Hypervalent iodine(III)-mediated tandem oxidative reactions: Application for the synthesis of bioactive polyspirocyclohexa-2,5-dienones

Article abstract of DOI:10.1016/j.tet.2010.04.135

In 2002, we reported the first total syntheses of potent antimalarial natural products, the aculeatins, employing the concept of tandem oxidative reactions mediated by hypervalent iodine(III) reagent to access to polyspirocyclohexa-2,5-dienone cores in ve

Full text of DOI:10.1016/j.tet.2010.04.135

Tetrahedron 66 (2010) 5863e5872
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Tetrahedron
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Hypervalent iodine(III)-mediated tandem oxidative reactions: application for the
synthesis of bioactive polyspirocyclohexa-2,5-dienones
*
Mariam Traoré, Soumeth Ahmed-Ali, Marine Peuchmaur, Yung-Sing Wong
Département de Pharmacochimie Moléculaire, Université de Grenoble, CNRS UMR 5063, CNRS ICMG FR 2607, bâtiment André Rassat, 470 rue de la Chimie, F-38 041 Grenoble Cedex
9, France
a r t i c l e i n f o
a b s t r a c t
Article history:
In 2002, we reported the first total syntheses of potent antimalarial natural products, the aculeatins,
employing the concept of tandem oxidative reactions mediated by hypervalent iodine(III) reagent to
access to polyspirocyclohexa-2,5-dienone cores in very concise manner. Efforts in this field have allowed
to identify cyclohexa-2,5-dienone group as a new potent class of pharmacophoric group for treating
malaria disease. This article sums up recent contributions devoted to the synthesis of complex and di-
verse polycyclic structures using the concept of tandem oxidative activations, with p-phenol as co-re-
actant. More recently, we have explored a variant of the new tandem oxidative reactions that employs
a catalytic amount of 4-iodotoluene in the presence of mCPBA as the stoichiometric oxidant (Kita’s
procedure).
Received 31 March 2010
Received in revised form 29 April 2010
Accepted 29 April 2010
Available online 6 May 2010
Keywords:
Tandem reactions
Hypervalent iodine
Phenolic oxidation
Furanyl-2-methanol oxidation
Cyclohexa-2,5-dienone
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
Hypervalent phenyliodine reagents have emerged as oxidants of
choice for mediating various transformations in an efficient man-
ner.1 These mild organic oxidants possess low toxicity, thus pro-
viding a sustainable alternative to reagents based on harmful heavy
metals, such as lead, mercury and thallium. The advent of tech-
niques for the in situ generation of catalytic amounts of hypervalent
iodine, by the use of appropriate co-oxidants or under anodic
conditions, is realizing the promise of a green oxidizing agent2 and
it has culminated in the development of highly enantioselective
oxidations.3
Trivalent iodine reagents, such as phenyliodine(III) diacetate
(PhI(OAc)2, PIDA or DIB) or phenyliodine(III) bis(trifluoroacetate)
(PhI(OCOCF3)2, PIFA or BTI) (Fig. 1) are stable, commercially avail-
able, easily handled products, which are soluble in a wide range of
organic solvents and are safer than pentavalent iodine reagents,
such as 2-iodoxybenzoic acid (IBX) or Dess/Martin periodane. Ox-
idation with PhI(OAc)2 or PhI(OCOCF3)2 releases only iodobenzene
and weak nucleophilic carboxylic acids in the reaction medium
(Scheme 1). Hypervalent phenyliodine(III) reagents convert phe-
nols, such as 1 into a presumed electrophilic intermediate 3,
probably by the initial removal of one electron and one proton,
Figure 1. Hypervalent phenyliodine(III) reagents.
followed by the removal of a second electron (Scheme 1, Eq. 1). A
great deal of valuable synthetic chemistry relies on the capture of 3
with appropriate nucleophiles,4 that could be an oxygen, nitrogen,
fluorine or carbon sp2 atom, in inter-or intra-molecular fashion to
yield 4.5 This cyclohexa-2,5-dienone functional group has the
ability to react further as Michael acceptor or dienophile. In-
terestingly, an extra nucleophilic group arises from p-quinol
(Nu¼OH)
and
4-aza-substituted
cyclohexa-2,5-dienone
(Nu¼NHCOR3).
For some years, we have been involved in the synthesis of bi-
ologically active natural products in which the cyclohexa-2,5-
dienone moiety was identified as a new antimalarial pharmaco-
phoric group (vide infra).6 By anticipating the need for producing
larger libraries in drug optimisation process, we planned to develop
synthetic strategies that focus on ‘one pot’ transformations, espe-
cially those involving tandem or/and cascade reactions,
* Corresponding author. Tel.: þ33 476 63 5310; fax: þ33 476 63 5295; e-mail
address: yung-sing.wong@ujf-grenoble.fr (Y.-S. Wong).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.04.135

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M. Traoré et al. / Tetrahedron 66 (2010) 5863e5872
Scheme 1. Simple functional groups activated by hypervalent iodine(III) reagent.
maximizing the opportunity to make multiple bonds within a sin-
gle synthetic step. No doubt that the benefices in term of atom,
time, resources economies can make quite an impact on the ac-
cessibility of future libraries. In addition, tandem reaction processes
provide a unique opportunity to bring distinct and unstable species
to react together on the same reaction time scale, allowing trans-
formations that would be hardly possible with other reaction
conditions.
This article aims at exploring the effectiveness and the limita-
tions of tandem oxidative reactions mediated by hypervalent
phenyliodine(III) reagent, with p-phenol as co-reactant. One im-
portant challenge to face in this approach is the fine-tuning re-
activity of distinct transient species, which can have different
oxidation states. A comparison can be made with the successful use
of SmI2 for the tandem reductive reaction approach.7 Indeed, in the
course of phenolic oxidation mediated by hypervalent(III) iodine
reagent, many reactive facets of an oxidized phenol 1 can be
revealed like the radical intermediate 2, the highly reactive elec-
trophilic species 3, or the cyclohexa-2,5-dienone product 4. The
difficulty rests on the identification of the best intramolecular
partner to be paired off with the phenolic group. A few groups meet
certain advantageous criteria like efficient activation by hyper-
valent iodine(III) reagent in compatible solvents with the phenolic
oxidation, the requirement of none or at least minimum additive
and the ability to be run within a reasonable reaction time (Scheme
1, Eq. 2e7).
For furanyl-2-methanols 5 (Eq. 2), good reaction condition for its
conversion into the corresponding 5,6-dihydropyranone 8 was
reported by using PhI(OAc)2 in a mixture of (CF3)2CHOH/buffer
solution (1:1) within a few minutes.8 Like the phenolic oxidation,
this ring enlargement sequence involves different oxidation states.
A single electron transfer (SET) gave rise to a radical cation 6.9 This
latter underwent a second mono-electronic oxidation allowing
a rearrangement to occur and led to the formation of an electro-
philic species 7. The final trapping by a hydroxyl group afforded 8.
Other highly reactive electrophilic species can also be derived from
very simple functional groups (Eq. 3e5). The oxidation of primary
carboxamides 9 can rearrange into reactive isocyanates 10. A sub-
sequent nucleophilic addition would give either carbamate or urea
derivatives 11 (Eq. 3). Other possible partners involve the precursor
12, which is able to give N-acyl-nitrenium ions 13 under oxidative
condition10 (Eq. 4), and the conversion of
a-acyl sulphide 14 into

M. Traoré et al. / Tetrahedron 66 (2010) 5863e5872
5865
the corresponding sulphonium salt 15 (Eq. 5). The robust protecting
group dithioacetal 16 can be easily removed to form carbonyl group
17 (Eq. 6).11 Finally, the oxidation of aldoxime 18 (Eq. 7) can afford
the 1,3-dipolar nitrile oxide 19, amenable to make a subsequent
[3þ2] cyclization (vide infra).12
The resulting intermediate 21 underwent spontaneous intra-
molecular [3þ2] dipolar cyclization to yield the fused polycycles
22a,b in a highly diastereoselective manner. These authors pointed
out that both activating processes were asynchronous, cyclohexa-
2,5-dienone being formed almost instantaneously, whereas oxi-
dation of aldoxime to nitrile oxides took about 45e60 min for
complete conversion. This sequence of events was essential to en-
sure good yield by the gradual intramolecular trapping of the na-
scent nitrile oxide with the more stable cyclohexa-2,5-dienone
intermediate group.
This elegant tactic has been recently exemplified by the works of
Sorenson’s group in which the tandem oxidative reactions was
applied for the compound 23 bearing both phenol and aldoxime
functional groups (Scheme 3). The oxidation of 23 with PhI(OAc)2 in
fluorous solvent gave the intermediate 24, which then cyclized to
yield selectively 25, resulting in the formation of an advanced in-
termediate for the synthesis of (þ)-cortistatin A.14
The tandem, cascade or domino terminologies are used in this
article according to the Tietze’s definitions (Fig. 2).13 For an intra-
molecular reaction, tandem reactions are restricted to two or more
reactions occurring on the same molecule in isolation of one an-
other, whereas only one initiating process should be considered for
cascade or domino reaction. In the context of tandem reactions,
once the simultaneous activations have occurred, the reactions can
also further evolve to cascade processes.
