O–MeOH); [a]D20
+5.8 (c 0.22, MeOH); IR (liquid film): 3450, 2936, 1733, 1649,
1382, 1256, 1169, 1088 cm−1; 1H NMR: d (500 MHz, CD3CN)
6.42 (1H, dd, J = 14.9, 1.1 Hz, 49-CH), 6.14 (1H, dd, J = 14.9,
5.4 Hz, 48-CH), 5.92 (1H, dd, J = 10.0, 5.5 Hz, 35-CH) 5.86
(1H, dd, J = 10.1, 0.8 Hz, 34-CH), 5.46 (1H, br s, 51-CHaHb),
5.41 (1H, m, 29-CH), 5.36 (1H, br s, 51-CHaHb) 5.35 (1H, br t,
J = 11.0 Hz, 28-CH), 5.19 (1H, dd, J = 10.6, 1.6 Hz, 15-CH),
4.99 (1H, m, 27-CH), 4.94 (1H, br s, 5-CH), 4.90 (1H, br s,
3, DOI: 10.1039/b504146e; (b) I. Paterson, M. J. Coster, D. Y.-K.
Chen, K. R. Gibson and D. J. Wallace, Org. Biomol. Chem., 2005,
3, DOI: 10.1039/b504148a; (c) I. Paterson, M. J. Coster, D. Y.-K.
Chen, J. L. Acen˜a, J. Bach, L. E. Keown and T. Trieselmann, Org.
Biomol. Chem., 2005, 3, DOI: 10.1039/b504149j.
2 Completed altohyrtin/spongistatin total syntheses: (a) D. A. Evans,
P. J. Coleman and L. C. Dias, Angew. Chem., Int. Ed., 1997, 36, 2738–
2741; (b) D. A. Evans, B. W. Trotter, B. Cote and P. J. Coleman, Angew.
Chem., Int. Ed., 1997, 36, 2741–2744; (c) D. A. Evans, B. W. Trotter,
B. Cote, P. J. Coleman, L. C. Dias and A. N. Tyler, Angew. Chem., Int.
Ed., 1997, 36, 2744–2747; (d) D. A. Evans, B. W. Trotter, P. J. Coleman,
B. Cote, L. C. Dias, H. A. Rajapakse and A. N. Tyler, Tetrahedron,
1999, 55, 8671–8726; (e) J. Guo, K. J. Duffy, K. L. Stevens, P. I.
Dalko, R. M. Roth, M. M. Hayward and Y. Kishi, Angew. Chem.,
Int. Ed., 1998, 37, 187–192; (f) M. M. Hayward, R. M. Roth, K. J.
Duffy, P. I. Dalko, K. L. Stevens, J. Guo and Y. Kishi, Angew. Chem.,
Int. Ed., 1998, 37, 192–196; (g) A. B. Smith, III, V. A. Doughty,
Q. Lin, L. Zhuang, M. D. McBriar, A. M. Boldi, W. H. Moser, N.
Murase, K. Nakayama and M. Sobukawa, Angew. Chem., Int. Ed.,
2001, 40, 191–195; (h) A. B. Smith, III, Q. Lin, V. A. Doughty, L.
Zhuang, M. D. McBriar, J. K. Kerns, C. S. Brook, N. Murase and
K. Nakayama, Angew. Chem., Int. Ed., 2001, 40, 196–199; (i) A. B.
Smith, III, V. A. Doughty, C. Sfouggatakis, C. S. Bennett, J. Koyanagi
and M. Takeuchi, Org. Lett., 2002, 4, 783–786; (j) A. B. Smith, III, W.
Zhu, S. Shirakami, C. Sfouggatakis, V. A. Doughty, C. S. Bennett and
Y. Sakamoto, Org. Lett., 2003, 5, 761–764; (k) M. T. Crimmins and
D. G. Washburn, Tetrahedron Lett., 1998, 39, 7487–7490; (l) M. T.
Crimmins, J. D. Katz, L. C. McAtee, E. A. Tabet and S. J. Kirincich,
Org. Lett., 2001, 3, 949–952; (m) M. T. Crimmins and J. D. Katz,
Org. Lett., 2000, 2, 957–960; (n) M. T. Crimmins, J. D. Katz, D. G.
