An efficient route for the synthesis of chiral conduritol-derivative carboxamides via palladium-catalyzed aminocarbonylation of bromocyclohexenetetraols

Article abstract of DOI:10.1016/j.tet.2012.05.128

A family of chiral conduritol-derivative carboxamides was synthesized through palladium-catalyzed aminocarbonylation of diastereoisomeric bromocyclohexenetetraols, previously prepared through biotransformation of bromobenzene by mutant strains of Pseudomonas putida F39/D. The coupling reactions of bromocyclohexenetetraols with CO and different amines, such as tert-butylamine, aniline, and piperidine, were performed in the presence of in situ generated Pd(0)/PPh₃ catalyst. The methodology was applied to the corresponding iodo-cyclohexenetetraol derivative, using (L)-alanine and (L)-valine methyl ethers as N-nucleophiles. The resulting carboxamides were obtained in highly chemoselective reactions, isolated, and fully characterized.

Full text of DOI:10.1016/j.tet.2012.05.128

Tetrahedron 68 (2012) 6935e6940
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An efficient route for the synthesis of chiral conduritol-derivative carboxamides
via palladium-catalyzed aminocarbonylation of bromocyclohexenetetraols
a
b
b
b
c
ꢀ
ꢀ
ꢀ
Rui M.B. Carrilho , Viviana Heguaburu , Valeria Schapiro , Enrique Pandolfi , Laszlo Kollar ,
Mariette M. Pereira a
a Departamento de Química, Universidade de Coimbra, Rua Larga, 3004-535 Coimbra, Portugal
Departamento de Química Organica, Facultad de Química, UdelaR, C. P. 11800, Montevideo, Uruguay
Department of Inorganic Chemistry, University of Pecs, Ifjusag u. 6, H-7624 Pecs, Hungary
,
*
b
ꢀ
c
ꢀ
ꢀ ꢀ
ꢀ
a r t i c l e i n f o
a b s t r a c t
Article history:
A family of chiral conduritol-derivative carboxamides was synthesized through palladium-catalyzed
aminocarbonylation of diastereoisomeric bromocyclohexenetetraols, previously prepared through bio-
transformation of bromobenzene by mutant strains of Pseudomonas putida F39/D.
The coupling reactions of bromocyclohexenetetraols with CO and different amines, such as tert-butyl-
amine, aniline, and piperidine, were performed in the presence of in situ generated Pd(0)/PPh3 catalyst.
The methodology was applied to the corresponding iodo-cyclohexenetetraol derivative, using (L)-alanine
and (L)-valine methyl ethers as N-nucleophiles. The resulting carboxamides were obtained in highly
chemoselective reactions, isolated, and fully characterized.
Received 12 March 2012
Received in revised form 28 May 2012
Accepted 30 May 2012
Available online 8 June 2012
Keywords:
Glycomimic
Vinyl-bromides
Conduritol
Ó 2012 Elsevier Ltd. All rights reserved.
Carboxamide
Palladium
Carbon monoxide
Aminocarbonylation
1. Introduction
The biotransformation of monosubstituted arenes by mutant
strains of Pseudomonas putida,1 producing cis-dihydrodiols, is an ef-
ficienttoolforthe asymmetric synthesis ofnaturalproducts.2 Further
functionalization of these compounds leads to cyclohexenetetraol
derivatives that resemble the structure of sugars (i.e., conduritols).3
The design and synthesis of small molecules, which can mimic
complex carbohydrates involved in diverse cellular proc-
essesdglycomimics,4 may lead to a better understanding of carbo-
hydrates functions and can eventually culminate in potential drug
candidates.5 These glycomimics include carbasugars and amino-
carbasugars, which usually display various biological properties as
enzyme inhibitors,6 and may be involved in relevant biological
processes or biotechnological applications.7 For example, amino-
cyclitols8 as valienamine have demonstrated strong glucosidase
inhibitory activity, thus showing particular importance as chemo-
therapeutic agents (Fig. 1).9
Fig. 1. Structure of valienamine.
of an aryl halide, CO and nucleophiles such as alcohols or amines, as
effective carbonylation catalytic systems,10 many aspects of carbon-
ylation reactions have been recently reviewed.11 Particularly,
palladium-catalyzed carbonylation of iodoaromatics and iodoalkenes
has been extensively used in synthetic chemistry for the preparation
of a wide range of carboxylic acid derivatives.12 Boyd13 and Fang14
have applied the alkoxycarbonylation of iodine derivatives as one of
the steps for the total synthesis of, respectively, carbasugars and the
antiviral agent oseltamivir (TamifluÒ) (Scheme 1). Nevertheless, car-
bonylation reactions of bromoalkenes are less explored and they still
represent a great challenge, due to their lower reactivity, relatively to
corresponding iodine counterparts. Moreover, their application in
homogeneouscatalytic transformations15 ishighlysupported by both
lower cost and easier synthesis.
Sincethe seminalreportsbyHeckin1974, whichdescribedtheuse
of the first palladium-catalyzed three-component coupling reaction
Encouraged by the growing interest in glycomimics with potential
biological activity, herein we report the synthesis of a family of chiral
conduritol-derivative carboxamides, through Pd/PPh3-catalyzed
* Corresponding author. Tel.: þ351 239854474; fax: þ351 239827703; e-mail
address: mmpereira@qui.uc.pt (M.M. Pereira).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.05.128

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R.M.B. Carrilho et al. / Tetrahedron 68 (2012) 6935e6940
and piperidine (c)), in the presence of carbon monoxide and in situ
generated Pd(0) catalysts, in a stainless steel autoclave (Scheme 3).
Scheme 1. Alkoxycarbonylation step in the synthesis of TamifluÒ
.
aminocarbonylation of bromocyclohexenetetraols, using primary
and secondary amines as nucleophiles. Aiming to expand the struc-
tural motifs of these sugar mimics, retaining the resemblance with
natural products, two amino acid methyl esters were used as N-nu-
cleophiles in the aminocarbonylation of a similar substrate with
iodoalkene functionality.
Scheme 3. Aminocarbonylation reaction of bromocyclohexenetetraol derivatives.
The reactions’ progress was followed by TLC and GC analysis of
aliquots taken from the reactor via cannula, and the final conver-
sions were determined by GC and confirmed by 1H NMR spec-
troscopy of the crude mixture, through integration of the olefinic
protons of both substrate and reaction products.
2. Results and discussion
2.1. Synthesis of bromocyclohexenetetraols
The optimization for the aminocarbonylation reaction condi-
tions was performed using substrate 1 and tert-butylamine (a) as
nucleophile as models (Table 1).
