Synthesis of novel pyrrolidine 3,4-diol derivatives as inhibitors of α-L-fucosidases

Article abstract of DOI:10.1039/b819867e

The stereoselective synthesis of new 3,4-dihydroxypyrrolidine derivatives starting from D-mannose, D-ribose and L-fucose is presented. Two synthetic strategies employing organometallic addition to hemiacetalic sugars followed by selective nucleophilic dis

Full text of DOI:10.1039/b819867e

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www.rsc.org/obc | Organic & Biomolecular Chemistry
Synthesis of novel pyrrolidine 3,4-diol derivatives as inhibitors of
a-L-fucosidases†
Elena Moreno-Clavijo,a Ana T. Carmona,*a Yolanda Vera-Ayoso,a Antonio J. Moreno-Vargas,a Claudia Bello,b
Pierre Vogelb and Inmaculada Robina*a
Received 7th November 2008, Accepted 17th December 2008
First published as an Advance Article on the web 3rd February 2009
DOI: 10.1039/b819867e
The stereoselective synthesis of new 3,4-dihydroxypyrrolidine derivatives starting from D-mannose,
D-ribose and L-fucose is presented. Two synthetic strategies employing organometallic addition to
hemiacetalic sugars followed by selective nucleophilic displacement or conjugate addition of ammonia
to conjugate aldonic esters as key steps, are used. The new compounds were assayed for their inhibitory
activity towards 13 commercially available glycosidases. Compounds that share the absolute
configuration at C(2,3,4,5) of L-fucopyranosides and incorporate aromatic moieties are potent and
selective inhibitors of a-L-fucosidases in the nM range.
Iminoalditols having a carbon chain linked to the carbon adja-
Introduction
cent to nitrogen, the so-called homoazasugars (aza-C-glycosides)
The role of glycosidases and glycosyltransferases in the biosyn-
have received special importance due to their stability towards
thesis of glycoproteins1 and their control in recognition pro-
chemical and enzymatic degradation, at the same time as retaining
cesses including cell/cell, cell/invader and inflammation,2 has
stimulated the development of their inhibitors. Many of them
have shown great medicinal value as exemplified by the treat-
ment of the influenza virus, non-insulin-dependent diabetes, or
genetic disorders.3,4 In particular a-L-fucosidases are enzymes
that catalyze the hydrolysis of a-L-fucose units located on the
cell surface oligosaccharides5 and participate in a variety of
biological processes.6 The accumulation of fucose-containing
glycoconjugates, because of the absence or deficiency of a-L-fuco-
sidases leads to pathological modifications of normal cell be-
haviour such as inflammation,7 tumor cell growth and forma-
tion of metastases,8 neurovisceral disorders and cystic fibrosis.9
the same type of biological activity.16 Homoazasugars bear-
ing aminomethyl(ethyl), hydroxymethyl or 1,2-dihydroxyethylene
groups as side chains, have been recently described.17 With regard
to their enzymatic inhibitory activity it has been reported that
some homoanalogues of 1,5-dideoxy-1,5-iminoalditol derivatives
are more active than the parent compounds.18 Thus, b-homo-
analogues 4, 5 and 619 have been described as potent a-L-fuco-
sidase inhibitors in the nM range. Homoanalogues of 1,4-dideoxy-
1,4-iminoalditol 720 such as 8 and 9 are also potent inhibitors of
a-L-fucosidases (8, Ki 1.4 mM),21,22 (9, Ki 8 nM).23 Compounds
with an R configuration at C-5 (1024,25 and 1122,24,26) are inhibitors
in the mM range (Fig. 1). Compounds with a spyrocyclopropyl
moiety at C-5 have also been described as moderate inhibitors
of a-L-fucosidases.27 It has also been claimed that hydrophobic
groups attached to the iminosugar improve their inhibitory activity
through unspecific contributions to the binding with the enzyme.28
The incorporation of aromatic moieties to L-fuconojirimycin
derivatives increases the inhibitory activity remarkably29 as in
a-L-Fucosidase activity is
a diagnostic factor for several
carcinomas.10 a-L-fucosidases have been found in human seminal
plasma and in the membranes of human sperm cells and facilitate
sperm transport and sperm egg-interactions. Inhibitors of these
enzymes can have anticonceptive properties.11 Inhibitors of a-L-
fucosidases have been also found to inhibit the cytophatic effect
of HIV and reduce infection.4
Among the most powerful a-L-fucosidase inhibitors are
derivatives of 1,5-dideoxy-1,5-iminoalditols, such as 1-deoxy-
L-fuconojirimycin 1,12 homo-L-fuconojirimycin 213 and L-
fuconojirimycin (5-amino-5-deoxy-L-fucose) 3.14 1,4-Dideoxy-
1,4-iminoalditols are also an important class of glycosidase in-
hibitors, although their higher conformational flexibility reduces,
in some instances, their selectivity.15
aDepartamento de Qu´ımica Orga´nica, Facultad de Qu´ımica, Universidad
de Sevilla, P.O. Box 553, E-41071, Sevilla, Spain. E-mail: anatere@us.es,
robina@us.es; Fax: +34954624960; Tel: +34 954557151
bLaboratory of Glycochemistry and Asymmetric Synthesis, Swiss Fed-
eral Institute of Technology (EPFL), Lausanne, Switzerland. E-mail:
pierre.vogel@epfl.ch
† Electronic supplementary information (ESI) available: Further biological
assays details and copies of 1H- and 13C-NMR spectra for compounds
19–21, 24b, 25b, 39, 40, 42–47, 49,50,54, 59–61 and 63–66. See DOI:
10.1039/b819867e
Fig. 1 a-L-Fucosidase inhibitors.
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the case of amide 630 with inhibitory activity in the pM
range.
We and other authors have reported that the incorporation of
aromatic moieties to the pyrrolidine framework greatly improves
the activity and selectivity towards glycosidases.31,32 In this re-
gard, we have found that compounds 13 to 17 are better and
more selective inhibitors than simple meso-pyrrolidine-3,4-diol
(12) (Fig. 2). Recent work on the search of anti-cancer agents
has shown that a-mannosidase inhibitors such as 13 have low
cell membrane permeability and must be esterified to generate
compounds with anti-cancer activity.33 This suggests that less polar
compounds than fuconojirimycin analogue 6 might be required
to construct a-fucosidase inhibitors capable of penetrating cells.
Thus, we have decided to explore the use of pyrrolidine-3,4-diol
derivatives as templates for the creation of effective a-L-fucosidase
inhibitors that could play a part in the development of potential
drugs. With that aim a variety of 1,4-imino-C-heterocycles, aryl
aminoalkyl pyrrolidines and related homoanalogues 18–21 were
prepared by diversity oriented syntheses containing substitution
or modification at C-2 and C-5 of the pyrrolidine framework.34
It is believed that derivatives 18–21 with two hydroxyl groups
should penetrate the cells more readily than compound 6 which
has three hydroxyl groups. In addition, compound 18c which
bears a hydroxyethyl group on the pyrrolidine moiety and L-fuco
configuration on C(2,3,4,5) is an interesting C-5 tethered imino-
C-benzimidazole of interest for the preparation of affinity ligands
for the purification of a-L-fucosidases.35
Fig. 2 a-L-Fucosidase inhibitors containing aromatic moieties.
key intermediates, respectively. These intermediates are obtained
through conjugate addition of ammonia to unsaturated aldonic
esters derived by Wittig reaction from sugar hemiacetals and
tandem cyclization (pathway B).
Our synthetic strategies start from isopropylidene pro-
tected hemiacetalic sugars (D-mannose, D-ribose and L-fucose)
(Scheme 1). For the synthesis of compounds 18a,b and 20a,b
the key intermediate is carbaldehyde 22 which is prepared by
addition of methylmagnesium chloride as the key step, mesylation,
chemoselective SN2 and cyclization followed by acetal deprotec-
tion and glycol cleavage (pathway A). Compounds 18c, 19a, 19b,
21a and 21b are prepared from ester derivatives 23, 24 and 25 as
Results and discussion
Pathway A implies reaction of methylmagnesium chloride with
commercially available D-mannose diacetonide which afforded
Scheme 1 Synthetic strategies.
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a 1:1 mixture of diastereoisomeric diols (2R)-26 and (2S)-26 in
95% yield (Scheme 2). Standard mesylation of the diols provided
a 1:1 mixture of dimesylates (2R)-27 and (2S)-27 in 75% yield,
that after treatment with Me3SiN3 and Bu4NF in DMF afforded
a 3:1 mixture of azides (2S)-28 and (2R)-28 in 55% yield. This
result indicates that the chemoselective SN2 displacement of the
mesyloxy group at C-2 of 27 is somehow faster with (2R)-27 than
with (2S)-27.34
of the mesyloxy group at C-5 giving a 3:1 mixture of (5S)-29
and (5R)-29 in quantitative yield. Amine protection as benzyl-
carbamate followed by selective hydrolysis of the least sterically
hindered acetonides (Zn(NO3)2, H2O/MeCN)36 provided a 3:1
mixture of diols 30 and 31 that were readily separated by flash
chromatography on silica gel (58% overall yield in three steps).
Standard oxidative cleavage of the diols 30 and 31 with NaIO4
furnished aldehydes 32 (92%) and 34 (100%), respectively.