Washburn, S. P. Allwein and L. F. McAtee, J. Am. Chem. Soc., 2002,
124, 5661–5663; (o) J. L. Hubbs and C. H. Heathcock, J. Am. Chem.
Soc., 2003, 125, 12836–12843; (p) C. H. Heathcock, M. McLaughlin,
J. Medina, J. L. Hubbs, G. A. Wallace, R. Scott, M. M. Claffey, C. J.
Hayes and G. R. Ott, J. Am. Chem. Soc., 2003, 125, 12844–12849.
3 Formal total synthesis of altohyrtin C/spongistatin 2 by Nakata and
co-workers: T. Terauchi, T. Terauchi, I. Sato, W. Shoji, T. Tsukada,
T. Tsunoda, N. Kanoh and M. Nakata, Tetrahedron Lett., 2003,
44, 7741–7745; T. Terauchi, T. Tanaka, T. Terauchi, M. Morita, K.
Kimijima, I. Sato, W. Shoji, Y. Nakamura, T. Tsukada, T. Tsunoda,
G. Hayashi, N. Kanoh and M. Nakata, Tetrahedron Lett., 2003, 44,
7747–7751.
4 For previous communications of our work, see: (a) I. Paterson, R. M.
Oballa and R. D. Norcross, Tetrahedron Lett., 1996, 37, 8581–8584;
(b) I. Paterson and L. E. Keown, Tetrahedron Lett., 1997, 38, 5727–
5730; (c) I. Paterson and R. M. Oballa, Tetrahedron Lett., 1997,
38, 8241–8244; (d) I. Paterson, D. J. Wallace and K. R. Gibson,
Tetrahedron Lett., 1997, 38, 8911–8914; (e) I. Paterson, D. J. Wallace
and R. M. Oballa, Tetrahedron Lett., 1998, 39, 8545–8548; (f) I.
Paterson, D. Y.-K. Chen, M. J. Coster, J. L. Acena, J. Bach, K. R.
Gibson, L. E. Keown, R. M. Oballa, T. Trieselmann, D. J. Wallace,
A. P. Hodgson and R. D. Norcross, Angew. Chem., Int. Ed., 2001, 40,
4055–4060; (g) I. Paterson and M. J. Coster, Tetrahedron Lett., 2002,
43, 3285–3289; (h) I. Paterson, J. L. Acena, J. Bach, D. Y.-K. Chen
and M. J. Coster, Chem. Commun., 2003, 462–463; (i) I. Paterson
and M. J. Coster, in Strategy and Tactics in Organic Synthesis, ed.
M. Harmata, Elsevier, Oxford, 2004, vol. 4, ch. 8, pp. 211–245.
5 C. J. Cowden and I. Paterson, Org. React., 1997, 51, 1–200; I.
Paterson, C. J. Cowden, and D. J. Wallace, in Modern Carbonyl
Chemistry, ed. J. Otera, Wiley-VCH, Weinheim, 2000, pp. 249–297.
6 H. C. Brown, R. K. Dhar, K. Ganesan and B. Singaram, J. Org.
Chem., 1992, 57, 499–504.
