Sugar amino acids at the anomeric position of carbohydrates: synthesis of spirocyclic amino acids of 6-deoxy-l-lyxofuranose

Article abstract of DOI:10.1016/j.tetasy.2006.07.027

Two anomeric spirodiketopiperazines and one spirohydantoin of 6-deoxy-l-lyxofuranose have been prepared from l-fucono-δ-lactone via ring contraction to the corresponding tetrahydrofuran carboxylate and anomeric functionalization including regioselective b

Full text of DOI:10.1016/j.tetasy.2006.07.027

Tetrahedron: Asymmetry 17 (2006) 2276–2286
Sugar amino acids at the anomeric position
of carbohydrates: synthesis of spirocyclic amino acids
of 6-deoxy-L-lyxofuranose
a, ,
*
Michela I. Simone,a Mark R. Wormald,b Raymond A. Dwek,b
´
Yves Bleriot,
David J. Watkinc and George W. J. Fleeta,*
aChemistry Research Laboratory, Department of Chemistry, Oxford University, Mansfield Road, Oxford OX1 3TA, UK
bGlycobiology Institute, Biochemistry Department, Oxford University, South Parks Road, Oxford OX1 3QU, UK
cChemical Crystallography Laboratory, Oxford University, 9 Parks Road, Oxford OX1 3QU, UK
Received 10 July 2006; accepted 24 July 2006
Available online 23 August 2006
Abstract—Two anomeric spirodiketopiperazines and one spirohydantoin of 6-deoxy-L-lyxofuranose have been prepared from L-fucono-
d-lactone via ring contraction to the corresponding tetrahydrofuran carboxylate and anomeric functionalization including regioselective
bromination and azide displacement.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
thoroughly investigated dipeptide isosteres with significant
biological activity.10
Amino acids and carbohydrates are two major compo-
nents, which generate diversity in Nature. The combination
of the structural features of simple amino acids with those
of simple carbohydrates gives rise to glycosamino acids
(GAAs),1,2 which can be classified according to the posi-
tion of the amino acid moiety on the cyclic polyol. Sugar
amino acids (SAAs), which result from the direct incorpo-
ration of the amino acid moiety into the cyclic carbo-
hydrate scaffold, have emerged as a new class of promising
hybrids due to their restricted conformation generating b-
and c-turns as well as helices. As a consequence, SAAs have
found many applications as peptide scaffolds in combinato-
rial chemistry3 and as peptidomimetics.4 When oligomer-
ized or incorporated into peptide chains, these SAAs
generate carbopeptoids5 or foldamers6 with restricted sec-
ondary structure displaying novel catalytic and recognition
properties. Along with pyranose7 and oxetanose8 SAAs,
furanose tetrahydrofuran (THF) SAAs9 are the most
Among SAAs, a special situation occurs when both the
amino and carboxylate groups are born by the same car-
bon atom of the sugar ring. SAAs with the amino acid moi-
ety at C-2 or C-4 of the sugar template11,12 have been
described and biological activity has been observed when
the a-amino acid can incorporate the anomeric centre of
the carbohydrate scaffold. When the amine and the acid
functionalities are connected together to yield spirohydan-
toin and spirodiketopiperazines, which on their own have a
number of potential chemotherapeutic applications,13 this
can lead to anomeric spirocyclic amino acid carbohydrate
hybrids, which have been reported to exhibit chemothera-
peutic potency as in spirohydantoin-glucopyranose hybrid
1. This is a potent inhibitor of glycogen phosphorylase,14
the enzyme responsible for the regulation of blood sugar
level, this result leading to improved syntheses of 115 and
design of potent analogues.16 The natural product hydant-
ocidin 2, a spirohydantoin structure isolated from Strepto-
myces hygroscopicus17 incorporates a D-ribofuranosyl unit
and displays potent herbicidal and plant growth regulatory
activity through inhibition of an adenylosuccinate synthe-
tase.18 The biological activity of 2 and its unique structure
has stimulated considerable efforts towards the efficient
synthesis of 219 and its analogues (Fig. 1).20
*
Corresponding authors. Tel.: +33 1 44 32 33 35; fax: +33 1 44 32 33 97
(Y.B.); tel.: +44 1865 277 386; fax: +44 1865 277 378 (G.W.J.F.); e-mail
addresses: yves.bleriot@ens.fr; george.fleet@chemistry.oxford.ac.uk
´
´
Present address: Ecole Normale Superieure, Departement de Chimie,
UMR 8642, 24 rue Lhomond, 75231 Paris Cedex 05, France.
