Synthesis of orthogonally protected 2-deoxystreptamine stereoisomers

Article abstract of DOI:10.1016/j.tet.2004.01.063

Enantiomerically pure 4,6-diaminocyclohexenols are obtained from carbohydrate derived 1,7-dienes by ring-closing metathesis and palladium catalyzed allylic amination using o-nitrobenzenesulfonylamides as nucleophiles. In the latter reaction the use of a cyclic carbonate as a leaving group proved to be essential to facilitate a smooth substitution. The obtained compounds were converted into orthogonally protected diaminocyclitols, which are stereoisomers of the naturally occurring 2-deoxystreptamine, a constituent of aminoglycoside antibiotics.

Full text of DOI:10.1016/j.tet.2004.01.063

Tetrahedron 60 (2004) 2813–2822
Synthesis of orthogonally protected 2-deoxystreptamine
stereoisomers
Steven H. L. Verhelst,a Tom Wennekes,a Gijsbert A. van der Marel,a Herman S. Overkleeft,a
Constant A. A. van Boeckelb and Jacques H. van Booma
,
*
aBioorganic Synthetic Chemistry, Leiden Institute of Chemistry, PO Box 9502, 2300 RA Leiden, The Netherlands
bN.V. Organon, Lead Discovery Unit, PO Box 20, 5340 BH Oss, The Netherlands
Received 26 September 2003; revised 17 December 2003; accepted 22 January 2004
Abstract—Enantiomerically pure 4,6-diaminocyclohexenols are obtained from carbohydrate derived 1,7-dienes by ring-closing metathesis
and palladium catalyzed allylic amination using o-nitrobenzenesulfonylamides as nucleophiles. In the latter reaction the use of a cyclic
carbonate as a leaving group proved to be essential to facilitate a smooth substitution. The obtained compounds were converted into
orthogonally protected diaminocyclitols, which are stereoisomers of the naturally occurring 2-deoxystreptamine, a constituent of
aminoglycoside antibiotics.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
the A-site of 16S rRNA2 and its ability to induce misreading
of the genetic code.3 In the last decade aminoglycosides
have been shown to target a variety of other RNA structures
including hepatitis delta virus ribozyme,4 HIV trans-activat-
ing region (TAR),5 and HIV rev responsive element (RRE).6
It may be expected that the development of aminoglyco-
sides that can selectively target RNA structures will broaden
the application of aminoglycoside antibiotics.
RNA is involved in several important biological processes
including protein synthesis and regulation of transcription
and translation. Small molecules that are able to modulate
RNA functions are interesting compounds for the develop-
ment of drugs.1 For example, aminoglycoside antibiotics,
such as neomycin B and kanamycin B (Fig. 1), form a major
lead in RNA targeting drug research. The current clinical
use of aminoglycoside antibiotics is based on the binding to
The preparation of aminoglycoside analogs has attracted the
Figure 1. Examples of aminoglycoside antibiotics.
Keywords: Aminoglycoside antibiotics; 2-Deoxystreptamine; Cyclitols; Allylic substitution.
*
Corresponding author. Tel.: þ31-71-5274274; fax: þ31-71-5274307; e-mail address: j.boom@chem.leidenuniv.nl
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.01.063

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S. H. L. Verhelst et al. / Tetrahedron 60 (2004) 2813–2822
attention of synthetic chemists. Most recent studies are
based on the derivatization of natural aminoglycosides or
substructures thereof, such as neamine and 2-deoxystrepta-
mine (2-DOS; Fig. 1). For example, 2-DOS has been
functionalized with polyamines7 and aryl substituents.8
Another promising approach towards the construction of
aminoglycoside analogs is based on the glycosylation of
cyclitol building blocks. The naturally occurring 2-DOS can
be effectively obtained in its meso form by hydrolysis of
neomycin B,9 while protected and enantiomerically pure
2-DOS can be prepared by chemical transformation of
neamine10 or enzymatic desymmetrization of 2-DOS.11
Both 2-DOS and its 2,5-dideoxy congener12 have recently
been used in glycosylations to obtain analogs of amino-
glycoside antibiotics that closely resemble the natural
products.11,13,14
2. Results and discussion
The first objective in our approach comprises the trans-
formation of a carbohydrate derivative into a six-membered
carbocycle. A revolution in the synthesis of carbocycles was
caused by the development of powerful metathesis cata-
lysts.16 Specifically, cyclization of 1,7-dienes by ring-
closing metathesis proved to be an attractive method
to synthesize cyclitols.17,18 In the first instance, we used
1,7-dienes, prepared by the Vasella–Barbier reaction18 of
easily accessible 5-iodopentafuranosides, in the synthesis of
diaminocyclohexenols 14 and 16.19 1,7-Diene 2 was
synthesized from methyl 5-deoxy-5-iodo-2,3-isopropyli-
dene-b-D-ribofuranoside 1 in a one-pot process including
Vasella fragmentation, entrapment of the intermediate
aldehyde by an amine and subsequent Barbier type imine
allylation (Scheme 1).18 Similarly, the enantiomeric 1,7-
diene 6 was obtained starting from methyl 5-deoxy-5-iodo-
2,3-isopropylidene-b-D-lyxofuranoside (5).19 The second-
ary amino functions in compounds 2 and 6 were protected
with the o-nitrobenzenesulfonyl20 (nosyl, Ns) group to give
3 and 7 in 92 and 89% yield, respectively. Both protected
dienes smoothly underwent ring-closing metathesis using
0.5 mol% Grubbs’ catalyst (Cl2(PPh3)2Ru¼CHPh)16a to
give the fully protected cyclohexene derivatives 4 and 8.
The functionalization of synthetic, unnatural diaminocycli-
tols represents an attractive alternative strategy towards
selective RNA binding molecules. The stereochemically
more diverse aminoglycosides resulting from this approach
can be an important extension of the aminoglycoside
antibiotic research, since the three-dimensional positioning
of the amino groups in the aminoglycoside core may well be
decisive for selective interaction with the negatively
charged binding pockets in RNA.15
It was envisaged that a palladium catalyzed allylic
amination using nitrobenzenesulfonamides as nucleo-
philes21 could be employed to introduce the second amine
functionality on the carbocyclic ring. In order to enable
substitution, the protected allylic hydroxyl in compounds 4
and 8 had to be converted into a suitable leaving group. To
this end, several leaving groups were installed on ribose-
derived scaffold 4. 1,2-Diacetate 10 and 1,2-dimesylate 11,
were obtained by cleavage of the isopropylidene and
subsequent acetylation or mesylation of diol 9 (Scheme 2).
Unfortunately, both compounds were unreactive, which is
rather surprising, taken into consideration that especially
allylic acetates are often used in Pd(0)-catalyzed allylic
substitutions. It was expected that productive Pd(0)
catalyzed allylic substitution could be effected when the
hydroxyl functions of diol 9 were converted into methyl-
carbonates. This functionality has been described in the
literature to be favorable compared with acetates, as CO2 is
We here report the synthesis, starting from carbohydrate
derivatives, of chiral diaminocyclohexene derivatives A
(Fig. 2) and their conversion into orthogonally protected
stereoisomers of 2-deoxystreptamine (B), which are valu-
able compounds in the design of novel aminoglycoside
antibiotics having unnatural stereochemistry.
Figure 2. Strategy towards stereoisomers of 2-DOS.
Scheme 1. Reagents and conditions: (i) o-Nitrobenzenesulfonylchloride (NsCl), DCM/sat. Na2CO3, 3: 92%, 7:89%. (ii) Grubbs’ catalyst (0.5 mol%), quant.

S. H. L. Verhelst et al. / Tetrahedron 60 (2004) 2813–2822
2815
Scheme 2. Reagents and conditions: (i) AcOH/H2O 8:2, reflux. (ii) Ac2O, pyridine, 94% (2 streps from 4). (iii) MsCl (5 equiv.), pyridine, 69% (2 steps from 4).