Figure 2. Each yellow flash means a chain-initiating process.
2. Ciufolini’s tandem phenolic/aldoxime oxidative activations
Scheme 3. Application of tandem phenolic/aldoxime oxidation reactions for total
synthesis.
It was only recently demonstrated by Ciufolini and co-workers
that phenol and aldoxime groups are compatible partners in tan-
dem oxidative reactions (Scheme 2).12 The phenolic oxidation
condition that allowed the trapping of an external nucleophile
coming from the reaction medium (MeOH or MeCN) was suitable
for the tandem intramolecular conversion of aldoxime into the
nitrile oxide group.
3. Tandem phenolic/thioacetal oxidative activations
A few years ago, we reported the first total synthesis of
(ꢀ)-aculeatins A and B (Fig. 3) using a tandem phenolic/thioacetal
oxidation activations as key final step (Scheme 4).15 Since their first
isolation in 2000 from the rhizome of Amomum aculeatum by
Heilmann and co-workers,16 this class of natural product has in-
spired numerous synthetic studies due to their challenging poly-
spirocyclic structure17, their good cytotoxic activity, and their
potent biological property as antimalarial agent.16a The syntheses of
optically pure aculeatins A and B and their improved bioactive
synthetic analogues (ꢀ)-26 and 27, which hold the pharmacophore
group twice have allowed to confirm and clearly identify the
cyclohexa-2,5-dienone as an important functional group re-
sponsible for the biological activity.6 In addition, Kinghorn and co-
workers showed that aculeatin A was also active against cancer cell
lines (MCF-7, ED50¼0.2
m
M).18 Interestingly, a closely related nat-
ural product, EBC-23, was recently identified by Williams and co-
workers to be potent anticancer agent.19 This product shares with
aculeatins many structural similarities, such as a lipophilic side
chain, a spiroacetal moiety and a terminal cycle bearing at least one
electron poor carbonecarbon double bond. Williams argued that
the long aliphatic chain could be useful to control metabolism and
enable cell membrane permeability.
Hence, we have developed several synthetic approaches based
on tandem phenolic/thioacetal oxidation reactions. Our goal was to
Scheme 2. Ciufolini’s pioneer work in tandem phenolic/aldoxime oxidation reactions.

5866
M. Traoré et al. / Tetrahedron 66 (2010) 5863e5872
At this stage, when carrying out the tandem oxidative reactions
on 31 with PhI(OCOCF3)2 in wet MeCN at 0 ꢁC, the removal of thi-
oacetal was immediate, very likely at comparable rate to phenolic
oxidation. Thus, initial spiro-oxocarbenium species 32 might arise
from the trapping of phenoxenium ion by the newly deprotected
carbonyl group, which then in turn triggers the second spi-
roannulation to give aculeatins. This is very likely the way that
nature makes such compounds (biomimetic approach). This re-
action works equally well in Wu’s buffer condition that prevents
conversion of aculeatin B into aculeatin A by thermodynamic
equilibrium.
In the same vein, the polyphenolic compound 34 was obtained
in only two steps starting from 28 (Scheme 5).6 In the key step,
three tandem oxidation reactions mediated by PhI(OCOCF3)2 were
performed on the same molecule. We observed instantaneous
formation of final products by TLC. However, we left the reaction
running for 18 h at rt so that, after thermodynamic equilibrium
catalyzed by the acidic medium, two major polyspirocyclic prod-
ucts 36 and 37 were isolated. Remarkably, only one step converts
them into highly potent bioactive antimalarial agents 26 and 27.
Again, all these oxidative functional activations seem to occur at the
same rate level. We postulate that the intermediate 35 may exist,
with one oxidized phenol acting as strong electrophilic species
(spiro-oxocarbenium ion), whereas the second one would intercept
water to give the nucleophilic p-quinol, bringing out complemen-
tary partners to raise the final polyspirocyclic structures.
Figure 3. Natural and bioactive products, the aculeatins and EBC-23, and improved
bioactive analogues (ꢀ)-26 and 27.
Scheme 5. Triple tandem oxidative reactions to convert linear precursor 34 into
complex polyspirocyclic products.
Scheme 4. Tandem phenolic/thioacetal oxidative activation for the synthesis of
aculeatins.
4. Tandem phenol silyl ether/thioacetal oxidations and
silyloxy deprotection reactions
keep intact the cyclohexa-2,5-dienone moiety (pharmacophore)
and efforts have been mainly focused on triggering poly-
spiroannulation process initiated by phenolic oxidation (cascade
reaction). In our strategy, the thioacetal protecting group plays
a pivotal role. As a result, the arsenal of alkylating or reducing
agents can be used enabling key intermediates, such as 31 to be
assembled in racemic15 or enantiopure form17j in only three or five
steps, respectively, starting from the common precursor 28.
To construct the spirocyclic core of aculeatin C (Scheme 6), a few
years ago, we reported an approach that takes advantage of an
existing carbonyl group lacking in aculeatins A and B.17e This allows
to install on the synthetic precursor 43 a Michael acceptor acting as
terminal acceptor for the polyspiroannulation process. On the op-
posite side of 43, the phenolic group needs to be efficiently oxidized
into p-quinol in order to play the role of nucleophilic counterpart.

M. Traoré et al. / Tetrahedron 66 (2010) 5863e5872
5867
5. Study of a new approach by tandem phenolic/furanyl-2-
methanol oxidative activations
Looking at aculeatin and EBC-23 structures (see Fig. 3), and being
awarethatfightingagainstmalarialrequirestheaccesstoinexpensive
bioactive molecules, we though about developing the easy accessible
new polyspirocyclic compound 49 (Scheme 7) that can beregarded as
a hybrid molecule21 derived from these two natural products. This
product should arise from the intermediate 47 according to tandem
phenolic/furanyl-2-methanol oxidative reactions. The combination
on the same molecule of these two aromatic rings is quite challenging
since both can generate different reactive species at different oxida-
tion states. The furanyl group is polysubstituted at 2, 4 and 5 positions
thus preventing competitive Friedel/Craft additions or dimerisation
reactions by SET intermediates.
phenolic
oxidation
furanyl-2-methanol
O
oxidation
OH
HO
1 step to form ( )-48
mediated by
2
O
O
PhI(OCOR)2 ?
O
R1O
5
4
HO
O
( )-48: R1 = H
( )-49: R1 = -OCO(CH2)12CH3
47
Scheme 7. Adirectaccess toa newanalogue 49 starting froma bis-aromatic molecule 47.
We started our synthesis by converting the carboxylic acid 5022
into acyl chloride (Scheme 8). This latter reacted with Meldrum’s
acid 51 to give 52. The corresponding
by refluxing 52 in anhydrous ethanol for 3 h. Garcia/Gonzalez’s
reaction with DL-glyceraldehyde dimer 54 and -ketoester 53 using
b-ketoester 53 was obtained
b
CeCl3$7H2O as catalyst gave the desired adduct 55 in moderate
yield.23 Finally, LiALH4 reduction provided the key intermediate 47.
Scheme 6. Synthesis of aculeatin C central core.
This conversion is best performed starting from phenol silyl
ether.5d This new approach opens up prospects to explore other
functional groups able to be activated by PhI(OCOR)2 reagents. The
synthesis started by treating 28 with an excess of enolate of tert-
butyl acetate to give the b-ketoester 38. This latter was reduced by
NaBH4 to yield 39, which then underwent silylation on both phenol
and secondary alcohol to give 40. DIBAL-H selectively reduced the
ester to give aldehyde 41. Wittig reaction proceeded with
the phosphonium acetate reagent 4220 in reflux toluene to yield the
desired intermediate 43. When PhI(OCOCF3)2 was added to 43 in
the optimized condition (acetone/H2O, 10:1) at rt, the overall pro-
cess turned out to be slow (18 h to run into complete conversion).
Interestingly, the TFA generated by the reagent allowed the smooth
in situ deprotection of silyl secondary alcohol. However, addition of
TFA (1 equiv) with PhI(OCOCF3)2 was the best condition to obtain
45 and 46.
Scheme 8. Synthesis of key precursor 47.
When 47 was subjected to PhI(OAc)2 or PhI(OCOCF3)2 oxidation
under various solvent conditions ((CF3)2CHOH/Buffer,8 CF3CH2OH,
CH2Cl2, MeCN, acetone/H2O, THF), the desired product was not
detected. Instead, a complex mixture was formed in every case. At
this stage, it seems clear that activating both aromatic groups at the
same time leads to unwanted reaction behaviours. We then decided
to deconvolute the synthesis into two steps (Schemes 9 and 10), in
order to localize the problematic events. mCPBA is the reagent of

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M. Traoré et al. / Tetrahedron 66 (2010) 5863e5872
was also contaminated by other inseparable products (data not
shown). Addition of catalytic amount of TFA seems to decompose
56 rapidly. This can explain why PhI(OCOCF3)2 in the best solvent
condition gave a very poor yield of 48 (2%).