0957-4166/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2006.07.027

Y. Ble´riot et al. / Tetrahedron: Asymmetry 17 (2006) 2276–2286
2277
OH
HO
OH
HO
OH
HO
OH
O
O
O
HO
HO
OH
OH
O
HN
HN
H
N
HN
O
CH3
CH3
CH3
O
O
O
NH
NH
NH
HN
O
CH2OH
O
O
O
CH2OH
O
NH
N
H
O
O
1
2
5
3
4
Figure 1. Structure of spirocyclic glucopyranose 1, hydantocidin 2 and target compounds 3–5.
As part of a project devoted to the design of efficient glyco-
gen phosphorylase (GPb) inhibitors as possible therapeutic
agents for the treatment of diabetes, we were interested in
the synthesis of a range of spirohydantoin and spirodiketo-
piperazines at the anomeric position of carbohydrates in
the furanose form. Herein, we report the synthesis of the
spirocyclic amino acids of L-lyxofuranose 3–5 (Fig. 1),
which can be seen as ring-contracted anomeric SAAs ana-
logues of L-fucopyranose.
resulting open chain hydroxy-triflate with inversion of con-
figuration at C-2. Reprotection of the diol as its acetonide
afforded the required methyl ester 10. The generation of
THF a-amino acid derivatives requires functionalization
at C-2 of the suitably protected carbohydrate carboxylates,
and regioselective bromination of 10 was examined. Treat-
ment of 10 with lithium bis(trimethylsilyl)amide or LDA in
THF at ꢀ70 ꢁC and subsequent quenching of the transient
anion with carbon tetrabromide27 afforded the epimeric
bromoesters 11, which were treated with sodium azide in
dimethylformamide to give a combined yield of 36% of
the epimeric azides 12a and 12b, respectively, in a 9:1 ratio
as determined by NMR. This low yield led us to predict
another method to introduce the azido group based on
the relative stability of the captodative radical formed by
abstraction of hydrogen from C-2.28 Radical bromination
of 10 using N-bromosuccinimide in carbon tetrachloride29
in the presence of benzoyl peroxide as an initiator followed
by azide displacement afforded azides 12a and 12b in a 55%
combined yield. This moderate yield could be tentatively
explained by the difficult hydrogen abstraction at C-2 due
to the steric hindrance caused by the acetonide and the
methyl group. To improve this step and verify our hypoth-
esis, the synthesis of the epimeric methyl ester 15 was
achieved (Scheme 3).
2. Results and discussion
Our strategy is based upon the propensity of the 2-O-triflu-
oromethanesulfonates of carbohydrates c- and d-lactones
to ring contract in basic21 or acidic22 methanol to afford
the highly substituted tetrahydrofuran carboxylates. This
protocol has been applied to the elaboration of libraries
of C-glucofuranose based scaffolds.23 These tetrahydro-
furan carboxylates can be regioselectively brominated24
and subsequently displaced with sodium azide to give
access, after further processing, to a range of anomeric
THF amino acid monomers derived from a sugar template
(Scheme 1).