The substrates 1 and 2 have been synthesized, following the se-
quential pathway, represented in Scheme 2. The biotransformation of
bromobenzene with P. putida F39/D, in 2 g/L culture medium yield,1b
followed by the reaction with 2,2-dimethoxypropane16 yielded the
protected cis-cyclohexadienediol derivative (88% yield), whose fur-
ther oxygenation was followed by two different synthetic ap-
proaches. In the first one, the hydroxylation was performed using
OsO4 and NMO (N-methylmorpholine N-oxide) attaining the syn
dihydroxylated precursor as only product, with 80% yield.17 In a sec-
ond process, the anti dihydroxylated compound was exclusively
obtained through the reaction of the protected cis-cyclo-
hexadienediol with MCPBA (meta-chloroperoxybenzoic acid) fol-
lowed by epoxide ring opening with KOH.16 The subsequent
protections of the hydroxyl groups were carried out with acetic an-
hydride and triethylamine, reaching (1R,2R,3S,4S)-1,2-diacetyl-5-
bromo-3,4-O-isopropylidenecyclohex-5-en-1,2,3,4-tetraol (1) and
(1S,2R,3S,4S)-1,2-diacetyl-5-bromo-3,4-O-isopropylidenecyclohex-
5-en-1,2,3,4-tetraol (2), both in 99% yields.
In the first assessment, using the Pd/PPh3 catalyst, at 50 ꢀC
temperature and CO pressure of 30 bar, the reaction did not pro-
ceed after 24 h (Table 1, entry 1). To overcome the issues associated
with the low reactivity of this type of bromoalkenes, a temperature
of 100 ꢀC was employed, keeping the CO pressure in 30 bar. Under
these conditions, a conversion of 60% was achieved (Table 1, entry
2) with the same catalyst. However, at longer reaction time (48 h),
a complex mixture of products, containing mono- and double
carbonylated and hydrolyzed products, was evidenced by CG, 1H
NMR, and 13C NMR (Table 1, entry 3). With a 20 bar CO pressure,
a conversion of only 30% was obtained in 24 h (Table 1, entry 4).
Using methyl ethyl ketone as solvent, instead of DMF, higher con-
version was observed (90%), however with lower selectivity for the
target monocarboxamide (a 1:1 mixture of mono- and double
carbonylated products was obtained) (Table 1, entry 5). Further-
Scheme 2. Synthesis of bromocyclohexenetetraol precursors.
2.2. Aminocarbonylation of halocyclohexenetetraols
more, another ligand was evaluated in the reaction, namely the tris
[(S)-20-(benzyloxy)-1,10-binaphthyl-2-yl]phosphite, recently syn-
thesized by our group.18 However, no conversion was observed
with this Pd/monophosphite catalyst, in 24 h (Table 1, entry 6).
The bromocyclohexenetetraol derivatives 1 or 2 were subjected
to reaction with the desired amine (tert-butylamine (a), aniline (b),

R.M.B. Carrilho et al. / Tetrahedron 68 (2012) 6935e6940
6937
Table 1
yields did not dependon the stereoconfiguration of the substrate, but
were influencedbytheaminenucleophilicity, beinghigherwithalkyl
amines a and c than those achieved with the aromatic amine b. The
sensitivenessof theacetateprotectinggrouptohydrolysis, duringthe
isolation/purification process resulted in a slight decrease of isolated
yields, comparatively to reaction conversions (Table 2). It should be
noticed that the employed amine/substrate ratios were based on
several previous optimization studies, using a wide range of haloar-
ene and haloalkene substrates, and have mainly into account the
volatility properties of each amine.11,12 For instance, the most volatile
amine, tert-butylamine(a) hasto be used in (at least) threefold excess
to achieve good yields in reasonable reaction time, while in the case
of less volatile piperidine (c), a ratio of 1.5 to substrate is sufficient.
To extend the structural patterns of the conduritol-derivative
carboxamides, the aminocarbonylation of the corresponding
Optimization of reaction parameters for aminocarbonylation of 1 with tert-butyl-
amine (a) as nucleophile
Entry
1
Substrate
T
CO
Solvent Ligand Time (h) Conversiona
(%)
(ꢀC) (bar)
50 30
DMF
PPh3
24
d
2
3
100 30
100 30
DMF
DMF
PPh3
PPh3
24
48
60
Complex
mixture
30
4
5
100 20
100 30
DMF
Methyl PPh3
ethyl
PPh3
24
24
90b
1
ketone
6
100 30
DMF
P(OR)3 24
d
iodo-conduritol was performed, with (L)-alanine and (L)-valine
Reaction conditions: 0.3 mmol of substrate 1; 0.015 mmol of Pd(OAc)2; 0.03 mmol
methyl esters as N-nucleophiles (Scheme 4), using the same stan-
dard conditions employed for bromocyclohexenetetraols. These
amino acid methyl esters were used in hydrochloride form (solids),
and the ‘free’ nucleophiles were made available ‘in situ’ upon the
effect of triethylamine as HCl acceptor. Therefore only a slight ex-
cess of N-nucleophile to the substrate was necessary.
of ligand; 0.9 mmol tBuNH2; 0.25 mL Et3N, 7 mL solvent.
a
% of substrate converted in carboxamides at the indicated time, determined by
GC and 1H NMR.
b
1:1 mixture of carboxamide/ketocarboxamide.
Therefore, in order to convert this reaction into a real synthetic
tool for the preparation of conduritol-derivative carboxamides, the
reactions were performed using the following parameters as
standard: T¼100 ꢀC; P(CO)¼30 bar; Pd(OAc)2/PPh3 as catalyst; DMF
as solvent; reaction time¼24 h.
The isolated yields of the aminocarbonylation reactions, obtained
after the work-up and products purification using silica gel column
chromatography, are summarized in Table 2. While the amino-
Table 2
Aminocarbonylation of bromocyclohexenetetraol derivatives 1 and 2
Entry
Substrate
Amine
Product
conversiona
%
Scheme 4. Aminocarbonylation of iodo-cyclohexenetetraol derivative, using (L)-ala-
nine (d) and (L)-valine (e) methyl esters as N-nucleophiles.
(isolated yield %)
As expected, the aminocarbonylation of the iodo-cyclo-
hexenetetraol derivative occurred more efficiently than with the
vinylbromide counterpart, achieving complete conversions (99% in
1
a
3a 60 (50)
2
3
b
c
3b 57 (45)
3c 67 (56)
the case of (L)-alanine methyl ester and 93% with (L)-valine). After
work-up and purification, the carboxamide compounds 3d and 3e
were obtained with 85 and 66% isolated yields, respectively.