The structures of the 2,5-dideoxy-2,5-iminoalditol derivatives
30 and 31 were established by their spectral data and the relative
configurations confirmed by NOE.34 Oxidation of aldehyde 32
gave the corresponding carboxylic acid 33 (82% yield). Reac-
tion with o-phenylenediamine in the presence of PyBOP and
DIPEA and heating in AcOH at 50 ◦C followed by deprotection
under standard conditions yielded benzimidazole derivative 18a
(Scheme 2). The same reaction sequence applied to aldehyde 34
provided benzimidazole 18b.
The synthesis of 19a and 19b was carried out following
pathway B which starts from known hemiacetal 38 obtained
from D-ribose by applying Bols’ procedure.37 Reaction of lac-
tol 38 with ethoxycarbonylmethylene triphenylphosphorane in
dichloromethane under reflux afforded a mixture of alkenes 39
and 40 in 90% yield and a ratio Z:E = 5.2:1. Mesylation of 39 and
40 followed by treatment with ammonia in ethanol furnished the
corresponding pyrrolidines through tandem conjugate addition-
internal SN2 displacement. Starting from Z-alkene 39, pyrrolidine
24a was obtained as unique stereoisomer in 76% overall yield,
whereas the same procedure applied to E-alkene 40 afforded a
mixture of 24a and 24b in 60% overall yield, and a ratio, 24a:24b =
10:1 (Scheme 3). The structures of 24a and 24b were based on their
spectroscopic and analytical data.34
Scheme 2 Reagents and conditions: (a) MeMgCl, THF, r.t., 95%; (b)
MsCl, pyridine, DMAP, 75%; (c) TMSN3 (4 eq.)/TBAF (4 eq.), DMF,
90 ◦C, 4.5 h, 55% (74% from converted substrate); (d) (1) H2, Pd/C,
MeOH; (2) MeOH, DBU, 99% (1+2); (e) (1) CbzCl, NaHCO3, EtOH/H2O
(1/1); (2) Zn(NO3)2.6H2O, MeCN, 50 ◦C; (3) Flash chromatography; 58%
(1+2+3); (f) NaIO4, THF-H2O; (g) NaClO2, KH2PO4, ButOH-H2O; (h)
(1) o-phenylenediamine, PyBOP, DIPEA, DMF, 65%; (2) AcOH, 50 ◦C,
100%; (i) (1) THF:HCl 1 M 1:1; (2) H2, Pd/C, MeOH; 87% (1+2).
Catalytic hydrogenation of azides 28 gave a 3:1 mixture of
primary amines that were not isolated but treated directly with
DBU in MeOH. This promoted the intramolecular displacement
=
Scheme 3 Reagents and conditions: (a) Ph3P CH2COOEt, CH2Cl2 reflux,
90%. (b) (i) MsCl, Py. (ii) NH3, EtOH, 76% (from 39), 60% (from 40).
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When a similar synthetic route was applied to L-fucose, pyrro-
lidines 25a and 25b, epimers at C-6 of 24a and 24b, were obtained.
Thus, L-fucose acetonide formation followed by glycol cleavage,
basic hydrolysis and neutralization gave lactol 41. Subsequent
Wittig olefination afforded alkenes 42 and 43 in 70% yield and
a ratio Z:E = 1:5 (Scheme 4). The formation of pyrrolidines 25a
and 25b from 42 and 43 followed the same stereochemical outcome
than for the ribo series and is in accordance to that described for
the erythro and manno series.38 Pyrrolidine 25a was obtained as
a single diastereoisomer from Z-alkene 42 in 63% overall yield.
The same reaction conditions applied to E- alkene 43 afforded a
mixture of pyrrolidines 25a and 25b in a ratio 25a:25b = 5:1. Their
structures are based on their spectroscopic and analytical data.
NOESY spectrum of 25a showed NOEs between proton signals
H3(d = 3.44) and H4(d = 4.66) and Me-6(d = 1.05), indicating a
cis relationship between H3 and H4 and trans relationship between
H3 and H6. In the case of compound 25b the NOESY spectrum
showed NOEs between protons H2a(d = 2.7), H4(d = 4.29) and
H2b(d = 2.48), and between proton pairs H3(d = 3.41) and
H6(d = 3.20), which indicates a cis relative configuration between
H3 and H6 and trans relative configuration between H3 and H4.
Scheme 5 Reagents and conditions: (a) Boc2O, Py, 92%. (b) (i) NaOH,
EtOH. (ii) o-phenylenediamine, PyBOP, DIEA, DMF, 76% (for 45), 89%
(for 48). (c) AcOH, 50 ◦C, quant. (for 46 and 49). (d) (i) HCl. (ii) NH4OH,
64%. (e) CbzCl, EtOH, NaHCO3, 90%. (f) (i) H2, Pd/C, MeOH. (ii) HCl,
THF, 58%.
hydrogenolysis and acidic treatment gave 19b in 58% overall yield
(Scheme 5). However, in some instances, these deprotection steps
applied over 49 afforded the unexpected compound 50, isolated as
the major product which was fully characterized by its spectral
data (see Supporting Information). A possible mechanism for
the formation of compounds 19b or 50 is shown in Scheme 6.
Nucleophilic attack by a nitrogen of the benzimidazole ring
over the carbamate group under acidic conditions followed by
hydrogenolysis of the Ca-O and Ca¢-O bonds on intermediate D,
affords compound 50 with a methylene bridge between pyrrolidine
and benzimidazole nitrogens (Ha¢a (d = 5.26, d, Ja¢a,a¢b = 12.6) and
Ha¢b (d = 5.05, d)).
Scheme 4 Reagents and conditions: (a) (i) 2,2-DMP, PTSA. (ii) NaIO4,
=
H2O. (iii) NaOH. (iv) HCl, 65% (overall). (b) Ph3P CH2COOEt, toluene,
reflux, 70%. (c) (i) MsCl, Py. (ii) NH3, EtOH, 63% (from 42), 50%
(from 43).
The preparation of the benzimidazolyl derivative 19a started
from N-Boc protected pyrrolidine 44. Saponification followed by
reaction with o-phenylenediamine in the presence of PyBOP and
DIPEA afforded amide 45 in 76% yield. Subsequent cyclization
and acidic deprotection gave the target compound 19a (Scheme 5).
For the synthesis of the benzimidazolyl epimer 19b, a similar
synthetic route was applied but starting from benzyloxycarbonyl
carbamate 47. Cyclization of amide 48 in AcOH at 50 ◦C gave
quantitatively protected benzimidazolyl derivative 49. Elimina-
tion of the benzyloxycarbonyl and isopropylidene groups by
The synthesis of aminomethyl pyrrolidines 20a and 20b was
carried out starting from aldehyde 32. Reductive amination of 32
with aniline provided derivative 51 (75%), which after deprotection
under standard conditions, afforded diamine 20a in quantitative
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The synthesis of naphthalene-1-amino ethyl pyrrolidine 21a
was carried out by the reductive amination of aldehyde 54 with
naphthalene-1-amine (85%) followed by acidic deprotection. Car-
baldehyde 54 was obtained from 44 by reduction with DIBALH
in 74% yield (Scheme 8). Biphenylaminoethyl pyrrolidine 21b was
prepared starting from ethyl ester 44. Saponification and reaction
with biphenyl-4-amine in the presence of PyBOP and DIPEA
gave amide 56 in 71% yield. Reduction with BH3.SMe2 afforded
diamine 57, from which acidic deprotection gave 21b in 84% overall
yield (from 56).
Scheme 6 Proposed mechanism for the formation of 50.
yield. Following a similar synthetic route and using biphenyl-4-
amine for the condensation with the aldehyde 32, derivative 20b
was obtained (Scheme 7).
Scheme 8 Reagents and conditions: (a) (i) NaOH, EtOH. (ii) Ar-NH2,
PyBOP, DIEA, DMF, 71%. (b) DIBALH, CH2Cl2, -78 ◦C, 74%. (c)
ArNH2, NaBH(AcO)3, 85%. (d) (i) HCl (1M), THF. (ii) NH4OH, 62%
(for 21a), 97% (for 21b). (e) BH3, Me2S, THF, 89%.
The synthesis of 18c was carried out in a similar way (Scheme 9).
Thus, starting from a mixture 12:1 of pyrrolidines 58,38 selective
acetonide hydrolysis followed by chromatographic purification,
allowed for the separation of pyrrolidines 59 and 60. Oxidative
cleavage of major derivative 59 and subsequent coupling reaction
of the corresponding carboxylic acid 62 with o-phenylenediamine
followed by cyclization afforded benzimidazole derivative 64.
Protecting group manipulation followed by reduction of the
ester moiety and final deprotection afforded benzimidazole
derivative 18c.
Scheme 7 Reagents and conditions: (a) ArNH2, NaBH(AcO)3, 66–75%.
(b) (i) HCl (1M). (ii) H2, Pd/C, MeOH, quant.
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Scheme 9 Reagents and conditions: (a) Zn(NO3)2 · 6H2O, MeCN, 50 ◦C, 75%. (b) NaIO4, THF-H2O, 93%. (c) NaClO2, NaH2PO4, 2-methyl-2-butene,
87%. (d) o-phenylenediamine, PyBOP, DIEA, DMF, 88%. (e) AcOH, 50 ◦C, 96%. (f) H2, Pd/C, (Boc)2O, MeOH, 80%. (g) LiAlH4, THF, 0 ◦C, 96%. (h)
(i) HCl (4M). (ii) NH4OH, 92%.