Having selected the solvent condition CH2Cl2/(CF3)2CHOH (1:1)
and the oxidizing reagent (PhI(OAc)2), we decided to run a ‘one pot’
transformation, by adding first the mCPBA (Scheme 11). Once the
conversion of 47 to 56 was total (monitored by TLC), PhI(OAc)2 was
added. Again, we obtained a surprising yield of 18% for 48 (starting
from 47, the overall yield for the two steps sequences to give 48 was
55%). At this stage, it is worthy to note that the presence of the by-
product m-chlorobenzoic acid burdens the purification of this polar
and likely fragile product 48. The repeated purification by silica gel
or alumina chromatography may explain in part the lowering in
yield. Still, the presence of mCPBA or m-chlorobenzoic acid might
also be troublesome for the PhI(OAc)2 reactivity.
Scheme 9. Selective oxidation of furanyl-2-methanol with mCPBA.
Scheme 10.
choice since it can easily convert furanyl-2-methanol group into
5,6-dihydropyranone without reacting with phenol. We observed
that the conversion of 47 into 56 occurs in generally good yields. A
polar solvent needs to be used or co-added to make 47 soluble in
the reaction medium (Scheme 9).
Having 56 in hand, we set out to study the second step using PhI
(OAc)2 as oxidizing reagent, in order to optimize the trapping of the
intramolecular hemi-acetal group by the oxidized phenol species
(Scheme 10, Table 1). Unexpectedly, this reaction was clearly sol-
vent dependant and the use of the fluorous solvent (CF3)2CHOH has
Scheme 11. One pot procedure with PhI(OAc)2 introduced as second reagent.
We decided to explore the in situ generation of a catalytic
amount of hypervalent iodine(III) reagent using mCPBA as co-oxi-
dants.24 This approach should gradually consume reagent as this
latter is being formed, ensuring a low concentration of hypervalent
iodine(III) species. In this way, we hope to be able to mediate more
selective tandem reactions. According to Kita’s work, we selected 4-
iodobenzene 57 as catalyst24a (Scheme 12). To begin with this study,
we started with the ‘one pot’ sequential version, namely first ad-
dition of mCPBA (3 equiv) to convert all 47 into the 5,6-dihy-
dropyranone 56, and then addition of the catalyst 57 (Table 2,
entries 1e4).
Table 1
Various solvent conditions for the phenolic oxidation reaction to convert 56 to 48
Reagent
Solvent
(ꢀ)-48 Yield %
PhI(OAc)2
PhI(OAc)2
PhI(OAc)2
PhI(OAc)2
PhI(OAc)2
PhI(OCOCF3)2
CH2Cl2
CH2Cl2/MeCN(3:1)
THF
Acetone
CH2Cl2/(CF3)2CHOH (1:1)
CH2Cl2/(CF3)2CHOH (1:1)
<1
<1
<1
4
74
2
Scheme 12. ‘One pot’ transformation with mCPBA with 10 mol % of 4-iodotoluene 57.
a dramatic beneficial effect (Table 1). This solvent condition allows
for the conversion of phenol 56 into the desired polyspirocycle 48
in good yield (74%), whereas conventional solvents failed in giving
less than 4% yield. Use of the more nucleophilic and less hindered
CF3CH2OH solvent also gave 48 (as shown by NMR) but this latter
Under Kita’s condition (entry 1) that involves the use of TFA,
only traces of 48 were obtained, presumably due to the instability
of 56 with strong Brønsted acid. Without TFA (entry 2), the reaction
proceeded quite well as shown by TLC and permitted the isolation
Table 2
Entry
Solvent
Procedurea
(ꢀ)-48 Yield %
1
2
3
4
5
CH2Cl2/(CF3)2CHOH (1:1)
CH2Cl2/(CF3)2CHOH (1:1)
Acetone
Acetone/H2O (6:1)
CH2Cl2/(CF3)2CHOH (1:1)
mCPBA, 1 h, 0 ꢁCþ1 h, rt, then addition of 57 at rtþTFA (1 equiv), then 15 min at rt
mCPBA, 1 h, 0 ꢁCþ1 h, rt, then addition of 57 at rt, then 15 min at rt
mCPBA, 1 h, 0 ꢁCþ1 h, rt, then addition of 57 at rt, then 48 h at rt
mCPBA, 1 h, 0 ꢁCþ1 h, rt, then addition of 57 at rt, then 48 h at rt
mCPBAþ57, 1 h, rt
<1
22
7
<1
25
a
The reaction was run until disappearance of 47 or 56.

M. Traoré et al. / Tetrahedron 66 (2010) 5863e5872
5869
of 48 in 22% yield. At this stage, the purification was even more
difficult due to the use of a larger amount of mCPBA. A non fluorous
solvent like acetone gave a slower reaction and a lower yield (en-
tries 3 and 4). Interestingly, when the catalyst and mCPBA were
added simultaneously (entry 5), the reaction worked equally well
to give 48 in 25% yield. We monitored this reaction by TLC and were
able to see the formation of 56 at first, which was gradually con-
sumed to give 48. Very likely, mCPBA oxidation runs faster than the
catalytic amount of hypervalent phenyliodine (III) species can drive
phenolic oxidation into completion. It seems that the beneficial use
of Kita’s procedure cannot be attributed to the sole role of catalytic
hypervalent iodine reagent in these tandem oxidative reactions.
Finally, 48 underwent acylation reaction (Scheme 13) to put the
lipophilic side chain under the same reaction condition that led to
the formation of 26 and 27 from 36 and 37, respectively (see
Scheme 5). The lower yield obtained for 49 (38%) may reflect
somewhat the relative stability of 48.
NERMAG R1010C (EI, CI, FAB), ZQ Waters (ESI) and Autoflex Bruker
(MALDI) spectrometers. High resolution mass spectra were carried
out on a Micromass GCT spectrometer (EI) or a Micromass ZAB-
SPEC-TOF spectrometer (ESI, FAB) by CRMPO at the University of
Rennes.
6.2. Synthesis of 4-hydroxy-2-(2-oxopropyl)-1,7-dioxadispiro
[5.1.5.2]pentadeca-9,12-dien-11-one (45) and (46)
6.2.1. tert-Butyl 4-(2-(4-hydroxyphenethyl)-1,3-dithian-2-yl)-3-ox-
obutanoate (38). To
a
stirred solution of HNiPr2 (4,3 mL,
30.48 mmol) in dry THF (30 mL) was slowly added a solution of n-
BuLi 2.5 M in hexane (12.2 mL) at 0 ꢁC under argon atmosphere.
After 20 min, tert-butyl acetate (4.1 mL, 30.8 mmol) was added at
ꢂ78 ꢁC. After 30 min, a solution of 28 (1.99 g, 6.10 mmol) in dry THF
(15 mL) was added. After 30 min at ꢂ78 ꢁC then 30 min at 0 ꢁC, the
reaction was quenched by addition of AcOH (14 mL) then treated
with a saturated aqueous solution of K2CO3 (30 mL). The organic
phase was extracted with EtOAc, dried over MgSO4 and concen-
trated. The residue was subjected to silica gel column chromatog-
raphy (cyclohexane/EtOAc 85:15) to give 38 (1.94 g, 80%) as a pale
yellow oil; Rf (cyclohexane/EtOAc 7:3) 0.37; IR nmax (film, cmꢂ1
3447, 3406, 1728, 1709, 1514, 1258, 1150; UV (MeOH) 286, 277, 250,
224, 207 nm; 1H NMR (400 MHz, CDCl3)
1.47 (s, 9H, OC(CH3)3),
)
d
1.86e2.06 (m, 2H, SCH2CH2), 2.25e2.33 (m, 2H, ArCH2CH2),
2.68e2.75 (m, 2H, ArCH2), 2.77e2.93 (m, 4H, 2ꢃSCH2), 3.25 (s, 2H,
CH2CO), 3.53 (s, 2H, COCH2CO), 6.77 (d, J¼8.4 Hz, 2H, 2ꢃCHAr), 7.03
Scheme 13. Synthesis of the lipophilic analogue (ꢀ)-49.
(d, J¼8.4 Hz, 2H, 2ꢃCHAr); 13C NMR (100 MHz, CDCl3)
d 24.8
(SCH2CH2), 26.3 (2ꢃSCH2), 28.0 (OC(CH3)3), 29.7 (ArCH2), 41.0
(ArCH2CH2), 49.4 (CH2CO), 49.9 (SCS), 52.4 (COCH2CO), 82.6 (OC
(CH3)3), 115.4 (2ꢃCHAr), 129.5 (2ꢃCHAr), 132.9 (CAr), 154.2 (CAr),
166.7 (COOtBu), 200.0 (C]O); MS (EI) m/z (%) 396 [M]þ (18), 233
(100); HRMS (EI) m/z found 396.1422. C20H28O4S2 requires
396.1429.