1
2
4
5
a
4a 63 (52)
4b 45 (27)
3. Conclusion
b
An effective route for a family of chiral conduritol-derivative
carboxamides was developed through the synthesis of new di-
astereoisomeric bromocyclohexenetetraol derivatives, obtained
from bromobenzene biotransformation with mutant strains of P.
putida F39/D, followed by palladium-catalyzed coupling reaction of
the bromoalkenes with CO and different amines. Remarkable se-
lectivity for monocarboxamide compounds was achieved under
30 bar CO pressure and 100 ꢀC. The syn or anti stereochemistry of
the acetate groups in positions 1 and 2 of the ring did not affect the
reactivity, whereas significant differences in product yields were
apparently due to the nucleophilicity of the amine.
In spite of the widely known low reactivity of bromoalkenes in
homogeneous catalytic reactions, the carboxamides obtained
through aminocarbonylation of the corresponding tetraol de-
rivatives possessing bromoalkene functionality were isolated in
moderate isolated yields. The versatility of this methodology for the
preparation of conduritol-derivative carboxamides is demonstrated
by the diverse range of N-nucleophiles, as well as the possibility of
using either vinyl iodides or vinyl-bromides in such reactions.
6
c
4c 66 (53)
Reaction conditions: 0.3 mmol of substrate; 0.015 mmol of Pd(OAc)2; 0.03 mmol of
PPh3; 0.25 mL of triethylamine; solvent: 7 mL of DMF; T¼100 ꢀC; P(CO)¼30 bar;
amine/substrate molar ratios: a/substrate¼3; b/substrate¼2; c/substrate¼1.5.
Determined by GC and 1H NMR.
a
carbonylation of 1, using tert-butylamine (a) as nucleophile, attained
product 3a with isolated yield of 50%, when substrate 2 was
employed, using the same amine, a 52% isolated yield of product 4a
wasreached(Table 2, entries1and4). Usinganiline(b)asnucleophile
with the same reaction conditions, products 3b and 4b were
obtained, with 45% and 27% isolated yields, respectively (Table 2,
entries 2 and 5). The experiments with piperidine (c) gave 56% and
53% yields of products 3c and 4c, respectively (Table 2, entries 3 and
6). The overall results show that, even under moderate pressures
(30 bar CO) and temperature of 100 ꢀC, a total selectivity for the-
monocarboxamide product was achieved since no double carbonyl-
ation products (2-ketocarboxamides) were obtained.19 The reaction

6938
R.M.B. Carrilho et al. / Tetrahedron 68 (2012) 6935e6940
4. Experimental section
AcOeCHeCHeOeC), 2.12 (s, 3H, O]CeCH3), 2.10 (s, 3H, O]
CeCH3), 1.57 (s, 3H, CH3), 1.43 (s, 3H, CH3). 13C NMR (100 MHz,
CDCl3) (ppm): 170.3 (C]O), 169.9 (C]O), 130.8 (CH]CeBr), 121.4
(CH]CeBr), 111.7 (OeCeO), 77.2 (CH]CeCHeOeC), 75.1
(AcOeCHeCHeOeC), 70.5 (C]CHeCHeOAc), 70.3
(AcOeCHeCHeOeC), 27.7 (CH3), 26.4 (CH3), 20.9 (O]CeCH3), 20.8
(O]CeCH3). IR (KBr, cmꢂ1): 3465, 1747 (C]O), 1656 (C]C), 1381
(O]CeCH3), 1230 (CH3), 1073, 930, 530 (CeBr). HRMS (ESI) calcd
for C13H17BrO6Na [MþNa]þ: 371.0101, 373.0081 (1:1). Found:
371.0086, 373.0064 (1:1).
4.1. General
d
1H and 13C NMR spectra were recorded in CDCl3 solutions on
a Bruker Avance 400 spectrometer, at 400.13 MHz and 100.61 MHz,
respectively. Chemical shifts are expressed in parts per million, rela-
tively to an internal TMS standard. The absolute assignments of 1H
and 13C signals were based on two-dimensional experiments (COSY,
HSQC, and HMBC). High-resolution mass spectrometry analysis was
carried out on a Bruker Microtof apparatus, equipped with selective
ESI detector. Optical rotation was measured with an Optical Activity
Lda. polarimeter, using a 2 mL cell. All reagents werefromcommercial
origin (SigmaeAldrich and Fluka), except the chiral cyclo-
hexadienediols, which were synthesized according to the publi
shed procedure for the use of P. putida F39/D.20 Compounds
(1S,2R,3S,4S)-5-bromo-3,4-O-isopropylidenecyclohex-5-en-1,2,3,4-
tetraol,16 (1R,2R,3S,4S)-5-bromo-3,4-O-isopropylidenecyclohex-5-
en-1,2,3,4-tetraol,17 and (1R,2R,3S,4S)-5-iodo-3,4-O-isopropyliden
ecyclohex-5-en-1,2,3,4-tetraol21 were prepared according to pre-
viously described procedures. Spectroscopic data are in good agree-
ment with those reported.
4.2.3. (1R,2R,3S,4S)-1,2-Diacetyl-5-iodo-3,4-O-isopropylidenecycl-
ohex-5-en-1,2,3,4-tetraol (5). Yellow oil (99%, 1.25 g). ½a D25
ꢂ79.5 (c
ꢁ
7.3, CHCl2). 1H NMR (400 MHz, CDCl3)
d
(ppm) 6.45 (d, J¼3.7 Hz, 1H,
IeC]CH), 5.48 ppm (m, 2H, AcOeCHeCHeOAc), 4.72 (d, J¼5.7 Hz, 1H,
IeCeCHeOeC), 4.40 (t, J¼5.7 Hz, 1H AcOeCHeCHeOeC), 2.12 (s, 3H,
O]CeCH3), 2.08 (s, 3H, O]CeCH3), 1.49 (s, 3H, CH3), 1.43 (s, 3H, CH3).
(ppm): 170.1 (C]O), 169.9 (C]O), 135.8
(CH]CeBr), 110.4 (OeCeO), 101.2 (CH]CeI), 78.7 (CH]CeCHeOeC),
73.7 (AcOeCHeCHeOeC), 68.9 (C]CHeCHeOAc), 67.7
13C NMR (100 MHz, CDCl3)
d
(AcOeCHeCHeOeC), 27.6 (CH3), 26.1 (CH3), 20.8 (O]CeCH3), 20.7
(O]CeCH3). HRMS (ESI) calcd for C13H17IO6Na [MþNa]þ: 418.9962.
Found: 418.9973.
Note: OsO4 is highly poisonous, so the appropriate safety
procedures were taken for its manipulation. R: 26/27/28-34;
S: 1/2-7/9-26-45.