Table 1 Inhibitory activities of 3,4-dihydroxypyrrolidine derivatives 18,
19, 20 and 21 toward glycosidases. Percentage of inhibition at 1 mM, IC50
(in parentheses, mM) and Ki (bold, mM) if measured. Optimal pH, 35 ◦Ca,b,c
Biological evaluation of 3,4-dihydroxypyrrolidine derivatives
towards glycosidases
The new compounds 18a–c, 19a–b, 20a–b and 21a–b have been
assayed for their inhibitory activity towards 13 commercially
available glycosidases.39 At 1 mM concentration and under enzyme
optimal pH they did not inhibit the b-galactosidases from
Aspergillus niger and Escherichia coli, a-glucosidases from yeast
and rice, a-mannosidases from Jack beans, b-mannosidases
from snail, b-xylosidases from Aspergillus niger and b-
acetylglucosaminidase from Jack beans and from bovine kidney.
Table 1 summarises the inhibitory activity measured towards a-
L-fucosidase from bovine kidney, b-galactosidase from bovine
liver, amyloglucosidase from Aspergillus niger and b-glucosidase
from almonds. Apart from the benzimidazole derivatives 18a and
18c that inhibit only a-L-fucosidases at 1 mM concentration, the
other 5-methyl-3,4-dihydroxypyrrolidine derivatives present weak
inhibitory activity toward b-galactosidase from bovine liver, but
not towards other b-galactosidases. The former enzyme is known
to be poorly selective and to be inhibited by almost any amine,
so the results of Table 1 should not be taken as a lack of a-L
fucosidase selectivity of pyrrolidines 18b, 19a, 19b, 20b, 21a and
21b. As expected, the best inhibitory activities and selectivities
towards a-L-fucosidases were observed for pyrrolidines 18a (Ki =
80 nM) and 20b (Ki = 40 nM) that share the same absolute
configuration than C(2,3,4,5) of a-L-fucopyranosides.
a-fucosidase
b-galactosidase amyloglucosidase b-glucosidase
18a 100%
Ki = 0.080 (C) ni
18b 94%
ni
ni
94%
Ki = 240 (C)
18c 85% (140)
19a 95% (11)
Ki = 1.2 (C)
48%
ni
62%
ni
ni
37%
Ki = 46 (NC)
ni
32%
19b 79%
45%
ni
ni
ni
59%
ni
20a 99%
Ki = 0.237 (C)
20b 99% (0.3)
Ki = 0.040 (C)
21a 89% (24)
Ki = 2.4 (C)
47%
73%
83%
39%
ni
ni
ni
ni
21b 95% (21)
Ki = 2.4 (C)
18%
a For conditions of measurements see ref. 39. b (C): competitive, (NC):
non-competitive from Lineweaver-Burk plots, ni: no inhibition at 1 mM
concentration of the inhibitor. a-L-fucosidase from bovine kidney, b-
galactosidase from bovine liver, Amyloglucosidase from Aspergillus niger,
b-glucosidase from almonds.
c
of L-fucopyranosides are potent and selective inhibitors of a-L-
fucosidase from bovine kidney (Ki = 80 and 40 nM respectively).
We have found that the (5S)-5-methylsubstituent (compounds 19a,
20b, 21a, 21b) leads to significantly better inhibitory activities
than the (5R)-5-methyl substituent (compounds 18b, 19b) and that
substitution at C(2) of the pyrrolidine ring by a (2S)-substituent
(18a, 20b) generates better inhibitors than the corresponding
homoanalogues with (2R)-substituents (19a, 21b).
Conclusions
New 3,4-dihydroxypyrrolidine derivatives have been obtained in a
highly stereoselective manner starting from D-mannose, D-ribose
and L-fucose. They have been assayed for their inhibitory activity
towards 13 glycosidases. Compounds 18a and 20b with a (5S)-
methyl group that share the absolute configuration of C(2,3,4,5)
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diluted with dichloromethane (30 mL) and washed with H2O (2 ¥
30 mL) and brine (30 mL). The organic phase was dried, filtered
and concentrated. The obtained residue was dissolved in absolute
EtOH (20 mL), cooled to 0 ◦C and saturated with NH3. After
5 days at r.t., the solvent was evaporated and the residue was
treated with NH4OH (25%, 30 mL) and extracted with CH2Cl2
(5 ¥ 30 mL). The organic phase was washed with satd. aq. sol.
of NaHCO3 (30 mL) and H2O until neutral pH, dried (Na2SO4),
filtered and concentrated. The resulting residue was purified by
column chromatography (ether:acetone (5:1), Et3N (1%)) to give
pure 24a (0.389 g, 76%). [a]D -12.7 (c 1.2 in CH2Cl2). IR (n cm-1)
Experimental
General methods
Optical rotations were measured in a 1.0 cm or 1.0 dm tube
with a Perkin–Elmer 241MC spectropolarimeter. 1H and 13C
NMR spectra were obtained for solutions in CDCl3, [d6]DMSO,
CD3OD and D2O; J values are given in Hz and d in ppm.
All the assignments were confirmed by two-dimensional NMR
experiments. The FAB mass spectra were obtained using glycerol
or 3-nitrobenzyl alcohol as the matrix. TLC was performed on
silica gel HF254 (Merck), with detection by UV light charring with
H2SO4 or with Pancaldi reagent [(NH4)6MoO4, Ce(SO4)2, H2SO4,
H2O]. Silica gel 60 (Merck, 230 mesh) was used for preparative
chromatography.
3444 (b, NH), 2981, 2934, 1734 (C O), 1376, 1208, 1012. 1H
=
NMR (300 MHz, CDCl3, d ppm) d 1.20 (3H, d, JMe,6 = 6.6, 6-
Me), 1.26 (3H, t, 2JH,H = 7.1, CH2CH3), 1.30, 1.44 (3H each, 2 s,
C(CH3)2), 1.88 (1H, bs, NH), 2.57 (1H, dd, 2J2a,2b = 16.5, J2a,3
6.6, 2a-H), 2.66 (1H, dd, J2b,3 = 6.6, 2b-H), 2.86 (1H, qd, J6,5
=
=
Experimental procedures and characterization data for the new
compounds
4.0, 6-H), 3.14 (1H, td, J3,4 = 4.1, 3-H), 4.15 (2H, qd, J = 1.4,
CH2CH3), 4.47 (1H, dd, J5,4 = 5.5, 5-H), 4.62 (1H, dd, 4-H).
13C NMR (75.4 MHz, CDCl3, d ppm) d 13.4 (CH2CH3), 14.3 (6-
Me), 24.3, 25.8 (C(CH3)2), 33.6 (C-2), 57.7 (C-6), 58.8 (C-3), 60.7
(Z)- and (E)-Ethyl 2,3,7-trideoxy-4,5-O-isopropylidene-D-ribo-
hept-2-enoate (39 and 40). To a solution of 3837 (0.886 g,
5.09 mmol) in dry CH2Cl2 (31 mL), ethoxycarbonyltriphenyl-
methylenephosphorane (2.66 g, 7.63 mmol) was added, and the
mixture was heated under reflux for 6 h. After evaporation of the
solvent, the residue was purified by column chromatography (ethyl
acetate/petroleum ether 1:5) affording 39 (939 mg, 3.85 mmoles,
76%) and 40 (181 mg, 0.74 mmol, 14%) as oils. Data for 39: [a]D
=
(CH2CH3), 82.4 (C-4), 83.2 (C-5), 110.9 (C(CH3)2), 172.1 (C O).
CIMS 244 [(M + H)+, 90%]. CIHRMS m/z found 244.1551, calcd.
for C12H22NO4 (M + H)+: 244.1549. Anal. calcd. for C27H34N2O5:
C, 59.24; H, 8.70; N, 5.76. Found: C, 58.75; H, 8.82; N, 5.61.
Ethyl 2,3,6,7-tetradeoxy-3,6-imino-4,5-O-isopropylidene-L-gal-
acto-heptanoate and ethyl 2,3,6,7-tetradeoxy-3,6-imino-4,5-O-
isopropylidene-L-talo-heptanoate ((2R and 2S,3S,4R,5S)-2-
ethoxycarbonylmethyl-3,4-O-isopropylidene-5-methyl-pyrrolidine-
3,4-diol) (24a and 24b). Conventional mesylation of compound
40 (162 mg, 0.66 mmol) followed by NH3 treatment and
chromatographic purification as indicated for the preparation of
24a afforded pyrrolidines 24a (88.2 mg, 0.36 mmol, 55%) and
+47.5 (c 1.2 in CH2Cl2). IR (n cm-1) 3483 (OH), 2986, 2936, 1728
1
=
=
(C O), 1646 (C C), 1195, 1057, 871. H NMR (500 MHz, CDCl3,
d ppm) d 1.16 (3H, d, JMe-6,6 = 6.0, 6-Me), 1.28 (3H, t, 2JH,H = 7.5,
CH2CH3), 1.39, 1.51 (3H each, 2 s, C(CH3)2), 2.89 (1H, bs, OH),
3.74 (1H, dq, J6,5 = 7.5, 6-H), 4.14 (1H, dd, J5,4 = 6.5, 5-H), 4.19
(2H, qd, J = 1.0, CH2CH3), 5.54 (1H, ddd, J4,2 = 1.0, J4,3 = 8.5,
4-H), 6.00 (1H, dd, J2,3 = 11.5, 2-H), 6.28 (1H, dd, 3-H). 13C NMR
(125.7 MHz, CDCl3, d ppm) d 14.3 (CH2CH3), 19.8 (6-Me), 25.6,
28.0 (C(CH3)2), 61.3 (CH2CH3), 66.7 (C-6), 76.9 (C-4), 83.2 (C-5),
24b (8.8 mg, 0.036 mmol, 5%). Data for 24b: [a]D +4.5 (c 0.7 in
-1
=
CH2Cl2). IR (n cm ) 3448, (bs, NH), 2981, 2934, 1734 (C O).