In closing, hypervalent phenyliodine(III) reagent is an efficient
promoter that enable a variety of intramolecular oxidation activa-
tions to occur selectively. The combination of these reactive and
transient species can be exploited to make them to react and
converge for assembling complex and diverse molecular structures
in a very concise way. In addition, we are exploring the catalytic
version to overcome cases unresolved by the use of stoichiometric
amount of hypervalent phenyliodine(III) reagent in tandem oxi-
dative activations process. Undoubtedly, the tandem oxidative re-
actions mediated by hypervalent iodine(III) reagents will disclose
new attractive applications for the synthesis of complex natural
products in near future.
6.2.2. (ꢀ)-tert-Butyl 3-hydroxy-4-(2-(4-hydroxyphenethyl)-1,3-di-
thian-2-yl)butanoate ((ꢀ)-39). To a stirred solution of 38 (3.47 g,
8.75 mmol) in MeOH (70 mL) was slowly added NaBH4 (0.66 g,
17.50 mmol) at 0 ꢁC. After 15 min the reaction mixture was con-
centrated. The residue was dissolved in H2O and EtOAc. The organic
phase was dried over MgSO4 and concentrated. The residue was
subjected to silica gel column chromatography (cyclohexane/EtOAc
85:15) to give (ꢀ)-39 (3.00 g, 86%) as a colourless oil; Rf (cyclo-
hexane/EtOAc 7:3) 0.28; IR nmax (film, cmꢂ1) 3418, 3368, 3331, 2976,
2936, 1720, 1514, 1368, 1265, 1240, 1154; UV (MeOH) 285, 279, 249,
6. Experimental
6.1. General
225, 208 nm; 1H NMR (400 MHz, CDCl3)
d 1.46 (s, 9H, OC(CH3)3),
All reagents were used as purchased from commercial suppliers.
Solvent was purified by conventional methods prior to use. For
reactions performed under anhydrous conditions, glassware was
oven-dried and reactions were performed under argon atmo-
sphere. Buffer solution pH 7 (phosphate compound) was purchased
by Roth (Art. Nr. A518.3). mCPBA (70e75%, balance with 3-chlor-
obenzoic acid and water) was purchased by Acros Organics and
used as such. Reactions were monitored by thin-layer chromatog-
raphy on precoated aluminium sheets (Merck, Silica gel 60, F254 and
Macherey/Nagel, Aluminium oxide N/UV254). Flash column chro-
matography was performed on silica gel: Macherey/Nagel 60 M,
0.04e0.063 mm (230e400 mesh), or on alumina: MP Alumina,
activity IIeIII (0.05e0.2 mm). 1H and 13C NMR spectra were recor-
ded at rt in deuterated solvents on a Bruker Avance 400 spec-
1.86e2.08 (m, 3H, SCH2CH2, CHHaCHOH), 2.11e2.30 (m, 2H,
ArCH2CH2), 2.37 (dd, J¼15.2, 8.8 Hz, 1H, CHHbCHOH), 2.42 (dd,
J¼15.6, 4.8 Hz, 1H, CHHaCOO), 2.52 (dd, J¼15.6, 7.6 Hz, 1H,
CHHbCOO), 2.62e2.97 (m, 6H, ArCH2, 2ꢃSCH2), 4.41e4.49 (m, 1H,
CHOH), 6.76 (d, J¼8.0 Hz, 2H, 2ꢃCHAr), 7.03 (d, J¼8.0 Hz, 2H,
2ꢃCHAr); 13C NMR (100 MHz, CDCl3)
d 24.9 (SCH2CH2), 26.1, 26.3
(2ꢃeSCH2e), 28.2 (eOC(CH3)3), 29.7 (ArCH2), 41.9 (ArCH2CH2), 43.5
(CH2COO), 44.0 (CH2CHOH), 51.9 (SCS), 65.9 (CHOH), 81.5 (eOC
(CH3)3), 115.5 (2ꢃCHAr), 129.5 (2ꢃCHAr), 133.2 (CAr), 154.4 (CAr),
171.6 (COO); MS (EI) m/z (%) 398 [M]þ (13), 107 (100); HRMS (EI) m/
z found 396.1569. C20H28O4S2 requires 396.1586.
6.2.3. (ꢀ)-tert-Butyl 3-(tripropylsilyloxy)-4-(2-(4-(tripropylsilyloxy)
phenethyl)-1,3-dithian-2-yl)butanoate ((ꢀ)-40). To a stirred solu-
tion of (ꢀ)-39 (1.31 g, 3.29 mmol) in dry DMF (12 mL) were added
imidazole (6 equiv) and triisopropylsilyl chloride (3 equiv) at 0 ꢁC.
After stirring for 18 h, a saturated aqueous solution of NH4Cl was
added. The organic phase was extracted with Et2O, dried over
MgSO4 and concentrated. The residue was subjected to silica gel
column chromatography (cyclohexane/EtOAc 95:5) to give (ꢀ)-40
trometer. Chemical shifts
d are given relative to TMS as internal
standard or relative to the solvent. IR spectra were collected on
a Bruker Vector 22 spectrometer. UV spectra were obtained on
a ThermoSpectronic Helios Gamma UV/Vis spectrophotometer in
MeOH. Optical rotations were recorded on a Perkin/Elmer 341
polarimeter. Mass spectra (low resolution) were recorded with

5870
M. Traoré et al. / Tetrahedron 66 (2010) 5863e5872
(2.22 g, 95%) as a colourless oil; Rf (cyclohexane/EtOAc 9:1) 0.78; IR
nmax (film, cmꢂ1) 3423, 2961, 1721, 1640, 1509, 1258, 1154, 1063; UV
CDCl3)
d
16.7e18.5 (6ꢃSiCH2CH2CH3), 25.1 (SCH2CH2), 26.2, 26.4
(2ꢃSCH2), 26.7 (COCH3), 30.3 (ArCH2), 41.7 (ArCH2CH2), 42.2
(CH2CH]CH), 46.0 (CH2CHOSi), 52.5 (SCS), 68.7 (CHOSi), 119.8
(2ꢃCHAr), 129.3 (2ꢃCHAr), 133.9 (CH]CHC]O), 134.3 (CAr), 144.3
(CH]CHC]O), 153.8 (CAr), 198.1 (C]O); MS (ESIþ) m/z (%) 701
[MþNa]þ (15), 679 [MþH]þ (100); HRMS (ESIþ) m/z found
701.3888. C37H66O3S2Si2Na requires 701.3890.
(MeOH) 283, 236, 212 nm; 1H NMR (400 MHz, CDCl3)
d 0.56e0.64
(m, 6H, 3ꢃSiCH2CH2), 0.69e0.75 (m, 6H, 3ꢃSiCH2CH2), 0.93 (t,
J¼7.2 Hz, 9H, 3ꢃSi(CH2)2CH3), 0.97 (t, J¼7.2 Hz, 9H, 3ꢃSi(CH2)2CH3),
1.29e1.45 (m, 12H, 6ꢃSiCH2), 1.46 (s, 9H, OC(CH3)3), 1.88e2.03 (m,
2H, SCH2CH2), 2.10 (dd, J¼15.2, 7.2 Hz, 1H, CHHaCHOSi), 2.18e2.24
(m, 2H, ArCH2CH2), 2.37 (dd, J¼15.2, 4.0 Hz, 1H, CHHbCHOSi), 2.49
(dd, J¼14.8, 4.8 Hz, 1H, CHHaCOO), 2.56 (dd, J¼14.8, 7.6 Hz, 1H,
CHHbCOO), 2.71e2.93 (m, 6H, ArCH2, 2ꢃSCH2), 4.44e4.52 (m, 1H,
CHOSi), 6.76 (d, J¼8.4 Hz, 2H, 2ꢃCHAr), 7.04 (d, J¼8.4 Hz, 2H,
6.2.6. (ꢀ)-(2R,4R,6R)-4-Hydroxy-2-(2-oxopropyl)-1,7-dioxadispiro
[5.1.5.2]pentadeca-9,12-dien-11-one ((ꢀ)-45) and (ꢀ)-(2R,4S,6R)-4-
hydroxy-2-(2-oxopropyl)-1,7-dioxadispiro[5.1.5.2]pentadeca-9,12-
dien-11-one ((ꢀ)-46). To a stirred mixture of (ꢀ)-43 (308 mg,
0.45 mmol) in acetone/H2O (10:1; 15.4 mL) was injected TFA
(37 mL) followed by the addition of solid PhI(OCOCF3)2 (1.17 g,
6 equiv) in one portion in darkness. The mixture was stirred for 18 h
at rt and was quenched with a saturated solution of NaHCO3. After
extraction with EtOAc, the organic layer was dried over MgSO4 and
concentrated. The residue was subjected to silica gel column
chromatography (100% CH2Cl2 then 1% MeOH in CH2Cl2) to give
(ꢀ)-45 (32 mg, 24%) and (ꢀ)-46 (55 mg, 41%); (ꢀ)-45: Rf (CH2Cl2/
MeOH 98:2) 0.46; IR nmax (film, cmꢂ1) 3418, 2937, 1713, 1665, 1624,
1167, 1094, 1045; UV (MeOH) 338, 227, 204 nm; 1H NMR (500 MHz,
2ꢃCHAr); 13C NMR (100 MHz, CDCl3)
d 16.8, 17.0, 17.1, 17.4, 18.5, 18.7
(6ꢃSiCH2CH2CH3), 25.3 (SCH2CH2), 26.2, 26.6 (2ꢃSCH2), 28.3 (-OC
(CH3)3), 30.1 (ArCH2), 42.0 (ArCH2CH2), 45.4 (CH2COO, CH2CHOSi),
52.6 (SCS), 67.8 (CHOSi), 80.7 (eOC(CH3)3), 119.9 (2ꢃCHAr), 129.5
(2ꢃCHAr),134.7 (CAr),153.7 (CAr),170.8 (COO); MS (ESIþ) m/z (%) 733
[MþNa]þ (100); HRMS (ESIþ) m/z found 733.4152. C38H70O4S2Si2Na
requires 733.4152.