(iv) Methyl chloroformate (5 equiv.), pyridine (6 equiv.), DCM. (v) NsNHBn (2.2 equiv.), Pd2(dba)3·CHCl3 (2.5 mol%), PPh3 (25 mol%), Et3N (3 equiv.),
THF. (vi) Phosgene (1.1 equiv.), pyridine, DCM, 12: 98%. (vii) NsNHBn (1.3 equiv.), Pd2(dba)3–CHCl3 (0.25 mol%), PPh3 (2.5 mol%), Et3N (3 equiv.),
THF, 14: 87%. 16: 76% (three steps).
liberated upon substitution, leading to a favorable entropic
contribution.22 However, the installation of methylcarbon-
ate functionalities on the hydroxyls of compound 9 did not
proceed efficiently. Reaction of 9 with an excess of
methylchloroformate led to the formation of a mixture of
cyclic carbonate 12 and monosubstituted compound 13.
Subjection of 13 to the Pd(0)-catalyzed allylic amination
using N-benzyl-nosylamide as a nucleophile, led to the
sluggish formation of cyclic carbonate 12, presumably via
intramolecular attack of the free hydroxyl group on the
carbonyl function (Scheme 2). Apart from this, a small
amount of target molecule 14 was detected, probably
originating from substitution of the in situ formed cyclic
carbonate 12. The latter reaction did not go to completion
due to degradation of the palladium catalyst, as judged by
the color of the reaction mixture, which turned from bright
yellow to dark brown. However, cyclic carbonate 12 could
be prepared on a large scale by hydrolysis of acetonide 4
under standard conditions and subsequent reaction of the
diol with a slight excess of phosgene (98%; Scheme 2).
Pd(0) catalyzed allylic amination of 12 gave the diamino-
cyclohexene derivative 14 in 87% yield. The regio- and
stereoselectivity of this reaction originates from the
formation of the p-allyl complex 15 and subsequent attack
of the nucleophile at the less hindered carbon atom.
Subjection of the enantiomeric carbocycle 8 to the same
reaction conditions gave the diaminocyclohexene derivative
16, which was isolated in 76% yield over 3 steps (Scheme 2).
formation of the p-allyl complex provides a favorable
energetic contribution resulting in a smooth and high
yielding reaction. We expected that cyclic sulfite 17,
accessible after reaction of diol 9 with thionylchloride,
would follow a similar course to give compound 14.
However, subjection of 17 to the paladium catalyzed allylic
amination gave the unexpected cyclohexenone derivative
18 in a non-optimized yield of 30%. The formation of 18
may be explained by the mechanism proposed in Scheme 3.
Instead of substitution of the p-allyl complex by the
nitrosulfonamide nucleophile, elimination of palladium
takes place followed by liberation of sulfur dioxide to
form the a,b-unsaturated ketone 18. The observation that
performing the reaction in the absence of catalyst did not
result in the formation of 18 illustrates that the Pd(0) species
plays a crucial role.23
The observation that cyclic carbonate 12, but not its acyclic
counterpart 13, was a useful substrate indicates that the
release of carbon dioxide and possibly the relief of strain in
the five-six fused ring system of compound 12 upon
Scheme 3. Reagents and conditions: (i) NsNHBn (2.2 equiv.), Pd2(dba)3·
CHCl3 (2.5 mol%), PPh3 (25 mol%), Et3N (3 equiv.), THF.

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Table 1. Transformation of 5 into 4,6-diaminocyclohexene derivativesa
Entry Product Yield (%)
S. H. L. Verhelst et al. / Tetrahedron 60 (2004) 2813–2822
The scope of the allylic amination of cyclic carbonate 12
was broadened by the use of other nosylamides as
nucleophiles, leading to highly functionalized diamino-
cyclohexene derivatives (Table 1). Application of Ns-glycine
methyl ester and 1-Ns-a-Boc-L-lysine methyl ester as
nucleophiles led to the formation of peptide derivatives 19
and 20 in 85 and 71%, respectively. Lysine, glutamic acid
and phenylalanine derivatives 21–23 were synthesized
using the respective amino acids with a Ns-group at the
a-amino functions. However, yields were lower compared
to those in entry 1 and 2, probably due to steric hindrance
around the nucleophilic center. A double amount of
palladium catalyst only led to a slight increase in yield
(see entry 5). In an attempt to improve the yield of the
substitution by a-amino acids, several additional experi-
ments were conducted using phenylalanine derivatives.
However, the use of the less sterically demanding
p-nitrobenzenesulfonyl group and the more electron with-
drawing di-nitrobenzenesulfonyl group did not have a
beneficial effect on the outcome of the reaction.
1
19
85
2
20
71
3
21
36
Besides nosyl-protected amino acids, acridine and galactose
derivatives featuring a terminal nosylated amine were
reacted with cyclic carbonate 12 to give compounds 24
and 25 in satisfactory yields (entry 6 and 7). The latter two
compounds are of particular interest in the synthesis of
aminoglycoside analogs. Acridine conjugate 24 can com-
bine the RNA binding properties of positively charged
amino functions on the aminocyclitol with the intercalating
properties of acridine. Compound 25 illustrates that the
cyclitol moiety can be easily appended to carbohydrates via
an amine bond instead of a more difficult to introduce
glycosidic linkage.
4
22
37
At this stage, we focused our attention on the conversion
(Scheme 4) of the 4,6-diaminocyclohexene derivatives 14
and 16 into orthogonally protected 2-deoxystreptamine
stereoisomers 31 and 32. The first step entails protection of
the allylic alcohol function in 16. It was anticipated that the
difference in reactivity of the equatorial and axial hydroxyl
function, resulting from dihydroxylation of the double bond,
could be utilized for selective introduction of a protective
group. For example, the use of organotin derivatives in
alkylations is a well-established method to discriminate
between equatorial and axial hydroxyl functions.24 With the
purpose to regioselectively introduce an allyl protecting
group, we first acetylated the alcohol function in compound
16. Dihydroxylation of 26 using N-methylmorpholine-N-
oxide (NMO) and a catalytic amount of osmium tetroxide
yielded 28 in 92% yield (Scheme 4). Several attempts to
allylate the equatorial hydroxyl in 28 via the tin-ketal
procedure were abortive. Exploration of a recently reported
regioselective alkylation of cyclic phenylboronate deriva-
tives25 on our substrates was also not successful. It may
therefore be concluded that the hydroxyl functions in 28 are
not reactive enough due to the electron withdrawing
protecting groups on the nitrogen and oxygen functionali-
ties. On the other hand, it is well documented that the
opening of an orthoester of pyranose derivatives proceeds to
give the axial acetate. Therefore, we decided to use this
method in our route. The synthesis of the required orthoester
31 was accomplished by the following steps. The free
hydroxyl in compound 16 was protected with a TBS group
5
23
44 (51)b
6
24
80
7
25
58
a
General conditions: NsNHR (1.5 equiv.), Pd2(dba)3·CHCl3 (2.5 mol%),
PPh3 (25 mol%), Et3N (3 equiv.), THF.
10% Pd(0) catalyst was used.
b

S. H. L. Verhelst et al. / Tetrahedron 60 (2004) 2813–2822
2817
Scheme 4. Reagents and conditions: (i) Ac2O, pyridine, quant. (ii) TBSCl (3 equiv.), imidazole (4 equiv.), DMF, 59% or TBSOTf (1.2 equiv.), pyridine
(5 equiv.), DCM, 89%. (iii) NMO (2.2 equiv.), K2OsO4·2H2O (1 mol%); 28: 92%, 29: 94%. (iv) (MeO)3CHMe, p-TsOH, DCM; (v) AcOH/H2O (v/v); 31:
95%. 32 71% (4 steps).
under standard conditions (TBSCl, imidazole, DMF) to give
compound 27 in a yield of 59%. The more reactive silylating
agent TBS triflate yielded 27 in 89%. Dihydroxylation of 27
using a catalytic amount of osmium tetroxide and NMO as a
co-oxidant provided 2-DOS stereoisomer 29 in 94% yield.