1H NMR (300 MHz, CDCl3, d ppm) d 1.20 (d, 3H, JMe,6 = 6.6,
6-Me), 1.25 (3H, t, 2JH,H = 7.2, CH2CH3), 1.30, 1.46 (3H each, 2 s,
=
109.4 (C(CH3)2), 122.0 (C-2), 146.8 (C-3), 167.2 (C O). FABMS
267 [(M + Na)+, 93%], 245 [(M + H)+, 100%]. FABHRMS m/z
C(CH3)2), 1.97 (1H, bs, NH), 2.33 (1H, dd, 2J2a,2b = 15.3, J2a,3
7.8, 2a-H), 2.41 (1H, dd, J2b,3 = 7.8, 2b-H), 3.07 (1H, qd, J6,5
=
=
found 267.1210, calcd. for C12H20O5Na (M + Na)+: 267.1208. Data
for 40: [a]D -4.0 (c 0.5 in CH2Cl2). IR (n cm-1) 3447 (OH), 2983,
3.6, 6-H), 3.59 (1H, t, 3-H), 4.16 (2H, q, CH2CH3), 4.46–4.52
(2H, m, 4-H, 5-H). 13C NMR (75.4 MHz, CDCl3, d ppm) d 13.5
(6-Me), 14.3 (CH2CH3), 24.2, 26.2 (C(CH3)2), 36.8 (C-2), 56.2
1
=
2927, 1720 (C O), 1371, 1302. H NMR (300 MHz, CDCl3, d
2
ppm) d 1.27 (d, 3H, JMe,6 = 6.3, 6-Me), 1.28 (3H, t, JH,H = 7.2,
CH2CH3), 1.38, 1.49 (3H each, 2 s, C(CH3)2), 1.86 (1H, bs, OH),
3.75 (1H, dq, J6,5 = 8.1, 6-H), 4.00 (1H, dd, J5,4 = 6.6, 5-H),
(C-6), 60.7 (CH2CH3), 61.2 (C-3), 83.2, 86.5 (C-5, C-4), 111.2
+
=
(C(CH3)2), 171.5 (C O). CIMS 244 [(M + H) , 47%]. CIHRMS
m/z found 244.1548, calcd. for C12H22NO4 (M + H)+: 244.1549.
4.19 (2H, q, CH2CH3), 4.81 (1H, m, 4-H), 6.09 (1H, dd, J2,3
=
15.6, J2,4 = 1.5, 2-H), 7.09 (1H, dd, J3,4 = 5.4, 3-H).13C NMR
(75.4 MHz, CDCl3, d ppm) d 14.4 (CH2CH3), 21.1 (6-Me), 25.6,
27.7 (C(CH3)2), 60.7 (CH2CH3), 66.5 (C-6), 76.8 (C-4), 82.1 (C-5),
Ethyl N-(tert-butoxycarbonyl)-2,3,6,7-tetradeoxy-3,6-imino-4,
5-O-isopropylidene-L-galacto-heptanoate ((2R,3S,4R,5S)-N-(tert-
butoxycarbonyl)-2-ethoxycarbonylmethyl-3,4-O-isopropylidene-5-
methyl-pyrrolidine-3,4-diol) (44). To a solution of 24a (0.306 g,
1.26 mmol) in dry pyridine (4.3 mL) was added a solution of
Boc2O (0.696 g, 2.99 mmol) in dry pyridine (2.9 mL). The mixture
was left at r.t. for 3 h. After evaporation of the solvent, the residue
was dissolved in AcOEt (25 mL) and washed twice with brine
(25 mL). The dried organic phase was evaporated and the resulting
residue was purified by column chromatography (ether:petroleum
=
109.4 (C(CH3)2), 122.5 (C-2), 144.1 (C-3), 166.5 (C O). FABMS
267 [(M + Na)+, 100%]. FABHRMS m/z found 267.1207, calcd.
for C12H20O5Na (M + Na)+: 267.1208.
Ethyl 2,3,6,7-tetradeoxy-3,6-imino-4,5-O-isopropylidene-L-gal-
acto-heptanoate ((2R,3S,4R,5S)-2-ethoxycarbonylmethyl-3,4-O-
isopropylidene-5-methyl-pyrrolidine-3,4-diol) (24a). A solution of
39 (0.543 g, 2.23 mmol) in dry CH2Cl2 (5 mL) was added dropwise
to a stirred solution of MsCl (0.54 mL, 6.99 mmol) in dry pyridine
(2.2 mL) cooled to 0 ◦C. After stirring at r.t. overnight, the mixture
was cooled to 0 ◦C, H2O (5 mL) was added and the reaction stirred
for 15 min at r.t. The solvent was then evaporated, the crude was
ether, 1:2) to give pure 44 (0.401 g, 93%) as a syrup. [a]D -12.8
-1
=
=
(c 1 in CH2Cl2). IR (n cm ) 2981, 2937, 1736 (C O), 1696 (C O),
1383, 1171. 1H NMR (500 MHz, DMSO-d6, d ppm) d 1.15 (3H, d,
JMe,6 = 7.0, 6-Me), 1.19 (3H, t, 2JH,H = 7.2, CH2CH3), 1.29 (3H, s,
1198 | Org. Biomol. Chem., 2009, 7, 1192–1202
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C(CH3)2), 1.41 (9H, s, C(CH3)3), 1.45 (3H, s, C(CH3)2), 2.47 (1H,
H)+, 15%]. CIHRMS m/z found 387.2154, calcd. for C21H29N3O4
2
dd, J2a,2b = 16.0, J2a,3 = 10.5, 2a-H), 2.67 (1H, dd, J2b,3 = 4.5,
(M)+: 387.2158.
2b-H), 3.94 (1H, q, J6,5 = 7.0, 6-H), 4.06 (2H, m, CH2CH3), 4.26
(1H, ddd, J3,4 = 7.0, 3-H), 4.73 (1H, t, J5,4 = 7.0, 5-H), 4.79 (1H,
t, 4-H). 13C NMR (125.7 MHz, DMSO-d6, d ppm) d 13.5 (6-Me),
15.8 (CH2CH3), 24.2, 24.5 (C(CH3)2), 27.7 (C(CH3)3), 35.8 (C-2),
53.9 (C-6), 55.4 (C-3), 59.1 (CH2CH3), 78.1 (C-4), 78.7 (C(CH3)3),
(2R,3S,4R,5S)-2-(1H -Benzoimidazol-2-yl-methyl)-5-methyl-
pyrrolidine-3,4-diol (19a). A solution of 46 (47.2 mg, 0.122 mmol)
in 4M HCl (3 mL) was stirred at r.t. for 8 h. The solvent was then
evaporated and the resulting residue dissolved in H2O (1 mL).
NH4OH (1 mL) was added and the mixture was left at r.t. for 2 h.
Then, the solvent was evaporated and the resulting residue was
purified by column chromatography (CH2Cl2:MeOH:NH4OH,
5:1:0.1) to give pure 19a (19.4 mg, 64%). [a]D +29.1 (c 1.3 in
MeOH). IR (n cm-1) 3500–3200 (OH,NH), 2926, 1445. 1H NMR
(300 MHz, CD3OD, d ppm) d 1.23 (3H, d, JMe,5 = 6.6, 5-Me), 3.13
(1H, dd, 2J1¢a,1¢b = 15.3, J1¢a,2 = 8.4, 1¢a-H), 3.22 (1H, m, 5-H), 3.35
(1H, m, 1¢b-H), 3.71 (1H, td, J2,1¢b = 8.4, J2,3 = 6.0, 2-H), 4.09 (1H,
t, J4,3 = J4,5 = 5.1, 4-H), 4.26 (1H, dd, 3-H), 7.21 (2H, dd, J = 6.0,
J = 3.3, H-arom.), 7.51 (2H, dd, H-arom). 13C NMR (75.4 MHz,
CD3OD, d ppm) d 13.9 (5-Me), 29.5 (C-1¢), 57.7 (C-5), 60.7 (C-2),
73.5 (C-3), 73.8 (C-4), 115.5, 123.3, 139.6, 154.0 (C-Ar). CIMS
248 [(M + H)+, 32%]. CIHRMS m/z found 248.1394, calcd. for
C13H18N3O2 (M + H)+: 248.1399.
=
79.2 (C-5), 111.3 (C(CH3)2), 153.0 (C O of Boc), 170.0 (COOEt).
CIMS 343 [(M)+, 4%], 244 [(M - Boc + 2H)+, 100%]. CIHRMS
m/z found 343.1990, calcd. for C17H29NO6 (M)+: 343.1994.