6.2.4. (ꢀ)-3-(Tripropylsilyloxy)-4-(2-(4-(tripropylsilyloxy)phe-
nethyl)-1,3-dithian-2-yl)butanal ((ꢀ)-41). To a stirred solution of
(ꢀ)-40 (2.00 g, 2.81 mmol) in dry toluene (10 mL) was slowly added
DIBAL-H (1.7 M in toluene, 1.05 equiv) at ꢂ78 ꢁC. After stirring for
15 min, the reaction was quenched by addition of MeOH and the
reaction mixture was warmed up to rt. After addition of an aqueous
solution of NaOH 1 N, the organic phase was extracted with EtOAc,
dried over MgSO4 and concentrated. The residue was subjected to
silica gel column chromatography (cyclohexane/EtOAc 95:5) to give
(ꢀ)-41 (1.47 g, 82%) as a colourless oil; Rf (cyclohexane/EtOAc 9:1)
0.30; IR nmax (film, cmꢂ1) 3429, 2958, 1724, 1609, 1509, 1455, 1259,
1206,1064,1005; UV (MeOH) 279, 224, 203 nm; 1H NMR (400 MHz,
CDCl3)
d
1.50 (ddd, J¼13.1, 12.6, 2.6 Hz, 1H, CHHaCHOH), 1.76e1.81
(m, 1H, CHHbCHOH), 1.92e2.05 (m, 4H, CHOHCH2COO, CHHaCH2
-
COO, CH2CHHaCOO), 2.15e2.24 (m, 1H, CH2CHHbCOO), 2.22 (s, 3H,
CH3), 2.27e2.38 (m, 1H, CHHbCH2COO), 2.47 (dd, J¼16.4, 2.8 Hz, 1H,
CHHC]O), 2.75 (dd, J¼16.4, 9.7 Hz, 1H, CHHC]O), 4.13e4.18 (m,
1H, CHOH), 4.67e4.72 (m, 1H, CHOC), 6.11 (dd, J¼10.0, 2.0 Hz, 1H,
CH]CHC]O), 6.24 (dd, J¼10.0, 2.0 Hz, 1H, CH]CHC]O), 6.77 (dd,
J¼10.0, 2.8 Hz, 1H, CH]CHC]O), 7.27 (dd, J¼10.0, 2.8 Hz, 1H, CH]
CHC]O); 13C NMR (125 MHz, CDCl3)
d 31.5 (CH3), 34.2
CDCl3)
d
0.58e0.64 (m, 6H, 3ꢃSiCH2CH2), 0.69e0.75 (m, 6H,
(CH2CH2COO), 37.7 (CH2CHOH), 39.0 (CH2COO), 39.1 (CHOHCH2
-
3ꢃSiCH2CH2), 0.94 (t, J¼7.2 Hz, 9H, 3ꢃSi(CH2)2CH3), 0.97 (t,
COO), 49.2 (CH2C]O), 62.0 (CHOC), 64.8 (CHOH), 80.3 (C), 109.0
(OCO), 127.3 (CH]CHC]O), 127. 7 (CH]CHC]O), 148.6 (CH]
CHC]O), 151.7 (CH]CHC]O), 185.7 (C]O), 206.6 (CH3C]O); MS
(ESIþ) m/z (%) 292 [M]þ (10), 280 (100), 258 (95); HRMS (ESIþ) m/z
found 315.1202. C16H20O5Na requires 315.1208. Compound (ꢀ)-46:
Rf (CH2Cl2/MeOH 98:2) 0.34; IR nmax (film, cmꢂ1) 3425, 2930, 1712,
1668, 1628, 1385, 1167, 1053; UV (MeOH) 229, 200 nm; 1H NMR
J¼7.2 Hz, 9H, 3ꢃSi(CH2)2CH3), 1.30e1.47 (m, 12H, 6ꢃSiCH2),
1.90e1.98 (m, 2H, SCH2CH2), 2.15 (dd, J¼14.8, 5.6 Hz, 1H, CHHa
-
CHOSi), 2.18e2.24 (m, 2H, ArCH2CH2), 2.27 (dd, J¼14.8, 5.6 Hz, 1H,
CHHbCHOSi), 2.63 (ddd, J¼16.4, 4.8, 2.4 Hz, 1H, CHHaC]O),
2.72e2.83 (m, 6H, ArCH2, 2ꢃSCH2), 2.87 (ddd, J¼16.4, 5.6, 1.2 Hz,
1H, CHHbC]O), 4.59e4.64 (m, 1H, CHOSi), 6.73 (d, J¼8.4 Hz, 2H,
2ꢃCHAr), 7.04 (d, J¼8.4 Hz, 2H, 2ꢃCHAr), 9.83 (t, J¼2.0 Hz, 1H, O]
(500 MHz, CDCl3)
d
1.24 (ddd, J¼11.8, 11.8, 11.8 Hz, 1H, CHHaCHOH),
CH); 13C NMR (100 MHz, CDCl3)
d
16.7, 16.9, 17.0, 17.3, 18.4, 18.6
1.64 (dd, J¼11.8, 11.8 Hz, 1H, CHOHCHHaCOO), 1.92e2.04 (m, 2H,
CHHaCH2COO, CHHbCHOH), 2.05e2.12 (m, 1H, CHOHCHHbCOO),
2.13e2.23 (m, 2H, CH2CH2COO), 2.21 (s, 3H, CH3), 2.26e2.40 (m, 1H,
CHHbCH2COO), 2.48 (dd, J¼16.4, 3.1 Hz, 1H, CHHaC]O), 2.76 (dd,
J¼16.4, 9.2 Hz, 1H, CHHbC]O), 4.13e4.18 (m, 1H, CHOH), 4.33e4.38
(m, 1H, CHOC), 6.10 (dd, J¼10.3, 2.1 Hz, 1H, CH]CHC]O), 6.19 (dd,
J¼10.3, 2.1 Hz, 1H, CH]CHC]O), 6.77 (dd, J¼10.3, 2.8 Hz, 1H, CH]
CHC]O), 7.15 (dd, J¼10.3, 2.8 Hz, 1H, CH]CHC]O); 13C NMR
(6ꢃSiCH2CH2CH3), 25.1 (SCH2CH2), 26.1, 26.4 (2ꢃSCH2), 30.2
(ArCH2), 42.0 (ArCH2CH2), 46.2 (CH2CHOSi), 52.2 (SCS), 52.7
(CH2C]O), 66.0 (CHOSi), 119.8 (2ꢃCHAr), 129.3 (2ꢃCHAr), 134.3
(CAr), 153.8 (CAr), 201.6 (C]O); HRMS (ESIþ, CH3CN) m/z found
661.3571. C34H62O3S2Si2Na requires 661.3570.
6.2.5. (ꢀ)-(E)-6-(Tripropylsilyloxy)-7-(2-(4-(tripropylsilyloxy)phe-
nethyl)-1,3-dithian-2-yl)hept-3-en-2-one ((ꢀ)-43). To a stirred so-
lution of (ꢀ)-39 (368 mg, 0.58 mmol) in dry toluene (3 mL) was
added 1-(triphenylphosphoranylidene)propan-2-one 42 (459 mg,
1.44 mmol) at rt. After refluxing for 10 h, the reaction mixture was
concentrated. The residue was subjected to silica gel column
chromatography (cyclohexane/EtOAc 95:5) to give (ꢀ)-41 (368 mg,
94%) as a colourless oil; Rf (cyclohexane/EtOAc 9:1) 0.40; IR nmax
(film, cmꢂ1) 2954, 2926, 2868, 1679, 1509, 1455, 1257, 1064; UV
(100 MHz, CDCl3)
d 31.5 (CH3), 34.6 (CH2COO), 38.8 (CH2CH2COO),
40.2 (CH2CHOH), 42.8 (CHOHCH2COO), 49.2 (CH2C]O), 64.8
(CHOC), 65.3 (CHOH), 79.4 (C), 109.0 (OCO), 127.0 (CH]CHC]O),
127.3 (CH]CHC]O), 149.4 (CH]CHC]O), 152.4 (CH]CHC]O),
185.9 (C]O), 206.8 (CH3C]O); MS (ESIþ) m/z (%) 607 [2MþNa]þ
(100), 315 [MþNa]þ (75); HRMS (ESIþ) m/z found 315.1208.