4.3. General procedure for aminocarbonylation reactions
In a typical experiment Pd(OAc)2 (3.4 mg, 0.015 mmol), PPh3
(7.9 mg, 0.03 mmol), the halocyclohexenetetraol derivative 1, 2, or 5
(0.30 mmol), and the desired amine (0.33e0.90 mmol) (see Table 1)
were dissolved in 7 mL of DMF under N2 atmosphere. The homo-
geneous yellow solution was transferred to a stainless steel auto-
clave and triethylamine (0.25 mL) was added. The reaction vessel
was then pressurized with 30 bar of carbon monoxide and the
mixture was magnetically stirred for 24 h at 100 ꢀC. At the end of
the reaction, some metallic palladium was formed and precipitated,
which was filtered off. The mixture was then concentrated and
evaporated to dryness. The residue was dissolved in chloroform
(20 mL), then washed with water (3ꢃ20 mL), dried over Na2SO4,
and concentrated to a red/orange waxy oil. The chemically pure
products 3aee and 4aec were isolated from the reaction mixtures
by column chromatography (Silicagel, chloroform/ethyl acetate or
n-hexane/ethyl acetate; exact ratios are specified in the character-
ization for each compound).
4.2. Synthesis of substrates
A
solution of (1S,2R,3S,4S)-5-bromo-3,4-O-isopropylidenecy
clohex-5-en-1,2,3,4-tetraol or (1R,2R,3S,4S)-5-bromo-3,4-O-iso-
propylidenecyclohex-5-en-1,2,3,4-tetraol (1 g, 3.8 mmol) in 20 mL
CH2Cl2, was cooled in an ice bath. Under N2 atmosphere, acetic an-
hydride (1.4 mL, 15.9 mmol), NEt3 (4.2 mL, 30.2 mmol), and a small
spatula tip of DMAP were added. After stirring for 2 h, a cooled sat-
urated solution of Na2CO3 was added. Upon extraction with diethyl
ether, the combined organic phase was successively washed with
water, a saturated solution of CuSO4, and brine, dried over Na2SO4,
and the solvent was evaporated under vacuum. The products were
purified by silica gel column chromatography, using a mixture of n-
hexane/EtOAc (7:3) as eluent.
The
substrate
(1R,2R,3S,4S)-1,2-diacetyl-5-iodo-3,4-O-iso-
propylidenecyclohex-5-en-1,2,3,4-tetraolwaspreparedthroughthe
same synthetic methodology used for (1R,2R,3S,4S)-1,2-diacetyl-5-
bromo-3,4-O-isopropylidenecyclohex-5-en-1,2,3,4-tetraol.
4.4. Products characterization
4.2.1. (1R,2R,3S,4S)-1,2-Diacetyl-5-bromo-3,4-O-isopropylidenecycl-
ohex-5-en-1,2,3,4-tetraol (1). Colorless oil (99%, 1.30 g). ½a D25
ꢁ
ꢂ98.8 (c
4.4.1. (1R,2R,3R,4R)-1,2-Diacetyl-5-tert-butylcarbamoyl-3,4-O-iso-
propylidenecyclohex-5-en-1,2,3,4-tetraol (3a). Yellow oil (50%
4.0, CH2Cl2). 1H NMR (400 MHz, CDCl3)
d
(ppm) 6.17 (d, J¼4.1 Hz, 1H,
CH]CeBr), 5.50 (t, J¼3.9 Hz, 1H, C]CHeCHeOAc), 5.40 (dd, J1¼3.7 Hz,
J2¼6.6 Hz, 1H, AcOeCHeCHeOeC), 4.70 (d, J¼5.6 Hz, 1H, CH]
CeCHeOeC), 4.43 (t, J¼6.2 Hz, 1H, AcOeCHeCHeOeC), 2.08 (s, 3H,
O]CeCH3), 2.05 (s, 3H, O]CeCH3), 1.45 (s, 3H, CH3), 1.39 (s, 3H, CH3).
0.055 g). ½a 2D5
ꢁ
ꢂ50.0 (c 0.5, CH2Cl2). Rf: 0.35 (EtOAc/n-hexane 4:6). 1H
NMR (400 MHz, CDCl3)
d
(ppm): 6.64 (d, J¼4.8 Hz, 1H, CH]C), 6.60
(br s, 1H, NH), 5.67 (dd, J1¼3.8 Hz, J2¼4.8 Hz, 1H, C]CHeCHeOAc),
5.40 (dd, J1¼3.8 Hz, J2¼6.6 Hz, 1H, CeOeCHeCHeOAc), 4.87 (d,
J¼5.8 Hz, 1H, CH]CeCHeOeC), 4.44 (dd, J1¼5.8 Hz, J2¼6.6 Hz, 1H,
13C NMR (100 MHz, CDCl3)
d (ppm) 170.0 (C]O), 169.8 (C]O), 128.1
(CH]CeBr), 125.1 (CH]CeBr), 110.8 (OeCeO), 76.6 (CH]
CeCHeOeC), 73.8 (AcOeCHeCHeOeC), 69.0 (AcOeCHeCHeOeC),
67.1 (C]CHeCHeOAc), 27.6 (CH3), 26.1 (CH3), 20.8 (O]CeCH3), 20.7
(O]CeCH3). IR (KBr, cmꢂ1): 3460, 3007, 2945 (CH3), 1752 (C]O), 1654
(C]C), 1387 (O]CeCH3), 1240 (CH3), 1233 (CH3), 1190, 1020, 880, 520
(CeBr). HRMS (ESI) calcd for C13H17BrO6Na [MþNa]þ: 371.0101,
373.0081 (1:1). Found: 371.0092, 373.0067 (1:1).
AcOeCHeCHeOeC), 2.07 (s, 3H, O]CeCH3), 2.05 (s, 3H, O]CCH3),
1.44 (s, 3H, OeCeCH3), 1.42 (s, 3H, OeCeCH3), 1.40 (s, 9H, Bu). 13
C
t
NMR (100 MHz, CDCl3)
d (ppm): 170.2 (OeC]O), 169.9 (OeC]O),
164.4 (NHeC]O), 134.8 (CH]CeC]O), 131.0 (AcOeCHeCH]C),
110.7 (OeCeO), 73.4 (AcOeCHeCHeOeC), 71.5 (CH]CeCHeOeC),
69.5 (AcOeCHeCHeOeC), 68.2 (C]CHeCHeOAc), 51.4 (C(CH3)3),
28,7 (3C, C(CH3)3), 27.6 (OeCeCH3), 26.1 (OeCeCH3), 20.8 (O]
CeCH3), 20.7 (O]CeCH3). HRMS (ESI) calcd for C18H27NO7Na
[MþNa]þ: 392.1680. Found: 392.1684.