(2R,3S,4R,5S)-N-(tert-Butoxycarbonyl)-2-(2-aminophenylcar-
bamoylmethyl)-3,4-O-isopropylidene-5-methylpyrrolidine-3,4-diol
(45). A solution of 44 (132 mg, 0.38 mmol) in 2:1 EtOH:NaOH
(12 mL) was heated at 50 ◦C for 2 h. The mixture was then
neutralized with IRA-120H+, filtered and concentrated. The crude
acid thus obtained was dissolved in DMF and o-phenylenediamine
(45 mg, 0.42 mmol), DIPEA (130 mL, 0.76 mmol) and PyBOP
(218 mg, 0.42 mmol) were added. The mixture was stirred
overnight at r.t. Then, the solvent was evaporated and the residue
dissolved in CH2Cl2 (40 mL) and washed with satd. aq. sol. of
citric acid (2 ¥ 30 mL) and brine (30 mL). The organic phase was
dried (Na2SO4), filtered and concentrated. The resulting crude was
purified by column chromatography (CH2Cl2:MeOH, 30:1) to give
Reductive amination: general procedure
To a solution of the corresponding aldehyde (0.10 mmol) in 1,2-
dichloroethane (1 mL), the corresponding amine (0.11 mmol) and
NaBH(OAc)3 (0.14 mmol) were added. The reaction mixture was
stirred at r.t. under N2 for 3 h. Then, aq. sat. sol. of NaHCO3 was
added and the mixture extracted with AcOEt, dried (Na2SO4),
filtered and evaporated in vacuo. Purification of the residue gave
the corresponding amino pyrrolidines.
pure 45 (132 g, 76%) as a white foam. [a]D -29.2 (c 0.9 in CH2Cl2).
-1
=
IR (n cm ) 3545 (NH), 3365 (NH), 2981, 2935, 1689 (C O), 1391,
1168. 1H NMR (300 MHz, CDCl3, d ppm) d 1.24 (3H, d, JMe,5
=
7.2, 5-Me), 1.36 (3H, s, C(CH3)2), 1.47 (9H, s, C(CH3)3), 1.59
(3H, s, C(CH3)2), 2.73 (1H, dd, 2J1¢a,1¢b = 14.4, J1¢a,2 = 9.6, 1¢a-H),
2.95 (1H, dd, J1¢b,2 = 4.8, 1¢b-H), 4.07 (1H, q, J5,4 = 7.2, 5-H), 4.48
(1H, ddd, J2,3 =7.2, 2-H), 4.75(1H, t, J4,3 =7.2, 4-H), 4.91(1H, t, 3-
H), 6.72–6.77 (2H, m, H-arom.), 7.04 (1H, m, H-arom.), 7.15 (1H,
m, H-arom.), 7.52 (1H, bs, CONH). 13C NMR (75.4 MHz, CDCl3,
d ppm) d 17.0 (5-Me), 24.9, 25.6 (C(CH3)2), 28.6 (C(CH3)3), 39.0
(C-1¢), 55.2 (C-5), 56.4 (C-2), 80.3 (C-3, C-4), 80.5 (C(CH3)3),
(2S,3S,4R,5S)-2-[2-(1,1¢-Biphenyl-4-ylamino)methyl]-5-methyl-
pyrrolidine-3,4-diol hydrochloride (20b). Reductive amination of
3234 with biphenyl-4-amine gave, after column chromatography
on silica gel (ether:petroleum ether 1:1), protected derivative 53
(101 mg, 66%). A solution of 53 (70 mg, 0.148 mmol in MeOH
(6 mL) was hydrogenated over Pd/C for 3 h. The mixture was
filtered through celite and evaporated. The crude product was
then treated with 4 N HCl (2 mL) and stirred at r.t. overnight.
Evaporation of the solvent afforded 20b (28 mg, 89%). [a]D -43.7
112.9 (C(CH3)2), 117.5, 119.0, 123.8, 125.9, 127.4, 141.6 (6 C-Ar),
+
=
154.3 (C O of Boc), 169.7 (CONH). CIMS 406 [11%, (M + H) ],
405 [(M)+, 20%], 306 [(M - Boc + 2H)+, 100%]. CIHRMS m/z
found 405.2269, calcd. for C21H31N3O5 (M)+: 405.2264.
1
(c 0.67 in MeOH). H NMR (300 MHz, CD3OD, d ppm) d 1.43
(2R,3S,4R,5S)-N -(tert-Butoxycarbonyl)-(2-(1H -benzoimida-
zol-2-ylmethyl)-3,4-O-isopropylidene-5-methylpyrrolidine-3,4-diol
(46). A solution of 45 (87.8 mg, 0.216 mmol) in glacial AcOH
was stirred at 55 ◦C for 5 h. Then, the solvent was evaporated
and the resulting residue was purified by column chromatography
(CH2Cl2:MeOH, 25:1) to give pure 46 (83.6 mg, 100%) as a foam.
(3H, d, JMe,5 = 6.6, 5-Me), 3.76–3.86 (4H, m, 5-H, 2-H, 1¢a-H,
1¢b-H), 4.06 (1H, t, J3,4 = J3,2 = 2.7, 3-H), 4.22 (1H, m, 4-H),
7.31–7.34 (3H, m, H-arom.), 7.42 (2H, brt, J = 7.5, H-arom.), 7.59
(2H, brd, J = 7.9, H-arom.), 7.66 (2H, brd, J = 8.7, H-arom.).
13C NMR (75.4 MHz, MeOD, d ppm) d 12.0 (5-Me), 48.1–49.8
(C-1¢, under MeOD), 59.0, 60.1 (C-2, C-5), 72.9 (C-3), 76.0 (C-4),
119.7, 127.6, 128.3, 129.4, 129.9 (C arom.), 138.5, 141.4, 141.7
(Cq arom.). CIMS 299 [(M + H)+, 100%]. CIHRMS m/z found
299.1753, calcd. for C15H25NO5 (M + H)+: 299.1733.
[a]D +3.4 (c 1 in CH2Cl2). IR (n cm-1) 3464 (NH), 2980, 2934,
1
=
1691 (C O), 1383, 1210, 1167, 1100, 1028, 868, 743. H NMR
(300 MHz, CDCl3, d ppm) d 1.26 (3H, d, JMe,5 = 6.9, 5-Me), 1.39
(3H, s, C(CH3)2), 1.43 (9H, s, C(CH3)3), 1.61 (3H, s, C(CH3)2),
2
3.28 (1H, dd, J1¢a,1¢b = 15.3, J1¢a,2 = 6.0, 1¢a-H), 3.44 (1H, dd,
(2R,3S,4R,5S)-N -(tert-Butoxycarbonyl)-2-[(1,1¢-biphenyl-4-
carbamoyl)methyl]-3,4-O-isopropylidene-5-methylpyrrolidine-3,4-
diol (56). A solution of 44 (0.116 g, 0.337 mmol) in 2:1 EtOH:
NaOH (12 mL) was heated at 50 ◦C for 2 h. The mixture was
then neutralized with IRA-120H + , filtered and concentrated. The
crude acid thus obtained was dissolved in DMF and biphenyl-
4-amine (68 mg, 0.40 mmol), DIPEA (0.13 mL, 0.78 mmol)
and PyBOP (0.21 g, 0.40 mmol) were added. The mixture was
stirred overnight at r.t. Then, the solvent was evaporated and the
J1¢b,2 = 7.2, 1¢b-H), 4.13 (1H, q, J5,4= 6.9, 5-H), 4.44 (1H, m, 2-H),
4.79 (1H, t, J4,3 = 6.9, 4-H), 4.83 (1H, t, J3,2 = 6.9, 3-H), 7.19
(2H, dd, J = 6.0, J = 3.0, H-arom.), 7.55 (2H, dd, H-arom.).
13C NMR (75.4 MHz, CDCl3, d ppm) d 16.8 (5-Me), 25.0, 25.4
(C(CH3)2), 28.5 (C(CH3)3, 32.2 (C-1¢), 55.0 (C-5), 57.5 (C-2), 79.4,
80.2 (C-3, C-4), 80.9 (C(CH3)3), 110.8 (C(CH3)2), 114.9, 122.1,
+
=
138.8, 152.7 (C-Ar), 154.8 (C O). CIMS 388 [(M + H) , 76%],
387 [(M)+, 33%], 288 [(M - Boc + 2H)+, 100%], 287 [(M - Boc +
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residue dissolved in CH2Cl2 (30 mL) and washed with 1 M HCl
(25 mL) and brine (25 mL). The organic phase was dried (Na2SO4),
filtered and concentrated. Purification by column chromatography
(CH2Cl2:MeOH, 60:1) afforded pure 56 (0.111 g, 71%) as a white
(1H, t, J3,2 = 5.1, 3-H), 6.75 (2H, d, J = 8.7, H-arom.), 7.20 (1H,
tt, J = 7.5, H-arom.), 7.35 (2H, t, J = 7.5, H-arom.), 7.41 (2H, d,
J = 8.7, H-arom.), 7.51 (2H, dd, J = 8.4, J = 1.2, H-arom.). 13
C
NMR (75.4 MHz, CD3OD, d ppm) d 13.6 (5-Me), 28.7 (C-1¢), 42.1
(C-2¢), 57.7, 60.4 (C-2, C-5), 72.9, 73.2 (C-3, C-4), 114.3, 126.9,
128.6, 129.7, 131.1, 142.7, 149.5 (C-Ar). CIMS 313 [(M + H)+,
95%], 312 [(M)+, 69%]. CIHRMS m/z found 313.1904, calcd. for
C19H25N2O2 (M + H)+: 313.1916.