C16H20O5Na requires 315.1208.
(MeOH) 279, 224, 203 nm; 1H NMR (400 MHz, CDCl3)
d
0.58e0.65
6.3. Syntheses of 2-[5-(hydroxymethyl)-2H-Pyran-3-(6H)-
one]-1-oxaspiro[4.5]deca-6,9-dien-8-one (48) and 2-[(5,6-
dihydro-5-oxo-2H-pyran-3-yl)methyl tetradecanoate]-1-
oxaspiro[4.5]deca-6,9-dien-8-one (49)
(m, 6H, 3ꢃSiCH2CH2), 0.70e0.76 (m, 6H, 3ꢃSiCH2CH2), 0.94 (t,
J¼7.2 Hz, 9H, 3ꢃSi(CH2)2CH3), 0.97 (t, J¼7.2 Hz, 9H, 3ꢃSi(CH2)2CH3),
1.31e1.47 (m, 12H, 6ꢃSiCH2), 1.89e1.97 (m, 2H, SCH2CH2), 2.05 (dd,
J¼15.0, 5.6 Hz, 1H, CHHaCHOSi), 2.12 (dd, J¼15.0, 5.2 Hz, 1H,
CHHbCHOSi), 2.18e2.24 (m, 2H, ArCH2CH2), 2.25 (s, 3H, C]OCH3),
2.42e2.51 (m, 1H, CHHaCH]C), 2.59e2.88 (m, 7H, ArCH2, 2ꢃSCH2,
CHHbCH]C), 4.28e4.34 (m,1H, CHOSi), 6.15 (d, J¼16.0 Hz,1H, CH]
CHC]O), 6.74 (d, J¼8.2 Hz, 2H, 2ꢃCHAr), 6.86 (dt, J¼16.0, 7.2 Hz, 1H,
CH]CHC]O), 7.03 (d, J¼8.2 Hz, 2H, 2ꢃCHAr); 13C NMR (100 MHz,
6.3.1. 4-[3-(2,2-Dimethyl-4,6-dioxo-1,3-dioxan-5-ylidene)-3-hydroxy-
propyl]-phenyl acetate (52). To a solution of 3-(4-acetoxyphenyl)
propanoic acid 5022 (16.4 g, 77.1 mmol) in dry CH2Cl2 (190 mL) was
added dropwise oxalyl chloride (13.3 mL, 154 mmol) at rt followed
by addition of few drops of DMF and the mixture was stirred for 3 h

M. Traoré et al. / Tetrahedron 66 (2010) 5863e5872
5871
at rt. The solvent was removed in vacuo to give a yellow oil. To
a solution of Meldrum’s acid 51 (11.21 g, 77.11 mmol) in dry CH2Cl2
(72 mL) was added dropwise at 0 ꢁC dry pyridine (12.45 mL,
154.20 mmol). After stirring for 1 h, the freshly prepared acyl chlo-
ride in dry CH2Cl2 (30 mL) was added dropwise into the mixture.
After stirring for 16 h at 0 ꢁC and 2 h at rt, the mixture was quenched
by addition of a HCl solution 1 N. The product was extracted with
CH2Cl2, the combined solution dried over MgSO4 and concentrated
to give an orange oil, which crystallized in dry EtOH to give a pale
yellow solid 52 (18.2 g, 77%); Rf (cyclohexane/EtOAc 8:2) 0.17; IR nmax
(film, cmꢂ1) 1739, 1665, 1578, 1508, 1409, 1292, 1197, 1019, 912; UV
residue was subjected to silica gel column chromatography (cy-
clohexane/EtOAc 20:80) to give 47 (0.67 mg, 86%); Rf (cyclohexane/
EtOAc 2:8) 0.30; IR nmax (film, cmꢂ1) 3350, 2946, 2918, 1611, 1518,
1445, 1364, 1235, 1174, 1146, 1082, 1002, 827; UV (MeOH) 278,
225 nm; 1H NMR (400 MHz, CDCl3)
d 2.74e2.86 (m, 4H, ArCH2CH2),
4.14 (s, 2H, OCH2OH), 4.45 (s, 2H, CH2OH), 6.22 (s, 1H, CHCCH2OH),
6.68 (d, J¼8.5 Hz, 2H, 2ꢃCHAr), 6.91 (d, J¼8.5 Hz, 2H, 2ꢃCHAr); 13C
NMR (100 MHz, CDCl3)
d 29.7 (ArCH2CH2), 35.1 (ArCH2CH2), 56.2
(CH2OH), 57.5 (OCH2OH), 110.1 (CCH2OH), 116.1 (2ꢃCHAr), 121.4
(CHCH2OH), 130.5 (2ꢃCHAr), 133.4 (CH2CAr), 153.0 (OCCH2OH),
153.7 (COC), 156.5 (CArOH); MS (ESIþ) m/z (%) 271 [MþNa]þ (100),
218 (20), 231 (15); HRMS (ESIþ) m/z found 271.0941. C20H28O4S2
requires 271.0943.
(MeOH) 263, 208 nm; 1H NMR (400 MHz, CDCl3)
d 1.65 (s, 6H, OOC
(CH3)2), 2.28 (s, 3H, OOCCH3), 3.01 (t, J¼7.2 Hz, 2H, ArCH2CH2), 3.40
(t, J¼7.2 Hz, 2H, ArCH2CH2), 7.01 (d, J¼8.7 Hz, 2H, 2ꢃCHAr), 7.27 (d,
J¼8.7 Hz, 2H, 2ꢃCHAr); 13C NMR (100 MHz, CDCl3)
d
20.3 (OOCCH3),
6.3.5. 6-(4-Hydroxyphenethyl)-6-hydroxy-5-(hydroxymethyl)-2H-
pyran-3(6H)-one (56). To a solution of 47 (230 mg, 0.93 mmol) in
CH2Cl2/1,1,1,3,3,3-hexafluoro-2-propanol (1:1) was added at 0 ꢁC
mCPBA (176 mg, 1.02 mmol). After stirring for 1 h at 0 ꢁC and 1 h at
rt, the mixture was quenched with an aqueous solution of Na2S2O3.
The product was extracted with EtOAc, dried over MgSO4 and
concentrated. The residue was subjected to silica gel column
chromatography (cyclohexane/EtOAc 40:60) to give 56 (182.2 mg,
74%); Rf (cyclohexane/EtOAc 3:7) 0.29; IR nmax (film, cmꢂ1) 3362,
1674, 1508, 1436, 1303, 1254, 1052, 1016, 826, 746; UV (MeOH) 278,
27.2 (CH2CH2), 32.9 (CH2CH2), 96.3 (OOCCOH), 104.6 (OOC(CH3)2),
121.5 (2ꢃCHAr), 129.2 (2ꢃCHAr), 138.1 (CH2CAr), 186.6 (OHCAr); MS
(ESIþ) m/z (%) 357 [MþNa]þ (100); HRMS (ESIþ) m/z found 357.0945.
C17H18O7Na requires 357.0948.
6.3.2. Ethyl-5-(4-acetoxyphenyl)-3-oxopentanoate (53). A solution
of 52 (4.51 g, 13.5 mmol) in dry EtOH was stirred at reflux for 3 h.