In our case, L-fucono-d-lactone is the relevant precursor to
access the target compounds 3–5. The anomeric azidoester
intermediate was obtained as follows (Scheme 2). Acetona-
tion of the cis 3,4 diol of L-fucose with 2,2-dimethoxypro-
pane in the presence of anhydrous copper sulfate in acetone
gave the known monoacetonide 6 in 55% yield.25 The oxi-
dation of compound 6 with bromine–water buffered with
barium carbonate, afforded L-fucono-d-lactone 7 in 73%
yield.26 Triflation of the free secondary alcohol in 7 with
trifluoromethanesulfonic anhydride in the presence of pyr-
idine at ꢀ30 ꢁC gave the crude triflate 8, which was reacted
with hydrogen chloride in methanol to afford the deprotec-
ted methyl ester 9 in an overall yield of 70% from 7. The
formation of methyl ester 9 most likely proceeds with
hydrolysis of the acetonide, methanolysis of the lactone
and subsequent intramolecular SN2 ring closure of the
The initial reaction of crude triflate 8 with sodium trifluoro-
acetate in DMF, followed by aqueous work-up with con-
comitant hydrolysis of the resulting trifluoroacetate ester,
gave the inverted 6-deoxy-L-talono-d-lactone 13 in 62%
yield. Triflation of compound 13 with triflic anhydride gave
triflate 14 (87% yield), which upon treatment with methan-
olic hydrogen chloride followed by acetonation afforded
the fully protected tetrahydrofuran carboxylate 15 in 97%
yield. Radical bromination of 15 afforded a mixture of
crude bromides 11a and 11b, which were displaced with
sodium azide to yield an inseparable mixture of epimeric
azidoester 12a and 12b in good 74% yield (from 15) and
in a 10:1 ratio, respectively. This is indicative of a stereose-
lective bromination, an observation most often reported
with substrates possessing a 3,4-O-isopropylidene-protected
OP
ring
regioselective
bromination
PO
OP
HO
OH
PO
OP
functionalisation
N3
MeO2C
contraction
TfO
O
OP
HRN
R'HNC
O
azide
CH2OP
CH2OH
CH2OP
MeO2C
O
O
O
O
CH2OP
displacement
Scheme 1. General strategy for the generation of THF a-amino acid monomers.

2278
Y. Ble´riot et al. / Tetrahedron: Asymmetry 17 (2006) 2276–2286
OH
O
O
O
O
O
O
O
HO
HO
OH
HO
HO
O
HO
O
O
TfO
O
O
(iii)
(i)
(ii)
CH3
CH3
CH3
CH3
6
7
8
L-Fucose
OH
HO OH
O
O
(iv)
TfO
OH
CH3
(v)
8
MeO2C
CH3
CH3
MeO2C
MeO2C
O
O
HO
9
10
(vi)
O
O
O
O
(vii)
N3
MeO2C
Br
MeO2C
CH3
CH3
O
12
O
11
Scheme 2. Synthesis of azidoesters 12a and 12b from L-fucose. Reagents and conditions: (i) CuSO4, acetone, 55%; (ii) Br2, BaCO3, H2O, 73%; (iii) Tf2O,
pyridine, dichloromethane, ꢀ30 ꢁC; (iv) 1% HCl in MeOH; (v) 2,2-dimethoxypropane, acetone, CSA, 70% over two steps; (vi) NBS, CCl4, (PhCOO)2;
(vii) NaN3, DMF, rt 55% over two steps.
cis-diol function.30 Azide displacement of the bromide of a
highly hindered a-bromotetrahydrofuran ester has been
shown to proceed with inversion of configuration.31
NHꢁ ꢁ ꢁH-3 and a strong NOE was observed for NHꢁ ꢁ ꢁ
H-5. This is only consistent with compound 19 having a
trans H-3/NH relationship and compound 20 having
a cis H-3/NH and a cis H-5/NH relationships. The struc-
ture of compound 20 was firmly established by single
X-ray crystallographic analysis.32 Removal of the aceto-
nide group in spirodiketopiperazines 19 and 20 with
TFA furnished the spirocyclic sugar amino acids 3
and 4.