foam. [a]D -3.5 (c 1 in CH2Cl2). IR (n cm-1) 3466, 2981, 2934,
1
=
=
1692 (C O), 1666 (C O), 1529, 1392, 1168. H NMR (300 MHz,
CDCl3, d ppm) d 1.24 (3H, d, JMe,5 = 6.9, 5-Me), 1.39 (3H, s,
C(CH3)2), 1.48 (9H, s, C(CH3)3), 1.59 (3H, s, C(CH3)2), 2.86 (2H,
m, 1¢a-H, 1¢b-H), 4.07 (1H, q, J5,4 = 6.9, 5-H), 4.44 (1H, m, 2-
H), 4.77 (1H, t, J4,3 =6.9, 4-H), 4.89 (1H, t, J3,2 = 6.9, 3-H), 7.32
(1H, m, H-arom.), 7.42 (2H, m, H-arom), 7.53–7.62 (6H, m, H-
arom.), 8.21 (1H, brs, CONH). 13C NMR (75.4 MHz, CDCl3, d
ppm) d 17.1 (5-Me), 24.9, 25.5 (C(CH3)2), 28.6 (C(CH3)3), 40.0 (C-
1¢), 55.1 (C-5), 56.2 (C-2), 79.7, 79.8 (C-3, C-4), 80.7 (C(CH3)3),
113.0 (C(CH3)2), 122.1, 126.9, 127.2, 127.7, 128.9, 136.9, 137.8,
N -(tert-Butoxycarbonyl)-2,3,6,7-tetradeoxy-3,6-imino-4,5-O-
isopropylidene-L-galacto-2-heptose ((2R,3S,4R,5S)-N -(tert-but-
oxycarbonyl)-2-formylmethyl-3,4-O-isopropylidene-5-methyl-pyr-
rolidine-3,4-diol) (54). To a solution of 44 (165 mg, 0.48 mmol)
in dry CH2Cl2 (2.3 mL) cooled to -78 ◦C, 1M DIBALH in CH2Cl2
(0.95 mL) was added dropwise under a nitrogen atmosphere.
After stirring for 30 min, MeOH (1.5 mL) was added and the
mixture slowly warmed up to r.t. Then, aqueous 1 M HCl
(4 mL) was added in an ice-cold bath and the aqueous phase was
extracted with CH2Cl2 (4¥5 mL). The combined organic phases
were washed with satd. aq. sol. of NaHCO3, dried (Na2SO4),
filtered and concentrated. The resulting crude was purified by
column chromatography (ethyl acetate:petroleum ether, 1:4) to
=
140.8 (2Ph), 154.5 (C O of Boc), 169.2 (CONH). CIMS 467 [(M
+ H)+, 14%], 466 [(M)+, 17%], 367 [(M - Boc + 2H)+, 100%], 366
[(M - Boc + H)+, 10%]. CIHRMS m/z found 466.2491, calcd.
for C27H34N2O5 (M)+: 466.2468. Anal. calcd. for C27H34N2O5: C,
69.50; H, 7.35; N, 6.00. Found: C, 69.40; H, 7.74; N, 5.62.
(2R,3S,4R,5S)-N-(tert-Butoxycarbonyl)-2-[2-(1,1¢-biphenyl-4-
ylamino)ethyl]-3,4-O-isopropylidene-5-methylpyrrolidine-3,4-diol
(57). To a 0 ◦C solution of amide 56 (94.3 mg, 0.20 mmol) in dry
THF (5 mL), BH3·SMe2 (2 M in THF) (0.5 mL, 1 mmol) was added
dropwise under argon atmosphere. The reaction mixture was
then heated under reflux for 3 h. After cooling, the reaction was
quenched by slow addition of MeOH (5 mL). After evaporation of
the solvent, the residue was purified by column chromatography
(ether:petroleum ether, 1:2) to give 57 (80.8 mg, 89%) as a foam.
give pure 54 (106 mg, 74%). [a]D -13.6 (c 0.9 in CH2Cl2). IR
-1
=
=
(n cm ) 2981, 2936, 1724 (C O), 1693 (C O), 1384, 1169, 1028.
1H NMR (300 MHz, CDCl3, d ppm) d 1.20 (3H, d, JMe,6 = 6.7,
6-Me), 1.33 (3H, s, C(CH3)2), 1.44 (9H, s, C(CH3)3), 1.50 (3H, s,
C(CH3)2), 2.80 (2H, m, 2a-H, 2b-H), 4.03 (1H, q, 6-H), 4.44 (1H,
m, 3-H), 4.73 (1H, t, J5,6 = J5,4 = 6.9, 5-H), 4.82 (1H, t, J4,3
=
6.9, 4-H), 9.76 (1H, t, JCHO,2a = JCHO,2b = 1.5, CHO). 13C NMR
(75.4 MHz, CDCl3, d ppm) d 16.7 (6-Me), 24.8, 25.3 (C(CH3)2),
28.5 (C(CH3)3), 46.0 (C-2), 54.9, 55.1 (C-3, C-6), 79.1 (C-5), 80.0
[a]D +14.6 (c 0.9 in CH2Cl2). IR (n cm-1) 3402 (NH), 2979, 2916,
1
=
1689 (C O), 1613, 1391. H NMR (300 MHz, CDCl3, d ppm) d
=
(C-4), 80.4 (C(CH3)3), 112.9 (C(CH3)2), 154.1 (C O of Boc), 200.6
1.21 (3H, d, JMe,5 = 6.6, 5-Me), 1.39 (3H, s, C(CH3)2), 1.49 (9H, s,
C(CH3)3), 1.57 (3H, s, C(CH3)2), 1.89 (1H, m, 1¢a-H), 2.14 (1H, m,
1¢b-H), 3.26 (2H, m, 2¢a-H, 2¢b-H), 4.04–4.13 (2H, m, 2-H, 5-H),
4.73 (1H, t, J4,5 = 7.2, 4-H), 4.79 (1H, t, J2,3 = J3,4 = 7.2, 3-H),
6.66 (2H, d, J = 8.4, H-arom.), 7.25 (1H, tt, J = 7.2, H-arom.),
7.36–7.46 (4H, m, H-arom.), 7.53 (2H, dd, J = 8.4, J = 1.5, H-
arom.). 13C NMR (75.4 MHz, CDCl3, d ppm) d 17.1 (5-Me), 25.0,
25.4 (C(CH3)2), 28.6 (C(CH3)3), 30.9 (C-1¢), 42.1 (C-2¢), 54.7, 56.7
(C-2, C-5), 79.8, 80.0 (C-3, C-4), 80.2 (C(CH3)3), 113.0 (C(CH3)2),
113.7, 126.2, 126.4, 128.1, 128.7, 130.7, 140.5, 147.1 (C-Ar), 154.6
(CHO). CIMS 300 [(M + H)+, 40%], 200 [(M - Boc + 2H)+, 71%].
CIHRMS m/z found 300.1824, calcd. for C15H26NO5 (M + H)+:
300.1811.
(2R,3S,4R,5S)-N -(tert-Butoxycarbonyl)-2-[(2-naphthalen-1-
ylamino)ethyl]-3,4-O-isopropylidene-5-methylpyrrolidine-3,4-diol
(55). Reductive amination of 54 with naphthylamine gave, after
column chromatography on silica gel (ether:petroleum ether 1:4),
the protected derivative 55 (101.3 mg, 85%) as a white foam. [a]D
-1
=
+18.6 (c 0.6 in CH2Cl2). IR (n cm ) 3418 (NH), 2979, 1690 (C O),
+
+
=
(C O of Boc). CIMS 453 [(M + H) , 48%], 452 [(M) , 65%], 353
1390, 1168, 768. 1H NMR (300 MHz, CDCl3, d ppm) d 1.23 (3H,
d, JMe,5 = 6.9, 5-Me), 1.45 (3H, s, C(CH3)2, 1.49 (9H, s, C(CH3)3),
[(M - Boc + 2H)+, 100%], 352 [(M Boc + H) , 35%]. CIHRMS
+
m/z found 452.2664, calcd. for C27H36N2O4 (M)+: 452.2675. Anal.
calcd. for C27H36N2O4: C, 71.65; H, 8.02; N, 6.12. Found: C, 71.23;
H, 7.93; N, 5.96.