The solvent was removed in vacuo. The residue was subjected to
silica gel column chromatography (cyclohexane/EtOAc 80:20) to
give 53 as a colourless oil (3.56 g, 95%); Rf (cyclohexane/EtOAc 8:2)
0.2; IR nmax (film, cmꢂ1) 2984, 1748, 1647, 1509, 1369, 1318, 1196,
1098, 1019, 913, 848; UV (MeOH) 270 nm; 1H NMR (400 MHz,
223 nm; 1H NMR (400 MHz, CDCl3)
d 1.92e2.07 (m, 2H, ArCH2CH2),
2.40e2.51 (m, 1H, OCOH), 2.67e2.79 (m, 1H, CH2OH), 3.29e3.33 (m,
2H, ArCH2CH2), 4.07 (d, J¼16.8 Hz, 1H, OCHHaC]O), 4.35 (t, J¼2 Hz,
2H, CH2OH), 4.67 (d, J¼16.8 Hz, 1H, OCHHbC]O), 6.25 (t, J¼1.6 Hz,
1H, C]CH), 6.28 (d, J¼8.6 Hz, 2H, 2ꢃCHAr), 6.98 (d, J¼8.6 Hz, 2H,
CDCl3)
d
1.29 (t, J¼7.1 Hz, 3H, CH3CH2), 2.28 (s, 3H, OOCCH3),
2.78e2.80 (m, 4H, ArCH2CH2, ArCH2CH2), 3.41 (s, 2H, OCH2O), 4.13
(q, J¼7.1 Hz, 2H, OCH2CH3), 6.80 (d, J¼8.6 Hz, 2H, 2ꢃCHAr), 7.00 (d,
2ꢃCHAr); 13C NMR (100 MHz, CDCl3)
d 30.3 (ArCH2CH2), 42.0
J¼8.6 Hz, 2H, 2ꢃCHAr); 13C NMR (100 MHz, CDCl3)
d
14.1 (CH3CH2),
(ArCH2CH2), 61.2 (CH2OH), 67.1 (OCH2C]O), 96.5 (OCOH), 116.4
(2ꢃCHAr), 122.1 (2ꢃCHAr), 130.3 (C]CH), 133.8 (2ꢃCHAr), 156.7
(CH2CAr), 166.5 (HOCAr), 197.6 (C]O); MS (ESIþ) m/z (%) 287
[MþNa]þ (100), 285 (28), 310 (27); HRMS (ESIþ) m/z found
287.0895. C14H16O5Na requires 287.0890.
20.3 (OOCCH3), 28.7 (ArCH2CH2), 41.4 (ArCH2CH2), 48.9 (OCH2O),
61.0 (CH3CH2), 121.5 (2ꢃCHAr), 129.2 (2ꢃCHAr), 138.1 (CH2CAr), 148.5
(CAr), 168.1 (OCCH2CH3), 169.0 (OOCCH3), 202.1 (C]O); MS (ESIþ)
m/z (%) 301 [MþNa]þ (100), 287 (45), 216 (37); HRMS (ESIþ) m/z
found 301.1046. C15H18O5Na requires 301.1047.
6.3.6. (ꢀ)-2[5-(Hydroxymethyl)-2H-pyran-3(6H)-one]-1-oxaspiro
[4.5]deca-6,9-dien-8-one ((ꢀ)-48). Method a: To a solution of 56
(11.3 mg, 0.043 mmol) in CH2Cl2/1,1,1,3,3,3-hexafluoro-2-propanol
(1:1) (1 mL) was added at 0 ꢁC PhI(OAc)2 (21.0 mg, 0.065 mmol).
After stirring for 30 min at 0 ꢁC, solid NaHCO3 was added. The solid
was then removed by filtration and the solution was concentrated
in vacuo. The residue was subjected to silica gel column chroma-
tography (cyclohexane/EtOAc 40:60) to give (ꢀ)-48 (8.5 mg, 74%).
Method b: To a solution of 47 (160.4 mg, 0.65 mmol) in CH2Cl2/
1,1,1,3,3,3-hexafluoro-2-propanol (6 mL) was added at 0 ꢁC mCPBA
(124.0 mg, 0.72 mmol). After stirring for 1 h at 0 ꢁC and 1 h at rt, 4-
iodotoluene 57 (14.2 mg, 0.065 mmol) was added at rt. After
completion (about 15 min) solid NaHCO3 was added. The solid was
then removed by filtration and the solution was concentrated in
vacuo. The residue was subjected to alumina column chromatog-
raphy (cyclohexane/EtOAc 20:80) to give (ꢀ)-48 (37.8 mg, 22%).
Method c: To a solution of 47 (30.9 mg, 0.12 mmol) in CH2Cl2/
1,1,1,3,3,3-hexafluoro-2-propanol (2 mL) were added at rt mCPBA
(45.0 mg, 0.26 mmol) and 4-iodotoluene 57 (2.7 mg, 0.012 mmol).
After stirring until completion (1 h), solid NaHCO3 was added. The
solid was then removed by filtration and the solution was con-
centrated in vacuo. The residue was subjected to alumina column
chromatography (cyclohexane/EtOAc 20:80) to give (ꢀ)-48 (7.8 mg,
25%); Rf (cyclohexane/EtOAc 3:7) 0.25; IR nmax (film, cmꢂ1) 3343,
2954,1675,1631,1457,1429,1247,1162,1082,1013, 860; UV (MeOH)
6.3.3. Ethyl-5-(hydroxymethyl)-2-(4-hydroxyphenyl)furan-3-car-
boxylate(55). To a solution of 53 (0.78 g, 2.79 mmol) in 1,4-diox-
anne (6 mL) were added distilled water (3.5 mL), CeCl3.7H2O (0.5 g,
1.33 mmol) and DL-glyceraldehyde dimer 54 (0.30 g, 1.67 mmol).
The mixture was stirred at 90 ꢁC for 10 h. The mixture was con-
centrated by repeating co-evaporation with toluene. The residue
was directly subjected to silica gel column chromatography (cy-
clohexane/EtOAc 65:35) to give 55 (1.06 g, 56%); Rf (cyclohexane/
EtOAc 4:6) 0.19; IR nmax (film, cmꢂ1) 3362, 2982, 1711, 1680, 1615,
1574, 1518, 1457, 1304, 1215, 1070, 1017, 827; UV (MeOH) 249,
202 nm; 1H NMR (400 MHz, CDCl3)
d
1.33 (t, J¼7.1 Hz, 3H,
CH3CH2O), 2.85 (t, J¼8.0 Hz, 2H, ArCH2CH2), 3.23 (t, J¼8.0 Hz, 2H,
ArCH2CH2), 4.26 (q, J¼7.1 Hz, 2H, CH3CH2O), 4.55 (s, 2H, CH2OH),
6.54 (s, 1H, CH]CCH2OH), 6.75 (d, J¼8.4 Hz, 2H, 2ꢃCHAr), 7.20 (d,
J¼8.4 Hz, 2H, 2ꢃCHAr); 13C NMR (100 MHz, CDCl3)
d 14.5
(CH3CH2O), 30.3 (ArCH2CH2), 33.6 (ArCH2CH2), 57.4 (CH2OH), 60.6
(CH3CH2O), 109.0 (CHCCOH), 114.3 (CC]O), 115.4 (2ꢃCHAr), 129.7
(2ꢃCHAr), 132.9 (CArCH2), 152.1 (CCH2OH), 154.3 (CArOH), 162.5 (C]
O) 164.2 (CH2COC); MS (ESIþ) m/z (%) 313 (100) [MþNa]þ, 301 (75),
167 (40); HRMS (ESIþ) m/z found 313.1046. C16H18O5Na requires
313.1045.
6.3.4. (5-(4-Hydroxyphenethyl)furan-2,4-diyl)dimethanol (47). To
a solution of 55 (0.91 g, 3.12 mmol) in dry THF (37 mL) was added
dropwise at 0 ꢁC and under argon a solution of LiAlH4 in THF
(15.6 mL, 15.6 mmol, 1 M in THF). The mixture was stirred at rt
overnight. The mixture was quenched by carefully addition of
EtOAc, followed by an aqueous solution of NH4Cl. The product was
extracted with EtOAc, dried over MgSO4 and concentrated. The
203 nm; 1H NMR (400 MHz, CDCl3)
d 2.17e2.26 (m, 1H,
CCHHaCH2C), 2.29e2.35 (m, 1H, CCHHbCH2C), 2.43e2.57 (m, 2H,
CCH2CH2C), 4.15 (d, J¼17.2 Hz, 1H, OCHHaC]O), 4.30 (dd, J¼20.0,
2.0 Hz,1H, CHHaOH), 4.43 (dd, J¼20.0, 2.0 Hz, 1H, CHHbOH), 4.45 (d,
J¼17.2 Hz, 1H, OCHHbC]O), 6.12 (dd, J¼25.2, 2.0 Hz, 1H, CH]CHC

5872
M. Traoré et al. / Tetrahedron 66 (2010) 5863e5872
Ed. 2008, 47, 3787e3790; (b) Quideau, S.; Lyvinec, G.; Marguerit, M.; Bathany,
K.; Ozanne-Beaudenon, A.; Buffeteau, T.; Cavagnat, D.; Chénedé, A. Angew.
Chem., Int. Ed. 2009, 48, 4605e4609; (c) Uyanik, M.; Yasui, T.; Ishihara, K. Angew.
Chem., Int. Ed. 2010, 49, 2175e2177.