Treatment of cis-diol 29 with trimethyl orthoacetate and
subsequent acid mediated cleavage of the resulting
orthoester yielded the desired orthogonally protected
derivative 31 in 95%. Similarly, enantiomer 14 gave the
second 2-deoxystreptamine stereoisomer 32 in 71% yield
over the four last steps.
relative to tetramethyl silane (0.0) or CDCl3 (77.0) as
internal standards. Mass spectra were recorded on a Perkin–
Elmer Sciex API 165 equipped with a custom made
electrospray interface (ESI). Column chromatography was
performed on silica gel 60 (230–400 mesh, Fluka). TLC-
analysis was conducted on TLC-plastic sheets 60 F254
(Merck) with detection by UV absorption (254 nm) where
applicable and/or by spraying with 20% H2SO4 in EtOH or a
solution of molybdate (ammonium molybdate 25 g/L) and
ceric ammonium sulfate (10 g/L in 10% aq. H2SO4)
followed by charring at ,150 8C. Olefins were visualized
by spraying with a permanganate solution (2% KMnO4 and
1% K2CO3 in water).
3. Conclusion
4.2. Experimental procedures
In this paper, we presented a route towards chiral, 4,6-
diaminocyclohexene derivatives starting from carbohydrate
derived 1,7-dienes. The versatility of our approach was
demonstrated by the use of structurally diverse nucleophiles
including amino acid, carbohydrate and intercalator derived
nosyl amides. Two of the thus obtained diaminocyclo-
hexene derivatives were converted into orthogonally
protected diaminocyclitols via a four-step procedure. The
use of 2-deoxystreptamine stereoisomers 31 and 32 in the
construction of novel, stereochemically diverse amino-
glycoside antibiotics, is currently under investigation.
Before performing reactions that require anhydrous con-
ditions, traces of water were removed from the starting
material by coevaporation with 1,2-dichloroethane, 1,4-
dioxane or toluene. Reactions were run at ambient
temperature unless stated otherwise.
4.3. General procedure for the Pd(0) catalyzed allylic
aminations
THF was freshly distilled from LiAlH4 under argon.
Triethylamine was distilled from LiAlH4 and stored on
KOH. To a solution of the carbocycle and the appropriate
nosylamide (1.5 equiv.) in THF (final concentration of
carbocycle: 0.1 M) under argon was added 3 equiv. of Et3N,
2.5 mol% of Pd2(dba)3·CHCl3 and 25 mol% of triphenyl-
phosphine. The red mixture turned into a bright yellow
solution within1 min. After TLC analysis indicated nochange
in the composition of the reaction mixture, the solvent was
evaporated and the reaction mixture was purified by column
chromatography. Reactions were performed on a 50–100 mg
scale. Note that ona large scale (see compounds 14and 16) the
amount of catalyst was reduced to 0.25 mol% Pd2(dba)3·
CHCl3 and 2.5 mol% PPh3.
4. Experimental
4.1. General methods and materials
Proton nuclear magnetic resonance (1H NMR) and carbon
nuclear magnetic resonance (13C NMR) spectra were
recorded with a Bruker AC-200 (200 MHz, 50.1 MHz,
respectively), a Bruker DPX-300 (300 MHz, 75.1 MHz
respectively), a Bruker AV-400 (400 MHz, 100 MHz
respectively) or a DMX-600 (600 MHz, 150 MHz respec-
1
tively). H and 13C chemical shifts (d) are given in ppm

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S. H. L. Verhelst et al. / Tetrahedron 60 (2004) 2813–2822
4.4. o-Nitrobenzenesulfonyl-N-benzylamine
CHH Bn, H1, H2, H6), 2.55–2.40 (m, 1H, CHH H5), 2.19–
2.04 (m, 1H, CHH H5), 1.33 (s, 3H, Me isoprop), 1.26
(s, 3H, Me isoprop). 13C NMR (CDCl3, 50.1 MHz): dC
147.0, 137.3, 134.0 (Cq, arom), 133.0, 131.2, 130.5, 127.8,
127.7, 126.9, 126.7, 125.9, 123.6 (CHarom, C3, C4), 109.7
(Cq isoprop), 76.1, 74.8 (C1, C2), 55.1 (C6), 49.0 (CH2 Bn),
27.5, 26.5 (Me isoprop), 25.1 (C5). ESI-MS: m/z 467.2
[MþNa]þ, 911.4 [2MþNa]þ.
Benzylamine (8.7 mL, 80 mmol) was added to a mixture of
NaHCO3 (13.44 g, 160 mmol), dioxane (200 mL) and water
(200 mL). To the white suspension, NsCl (19.5 g, 88 mmol,
1.1 equiv.) was added in portions. The reaction mixture was
stirred for 2 h followed by evaporation of the solvents. The
light yellow residue was dissolved in water (150 mL) and
extracted EtOAc (4£150 mL). The combined organic layers
were dried (MgSO4) and concentrated under reduced
pressure. The solid material was recrystallized from
toluene/PE, affording the title compound (21.93 g,
75 mmol, 94%) as white crystals, mp 97 8C. nmax (neat):
4.4.3. (1S,2R,6S)-6-(N-Benzyl)-o-nitrobenzenesulfona-
mino-cyclohex-3-ene-1,2-diol (9). Crude product 4 was
refluxed in AcOH/H2O (8:2, v/v, 0.2 M final concentration)
for 2 h. After TLC analysis had showed complete conver-
sion to a lower running product, the mixture was con-
centrated with coevaporation from toluene to remove traces
of water and acetic acid. The crude diol was immediately
used for protection of the hydroxyl functions.
3294, 1541, 1367, 1340, 1171 cm21 1H NMR (CDCl3,
.
200 MHz): dH 8.03–7.98 (m, 1H, Harom), 7.85–7.81 (m,
1H, Harom), 7.72–7.60 (m, 2H, Harom), 7.22 (s, 5H, Harom),
5.72 (m, 1H, NH), 4.32 (d, 2H, CH2 Bn, J¼6.6 Hz). ESI-
MS: m/z: 315.0 [MþNa]þ, 607.2 [2MþNa]þ. HRMS:
MNH4þ, found 310.0849, C13H16N3O4S requires 310.0862.
4.4.4. (1S,2R,6S)-1,2-Di-O-acetyl-6-(N-benzyl)-o-nitro-
benzenesulfonamino-cyclohex-3-ene-1,2-diol (10). A solu-
tion of compound 9 (888 mg, 2.0 mmol, 0.2 M in pyridine/
Ac2O) and dimethylaminopyridine (cat.) was stirred over-
night. Solvents were removed under reduced pressure. 1 M
HCl was added and the mixture was extracted two times
with EtOAc. Combined organic layers were washed with
sat. NaHCO3 and brine. Water phases were backextracted.
The combined organic phases were dried (MgSO4) and
concentrated under reduced pressure. Column chromato-
graphy yielded title compound 10 (914 mg, 1.87 mmol,
94%) as a white solid, mp 132 8C. [a]2D0¼255 (c¼0.50,
CHCl3). nmax (neat): 1740, 1539, 1373, 1219, 1165, 1034,
4.4.1. (3R,4S,5S)-3,4-O-Isopropylidene-5-(N-benzyl)-o-
nitro-benzenesulfon-amino-octa-1,7-dien-3,4-diol
(3).