1.63 (3H, s, C(CH3)2), 2.08 (1H, dq, 2J1¢a,1¢b = 13.8, J1¢a,2¢a = J1¢a,2¢b
=
J1¢a,2 = 5.1, 1¢a-H), 2.32 (1H, m, 1¢b-H), 3.38 (2H, m, 2¢a-H, 2¢b-H),
4.07–4.12 (2H, m, 5-H, 2-H), 4.76 (1H, t, J4,5 = J4,3 = 7.2, 4-H),
4.86 (1H, t, J3,2 = 7.2, 3-H), 6.58 (1H, d, J = 7.5, H-arom.), 7.18
(1H, d, J = 8.1, H-arom), 7.32 (1H, d, J = 7.8, H-arom), 7.36–7.43
(2H, m, H-arom), 7.77 (1H, dd, J = 9.3, J = 1.8 H-arom), 7.90
(1H, dd, J = 8.1, H-arom). 13C NMR (75.4 MHz, CDCl3, d ppm)
d 17.2 (5-Me), 25.1, 25.6 (C(CH3)2), 28.6 (C(CH3)3), 30.5 (C-1¢),
42.2 (C-2¢), 54.7, 57.9 (C-2, C-5), 77.3 (C(CH3)3), 79.9, 80.0 (C-
3, C-4), 113.1 (C(CH3)2), 113.7, 116.7, 120.5, 123.5, 124.4, 125.7,
(2R,3S,4R,5S)-2-[2-(1,1¢-Biphenyl-4-ylamino)ethyl]-5-methyl-
pyrrolidine-3,4-diol (21b). A solution of 57 (32.1 mg, 0.07 mmol)
in 4 N HCl (2 mL) was stirred at r.t. overnight. The solvent was
then evaporated, the residue dissolved in H2O (1 mL), NH4OH
was added (1 mL) and the mixture stirred at r.t. for 2 h. After
evaporation of the solvent, the resulting residue was purified
by column chromatography (CH2Cl2:MeOH:NH4OH, 5:1:0.1) to
give pure 21b (21.4 mg, 97%). [a]D -3.7 (c 0.9 in MeOH). IR
(n cm-1) 3310 (OH, NH), 2928, 1611, 1526. 1H NMR (300 MHz,
CD3OD, d ppm) d 1.30 (3H, d, JMe,5 = 6.6, 5-Me), 1.92 (1H, m,
1¢a-H), 2.15 (1H, m, 1¢b-H), 3.29 (2H, m, 2¢a-H, 2¢b-H), 3.34–3.41
(2H, m, 5-H, 2-H), 4.17 (1H, dd, J4,5 = 5.7, J4,3 = 5.1, 4-H), 4.24
=
126.9, 128.6, 134.5, 144.0 (Ar), 154.3 (C O of Boc). CIMS 427
[(M + H)+, 76%], 426 [(M)+, 100%], 327 [(M - Boc + 2H)+, 36%],
326 [(M - Boc + H)+, 29%]. CIHRMS m/z found 426.2522, calcd.
for C25H34N2O4 (M)+: 426.2519. Anal. calcd. for C25H34N2O4: C,
70.39; H, 8.03; N, 6.57. Found: C, 70.26; H, 8.19; N, 6.43.
1200 | Org. Biomol. Chem., 2009, 7, 1192–1202
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(2R,3S,4R,5S)-2-[(2-Naphthalen-1-ylamino)ethyl]-5-methylpyr-
rolidine-3,4-diol (21a). Conventional acidic deprotection of 55
(53.1 mg, 0.124 mmol) in 4 N HCl:THF (2:1, 3 mL), followed by
neutralization with NH4OH, gave after column chromatography
(CH2Cl2/MeOH/NH4OH 10:1:0.1→5:1:0.1) derivative 21a
(21.9 mg, 62%). [a]D +10.9 (c 0.56 in MeOH). IR (n cm-1) 3377,
and K. Sakata, Bioorg. Med. Chem. Lett., 2001, 11, 467; A. Bordier,
P. Compain, O. R. Martin, K. Ikeda and N. Asano, Tetrahedron:
Asymmetry, 2003, 14, 47; Y. Bleriot, D. Gretzke, T. M. Kruelle, T. D.
Butters, R. A. Dwek, R. J. Nash, N. Asano, N. and G. W. J. Fleet,
Carbohydr. Res., 2005, 340, 2713; B. Winchester, C. Barker, S. Baines,
G. S. Jacob, S. K. Namgoong and G. W. J. Fleet, Biochem. J., 1990, 265,
277.
13 G. W. J. Feet, S. K. Namgoong, C. Barker, S. Baines, G. S. Jacob and
B. Winchester, B., Tetrahedron Lett., 1989, 30, 4439.
1
3049 (NH, OH), 2928, 1581, 1532, 1410. H NMR (300 MHz,
CD3OD, d ppm) d 1.19 (3H, d, JMe,5 = 6.9, 5-Me), 1.90 (1H, m,
1¢a-H), 2.17 (1H, m, 1¢b-H), 2.94–3.05 (2H, m, 5-H, 2-H), 3.38
(2H, m, 2¢a-H, 2¢b-H), 4.02 (1H, t, J4,5= J4,3= 5.4, 4-H), 4.12 (1H,
t, J3,2 = 5.4, 3-H), 6.61 (1H, d, J = 7.5, H-arom.), 7.13 (1H, d,
J = 8.4, H-arom), 7.28 (1H, t, J = 7.8, H-arom), 7.35–7.42 (2H,
m, H-arom), 7.72 (1H, m, H-arom), 8.00 (1H, m, H-arom). 13C
NMR (75.4 MHz, CD3OD, d ppm) d 14.5 (5-Me), 29.4 (C-1¢),
42.9 (C-2¢), 57.5, 61.0 (C-2, C-5), 74.1, 74.4 (C-3, C-4), 104.9,
117.6, 121.9, 125.1, 125.3, 126.5, 127.7, 129.3, 135.9, 145.3 (Ar).
CIMS 287 [(M + H)+, 100%], 286 [(M)+, 95%]. CIHRMS m/z
found 287.1748, calcd. for C17H23N2O2 (M + H)+: 287.1759.
14 M. Dubernet, A. Defoin and C. Tarnus, Bioorg. Med. Chem. Lett.,
2006, 61, 1172.
15 Iminosugars as Glycosidase Inhibitors. Nojirimycin and Beyond,
A. E. Stu¨tz, Ed.; Wiley-VCH, 1999, Weinheim, Germany; P. E. Goss, J.
Baptiste, B. Fernandes, M. Baker and J. W. Dennis, Cancer Res., 1994,
54, 1450.
16 J. R. Wheatley, R. J. Nash, A. A. Watson, R. C. Griffiths, T. D. Butters,
M. Muller, D. J. WatKin, D. A. Winkler and G. W. J. Fleet, J. Chem.
Soc., Perkin Trans. 1, 1999, 2735.
17 A. Dondoni, P. P. Giovannini and D. Perrone, J. Org. Chem., 2002,
67, 7203; C. Asiego, M. S. Pino-Gonzalez and F. J. Lo´pez-Herrera,
Tetrahedron Lett., 2004, 45, 2611; F. Cardona, I. Robina and P. Vogel,
J. Carbohydr. Chem., 2000, 19, 555; C. Marquis, F. Cardona, I. Robina,
G. Wurth and P. Vogel, Heterocycles, 2002, 56, 181. For a review on
aza-disaccharides containing homoazasugar moieties: I. Robina and
P. Vogel, Synthesis, 2005, 675.
18 C.-H. Wong, L. Provencher, J. A. Porco, Jr., S.-H. Jung, Y.-F. Wang,
L. Chen, R. Wang and D. H. Steensma, J. Org. Chem., 1995, 60, 1492;
G. W. J. Fleet, N. G. Ramsden and D. R. Witty, Tetrahedron, 1989, 45,
319; J. P. Shilvock, K. Y. Hsia, R. J. Nash, J. D. Lloyd, A. L. Winters,
N. Asano and G. W. J. Fleet, Tetrahedron: Asymmetry, 1998, 9, 4157;
J. P. Shilvock and G. W. J. Fleet, Synlett, 1998, 554.
19 C.-Y. Wu, C.-F. Chang, J. S.-Y. Chen, C.-H. Wong and C.-H. Lin,
Angew. Chem., Int. Ed., 2003, 42, 4661; C. W. Ho, Y. N. Lin, C.-F.
Chang, S.-T. Li, Y.-T. Wu, C.-Y. Wu, C.-Y., C., C.-F., S.-W. Liu, Y.-K.
Li and C.-H- Lin, Biochemistry, 2006, 45, 5695; N. Asano, K. Yasuda,
H. Kizu, A. Kato, J.-Q. Fan, R. J. Nash, G. W. J. Fleet and R. J.
Molyneux, Eur. J. Biochem., 2001, 268, 35; T. Yamashita, K. Yasuda,
H. Kizu, Y. Kameda, A. A. Watson, R. J. Nash, G. W. J. Fleet, G. W. J.
and N. Asano, J. Nat. Prod., 2002, 65, 1875.
Acknowledgements
We thank the Ministerio de Educacio´n y Ciencia of Spain
(CTQ2004-00649/BQU; CTQ2007-61254/BQU, CTQ2008-
01565/BQU), the Junta de Andaluc´ıa (FQM-345) and the Swiss
National Science Foundation (Bern) for financial support.
Notes and references
1 D. H. Dube and C. R. Bertozzi, Curr. Opinion Chem. Biol., 2003, 7,
616; N. Branza-Nichita, A. J. Petrescu, G. Negroiu, R. A. Dwek and
S. M. Petrescu, Chem. Rev., 2000, 100, 4697.
2 A. Varki, Glycobiology, 1993, 3, 97; M. Sperandio, FEBS J., 2006, 273,
4377.
3 N. Asano, Glycobiology, 2003, 102, 93R; R. A. Dwek, Chem Rev., 1996,
96, 683; A. D. Elbein and R. J. Molyneux, Iminosugars as Glycosidase
Inhibitors:Nojirimycin and Beyond (Ed.: A. E. Stu¨tz), Wiley-VCH, 235.
Weinheim, 1999, pp. 216–252.