=
=
45-C CHaHb), 4.89 (1H, br s, 45-C CHaHb), 4.84 (2H, br s,
13-C CH2), 4.79 (1H, dd, J = 11.0, 9.2 Hz, 41-CH), 4.48 (1H,
=
br t, J = 11.3 Hz, 11-CH), 4.41 (1H, d, J = 10.5 Hz, 25-OH),
4.35 (1H, m, 47-CH), 4.27 (1H, br t, J = 11.3 Hz, 3-CH), 4.02
(1H, br t, J = 11.1 Hz, 19-CH), 3.94 (1H, br m, 25-CH), 3.90
(1H, d, J = 5.0 Hz, 42-OH), 3.88 (1H, br d, J = 10.4 Hz, 33-
CH), 3.82 (1H, d, J = 10.3 Hz, 39-CH), 3.49 (2H, m, 43-CH +
21-CH), 3.30 (1H, d, J = 10.5 Hz, 38-CH), 3.27 (3H, s, 21-
OCH3), 3.23 (1H, d, J = 5.0 Hz, 47-OH), 3.17 (1H, td, J = 9.0,
4.9 Hz, 42-CH), 3.04 (1H, dq, J = 10.8, 7.0 Hz, 16-CH), 2.91
(1H, d, J = 10.8 Hz, 38-OH), 2.89 (1H, m, 14-CH), 2.83 (1H,
dd, J = 19.4, 10.0 Hz, 18-CHaHb), 2.77 (1H, br d, J = 13.9 Hz,
44-CHaHb), 2.62 (1H, br d, J = 18.1 Hz, 18-CHaHb), 2.59 (1H,
dd, J = 16.5, 1.6 Hz, 2-CHaHb), 2.51 (1H, dd, J = 16.5, 10.5 Hz,
2-CHaHb), 2.31 (3H, m, 46-CHaHb + 24-CHaHb + 12-CHaHb),
2.20 (1H, dd, J = 13.7, 6.1 Hz, 46-CHaHb), 2.03–2.12 (5H, m, 12-
CHaHb + 20-CHaHb + 22-CHaHb + 30-CHaHb + 44-CHaHb),
1.98 (3H, s, COCH3), 1.94 (2H, m, 34-CH + 40-CH), 1.85 (3H, s,
COCH3), 1.80 (2H, m, 4-CHaHb + 30-CHaHb), 1.67 (2H, m, 4-
CHaHb + 6-CHaHb), 1.54–1.59 (7H, m, 6-CHaHb + 8-CHaHb +
10-CHaHb + 24-CHaHb + 26-CH2 + 31-CHaHb), 1.47 (2H, m,
8-CHaHb + 32-CHaHb), 1.28 (1H, m, 10-CHaHb), 1.21 (2H, m,
31-CHaHb + 32-CHaHb), 1.18 (3H, d, J = 6.9 Hz, 16-CHCH3),
1.09 (1H, t, J = 12.1 Hz, 22-CHaHb), 1.06 (3H, s, 9-CCH3),
1.00 (3H, d, J = 6.9 Hz, 14-CHCH3), 0.91 (1H, ddd, J = 11.9,
11.9, 11.9 Hz, 20-CHaHb), 0.91 (3H, d, J = 7.0 Hz, 34-CHCH3),
0.77 (3H, d, J = 6.7 Hz, 40-CHCH3); 13C NMR: d (125 MHz,
CD3CN) 213.0, 172.9, 171.5, 170.0, 148.1, 143.9, 139.1, 139.0,
134.4, 133.0, 131.7, 127.6, 126.8, 116.3, 116.3, 114.6, 99.8, 99.2,
95.8, 81.3, 80.2, 78.6, 75.1, 73.8, 73.2, 72.6, 71.1, 70.3, 69.0, 67.0,
66.0, 64.5, 64.1, 62.4, 61.3, 55.6, 51.7, 47.3, 46.9, 45.0, 44.3, 44.1,
43.9, 40.6, 40.0, 39.3, 38.2, 37.6, 37.2, 36.4, 34.7, 34.4, 33.4, 32.3,
30.1, 27.9, 26.5, 21.7, 20.9, 13.7, 13.7, 12.6, 12.0; m/z: (+ESI)
1227 ([M + Na]+, 100), 734 (26), 576 (20), 445 (31), 413 (38), 381
(26).
Acknowledgements
7 P. L. Hall, J. H. Gilchrist and D. B. Collum, J. Am. Chem. Soc., 1991,
113, 9571–9574.