Aminodiene 2 (16.2 g, 56.5 mmol) was dissolved in
DCM/sat Na2CO3 (1:1 v/v, 250 mL) and NsCl (18.8 g,
84.8 mmol, 1.5 equiv.) was added. The reaction mixture
was stirred vigorously overnight. Pyridine was added to
destroy the excess of NsCl and, after stirring for 15 min, the
solvent was removed under reduced pressure. Water was
added to the residue and the mixture was extracted three
times with EtOAc. The combined organic layers were
washed with brine, dried (MgSO4) and concentrated under
reduced pressure. Silicagel column chromatography (elu-
tion 10%!20% EtOAc in light petroleum) yielded 3
(24.7 g, 52.2 mmol, 92%) as a white, crystalline solid, mp
90–91 8C. [a]2D0¼þ86 (c¼0.50, CHCl3). nmax (neat): 1541,
1371, 1340, 1159, 1024 cm21. 1H NMR (CDCl3, 200 MHz):
dH 7.54–7.15 (m, 9H, Harom), 6.07–5.89 (m, 1H, H2 or H7),
5.73–5.65 (m, 1H, H2 or H7), 5.54–5.35 (m, 4H, H1, H8),
5.00–4.79 (m, 2H, H3, H4), 4.75 (d, 1H, CHH Bn,
J¼15.4 Hz), 4.56 (d, 1H, CHH Bn, J¼15.4 Hz), 4.21–
4.07 (m, 1H, H5), 2.47–2.34 (m, 1H, CHH H6), 2.22–2.11
(m, 1H, CHH H6), 1.47 (s, 3H, Me isoprop), 1.26 (s, 3H, Me
isoprop). 13C NMR (CDCl3, 50.1 MHz): dC 147.0, 136.7,
134.1 (Cq, arom), 134.3, 132.9, 131.1, 130.9, 128.8, 127.9,
127.1, 123.5 (CHarom, H2, H7), 118.3, 117.0 (C1, C8), 108.3
(Cq isoprop), 81.1, 78.2 (C3, C4), 59.0 (C5), 48.5 (CH2 Bn),
32.1 (C6), 26.1, 24.1 (Me isoprop). HRMS: MNH4þ, found
490.2058, C24H32N3O6S requires 490.2012.
1
1024 cm21. H NMR (CDCl3, 400 MHz): d 7.64–7.16 (m,
9H, Harom), 5.86–5.81 (m, 1H, Holef), 5.65–5.58 (m, 2H,
H1, H2), 5.42–5.39 (m, 1H, Holef), 4.75 (d, 1H, CHH Bn,
J¼16.6 Hz), 4.59 (d, 1H, CHH Bn, J¼16.6 Hz), 4.51 (dd,
1H, H6, J¼5.6, 11.2 Hz), 2.65–2.56 (m, 1H, CHH H5), 2.26
(dt, 1H, CHH H5, J¼5.4, 17.0 Hz), 1.94 (s, 3H, Me Ac),
1.90 (s, 3H, Me Ac). 13C NMR (CDCl3, 100 MHz): d 169.9,
169.7 (CO), 137.0, 134.0 (Cq, arom), 133.5, 131.7, 131.2,
128.5, 127.4, 127.2, 124.3, 124.0 (C3, C4, CHarom), 70.6,
69.6 (C1, C2), 53.8 (C6), 49.0 (CH2Bn), 26.8 (C5), 20.9,
20.7 (Me Ac). ESI-MS: m/z¼511.2 [MþNa]þ, 977þ.4
[MþMþH]þ, 999.3 [MþMþNa]þ. HRMS: MNH4
,
found 506.1605, C23H28N3O8S requires 506.1597.
4.4.5. (1S,2R,6S)-6-(N-Benzyl)-o-nitrobenzenesulfon-
amino-1,2-di-O-methanesulfonyl-cyclohex-3-ene-1,2-
diol (11). Methanesulfonylchloride (131 mL, 1.69 mmol,
10 equiv.) was added to a solution of compound 9 (150 mg,
0.338 mmol) in pyridine (3 mL). The solution was stirred
overnight and concentrated under reduced pressure. EtOAc
was added and the solution was washed with 1 M HCl, sat.
NaHCO3 and brine. Water phases were separately back-
extracted with EtOAc and the combined organic phases
were dried (MgSO4) and concentrated under reduced
pressure. Column chromatography yielded compound 11
(131 mg, 0.234 mmol, 69%) as a yellowish oil. nmax (neat):
4.4.2. (1S,2R,6S)-3-(N-Benzyl)-o-nitrobenzenesulfon-
amino-1,2-O-isopropylidene-cyclohex-3-en-1,2-diol (4).
Oxygen was removed from a solution of compound 3
(24.7 g, 52.2 mmol) in DCM (500 mL) by purging with
argon for 15 min. Grubbs’ catalyst Cl2(PPh3)2Ru¼CHPh
(210 mg, 0.5 mol%) was added and the solution was stirred
overnight under argon. The solvent was evaporated under
reduced pressure affording crude 4 as a light brown foam.
Crude RCM-product was applied in the next step without
purification. A small purified sample was used for
1
1539, 1340, 1159 cm21. H NMR (CDCl3, 200 MHz): dH
7.59–7.13 (m, 9H, Harom), 5.99–5.89, 5.63–5.36 (m, 4H,
H1, H2, H3, H4), 5.02 (d, 1H, CHH Bn, J¼16.8 Hz), 4.75
(d, 1H, CHH Bn, J¼16.8 Hz), 4.69–4.61 (m, 1H, H6), 3.17
(s, 3H, Ms), 3.12 (s, 3H, Ms), 2.61–2.26 (m, 2H, H5). 13C
NMR (CDCl3, 50.1 MHz): dC 147.0, 136.4, 133.8 (Cq, arom),
1
characterization. [a]2D0¼250.0 (c¼1.0, CHCl3). H NMR
(CDCl3, 200 MHz): dH 7.60–7.12 (m, 9H, Harom), 5.75–
5.68 (m, 1H, Holef), 5.56–5.50 (m, 1H, Holef), 4.94 (d, 1H,
CHH Bn, J¼16.1 Hz), 4.77–4.69, 4.49–4.39 (2m, 4H,

S. H. L. Verhelst et al. / Tetrahedron 60 (2004) 2813–2822
2819
133.8, 133.5, 131.9, 131.1, 130.0, 128.2, 127.6, 127.4,
123.8, 122.3 (C3, C4, CHarom), 79.9, 76.2 (C1, C2), 53.7
(C6), 48.9 (CH2 Bn), 39.5, 38.0 (2£ Ms), 26.7 (C5).
4.4.8. (1S,2R,6S)-6-(N-Benzyl)-o-nitrobenzenesulfon-
amino-1,2-O-sulfonyl-cyclohex-3-ene-1,2-diol (17). A solu-
tion of pyridine (170 mL, 2.1 mmol, 2.1 equiv.) in EtOAc
(1 mL) was added to a solution of compound 9 (444 mg,
1.0 mmol) and SOCl2 (77 mL, 1.05 mmol) in EtOAc (4 mL)
cooled in the waterbath. After TLC analysis indicated
complete conversion to a higher running product (^1 h), the
reaction was diluted with 1 M HCl and extracted twice with
EtOAc. Organic phase was washed with sat. NaHCO3 and
brine, dried (MgSO4) and concentrated under reduced
pressure. Column chromatography (elution 0%!12.5%
EtOAc in toluene) afforded cyclic sulfite 17 (350 mg,
0.77 mmol, 77%) as a white foam, being a mixture of two
diastereoisomers of the sulfur ylide. nmax (neat): 1541, 1369,
1346, 1209, 1161, 1124 cm21. 1H NMR (CDCl3, 400 MHz):
dH 7.59–7.10 (m, 9H, Harom), 5.97–5.81, 5.60–5.56, 5.40–
5.37 (3£ m, 4H, H1, H2, H3, H4), 5.02–4.89 (m, 1H,
benzylic H), 4.80–4.63 (m, 2H, H6, benzylic H), 2.69–
2.61, 2.48–2.22 (2£ m, 2H, H5). 13C NMR (CDCl3,
100 MHz): dC 136.1, 136.0 (Cq, arom), 133.4, 133.2, 131.7,
131.6, 131.3, 131.5, 129.9, 129.8, 128.4, 128.3, 128.2,
127.7, 127.5, 124.1, 124.0, 123.7, 122.4 (C3, C4, CHarom),
85.0, 81.3, 80.2, 79.0 (C1, C2), 55.2, 53.8 (C6), 49.4, 49.3
4.4.6. (1S,2R,6S)-6-(N-Benzyl)-o-nitrobenzenesulfon-
amino-1,2-O-carbonyl-cyclo-hex-3-ene-1,2-diol (12). Com-
pound 9 (52.2 mmol) was dissolved in pyridine (19 mL) and
DCM (40 mL), placed under argon and cooled to 0 8C. Next,
phosgene (30 mL, 1.93 M in toluene, 58 mmol, 1.1 equiv.)
was carefully added over a period of approximately 2 min.