4. (a) Moriarty, R. M.; Prakash, O. Org. React. 2001, 51, 327e415; (b) Tohma, H.;
Kita, Y. In Hypervalent Iodine Chemistry-Modern Development in Organic Syn-
thesis; Wirth, T., Ed.; Top. Curr. Chem.; Springer: Berlin, Heidelberg, 2003;
pp 209e248; (c) Rodriguez, S.; Wipf, P. Synthesis 2004, 2767e2783; (d)
Magdziak, D.; Meek, S. J.; Pettus, T. R. R. Chem. Rev. 2004, 104, 1383e1430; (e)
Ciufolini, M. A.; Canesi, S.; Ousmer, M.; Braun, N. A. Tetrahedron 2006, 62,
5318e5337; (f) Pouységu, L.; Deffieux, D.; Quideau, S. Tetrahedron 2010, 66,
2235e2261.
5. For pioneer works in the synthesis of cyclohexa-2,5-dienone by hypervalent
phenyliodine(III) reagents with different nucleophilic species, see: (a) Tamura,
Y.; Yakura, T.; Haruta, J.; Kita, Y. J. Org. Chem. 1987, 52, 3927e3930; (b) Lewis, N.;
Wallbank, P. Synthesis 1987, 1103e1106; (c) Pelter, A.; Elgendy, S. M. A. J. Chem.
Soc., Perkin Trans. 11993, 1891e1896; (d) McKillop, A.; McLaren, L.; Taylor, R. J. K.
J. Chem. Soc., Perkin Trans. 1 1994, 2047e2048; (e) Kacan, M.; Koyuncu, D.;
McKillop, A. J. Chem. Soc., Perkin Trans. 1 1993, 1771e1776; (f) Marsini, M. A.;
Huang, Y.; Van De Water, R. W.; Pettus, T. R. R. Org. Lett. 2007, 9, 3229e3232; (g)
Braun, N. A.; Ciufolini, M. A.; Peters, K.; Peters, E.-M. Tetrahedron Lett. 1998, 39,
4667e4670; (h) Canesi, S.; Bouchu, D.; Ciufolini, M. A. Org. Lett. 2005, 7,
175e177; (i) Karam, O.; Jacquesy, J.-C.; Jouannetaud, M.-P. Tetrahedron Lett.
1994, 35, 2541e2544; (j) Kita, Y.; Yakura, T.; Tohma, H.; Kikuchi, K.; Tamura, Y.
Tetrahedron Lett. 1989, 30, 1119e1120; (k) Callinan, A.; Chen, Y.; Morrow, G. W.;
Swenton, J. S. Tetrahedron Lett. 1990, 31, 4551e4552; (l) Kita, Y.; Takada, T.;
Ibaraki, M.; Gyoten, M.; Mihara, S.; Fujita, S.; Tohma, H. J. Org. Chem. 1996, 61,
223e227; (m) Honda, T.; Shigehisa, H. Org. Lett. 2006, 8, 657e659; (n) Sabot, C.;
Commare, B.; Duceppe, M.-A.; Nahi, S.; Guerard, K. C.; Canesi, S. Synlett 2008,
3226e3230; (o) Guerard, K. C.; Sabot, C.; Racicot, L.; Canesi, S. J. Org. Chem.
2009, 74, 2039e2045.
(O)CH]CH), 6.13 (dd, J¼5.2, 1.6 Hz, 1H, CH]CHC(O)CH]CH), 6.29
(t, J¼3.6 Hz, 1H, HOCH2C]CH), 7.02 (dd, J¼20.6, 4.0 Hz, 1H, CH]
CHC(O)CH]CH), 7.03 (dd, J¼7.2, 4.0 Hz, 1H, CH]CHC(O)CH]CH);
13C NMR (100 MHz, CDCl3)
d 35.7 (CCH2CH2C), 36.0 (CCH2CH2C),
61.5 (CH2OH), 68.1 (OCH2C]O), 80.8 (CCH2CH2CO), 107.2
(CCH2CH2CO), 124.0 (HOCH2C]CH), 128.0 (CH]CHC(O)CH]CH),
128.4 (CH]CHC(O)CH]CH), 150.6 (CH]CHC(O)CH]CH), 152.8
(CH]CHC(O)CH]CH), 162.0 (HOCH2C]CH), 187.3 (CH]CHC(O)
CH]CH), 196.8 (C]CHC]O); MS (ESIþ) m/z (%) 285 [MþNa]þ
(100), 263 (16%), 264 (2%); HRMS (ESIþ) m/z found 285.0733.
C14H14O5Na requires 285.0736.
6.3.7. (ꢀ)-2-[(5,6-Dihydro-5-oxo-2H-pyran-3-yl)methyl tetradeca-
noate]-1-oxaspiro[4.5]deca-6,9-dien-8-one ((þ/ꢂ)-49). To a solu-
tion of 48 (34.6 mg, 0.13 mmol) in dry CH2Cl2 (2 mL) were added at
0 ꢁC DMAP (16.1 mg, 0.13 mmol), myristol chloride (42.4 mg,
0.17 mmol) and Et3N (17.3 mg, 0.17 mmol). After 30 min at 0 ꢁC and
2 h at rt, an aqueous solution of HCl 1 N was added. The product
was extracted with CH2Cl2, dried over MgSO4 and concentrated.
The residue was subjected to silica gel column chromatography
(cyclohexane/EtOAc 70:30) to give 49 (23.5 mg, 38%); Rf
(cyclohexane/EtOAc 7:3) 0.18; IR nmax (film, cmꢂ1) 2914, 2845, 1752,
1683, 1469, 1275, 1251, 1162, 1025, 1013, 900, 847; UV
(MeOH) 221 nm; 1H NMR (400 MHz, CDCl3)
d
0.88 (t,
6. Peuchmaur, M.; Saidani, N.; Botté, C.; Maréchal, E.; Vial, H.; Wong, Y.-S. J. Med.
J¼6.8 Hz, 3H, CH3(CH2)10CH2CH2C]O), 1.26e1.28 (m, 20H,
CH3(CH2)10CH2CH2C]O), 1.67e1.75 (m, 2H, CH3(CH2)10CH2CH2C]
O), 2.19e2.29 (m, 2H, CCH2CH2C), 2.23e2.38 (m, 2H, CCH2CH2C),
2.52e2.60 (CH3(CH2)10CH2CH2C]O), 4.18 (d, J¼16.8 Hz, 1H, OCH-
HaC]O), 4.51 (d, J¼16.8 Hz, 1H, OCHHbC]O), 4.72 (dd, J¼20.0,
1.6 Hz, 1H, CH]CCHHaOC]O), 4.91 (dd, J¼1.6 Hz, 1H, CH]
CCHHbOC]O), 6.19 (dd, J¼11.6, 2.0 Hz, 1H, CH]CHC(O)CH]CH),
6.22 (dd, J¼11.6, 2.0 Hz, 1H, CH]CHC(O)CH]CH), 6.25 (t, J¼1.6 Hz,
1H, CH]CCH2OC]O), 6.80 (dd, J¼10.0, 3.2 Hz, 1H, CH]CHC(O)
CH]CH), 6.89 (dd, J¼10.0, 3.2 Hz, 1H, CH]CHC(O)CH]CH); 13C
Chem. 2008, 51, 4870e4873.
7. (a) Molander, G. A.; Harris, C. R. Chem. Rev. 1996, 96, 307e338; (b) Molander, G.
A.; Harris, C. R. Tetrahedron 1998, 54, 3321e3354.
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3553e3556; (b) De Mico, A.; Margarita, R.; Piancatelli, G. Gazz. Chem. Ital. 1995,
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Tetrahedron 2005, 61, 2353e2363; (b) Alvarez-Bercedo, P.; Falomir, E.; Carda,
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kateswarlu, Y. Tetrahedron: Asymmetry 2008, 19, 1509e1513; (h) Zhen, Z.-B.;
Gao, J.; Wu, Y. J. Org. Chem. 2008, 73, 7310e7316; (i) Kamal, A.; Reddy, P. V.;
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NMR (100 MHz, CDCl3)
d
14.3 (CH3CH2CH2(CH2)8), 22.9
(CH3CH2CH2(CH2)8), 25.0 (CH3CH2CH2(CH2)8CH2CH2C]O), 29.2
(CH3CH2CH2(CH2)8), 30.1 (CH3CH2CH2(CH2)8CH2CH2C]O), 61.7
(CH]CCH2OC]O), 67.0 (OCH2C]O), 79.7 (CCH2CH2CO), 105.9
(OCCH2CH2CO), 125.4 (CH]CCH2OC]O), 128.0 (CH]CHC(O)CH]
CH), 147.2 (CH]CHC(O)CH]CH), 149.7 (CH]CCH2OC]O), 173.3
(CH]CCH2OC]O), 185.1 (CH]CHC(O)CH]CH), 194.7 (C]CHC]
O); MS (ESIþ) m/z (%) 495 [MþNa]þ (100), 143 (95), 245 (65), 217
(40); HRMS (ESIþ) m/z found 495.2717. C28H40O6Na requires
495.2718.
Supplementary data
Supplementary data associated with this article can be found in
the online version at doi:10.1016/j.tet.2010.04.135.
References and notes
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