8 J. A. Dale, D. L. Dull and H. S. Mosher, J. Org. Chem., 1969, 34,
2543–2549; J. A. Dale and H. S. Mosher, J. Am. Chem. Soc., 1973,
95, 512–519; I. Ohtani, T. Kusumi, Y. Kashman and H. Kakisawa,
J. Am. Chem. Soc., 1991, 113, 4092–4096.
Financial support was provided by the EPSRC (GR/L41646),
EC (Marie Curie Fellowship to J.L.A.), Churchill College
(Research Fellowship to D.J.W.), Cambridge Commonwealth
Trust (M.J.C.), King’s College and Sim’s Fund, Cambridge
(D.Y.-K.C.). We thank Merck, AstraZeneca and Novartis
Pharmaceuticals for generous support, Dr Kenneth W. Bair,
Dr Frederick R. Kinder, Jr., Dr Peter T. Lassota and Dr Erik
F. Sorensen at Novartis for providing the biological data,21 and
Dr Anne Butlin (AZ) and Dr Nick Bampos (Cambridge) for
valuable assistance.
9 S. V. Ley, J. Norman, W. P. Griffith and S. P. Marsden, Synthesis,
1994, 639–666.
10 I. Paterson, C. J. Cowden, V. S. Rahn and M. D. Woodrow, Synlett,
1998, 915–917.
11 A similar result was observed by the Kishi group (ref. 2f ).
12 R. B. Woodward, K. Heusler, J. Gosteli, P. Naegeli, W. Oppolzer,
R. Ramage, S. Ranganathan and H. Vorbru¨ggen, J. Am. Chem.
Soc., 1966, 88, 852–853; G. Jou, I. Gonzalez, F. Albericio, P. Lloyd-
Williams and E. Giralt, J. Org. Chem., 1997, 62, 354–366.
References
1 For a full introduction, background and the synthesis of the AB-,
CD- and EF-subunits of altohyrtin A, see the preceding papers
in this series: (a) I. Paterson, M. J. Coster, D. Y.-K. Chen, R. M.
Oballa, D. J. Wallace and R. D. Norcross, Org. Biomol. Chem., 2005,
13 J. Inanaga, K. Hirata, H. Saeki, T. Katsuki and M. Yamaguchi, Bull.
Chem. Soc. Jpn., 1979, 52, 1989–1993.
1
14 See the electronic supplementary information for tabulated H and
13C NMR data and copies of spectra.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 4 3 1 – 2 4 4 0
2 4 3 9

View Article Online
15 M. Kobayashi, S. Aoki, H. Sakai, K. Kawazoe, N. Kihara, T. Sasaki
and I. Kitagawa, Tetrahedron Lett., 1993, 34, 2795–2798.
16 G. R. Pettit, Z. A. Chicacz, F. Gao, C. L. Herald, M. R. Boyd,
J. M. Schmidt and J. N. A. Hooper, J. Org. Chem., 1993, 58, 1302–
1304.
17 We thank Professors Pettit and Kishi for kindly providing compari-
son NMR spectra.
19 F. M. Uckun, C. Mao, A. O. Vassilev, H. Huang and S.-T. Jan, Bioorg.
Med. Chem. Lett., 2000, 10, 541–545; H. Huang, C. Mao, S.-T. Jan
and F. M. Uckun, Tetrahedron Lett., 2000, 41, 1699–1702.
20 A C50 chlorine substituent (as in altohyrtin A/spongistatin 1) confers
somewhat greater cell growth inhibitory activity than the des-chloro
version (altohyrtin C/spongistatin 2), see: J. Pietruszka, Angew.
Chem., Int. Ed., 1998, 37, 2629–2636.
18 (a) A. B. Smith and Q. Lin, Bioorg. Med. Chem. Lett., 1998, 8, 567–
568; (b) A. B. Smith, R. M. Corbett, G. R. Pettit, J.-C. Chapuis, J. M.
Schmidt, E. Hamel and M. K. Jung, Bioorg. Med. Chem. Lett., 2002,
12, 2039–2042.
21 The biological assays were performed by Novartis Pharmaceuticals
Corporation, Summit, New Jersey.
22 M. C. Alley, C. M. Pacula-Cox, M. L. Hursey, L. R. Rubenstein and
M. R. Boyd, Cancer Res., 1991, 51, 1247–1256.
2 4 4 0
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 4 3 1 – 2 4 4 0