The reaction mixture was stirred for 2 h, after which the
excess phosgene was quenched with water. The resulting
mixture was poured into 1 M HCl. After separation of the
organic layer, the water layer was extracted twice with
DCM. Combined organic layers were washed with diluted
NaHCO3, dried (MgSO4) and concentrated under reduced
pressure. Purification by silicagel column chromatography
(elution 0%!16% EtOAc in toluene) furnished 12 (21.99 g,
51.1 mmol, 98%) as a white foam. [a]2D0¼276.4 (c¼1.0,
CHCl3). nmax (neat): 1798, 1539, 1369, 1344, 1153, 1126,
1
1024 cm21. H NMR (CDCl3, 600 MHz): dH 7.52–7.47
(m, 2H, Harom), 7.40–7.39 (d, 1H, Harom, J¼8.0, 1.4 Hz),
7.27–7.24 (m, 1H, Harom), 7.19–7.13 (m, 2H, Harom), 7.07–
7.04 (m, 3H, Harom), 6.04 (ddd, 1H, Holef, J¼10.2, 6.2,
1.9 Hz), 5.64–5.61 (m, 1H, Holef), 5.25–5.22 (m, 1H, H2),
5.09–5.07 (m, 1H, H1), 4.80 (d, 1H, CHH Bn, J¼15.9 Hz),
4.55–4.52 (m, 2H, H6, CHH Bn), 2.47–2.42 (m, 1H, CHH
H5), 2.32–2.28 (m, 1H, CHH H5). 13C NMR (CDCl3,
150 MHz): dC 154.1 (CO), 147.0, 135.7, 134.2 (Cq, arom),
133.4, 132.7, 131.7, 131.2, 128.3, 128.1, 127.7, 124.0, 121.1
(C1, C2, CHarom), 79.0, 75.1 (C1, C2), 54.4 (C6), 49.3
(CH2 Bn), 25.2 (C5). ESI-MS: m/z¼431.2 (MþH)þ.
HRMS: MNaþ, found 453.0672, C20H18N2O7SNa
requires 453.0732.
(CH2 Bn), 25.6, 25.2 (C5). ESI-MS: m/z¼450.9 [MþH]þ,
þ
468.2 [MþNH4]þ, 473.0 [MþNa]þ. HRMS: MNH4
,
found 468.0889, C19H22N3O7S2 requires 468.0899.
4.4.9. (6S)-6-[(N-Benyzl)-o-nitrobenzenesulfonamino]-
cyclo-hex-2-enone (18). Pd(0) catalyzed allylic amination
on cyclic sulfite 17 was performed according to the
general procedure. After column chromatography (elution
0%!15% EtOAc in toluene) compound 18 was isolated as a
light brown oil in an unoptimized yield of 13 mg (30%).
1
nmax (neat): 1688, 1539, 1346, 1159, 1122 cm21. H NMR
(CDCl3, 400 MHz): d 7.99–7.17 (m, 9H, Harom), 6.97–6.91
(m, 1H, H3), 6.04 (dd, 1H, H2, J¼2.5, 10.0 Hz), 4.96–4.86
(m, 2H, H6, CHH Bn), 4.14 (d, 1H, CHH Bn, J¼16.1 Hz),
2.67–2.55 (m, 1H, CHH H4), 2.48–2.35 (m, 1H, CHH H4),
2.26–2.18 (m, 1H, CHH H5), 1.95–1.81 (m, 1H, CHH H5).
13C NMR (CDCl3, 100 MHz): d195.0 (CO), 150.4 (C3),
137.0, 133.0 (Cq, arom), 132.7, 131.4, 130.9, 129.4, 128.7,
128.4, 128.2, 127.8, 127.6, 123.9 (CHarom, C2), 64.1 (C6),
50.0 (CH2 Bn), 30.4, 26.9 (C4, C5). ESI-MS: m/z 387.0
[MþH]þ, 409.1 [MþNa]þ, 795.2 [MþMþNa]þ. HRMS:
MNH4þ, found 404.1297, C19H22N3O5S requires 404.1280.
4.4.7. (1R,4R,6S)-4,6-Bis[(N-benzyl)-o-nitrobenzenesul-
fon-amino]-cyclohex-2-enol (14). To a solution of cyclic
carbonate 12 (14.63 g, 34 mmol) and o-nitrobenzenesul-
fonyl-N-benzylamine (12.9 g, 44.2 mmol, 1.3 equiv.) in
THF under argon, was added Et3N (14.2 mL, 102 mmol,
3 equiv.), Pd2(dba)3·CHCl3 (87 mg, 0.25 mol%) and tri-
phenylphosphine (223 mg, 2.5 mol%). The initial dark red
solution turned bright yellow, and the solution was stirred
for 3 h, followed by concentration under reduced pressure.
Silica column chromatography (elution 0%!12.5% EtOAc
in toluene) yielded the title compound (20.10 g, 29.6 mmol,
87%) as a white foam. [a]2D0¼217.8 (c¼1.0, CHCl3). nmax
4.4.10. N-o-Nitrobenzenesulfonyl-N-[(1R,4R,6S)-6-(N-
benzyl)-6-o-nitrobenzene-sulfonamino-cyclohex-2-enol-
4-yl]-glycine methyl ester (19). The title compound was
isolated as an off-white foam (67 mg, 85%). [a]2D0¼256
(c¼1.0, CHCl3). nmax (neat): 1749, 1541, 1346, 1159,
(neat): 1539, 1340, 1157 cm21
.
1H NMR (CDCl3,
600 MHz): dH 7.79–7.70 (m, 1H, Harom), 7.56–7.51
(m, 5H, Harom), 7.43–7.40 (m, 1H, Harom), 7.39–7.36
(m, 1H, Harom), 7.19–7.04 (m, 10H, Harom), 5.80 (ddd, 1H,
Holef, J¼10.0, 5.7, 2.6 Hz), 5.56–5.54 (m, 1H, Holef), 4.69–
4.65 (m, 1H, H4), 4.58 (d, 1H, CHH Bn, J¼16.4 Hz), 4.50
(d, 1H, CHH Bn, J¼15.8 Hz), 4.41 (d, 1H, CHH Bn,
J¼16.4 Hz), 4.27 (d, 1H, CHH Bn, J¼15.8 Hz), 4.14 (bs,
1H, H1), 3.96 (dt, 1H, H6, J¼13.1, 2.9 Hz), 2.04–1.97
(m, 1H, CHH H5), 1.80–1.74 (m, 1H, CHH H5), 1.53 (bs,
1H, OH). 13C NMR (CDCl3, 150 MHz): dC 147.49, 147.46,
137.28, 133.84 (Cq, arom), 133.78, 133.52, 133.39, 131.68,
131.65, 131.37, 131.32, 130.95, 130.92, 128.51, 128.38,
127.73, 127.68, 127.45, 124.12, 124.08 (C2, C3, CHarom),
66.72 (C1), 56.97, 56.75 (C4, C6), 49.29, 48.79 (CH2 Bn),
27.44 (C5). ESI-MS: m/z¼701.4 [MþNa]þ.