4.2.2. (1S,2R,3S,4S)-1,2-Diacetyl-5-bromo-3,4-O-isopropylidenecycl-
ohex-5-en-1,2,3,4-tetraol (2). Colorless oil (99%, 1.30 g). ½a D25
þ50.0
ꢁ
(c 2.0, CHCl2). 1H NMR (400 MHz, CDCl3)
d
(ppm) 6.18 (d, J¼2.2 Hz,
4.4.2. (1R,2R,3R,4R)-1,2-Diacetyl-5-phenylcarbamoyl-3,4-O-iso-
1H, CH]CeBr), 5.27e5.33 (m, 2H, AcOeCHeCHeOAc), 4.72 (d,
J¼6.1 Hz, 1H, CH]CeCHeOeC), 4.30e4.33 (m, 1H,
propylidenecyclohex-5-en-1,2,3,4-tetraol (3b). Yellow oil (45%,
0.053 g). ½a 2D5
ꢁ
ꢂ30.0 (c 0.7, CH2Cl2). Rf: 0.50 (EtOAc/n-hexane 1:9). 1H

R.M.B. Carrilho et al. / Tetrahedron 68 (2012) 6935e6940
6939
NMR (400 MHz, CDCl3)
d
(ppm): 8.69 (br s, 1H, NH), 7.57e7.58 (m, 2H,
(OeCeCH3), 19.9 (O]CeCH3), 19.7 (O]CeCH3). HRMS (ESI) calcd for
C20H23NO7Na [MþNa]þ: 412.1367. Found: 412.1357.
HAr), 7.33e7.36 (m, 2H, HAr), 7.12e7.16 (m, 1H, HAr), 6.82 (d, J¼3.3 Hz,
1H, CH]C), 5.75 (dd, J1¼3.3 Hz, J2¼3.7 Hz, 1H, C]CHeCHeOAc), 5.52
(dd, J1¼3.7 Hz, J2¼6.0 Hz, 1H, CeOeCHeCHeOAc), 5.01 (d, J¼5.5 Hz,
1H, CH]CeCHeO), 4.51 (dd, J1¼5.5 Hz, J2¼6.0 Hz, 1H,
AcOeCHeCHeOeC), 2.08 (s, 3H, O]CeCH3), 2.07 (s, 3H, O]CeCH3),
1.48 (s, 3H, OeCeCH3), 1.47 (s, 3H, OeCeCH3). 13C NMR (100 MHz,
4.4.6. (1S,2R,3R,4R)-1,2-Diacetyl-5-(N,N-pentan-1,5-diylcarbamoyl)-
3,4-O-isopropylidenecyclohex-5-en-1,2,3,4-tetraol (4c). Orange oil
(53%, 0.061 g). ½a D25
ꢁ
þ115 (c 1.0, CH2Cl2). Rf: 0.40 (CHCl3/EtOAc 5:1). 1H
NMR (400 MHz, CDCl3)
d (ppm): 5.66 (br s, 1H, CH]C), 5.31 (d,
CDCl3)
d
(ppm): 170.1 (OeC]O), 169.9 (OeC]O), 166.3 (NHeC]O),
J¼8.8 Hz, 1H, C]CHeCHeOAc), 5.22 (dd, J1¼8.8 Hz, J2¼9.0 Hz, 1H,
CeOeCHeCHeOAc), 4.98 (d, J¼6.4 Hz, 1H, CH]CeCHeO), 4.28 (dd,
J1¼6.4 Hz, J2¼9.0 Hz, 1H, AcOeCHeCHeOeC), 3.49e3.52 (m, 2H,
CH2eNeCH2), 3.26e3.28 (m, 2H, CH2eNeCH2), 2.08 (s, 3H, O]
CeCH3), 2.04 (s, 3H, O]CeCH3), 1.42e1.62 (m, 6H,
NeCH2e(CH2)3eCH2), 1.48 (s, 3H, OeCeCH3), 1.33 (s, 3H, OeCeCH3).
137.6 (AcOeCHeCH]C), 133.7 (CH]CeC]O), 133.2 (CAr), 129.1 (CAr),
124.8 (CAr), 120.3 (CAr), 111.7 (OeCeO), 73.6 (AcOeCHeCHeOeC), 71.2
(CH]CeCHeOeC),
CHeCHeOAc), 27.1 (OeCeCH3), 26.2 (OeCeCH3), 20.8 (2C, O]CeCH3).
HRMS (ESI) calcd for C20H23NO7Na [MþNa]þ: 412.1367. Found:
412.1355.
69.2
(AcOeCHeCHeOeC),
65.7
(C]
13C NMR (100 MHz, CDCl3)
d (ppm): 169.4 (OeC]O), 169.2 (OeC]O),
167.2 (NeC]O), 131.8 (CH]CeC]O), 131.0 (AcOeCHeCH]C), 110.5
(OeCeO), 74.1 (AcOeCHeCHeOeC), 71.7 (CH]CeCHeOeC), 70.8
4.4.3. (1R,2R,3R,4R)-1,2-Diacetyl-5-(N,N-pentan-1,5-diylcarbamoyl)-
3,4-O-isopropylidenecyclohex-5-en-1,2,3,4-tetraol (3c). Orange oil
(AcOeCHeCHeOeC),
69.4
(C]CHeCHeOAc),
46.2,
40.8
(56%, 0.064 g). ½a D25
ꢁ
ꢂ55.0 (c 1.0, CH2Cl2). Rf: 0.40 (CHCl3/EtOAc 5:1).
(CH2eNeCH2), 26.8 (OeCeCH3), 25.4 (NeCH2eCH2eCH2eCH2eCH2),
25.1 (OeCeCH3), 24.3 (NeCH2eCH2eCH2eCH2eCH2), 23.4
(NeCH2eCH2eCH2eCH2eCH2), 20.0 (O]CeCH3), 19.8 (O]CeCH3).
HRMS (ESI) calcd for C19H27NO7Na [MþNa]þ: 404.1680. Found:
404.1677.
1H NMR (400 MHz, CDCl3)
d
(ppm): 5.77 (d, J¼4.8 Hz, 1H, CH]C),
5.49 (dd, J1¼3.6 Hz, J2¼4.8 Hz, 1H, C]CHeCHeOAc), 5.12 (dd,
J1¼3.6 Hz, J2¼8.0 Hz, 1H, CeOeCHeCHeOAc), 5.03 (d, J¼6.0 Hz, 1H,
CH]CeCHeO),
4.44
(dd,
J1¼6.0 Hz,
J2¼8.0 Hz,
1H,
AcOeCHeCHeOeC), 3.39e3.51 (m, 4H, CH2eNeCH2), 2.03 (s, 3H,
O]CeCH3), 1.98 (s, 3H, O]CeCH3), 1.45e1.53 (m, 6H,
NeCH2e(CH2)3eCH2), 1.37 (s, 3H, OeCeCH3), 1.30 (s, 3H, OeCeCH3).