Completion of the synthesis of the anomeric spirocyclic
peptides was achieved as follows (Scheme 4). Hydrogena-
tion of azidoesters 12a and 12b in methanol in the presence
of Pd/C gave a mixture of epimeric aminoesters 16a and
16b (70% yield), which were coupled with Z-glycine under
standard conditions to afford dipeptide 17 in 17% yield
along with 56% of the epimeric dipeptide 18. Hydrogenol-
ysis of the Z protecting group in 17 afforded the
corresponding amine, which cyclized upon treatment with
t-BuOK in THF to afford the spirodiketopiperazine
compound 19 in 44% yield over two steps. The same
sequence was applied to dipeptide 18 to afford epimeric
spirocyclic sugar 20 in 69% yield. The anomeric configura-
tions of 19 and 20 were determined by performing NMR
The synthesis of the corresponding anomeric spirohydan-
toins was then examined (Scheme 5). Using an established
methodology for the construction of a spirohydantoin
ring,33 amine 16 was treated with potassium cyanate in ace-
tic acid at 65 ꢁC to afford the intermediate ureas, which
spontaneously cyclized in acetic acid to afford the spirocy-
clic derivative 21 in 74% yield. Final deprotection with
aqueous TFA led to the target spirohydantoin 5 in 94%
yield. Equilibration of compound 21 to the epimeric spiro-
cyclic compound by treatment with t-BuOK in THF
proved unsuccessful.
NOE experiments. For spirodiketopiperazine 19,
a
weak NOE was observed for NHꢁ ꢁ ꢁH-3. For spirodike-
topiperazine 20, a medium NOE was observed for
O
O
O
TfO
O
O
HO
O
O
TfO
O
O
(ii)
(i)
O
CH3
O
CH3
O
CH3
8
13
14
(iii)
O
O
O
O
O
O
(v)
(iv)
Br
MeO2C
N3
MeO2C
CH3
CH3
MeO2C
CH3
12α, 12β
O
O
O
11
15
Scheme 3. Synthesis of the azidoesters 12a and 12b from triflate 14. Reagents and conditions: (i) CF3COONa, DMF, 62% from 7; (ii) Tf2O, pyridine,
ꢀ30 ꢁC, 84%; (iii) 3% HCl in MeOH then 2,2-dimethoxypropane, CSA, acetone, 97%; (iv) NBS, CCl4, (PhCOO)2; (v) NaN3, DMF, rt, 74% over two steps.

Y. Ble´riot et al. / Tetrahedron: Asymmetry 17 (2006) 2276–2286
2279
O
O
O
O
O
O
O
O
ZHN
ZHN
(i)
(ii)
H2N
MeO2C
12
HN
HN
+
CH3
CH3
O
CH3
O
O
MeO2C
MeO2C
16α, 16β
17
(iii)
18
(iii)
O
O
O
O
O
O
HN
HN
CH3
CH3
O
O
NH
NH
19
20
O
O
(iv)
(iv)
O
O
HO OH
CH3
HO OH
CH3
HN
HN
O
O
NH
NH
3
4
O
O
Scheme 4. Synthesis of the spirodiketopiperazines 3 and 4. Reagents and conditions: (i) H2, Pd/C, MeOH, 70%; (ii) Z-glycine DCC, 1-hydroxy-
benzotriazole, dichloromethane, 73%; (iii) H2, Pd black, MeOH then t-BuOK, THF, 44–69%; (iv) 50% aq TFA, 80%.
O
O
O
O
HO
OH
O
O
H2N
(i)
(ii)
HN
O
HN
O
CH3
CH3
CH3
O
O
O
MeO2C
NH
NH
16
21
5
(iii)
X
O
O
O
HN
O
CH3
O
NH
Scheme 5. Synthesis of the spirohydantoin 5. Reagents and conditions: (i) KOCN, AcOH, 74%; (ii) 50% aq TFA, 94%; (iii) t-BuOK, THF.
3. Conclusion
AC 200 (200 MHz) or a Bruker AM 500 (500 MHz) spec-
trometer. 13C Nuclear magnetic resonance (dC) spectra
were recorded on a Varian Gemini 200 (50 MHz), a Bruker
AC 200 (50 MHz) or a Bruker AM 500 (125 MHz)
spectrometer and multiplicities were assigned using DEPT
sequence. All chemical shifts are quoted on the d-scale. The
following abbreviations were used to explain multiplicities:
s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; br,
broad; app, apparent. Infra-red spectra were recorded on a
Perkin–Elmer 1750 IR FT spectrophotometer. Mass spec-
tra were recorded on a VG Masslab 20-250, BIO-Q or
using desorption chemical ionization (DCI NH3), chemical
ionization (CI NH3), electrospray or thermospray, or
atmospheric pressure chemical ionization (APCI+ or
In summary, this paper reports an efficient synthesis of the
anomeric spirodiketopiperazines 3 and 4 and spirohydan-
toin 5 of 6-deoxy-L-lyxofuranose. The evaluation of these
compounds for their herbicidal activity and as glycogen
phosphorylase inhibitors is underway.