1
1124 cm21. H NMR (300 MHz): dH 8.18–8.15 (m, 1H,
Harom), 7.72–7.56 (m, 6H, Harom), 7.45–7.39 (m, 1H,
Harom), 7.26–7.12, m, 5H, Harom), 5.93 (ddd, 1H, Holef
,
J¼2.4, 5.7, 9.9 Hz), 5.63 (bd, 1H, Holef, J¼10.1 Hz), 4.79
(d, 1H, CHH Bn, J¼16.5 Hz), 4.73–4.67 (m, 1H, H4), 4.61
(d, 1H, CHH Bn, J¼16.5 Hz), 4.26 (bs, 1H, H1), 4.10–4.01
(m, 3H, H6, 2Ha), 3.62 (s, 3H, OMe), 2.13–2.03 (m, 1H,
CHH H5), 1.95–1.93 (m, 1H, CHH H5). 13C NMR
(50.1 MHz): dC 170.1 (CO), 147.7, 147.3, 137.1 (Cq, arom),
133.9 (CHarom), 133.4 (Cq, arom), 133.1 (CHarom), 132.6 (Cq,
arom), 132.0, 131.6, 131.4, 130.9, 129.8, 128.5, 127.7, 127.5,
124.3, 124.0 (C2, C3, CHarom), 66.7 (C1), 56.6, 56.5 (C4,

2820
S. H. L. Verhelst et al. / Tetrahedron 60 (2004) 2813–2822
C6), 52.3 (OMe), 49.4, 45.0 (Ca, CH2 Bn), 26.9 (C5). ESI-
MS: m/z 683.3 [MþNa]þ. HRMS: MNH4
(m, 4H, CHH H5, CHH Hb, 2Hg), 2.10–1.98 (m, 2H, CHH
H5, CHH Hb). 13C NMR (50.1 MHz): dC 173.0, 170.5 (2
CO), 147.5, 137.6 (Cq, arom), 133.9 (CHarom), 133.7 (Cq,
arom), 133.3, 132.1, 132.0, 131.7, 131.6, 131.1, 130.8, 130.5,
128.6, 128.4, 127.9, 127.8, 127.3, 124.1, 124.0 (CHarom),
66.8 (C1), 58.0, 57.3, 56.7 (C4, C6, Ca), 52.6, 51.8 (2
OMe), 49.4 (CH2 Bn), 30.8, 27.8, 26.9 (C5, Cb, Cg).
ESI-MS: m/z 769.3 [MþNa]þ. HRMS: MNH4þ, found
764.1862, C32H38N4O13S2 requires 764.1908.
þ
, found
678.1587, C28H32N5O11S2 requires 678.1540.
4.4.11. N a-t-Butyloxycarbonyl-N 1-o-nitrobenzenesul-
fonyl-N 1-[(1R,4R,6S)-6-(N-benzyl)-6-o-nitrobenzenesul-
fon-amino-cyclohex-2-enol-4-yl]-L-lysine methyl ester
(20). The title compound was isolated as an off-white
foam (68 mg, 71%). [a]2D0¼240 (c¼1.0, CHCl3). nmax
(neat): 2972, 2901, 1740, 1699, 1541, 1369, 1344, 1159,
1
1057 cm21. H NMR (300 MHz): dH 8.09–8.00 (m, 1H,
4.4.14. N-o-Nitrobenzenesulfonyl-N-[(1R,4R,6S)-6-(N-
benzyl)-6-o-nitrobenz-enesulfonamino-cyclohex-2-enol-
4-yl]-L-phenylalanine methyl ester (23). The title com-
pound was isolated as a slightly yellow foam (38 mg, 44%).
[a]2D0¼235 (c¼0.5, CHCl3). nmax (neat): 1742, 1541, 1369,
Harom), 7.74–7.09 (m, 12H, Harom), 5.99–5.94 (m, 1H,
Holef), 5.72 (d, 1H, Holef, J¼10.0 Hz), 5.10 (d, 1H, NH,
J¼8.7 Hz), 4.82 (d, 1H, CHH Bn, J¼16.6 Hz), 4.76 (d, 1H,
CHH Bn, J¼16.6 Hz), 6.64 (bs, 1H, H4), 4.29–4.22 (m, 2H,
H1, Ha), 4.19–4.08 (m, 1H, H6), 3.72 (s, 3H, OMe), 3.33–
3.24 (m, 1H, CHH, H1), 3.19–3.09 (m, 1H, CHH H1),
2.07–2.00 (m, 1H, CHH H5), 1.79–1.678 (m, 3H, CHH H5,
CHH Hd, CHH Hb), 1.63–1.51 (m, 2H, CHH Hb, CHH
Hd), 1.38 (s, 9H, Boc), 1.33–1.16 (m, 2H, Hg). 13C NMR
(50.1 MHz): dC 173.0 (CO ester), 155.5 (CO carbamate),
147.8, 147.5, 137.1, 133.6 (Cq, arom), 133.1 (CHarom), 131.9
(Cq, arom), 131.5, 131.1, 130.9, 128.3, 127.9, 127.3, 124.2,
123.9 (CHarom, C2, C3), 80.0 (Cq Boc), 67.0 (C1), 56.7, 56.3
(C4, C6), 52.3 (OMeþCa), 49.7, 44.7 (CH2 Bn, C1), 32.3,
1
1344, 1159, 1124, 1061 cm21. H NMR (300 MHz): dH
7.86–7.11 (m, 18H, Harom), 5.88 (ddd, 1H, Holef, J¼2.5, 5.8,
9.9 Hz), 5.35 (bd, 1H, Holef, J¼10.7 Hz), 4.90 (d, 1H, CHH
Bn, J¼16.5 Hz), 4.74 (d, 1H, CHH Bn, J¼16.5 Hz), 4.69–
4.34 (m, 1H, H4), 4.45 (dd, 1H, Ha, J¼5.9, 8.6 Hz), 4.23
(bs, 1H, H1), 4.15–4.05 (m, 1H, H6), 3.55 (s, 3H, OMe),
3.42 (dd, 1H, CHH Hb, J¼8.8, 13.9 Hz), 3.04 (dd, 1H, CHH
Hb, J¼5.9, 13.9 Hz), 2.50 (q, 1H, CHH H5, J¼12.0 Hz),
2.09–2.03 (m, 1H, CHH H5). 13C NMR (50.1 MHz): dC
170.5 (CO), 148.6, 147.3, 137.7, 136.7, 133.9 (Cq, arom),
133.3 (CHarom), 131.7 (Cq, arom), 130.9, 130.7, 129.5, 128.5,
127.7, 127.4, 127.0, 124.1 (C2, C3, CHarom), 66.9 (C1),
60.9, 57.1, 56.8 (C4, C5, Ca), 52.5 (OMe), 49.4 (CH2 Bn),
38.0 (Cb), 28.0 (C5). ESI-MS: m/z 773.3 [MþNa]þ.
HRMS: MNH4þ, found 768.1989, C35H38N5O11S2 requires
768.2009.
29.9, 27.0, 22.0 (C5, Cb, Cg, Cd), 28.1 (Me Boc). ESI-MS:
þ
m/z 732.4 [M-BocþH]þ 854.3 [MþNa]þ. HRMS: MNH4
,
found 849.2762, C37H49N6O13S2 requires 849.2799.
4.4.12. N 1-Benzyloxycarbonyl-N a-o-nitrobenzenesul-
fonyl-N a-[(1R,4R,6S)-6-(N-benzyl)-6-o-nitrobenzenesul-
fon-amino-cyclohex-2-enol-4-yl]-L-lysine methyl ester
(21). The title compound was isolated as an off-white
foam (37 mg, 36%). [a]2D0¼272 (c¼0.5, CHCl3). nmax
(neat): 1740, 1705, 1541, 1369, 1344, 1157, 1124 cm21. 1H
NMR (300 MHz): dH 7.96–7.93 (m, 1H, Harom), 7.72–7.12
(m, 17H, Harom), 5.95–5.89 (m, 1H, Holef), 5.67 (bd, 1H,
Holef, J¼10.2 Hz), 5.07 (s, 2H, CH2 Z), 4.91–4.82 (m, 2H,
CHH Bn, NH Z), 4.75 (d, 1H, CHH bn, J¼16.6 Hz), 4.59
(bs, 1H, H4), 4.25 (bs, 1H, H1), 4.18–4.07 (m, 2H, H6, Ha),
3.70 (s, 3H, OMe), 3.11 (q, 2H, H1, J¼6.4 Hz), 2.56–2.44
(m, 1H, CHH H5), 2.37 (bs, 1H, OH), 2.18–2.04 (m, 1H,
CHH H5), 1.76–1.64 (m, 2H, Hb), 1.50–1.28 (m, 4H, Hg,
Hd).13C NMR (50.1 MHz): dC 171.0 (CO ester), 156.5 (CO
carbamate), 148.3, 147.5, 137.6, 131.2, 133.8 (Cq, arom),
133.3, 131.7, 131.0, 130.8, 130.6, 128.5, 128.4, 128.1,
127.7, 127.3, 124.1, 124.0 (C2, C3, CHarom), 66.9 (C1), 66.6
(CH2 Z), 59.3, 57.3, 56.8, 52.5 (C4, C6, Ca, OMe), 49.4
(CH2 Bn), 40.5, 31.0, 29.3, 28.0, 23.8 (C5, Cb, Cg, Cd, C1).