4.4.7. (1R,2R,3R,4R)-1,2-Diacetyl-5-((R)-1-methoxy-1-oxopropan-2-
ylcarbamoyl)-3,4-O-isopropylidenecyclohex-5-en-1,2,3,4-tetraol
13C NMR (100 MHz, CDCl3)
d
(ppm): 169.5 (OeC]O), 169.1 (OeC]
(3d). Yellow oil (85%, 0.102 g). ½a D25
ꢁ
ꢂ50.0 (c 2.0, CHCl2). Rf: 0.40
O), 166.1 (NeC]O), 135.6 (CH]CeC]O), 132.0 (AcOeCHeCH]C),
109.2 (OeCeO), 71.6 (AcOeCHeCHeOeC), 71.5 (CH]CeCHeOeC),
(CHCl3/EtOAc 5:1). 1H NMR (400 MHz, CDCl3)
d (ppm) 7.24 (d,
J¼6.8 Hz, 1H, NH), 6.72 (d, J¼3.2 Hz, 1H, CH]C), 5.69 (br s, 1H, C]
CHeCHeOAc), 5.43e5.45 (m, 1H, CeOeCHeCHeOAc), 4.94 (d,
J¼5.4 Hz,1H, CH]CeCHeO), 4.64e4.71 (m, 1H, CH3eCHeNH), 4.45
(dd, J1¼5.4 Hz, J2¼6.0 Hz, 1H, AcOeCHeCHeOeC), 3.77 (s, 3H,
NHeCOOCH3), 2.06 (s, 3H, O]CeCH3), 2.05 (s, 3H, O]CeCH3), 1.46
(s, 3H, HNeCHeCH3), 1.45 (s, 3H, OeCeCH3), 1.44 (s, 3H, OeCeCH3).
69.8
(AcOeCHeCHeOeC),
64.7
(C]CHeCHeOAc),
45.8
(CH2eNeCH2), 39.6 (CH2eNeCH2), 26.5 (OeCeCH3), 25.5
(NeCH2eCH2eCH2eCH2eCH2) 25.3 (NeCH2eCH2eCH2eCH2eCH2),
24.4 (OeCeCH3), 24.1 (NeCH2eCH2eCH2eCH2eCH2), 19.9 (O]
CeCH3), 19.7 (O]CeCH3). HRMS (ESI) calcd for C19H27NO7Na
[MþNa]þ: 404.1680. Found: 404.1666.
13C NMR (100 MHz, CDCl3)
d (ppm): 173.0 (O]CeOCH3), 169.8
(OeC]O), 169.6 (OeC]O), 164.3 (HNeC]O), 133.2 (CH]CeC]O),
132.1 (AcOeCHeCH]C), 110.7 (OeCeO), 73.2 (AcOeCHeCHeOeC),
70.9 (CH]CeCHeOeC), 69.2 (AcOeCHeCHeOeC), 65.7 (C]
CHeCHeOAc), 52.3 (OCH3), 48.1 (HNeCHeCH3) 27.4 (OeCeCH3),
25.9 (OeCeCH3), 20.6 (O]CeCH3), 20.5 (O]CeCH3), 18.1
(HNeCHeCH3). HRMS (ESI) calcd for C18H25NO9Na [MþNa]þ:
422.1422. Found: 422.1437.
4.4.4. (1S,2R,3R,4R)-1,2-Diacetyl-5-tert-butylcarbamoyl-3,4-O-iso-
propylidenecyclohex-5-en-1,2,3,4-tetraol (4a). Yellow oil (52%,
0.058 g). ½a 2D5
ꢁ
þ100.0 (c 0.6, CH2Cl2). Rf: 0.35 (EtOAc/n-hexane 4:6). 1H
NMR (400 MHz, CDCl3)
d
(ppm): 6.63 (d, J¼2.0 Hz, 1H, CH]C), 6.48 (br
s, 1H, NH), 5.49 (dd, J1¼2.0 Hz, J2¼8.8 Hz, 1H, C]CHeCHeOAc), 5.23
(dd, J1¼8.8 Hz, J2¼9.2 Hz, 1H, CeOeCHeCHeOAc), 4.82 (d, J¼6.0 Hz,
1H, CH]CeCHeOeC), 4.29 (dd, J1¼6.0 Hz, J2¼9.2 Hz, 1H,
AcOeCHeCHeOeC), 2.10 (s, 3H, O]CeCH3), 2.09 (s, 3H, O]CeCH3),
1.55 (s, 3H, OeCeCH3), 1.44 (s, 3H, OeCeCH3), 1.39 (s, 9H, tBu). 13C NMR
4.4.8. (1R,2R,3R,4R)-1,2-Diacetyl-5-((S)-1-methoxy-3-methyl-1-
oxobutan-2-ylcarbamoyl)-3,4-O-isopropylidenecyclohex-5-en-
(100 MHz, CDCl3)
d
(ppm): 170.1 (OeC]O), 170.0 (OeC]O), 163.8
1,2,3,4-tetraol (3e). Yellow oil (66%, 0.085 g). ½a D25
ꢁ
ꢂ45.0 (c 2.0, CHCl2).
(NHeC]O), 135.0 (AcOeCHeCH]C), 132.3 (CH]CeC]O), 111.9
(OeCeO), 75.5 (AcOeCHeCHeOeC), 71.9 (CH]CeCHeOeC), 71.3
(AcOeCHeCHeOeC), 69.8 (C]CHeCHeOAc), 51.4 (C(CH3)3), 28.6 (3C,
C(CH3)3), 27.9 (OeCeCH3), 26.3 (OeCeCH3), 20.8 (2C, O]CeCH3).
HRMS (ESI) calcd for C18H27NO7Na [MþNa]þ: 392.1680. Found:
392.1672.