4 I. Robina, A. J. Moreno-Vargas, A. T. Carmona and P. Vogel, Curr.
Drug. Metabol., 2004, 5, 329.
5 A. Giannis, Angew. Chem., Int. Ed. Engl., 1994, 33, 178; H. M. Flowers,
Adv. Carbohydr. Chem. Biochem., 1981, 39, 279; T. K. Lindhorst, M.
Ludewig and J. Thiem, J. Carbohydr. Chem., 1998, 17, 1131.
6 B. Cobucci-Ponzano, M. Mazzone, M. Ro`ssi and M. Moracci,
Biochemistry, 2005, 44, 6331; P. T. Vanhooren and E. J. Vandamme,
J. Chem. Technol. Biotechnol., 1999, 74, 479; E. Staudacher, F. Altmann,
I. B. Wilson and L. Marz, Biochim. Biophys. Acta, 1999, 1473, 216;
L. A. Lasky, Annu. Rev. Biochem., 1995, 63, 113; M. S. Mulligan, J. C.
Paulson, S. DeFrees, Z. L. Zheng, J. B. Lowe and P. A. Ward, Nature,
1993, 364, 149; F. Schweizer, Angew. Chem., Int. Ed., 2002, 41, 230.
7 P. Compain and O. R. Martin, Bioorg. Med. Chem., 2001, 9, 3077; T. A.
Springer and L. A. Lasky, Nature, 1991, 349, 196.
20 D. Diez, M. T. Benitez, I. S. Marcos, N. M. Garrido, P. Basabe and J. G.
Urones, Tetrahedron: Asymmetry, 2002, 13, 639; D. Diez, M. T. Benitez,
I. S. Marcos, N. M. Garrido, P. Basabe and J. G. Urones, Synlett, 2001,
655; M. Joubert, A. Defoin, C. Tarnus and J. Streith, Synlett, 2000,
1366.
21 Y. F. Wang, D. P. Dumas and C.-H. Wong, Tetrahedron Lett., 1993, 34,
403.
22 L. Espelt, J. Bujons, T. Parella, J. Calveras, J. Joglar, A. Delgado and P.
Clapes, Chem.–Eur. J., 2005, 11, 1392.
23 C. Chevrier, D. Le Noue¨n, M. Neuburger, A. Defoin and C. Tarnus,
Tetrahedron Lett., 2004, 45, 5363.
24 A. Defoin, A. T. Sifferlen, J. Streith, I. Dosbaa and M.-J. Foglietti,
Tetrahedron: Asymmetry, 1997, 8, 363; I. Izquierdo, M. T. Plaza, J. A.
Tamayo, F. Franco and F. Sanchez-Cantalejo, Tetrahedron, 2008, 64,
4993.
25 A. M. Palmer and V. Jager, Eur. J. Org. Chem., 2001, 2547.
26 I. Izquierdo, M. T. Plaza, J. A. Tamayo, D. Lo Re and F. Sanchez-
Cantalejo, Synthesis, 2008, 1373; T. Sifferlen, A. Defoin, J. Streith, D.
Le Nouen, C. Tarnus, I. Dosbaa and M. J. Foglietti, Tetrahedron, 2000,
56, 971.
27 C. Laroche, J.-B. Behr, J. Szymoniak, P. Bertus, C. Schu¨tz, P. Vogel and
R. Plantier-Royon, Bioorg. Med. Chem., 2006, 14, 4047.
28 C. Legler, Adv. Carbohydr. Chem. Biochem., 1990, 48, 319; S. J.
Charnock, T. D. Spurway, H. Xie, M.-H. Beylot, R. Virden, R. A. J.
Warren, G. P. Hazlewood and H. J. Gilbert, J. Biol. Chem., 1998, 273,
32187.
29 C.-W. Ho, Y. N. Lin, C.-F. Chang, S.-T. Li, Y.-T. Wu, C.-Y. Wu, C.-F.
Chang, S.-W. Liu, Y.-K. Li and C.-H. Lin, Biochemistry, 2006, 45, 5695.
30 C.-F. Chang, C.-W. Ho, C.-Y. Wu, T.-A. Chao, C.-H. Wong and C.-H.
Lin, Chem. Biol., 2004, 11, 1301.
8 D. Ayude, J. Ferna´ndez-Rodr´ıguez, F. J. Rodr´ıguez-Berrocal, V. S.
Mart´ınez-Zorzano, A. de Carlos, E. Gil and M. P. de la Cadena,
Oncology, 2000, 59, 310.
9 J. C. MichalsKi and A. Klein, Biochim. Biophys. Acta, 1999, 1455, 69;
M. C. Glick, V. A. Kothari, A. Liu, L. I. Stoykova and T. F. Scanlin,
Biochimie, 2001, 83, 743; T. F. Scanlin and M. C. Glick, Biochim.
Biophys. Acta, 1999, 1455, 241.
10 J. Ferna´ndez-Rodr´ıguez, D. Ayude, M. P. de la Cadena, V. S. Mart´ınez-
Zorzano, A. de Carlos, A. Caride Castro, G. de Castro and F. J.
Rodr´ıguez-Berrocal, Cancer Detect. Prev., 2000, 24, 143.
31 For results on a-mannosidases see: S. Gerber-Lemaire, F. Popowycz, E.
Rodriguez-Garcia, A. T. Carmona, I. Robina and P. Vogel, Chem-
BioChem, 2002, 3, 466; S. Gerber-Lemaire, F. Popowycz, E. Rodr´ıguez-
Garcia, C. Schuetz, A. T. Carmona, I. Robina and P. Vogel, ARKIVOC,
2002, XII, 23; A. T. Carmona, F. Popowycz, S. Gerber-Lemaire, E.
Rodriguez-Garcia, C. Schutz, P. Vogel and I. Robina, Bioorg. Med.
11 S. Khunnsook, B. Bean, S. R. McGowan and J. A. Alhadeff, Biol.
Reprod., 2003, 68, 709; S. Khunnsook, J. A. Alhadeff and B. Bean,
Mol. Hum. Reprod., 2002, 8, 221.
12 A. De Raadt, C. W. Ekhart, M. Ebner and A. E. Stu¨tz, Topics Curr.
Chem., 1997, 187, 157; A. Peer and A. Vasella, Helv. Chim. Acta, 1999,
82, 1044; W. Guo, J. Hiratake, K. Ogawa, M. Yamamoto, S.-J. Ma
This journal is
The Royal Society of Chemistry 2009
Org. Biomol. Chem., 2009, 7, 1192–1202 | 1201
©

View Article Online
Chem., 2003, 11, 4897; F. Popowycz, S. Gerber-Lemaire, E. Rodriguez-
Garcia, C. Schutz and P. Vogel, Helv. Chim. Acta, 2003, 86, 1914; F.
Popowycz, S. Gerber-Lemaire, C. Schutz and P. Vogel, Helv. Chim.
Acta, 2004, 87, 800; C. Saotome, C.-H. Wong and O. Kanie, Chem.
Biol., 2001, 8, 1061.
34 For previous communications of this work see: A. J. Moreno-Vargas,
A. T. Carmona, F. Mora, P. Vogel and I. Robina, Chem. Commun.,
2005, 4949; E. Moreno-Clavijo, A. T. Carmona, A. J. Moreno-Vargas
and I. Robina, Tetrahedron Lett., 2007, 48, 159.
35 W. H. Pearson, L. Guo and T. M. Jewell, Tetrahedron Lett., 2002, 43,
32 For results on a-L-fucosidases, see: I. Robina, A. J. Moreno-Vargas,
J. G. Ferna´ndez-Bolan˜os, J. Fuentes, R. Demange and P. Vogel,
Bioorg. Med. Chem. Lett., 2001, 11, 2555; A. J. Moreno-Vargas, I.
Robina, R. Demange and P. Vogel, Helv. Chim. Acta, 2003, 86, 1894.
For cyclopentitols, see:; A. Blaser and J. L. Reymond, Org. Lett.,
2000, 2, 1733. For piperidines, see:; C.-F. Chang, C.-W. Ho, C.-Y.
Wu, T.-A. Chao, C.-H. Wong and C.-H. Lin, Chem. Biol., 2004, 11,
1301.
2175.
36 S. Vijayasaradhi, J. Singh and A. I. Singh, Synlett, 2000, 110.
37 H. H. Jenseb, A. Jensen, R. G. Hazell and M. Bols, J. Chem. Soc.,
Perkin Trans. 1, 2002, 1190.
38 I. Robina, R. P. Gearing, J. G. Buchanan and R. H. Wightman, J. Chem.
Soc., Perkin Trans. 1, 1990, 2622; D. K. Thompson, C. N. Hubert and
R. H. Wightman, Tetrahedron, 1993, 49, 3827.
39 R. Saul, J. P. Chambers, R. J. Molyneux and A. D. Elbein, Arch.
Biochem. Biophys., 1983, 221, 593; A. Brandi, S. Cicchi, F. M. Cordero,
R. Frignoli, A. Goti, S. Picasso and P. Vogel, J. Org. Chem., 1995, 60,
6806.
33 H. Fiaux, F. Popowycz, S. Faure, C. Schutz, P. Vogel, S. Gerber-
Lemaire and L. Juillerat-Jeanneret, J. Med. Chem., 2005, 48,
4237.
1202 | Org. Biomol. Chem., 2009, 7, 1192–1202
This journal is
The Royal Society of Chemistry 2009
©