ESI-MS: m/z 866.6 [MþH]þ 888.3 [MþNa]þ.
4.4.15. Acridine-9-carboxylic acid-(6-{N-o-nitroben-
zenesulfon-yl-N-[(1R,4R,6S)-6-(N-benzyl)-6-o-nitroben-
zenesulfon-amino-cyclohex-2-enol-4-yl]}-aminohexyl)
amide (24). The title compound was isolated as a yellow
foam (60 mg, 58%). nmax (neat): 2928, 1639, 1541, 1439,
1
1369, 1342, 1159, 1121 cm21. H NMR (300 MHz): dH
8.03–7.96 (m, 2H, Harom), 7.86–7.83 (m, 1H, Harom), 7.69–
7.03 (m, 18H, Harom), 5.79–5.74 (m, 1H, H20), 5.54 (bd, 1H,
H30, J¼10.3 Hz), 4.73 (d, 1H, CHH Bn, J¼16.3 Hz), 4.64–
4.59 (m, 2H, H40, CHH Bn), 4.18 (bs, 1H, H10), 4.04–4.00
(m, 1H, H60), 3.58 (q, 2H, H1, J¼6.5 Hz), 3.22 (t, 2H, H6,
J¼7.8 Hz), 2.30–2.19 (m, 1H, CHH H50), 1.82–1.79
(m, 1H, CHH H5), 1.67–1.60 (m, 4H, H2, H5), 1.42–1.22
(m, 4H, H3, H4). 13C NMR (50.1 MHz): dC 166.9 (CO),
147.72, 147.66, 147.1, 141.4, 137.1, 134.1, 133.6 (Cq, arom),
133.3 (CHarom), 133.1 (Cq, arom), 132.0, 131.8, 131.6, 131.4,
131.0, 130.8, 130.5, 128.7, 128.6, 128.3, 128.2, 127.8,
127.2, 126.6, 125.1, 124.1 123.8 (C2, C3, CHarom), 121.9
(Cq, arom), 66.6 (C1), 56.5 (br; C4, C6) 53.4, 49.9, 44.9, 39.8,
30.5, 29.0, 27.5, 25.8 (CH2 Bn, C5, CH2 hexyl) ESI-MS: m/z
893.4 [MþH]þ, 915.2 [MþNa]þ.
4.4.13. N-o-Nitrobenzenesulfonyl-N-[(1R,4R,6S)-6-(N-
benzyl)-6-o-nitro-benzenesulfonamino-cyclohex-2-enol-
4-yl]-L-glutamic acid methyl ester (22). The title com-
pound was isolated as an slightly yellow foam (31 mg,
37%). [a]2D0¼266 (c¼0.5, CHCl3). nmax (neat): 2957, 2901,
1736, 1541, 1371, 1346, 1161, 1124, 1065 cm21. 1H NMR
(300 MHz): dH 8.01 (d, 1H, Harom, J¼1.4 Hz), 7.69–7.10
(m, 12H, Harom), 5.96 (ddd, 1H, Holef, J¼2.5, 5.8, 9.8 Hz),
5.70 (bd, 1H, Holef, J¼10.0 Hz), 4.89 (d, 1H, CHH Bn,
J¼16.6 Hz), 4.77 (d, 1H, CHH Bn, J¼16.6 Hz), 4.61–4.59
(m, 1H, H4), 4.35–4.27 (m, 2H, H1, Ha), 4.11–4.07 (m, 1H,
H6), 3.65 (s, 3H, OMe), 3.62 (s, 3H, OMe), 2.55–2.37
4.4.16. 1,2,3,4-Di-O-isopropylidene-6-N-o-nitrobenzene-
sulfonyl-6-N-[(1R,4R,6S)-6-(N-benzyl)-6-o-nitro-benze-
nesulfonamino-cyclohex-2-enol-4-yl]-amino-D-galactose
(25). The title compound was isolated as a white foam
(77 mg, 80%). [a]D20¼294 (c¼1.0, CHCl3). nmax (neat):
1541, 1371, 1342, 1211, 1161, 1065 cm21 1H NMR
.
(300 MHz): dH 8.05–8.02 (m, 1H, Harom), 7.76–7.05 (m,
12H, Harom), 6.18–6.12 (ddd, 1H, H2, J¼2.4, 6.1, 9.8 Hz),
5.51 (dd, 1H, H3, J¼2.2, 10.0 Hz), 5.41 (d, 1H, H10,

S. H. L. Verhelst et al. / Tetrahedron 60 (2004) 2813–2822
2821
J¼5.0 Hz), 5.02 (d, 1H, CHH Bn, J¼16.4 Hz), 4.82 (d, 1H,
CHH Bn, J¼16.4 Hz), 4.76–4.70 (m, 1H, H4), 4.54 (dd, 1H,
H30), J¼2.5, 7.8 Hz), 4.32–4.29 (m, 2H, H1, H40), 4.23–
4.08 (m, 3H, H20, H50, H6), 3.61 (d, 1H, CHH H60,
J¼16.4 Hz), 3.25 (dd, 1H, CHH H60, J¼7.5, 16.4 Hz),
2.92–2.80 (m, 1H, CHH H5), 2.35–2.22 (m, 1H, CHH H5),
1.38 (s, 3H, Me isoprop), 1.30 (s, 3H, Me isoprop), 1.22 (s,
3H, Me isoprop), 1.03 (s, 3H, Me isoprop). 13C NMR
(50.1 MHz): dC 148.2, 127.1, 137.4, 134.7 (Cq, arom), 133.8,
133.0, 132.8, 132.0, 131.1, 130.9, 129.4, 128.0, 127.0,
124.3, 123.7 (C2, C3, CHarom), 109.4, 109.3 (Cq isoprop),
96.4 (C10), 72.3, 70.5, 70.1 (br), 67.80 (1, 20, 30, 40, 50),
56.6, 56.5 (C4, C6), 49.5, 46.5 (C6 , CH2 Bn), 29.1
(C6), 25.9, 25.5, 24.7, 24.3 (Me isoprop). ESI-MS: m/z
845.5 [MþNH4]þ. HRMS: MNH4þ, found 848.2440,
C37H46N5O14S2 requires 848.2483.
(d, 1H, CHH benzyl, J¼16.1 Hz), 4.41–4.36 (m, 2H, H6,
CHH benzyl), 4.21–4.14 (m, 1H, H4), 4.00 (bs, 1H, H1),
3.77 (bs, 1H, H2), 3.73–3.68 (m, 1H, H3), 2.76 (d, 1H, OH,
J¼1.9 Hz), 2.61 (d, 1H, OH, J¼5.4 Hz), 1.91–1.81 (m, 1H,
CHH H5), 1.68–1.63 (m, 1H, CHH H5), 0.87 (s, 9H, t-Bu),
0.13 (s, 3H, Me), 0.03 (s, 3H, Me). 13C NMR (CDCl3,
100 MHz): dC 147.5, 147.2, 137.5, 136.6, 134.6 (Cq, arom),
133.8. 132.9 (CHarom), 132.8 (Cq, arom), 132.2, 131.7, 131.4,
130.9, 128.7, 128.1, 137.9, 127.8, 127.2, 124.3, 123.8
(CHarom), 75.4, 72.4, 66.9 (C1, C2, C3), 57.1, 54.7 (C4, C6),
49.6, 48.2 (CH2 Bn), 29.0 (C5), 25.9 (Me t-Bu), 17.7
(Cq t-Bu), 24.6, 25.0 (2£ Me TBS). ESI-MS: m/z¼827.3
þ
[MþH]þ, 849.3 [MþNa]þ. HRMS: MNH4
, found
844.2657, C38H50N5O11S2Si requires 844.2718.