Rf: 0.45 (CHCl3/EtOAc 6:1). 1H NMR (400 MHz, CDCl3)
d (ppm) 7.23 (d,
J¼8.4 Hz, 1H, NH), 6.72 (br s, 1H, CH]C), 5.70 (br s, 1H, C]
CHeCHeOAc), 5.46 (br s, 1H, CeOeCHeCHeOAc), 4.95 (d, J¼4.8 Hz,
1H, CH]CeCHeO), 4.61e4.64 (m, 1H, NHeCHeCH(CH3)2), 4.46 (dd,
J1¼5.6 Hz, J2¼5.6 Hz, 1H, AcOeCHeCHeOeC), 3.75 (s, 3H,
NHeCOOCH3), 2.22e2.26 (m, 1H, NHeCHeCH(CH3)2) 2.06 (s, 3H, O]
CeCH3), 2.05 (s, 3H, O]CeCH3), 1.43 (s, 6H, OeCeCH3), 0.94 (dd,
J1¼6.8 Hz, J2¼2.2 Hz, 6H, NHeCHeCH(CH3)2). 13C NMR (100 MHz,
4.4.5. (1S,2R,3R,4R)-1,2-Diacetyl-5-phenylcarbamoil-3,4-O-iso-
propylidencyclohex-5-en-1,2,3,4-tetraol (4b). Yellow oil (27%,
CDCl3) d (ppm): 171.9 (O]CeOCH3), 169.8 (OeC]O), 169.5 (OeC]O),
164.4 (HNeC]O), 132.9 (CH]CeC]O), 132.1 (AcOeCHeCH]C), 110.6
(OeCeO), 73.2 (AcOeCHeCHeOeC), 71.0 (CH]CeCHeOeC), 69.0
0.032 g). ½a 2D5
ꢁ
þ110.0 (c 0.5, CH2Cl2). Rf: 0.50 (EtOAc/n-hexane 1:9). 1H
NMR (400 MHz, CDCl3) d (ppm): 8.40 (br s, 1H, NH), 7.47e7.49 (m, 2H,
HAr), 7.26e7.30 (m, 2H, HAr), 7.06e7.10 (m, 1H, HAr), 6.75 (d, J¼1.2 Hz,
1H, CH]C), 5.49 (d, J¼8.8 Hz,1H, C]CHeCHeOAc), 5.21 (dd, J1¼8.8 Hz,
J2¼9.2 Hz, 1H, CeOeCHeCHeOAc), 4.91 (d, J¼6.0 Hz, 1H, CH]
CeCHeOeC), 4.39 (dd, J1¼6.0 Hz, J2¼9.2 Hz, 1H, AcOeCHeCHeOeC),
2.05 (s, 3H, O]CeCH3), 2.02 (s, 3H, O]CeCH3), 1.53 (s, 3H, OeCeCH3),
(AcOeCHeCHeOeC),
65.6
(C]CHeCHeOAc),
57.1
(NHeCHeCHe(CH3)2), 51.9 (OCH3), 30.8 (HNeCHeCHe(CH3)2), 27.4
(OeCeCH3), 25.9 (OeCeCH3), 20.5 (O]CeCH3), 20.4 (O]CeCH3), 18.0
(HNeCHeCHe(CH3)2), 16.7 (HNeCHeCHe(CH3)2) . HRMS (ESI) calcd
for C20H30NO9 [MþH]þ: 428.1915. Found: 428.1915.
1.43 (s, 3H, OeCeCH3). 13C NMR (100 MHz, CDCl3)
OeC]O), 161.9 (NHeC]O), 136.8
d
(ppm): 169.3 (2C,
(CH]CeC]O), 136.1
Acknowledgements
(AcOeCHeCH]C), 130.9 (CAr), 128.4 (CAr), 124.1 (CAr), 119.6 (CAr), 111.7
(OeCeO), 74.9 (AcOeCHeCHeOeC), 71.0 (CH]CeCHeOeC), 70.5
(AcOeCHeCHeOeC), 69.0 (C]CHeCHeOAc), 26.8 (OeCeCH3), 25.5
ˇ
~
Authors are thankful to Portuguese FCT (Fundac¸ ao para a Ciencia
e a Tecnologia), QREN/FEDER/COMPETE-Programa Operacional

6940
R.M.B. Carrilho et al. / Tetrahedron 68 (2012) 6935e6940
8. (a) Mahmud, T. Nat. Prod. Rep. 2003, 20, 137e166; (b) Mehta, G.; Lakshminath,
Factores de Competitividade, PTDC/QUI-QUI/112913/2009, ANII
ꢀ
S.; Talukdar, P. Tetrahedron Lett. 2002, 43, 335e338; (c) Gomez, A. M.; Moreno,
ꢀ
ꢀ
(Agencia Nacional de Investigacion e Innovacion) from Uruguayan
government and PEDECIBA (Programa de Desarrollo de Ciencias
ꢀ
E.; Uriel, C.; Jarosz, S.; Valverde, S.; Lopez, J. C. Tetrahedron: Asymmetry 2005, 16,
2401e2407; (d) Mingeot-Leclercq, M.-P.; Glupczynski, Y.; Tulkens, P. M. Anti-
microb. Agents Chemother. 1999, 43, 727e737.
ꢀ
Basicas, PNUD/URU/06/004) and Hungarian Scientific Research
9. Chen, X.; Fan, Y.; Zheng, Y.; Shen, Y. Chem. Rev. 2003, 103, 1955e1977.
10. (a) Schoenberg, A.; Bartoletti, I.; Heck, R. F. J. Org. Chem. 1974, 39, 3318e3326;
(b) Schoenberg, A.; Heck, R. F. J. Org. Chem. 1974, 39, 3327e3331; (c) Schoen-
berg, A.; Heck, R. F. J. Am. Chem. Soc. 1974, 96, 7761e7764.
Fund (OTKA CK78553). R.M.B.C. thanks FCT for PhD grant SFRH/BD/
ꢀ
60499/2009. V.H. thanks AUGM (Asociacion de Universidades del
Grupo Montevideo) and the Coimbra Catalysis & Fine Chemistry
group, for a fellowship.
ꢀ
11. (a) Modern Carbonylation Methods; Kollar, L., Ed.; Wiley-VCH: Weinheim, 2008;
(b) Grigg, R.; Mutton, S. P. Tetrahedron 2010, 66, 5515e5548.
12. (a) Skoda-Foldes, R.; Kollar, L. Curr. Org. Chem. 2002, 6, 1097e1119; (b) Acs, P.;
ꢀ
€
ꢀ
Supplementary data
ꢀ
ꢀ
€
ꢀ
Takacs, A.; Szilagyi, A.; Wolfling, J.; Schneider, G.; Kollar, L. Steroids 2008, 73,
ꢀ
ꢀ
669e675; (c) Szilagyi, A.; Farkas, R.; Petz, A.; Kollar, L. Tetrahedron 2009, 65,
ꢀ
ꢀ
4484e4489; (d) Takacs, A.; Farkas, R.; Kollar, L. Tetrahedron 2008, 64, 61e66; (e)
Supplementary data related to this article can be found online at
http://dx.doi.org/10.1016/j.tet.2012.05.128.