4.4.19. 1L-(1,4,6/2,3)-4,6-Bis[(N-benzyl)-nitrobenzene-
sulfon-amino]-2-O-acetyl-1-O-(tert-butyldimethylsilyl)-
cyclo-hexane-1, 2, 3-triol (31). A solution of diol 29
(165 mg, 0.20 mmol), trimethylorthoacetate (0.25 mL,
2 mmol, 10 equiv.) and p-TsOH (4 mg, 0.1 equiv.) in
DCM (1 mL) was stirred for 1 h. TLC analysis (eluens:
toluene/EtOAc 2:1) indicated complete conversion to two
higher running products, being the two stereoisomers of
orthoester 30. The reaction was neutralized with triethyl-
amine and the solvents were removed under reduced
pressure. Sat. NaHCO3 was added and the mixture was
extracted three times with EtOAc. Combined organic layers
were dried (MgSO4) and evaporated to dryness. Crude
orthoester 30 (ESI-MS: m/z¼905.5 [MþNa]þ) was immedi-
ately used in the next step. It was dissolved in AcOH/H2O
(4:1 v/v) and stirred for 2 h, when TLC analysis indicated
complete disappearance of the orthoester. The reaction
mixture was diluted with toluene and concentrated under
reduced pressure. During evaporation of the solvents,
toluene was added several times to remove acetic acid
traces. Silica column chromatography (elution 10%!40%
EtOAc in toluene) provided orthogonally protected 2-
deoxystreptamine epimer 31 (165 mg, 0.190 mmol, 95%)
as a white foam. [a]D20¼þ88.4 (c¼1.0, CHCl3). nmax (neat):
1747, 1541, 1369, 1348, 1226, 1161, 1124, 1090, 1059,
4.4.17. (1S,4S,6R)-4,6-bis[(N-benzyl)-o-nitrobenzenesul-
fon-amino]-1-O-(tert-butyldimethylsilyl)-cyclohex-2-
enol (27). Pyridine (0.20 mL, 2.5 mmol, 5 equiv.) and tert-
butyldimethylsilyl triflate (0.138 mL, 0.6 mmol, 1.2 equiv.)
were added to a solution of compound 16 (339 mg, 0.5 mmol)
in DCM (2 mL). After stirring for 2.5 h sat. NaHCO3 was
added and the mixture was extracted three times with EtOAc.
Combinedorganiclayersweredried(MgSO4),andevaporated
under reduced pressure. Silica column chromatography
(elution 0%!20% EtOAc in toluene) afforded the title
compound (353 mg, 0.446 mmol, 89%) as a white foam.
[a]2D0¼þ60.8(c¼0.50, CHCl3).nmax (neat):1541, 1367, 1344,
1157, 1124, 1026 cm21. 1H NMR (CDCl3, 400 MHz): dH 7.96
(d, 1H, Harom, J¼8.3 Hz), 7.67–6.97 (m, 15H, Harom), 6.87
(d, 2H, Harom, J¼7.3 Hz), 5.86 (ddd, 1H, Holef, J¼2.3, 5.5,
9.9 Hz), 5.52 (d, 1H, Holef, J¼10.1 Hz), 4.91–4.84 (m, 1H,
H4), 4.70–4.65 (m, 2H, 2£ CHH benzyl), 4.45 (d, 1H, CHH
benzyl, J¼16.2 Hz), 4.39–4.33 (m, 2H, H1, CHH benzyl),
4.03 (bd, 1H, H6, J¼12.9 Hz), 2.24–2.15 (m, 1H, CHH H5),
1.99–1.91 (m, 1H, CHH H5), 0.91 (s, 9H, t-Bu), 0.19 (s, 3H,
Me),0.11(s, 3H, Me).13CNMR(CDCl3,100 MHz):dC 147.7,
147.3, 137.7, 136.2, 135.2, 134.0 (Cq, arom), 133.4, 132.8,
132.6, 131.8, 131.7, 131.1, 130.7, 129.8, 127.5, 127.3, 124.2,
123.7 (CHarom, C2, C3), 68.9 (C1), 57.3, 57.1 (C4, C6), 50.1,
48.7 (CH2 Bn), 28.3 (C5), 25.9 (Me t-Bu), 17.9 (Cq t-Bu),
24.0, 24.6 (2£ Me TBS). ESI-MS: m/z¼815.5 [MþNa]þ.
HRMS: MNH4þ, found 810.2603, C38H48N5O9S2Si requires
810.2663.
1
1045, 1030 cm21. H NMR (CDCl3, 400 MHz): dH 8.10–
8.07 (m, 1H, Harom), 7.72–7.02 (m, 15H, Harom), 6.81 (d, 2H,
Harom, J¼7.1 Hz), 4.94 (t, 1H, H2, J¼4.6 Hz), 4.76 (d, 1H,
CHH Bn, J¼16.0 Hz), 4.60 (d, 1H, CHH Bn, J¼16.3 Hz),
4.37–4.21 (m, 4H, H4, H6, 2£ CHH Bn), 4.11–4.09 (m, 1H,
H1), 3.99–3.94 (m, 1H, H3), 2.42 (d, 1H, OH, J¼7.8 Hz),
2.15 (s, 3H, Me Ac), 1.83–1.71 (m, 2H, H5), 0.89 (s, 9H,
Me t-Bu), 0.18 (s, 3H, Me TBS), 0.15 (s, 3H, Me TBS).
13C NMR (CDCl3, 100 MHz): dC 170.1 (CO), 147.6,
147.3, 137.1, 136.0, 134.5 (Cq, arom), 133.6 (CHarom),
133.1 (Cq, arom), 132.9, 131.7, 131.5, 131.1, 130.5, 128.7,
128.09, 128.05, 128.0, 127.3, 124.2, 123.6 (CHarom), 73.9
(C2), 73.3 (C1), 65.4 (C3), 57.6, 55.0 (C4, C6), 49.5, 48.0
(CH2 Bn), 30.0 (C5), 25.9 (Me t-Bu), 20.7 (Me Ac), 17.7 (Cq
4.4.18. 1L-(1,4,6/2,3)-4,6-Bis[(N-benzyl)-nitrobenzene-
sulfon-amino]-1-O-(tert-butyldimethylsilyl)-cyclo-
hexane-1, 2, 3-triol (29).26 N-Methyl-morpholine-N-oxide
(107 mg, 0.91 mmol, 2.2 equiv.) and K2Os2O4·2H2O
(1.2 mg, 0.75 mol%) were added to a solution of alkene
27 (328 mg, 0.414 mmol) in acetone/water (2 mL, 3:1 v/v).
After 72 h the reaction was quenched with aqueous NaHSO3
and extracted three times with EtOAc. Combined organic
layers were dried on MgSO4 and evaporated under reduced
pressure. Column chromatography (elution 10%!50%
EtOAc in toluene) yielded compound 29 (314 mg,
0.38 mmol, 92%) as a slightly yellow foam. [a]2D0¼þ72.4
(c¼0.50, CHCl3). nmax (neat): 1541, 1340, 1159, 1123,
t-Bu), 24.6, 25.2 (Me TBS). ESI-MS: m/z¼869.5
þ
[MþH]þ, 891.4 [MþNa]þ. HRMS: MNH4
, found
886.2781, C40H52N5O12S2Si requires 886.2823.
1
1087, 1059, 1030 cm21. H NMR (CDCl3, 400 MHz): dH
Acknowledgements
8.14–8.11 (m, 1H, Harom), 7.73–7.01 (m, 15H, Harom),
6.88–6.86 (m, 1H, Harom), 4.68 (d, 1H, CHH benzyl,
J¼16.5 Hz), 4.56 (d, 1H, CHH benzyl, J¼16.1 Hz), 4.48
The authors thank Hans van den Elst for recording mass
spectroscopy and Organon N.V. for funding.

2822
S. H. L. Verhelst et al. / Tetrahedron 60 (2004) 2813–2822
C.-H.; Rando, R. R. Bioorg. Med. Chem. Lett. 2003, 13,
901–903.
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