ꢀ
ꢀ
ꢀ
Takacs, A.; Petz, A.; Kollar, L. Tetrahedron 2008, 64, 8726e8730; (f) Takacs, A.;
ꢀ
Abreu, A. R.; Peixoto, A. F.; Pereira, M. M.; Kollar, L. Synth. Commun. 2009, 39,
1534e1548; (g) Takacs, A.; Szilagyi, A.; Acs, P.; Mark, L.; Peixoto, A. F.; Pereira,
M. M.; Kollar, L. Tetrahedron 2011, 67, 2402e2406; (h) Takacs, A.; Acs, P.; Farkas,
R.; Kokotos, G.; Kollar, L. Tetrahedron 2008, 64, 9874e9878; (i) Takacs, A.; Petz,
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
References and notes
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
A.; Kollar, L. Tetrahedron 2010, 66, 4479e4483.
1. (a) Gibson, D. T.; Koch, J. R.; Kallio, R. E. Biochemistry 1968, 7, 2653e2662; (b)
Hudlicky, T.; Gonzalez, D.; Gibson, D. T. Aldrichimica Acta 1999, 32, 35e62; (c)
Boyd, D. R.; Sharma, N. D.; Byrne, B.; Hand, M. V.; Malone, J. F.; Sheldrake, G. N.;
Blacker, J.; Dalton, H. J. Chem. Soc., Perkin Trans. 1 1998, 1935e1943.
13. (a) Boyd, D. R.; Sharma, N. D.; Llamas, N. M.; Malone, J. F.; O’Dowd, C. R.; Allen,
C. C. R. Org. Biomol. Chem. 2005, 3, 1953e1963; (b) Boyd, D. R.; Sharma, N. D.;
Acaru, C. A.; Malone, J. F.; O’Dowd, C. R.; Allen, C. C. R.; Stevenson, P. J. Org. Lett.
2010, 12, 2206e2209.
ꢀ
2. (a) Heguaburu, V.; Sa, M. M.; Schapiro, V.; Pandolfi, E. Tetrahedron Lett. 2008, 49,
14. Shie, J.-J.; Fang, J.-M.; Wong, C.-H. Angew. Chem., Int. Ed. 2008, 47, 5788e5791.
15. (a) Qu, B.; Haddad, N.; Han, Z. S.; Rodriguez, S.; Lorenz, J. C.; Grinberg, N.; Lee,
H.; Busacca, C. A.; Krishnamurthy, D.; Senanayake, C. H. Tetrahedron Lett. 2009,
50, 6126e6129; (b) Wu, X.-F.; Neumann, H.; Beller, M. Chem.dEur. J. 2010, 16,
6787e6790; (b) Hudlicky, T.; Reed, J. W. Synlett 2009, 685e703; (c) Labora, M.;
Pandolfi, E. M.; Schapiro, V. Tetrahedron: Asymmetry 2010, 21, 153e155.
3. (a) Cantekin, S.; Baran, A.; C¸ alis¸ kan, R.; Balci, M. Carbohydr. Res. 2009, 344,
426e431; (b) Cere, V.; Mantovani, G.; Peri, F.; Pollicino, S.; Ricci, A. Tetrahedron
2000, 56, 1225e1231; (c) Sanfilippo, C.; Patti, A.; Piattelli, M.; Nicolosi, G.
Tetrahedron: Asymmetry 1997, 8, 1569e1573.
4. (a)Xu,W.;Springfield,S. A.;Koh, J.T. Carbohydr. Res. 2000, 325,169e176;(b)Mehta,
G.; Reddy, D. S.; Ramesh, S. S.; Tatu, U. Tetrahedron Lett. 1999, 40, 9141e9144.
5. (a) Dwek, R. A. Chem. Rev. 1996, 96, 683e720; (b) Yu, S.-H.; Chung, S.-K.
Tetrahedron: Asymmetry 2005, 16, 2729e2747; (c) Ogawa, S. Trends Glycosci.
Glycotechnol. 2004, 16, 33e53; (d) Compain, P.; Martin, O. R. Bioorg. Med.
Chem. 2001, 9, 3077e3092.
6. (a) Mehta, G.; Ramesh, S. S. Tetrahedron Lett. 2001, 42, 1987e1990; (b) Blidi, L.
E.; Crestia, D.; Gallienne, E.; Demuynck, C.; Bolte, J.; Lemaire, M. Tetrahedron:
Asymmetry 2004, 15, 2951e2954; (c) Mehta, G.; Mohanrao, R.; Katukojvala, S.;
Landais, Y.; Sen, S. Tetrahedron Lett. 2011, 52, 2893e2897; (d) Nagy, V.; Benltifa,
ꢁ
ꢀ
ꢀ
9750e9753; (c) Barluenga, J.; Fernandez, M. A.; Aznar, F.; Valdes, C. Chem.dEur.
J. 2005, 11, 2276e2283; (d) Lee, P. O.; Lee, K.; Kang, Y. J. Am. Chem. Soc. 2006,
128, 1139e1146.
16. Hudlicky, T.; Luna, H.; Olivo, H. F.; Andersen, C.; Nugent, T.; Price, J. D. J. Chem.
Soc., Perkin Trans. 1 1991, 2907e2917.
17. Hudlicky, T.; Price, J. D.; Rulin, F.; Tsunoda, T. J. Am. Chem. Soc. 1990, 112,
9439e9440.
18. Carrilho, R. M. B.; Neves, A. C. B.; Lourenc¸ o, M. A. O.; Abreu, A. R.; Rosado, M. T.
ꢀ
ꢀ
ꢀ
S.; Abreu, P. E.; Eusebio, M. E. S.; Kollar, L.; Bayon, J. C.; Pereira, M. M. J. Orga-
nomet. Chem. 2012, 698, 28e34.
ꢀ
ꢀ
19. Carrilho, R. M. B.; Pereira, M. M.; Takacs, A.; Kollar, L. Tetrahedron 2012, 68,
204e207.
ꢀ
ꢀ
20. Hudlicky, T.; Stabile, M. R.; Gibson, D. T.; Whited, G. M. Org. Synth. 1999, 76,
77e85.
21. Entwistle, D. A.; Hudlicky, T. Tetrahedron Lett. 1995, 36, 2591e2594.
M.; Vidal, S.; Berzsenyi, E.; Teilhet, C.; Czifrak, K.; Batta, G.; Docsa, T.; Gergely, P.;
ꢀ
Somsak, L.; Praly, J.-P. Bioorg. Med. Chem. 2009, 17, 5696e5707.
7. Arjona, O.; Gomez, A. M.; Lopez, J. C.; Plumet, J. Chem. Rev. 2007, 107, 1919e2036.
ꢀ
ꢀ