4. Experimental
Melting points were recorded on a Kofler hot block and are
corrected. Proton nuclear magnetic resonance (dH) spectra
were recorded on a Varian Gemini 200 (200 MHz), Bruker

2280
Y. Ble´riot et al. / Tetrahedron: Asymmetry 17 (2006) 2276–2286
APCIꢀ) as stated. Optical rotations were measured on a
Perkin–Elmer 241 polarimeter with a path length of
1 dm. Concentrations are given in g/100 ml. Microanalyses
were performed by the microanalysis service of the Dyson
Perrins laboratory. Thin layer chromatography (TLC) was
carried out on plastic or aluminium sheets coated with 60
F254 silica, and plates were developed using a spray of
0.2% w/v cerium(IV) sulfate and 5% ammonium molybdate
in 2 M sulfuric acid. Flash chromatography was carried
out using Sorbsil C60 40/60 silica. Solvents and commer-
cially available reagents were dried and purified before
use according to standard procedures; hexane was distilled
at 68 ꢁC before use to remove less volatile fractions.
portions over 5 min. The solution was stirred at 0 ꢁC for
20 min and then stirred at room temperature for 3 h by
which time TLC (ethyl acetate) showed a major product
(Rf 0.8), a minor product (Rf 0.6) and a trace of the starting
material (Rf 0.5 and Rf 0.4). The excess of barium carbon-
ate was filtered off through a Celite plug, which was eluted
with water (150 ml). To bubble off the excess of bromine,
nitrogen was passed through the orange solution until all
the colour had disappeared. The aqueous solution was ex-
tracted with ethyl acetate (3 · 200 ml). The organic extracts
were combined, dried over magnesium sulfate and the sol-
vent removed under reduced pressure. The resulting white
solid was purified by flash chromatography (ethyl ace-
tate/hexane 1:2 then 1:1) to afford 3,4-O-isopropylidene-
L-fucono-1,5-lactone 7 (5.055 g, 73% yield) as a white
4.1. 3,4-O-Isopropylidene-L-fucose 6
crystalline solid: mp 92–94 ꢁC (ethyl acetate/hexane);
24
L-Fucose (19.54 g, 119 mmol) and anhydrous copper
sulfate (39 g, 244.4 mmol, 2 equiv) were suspended in HPLC
grade acetone (300 ml) under N2. The suspension was stir-
red for 16 h under N2 by which time, TLC (ethyl acetate)
showed some diacetonide (Rf 0.9), some monoacetonide
(Rf 0.5 and Rf 0.4) and some starting material (Rf 0.0).
The suspension was filtered through a sinta funnel topped
with a 2 mm filter sheet, which was eluted with acetone
(200 ml). The filter cake was dried on the vacuum line for
5 h, suspended again in acetone and stirred for 16 h under
N2. This procedure was repeated twice. The filtrates were
combined, concentrated in vacuo to afford a white solid,
which was preadsorbed on silica. Purification by flash chro-
matography (ethyl acetate/hexane 2:1 then ethyl acetate)
afforded 3,4-O-isopropylidene-L-fucose 6 (13.35 g, 55%
½aꢂD ¼ ꢀ148:2 (c 1.09, CHCl3) [lit. mp 98–99 ꢁC (ethyl ace-
21
tate); ½aꢂD ¼ ꢀ137 (c 0.1, CHCl3)]; mmax (film)/cmꢀ1: 3356
(br, OH), 1729 (C@O); dH (500 MHz, CDCl3): 1.36, 1.42
(6H, s, (CH3)2C), 1.45 (3H, d, J5,6 6.7 Hz, CH3), 4.37
(1H, dd, J4,5 1.9 Hz, J3,4 7.5 Hz, H-4), 4.38 (1H, d, J2,3
2.7 Hz, H-2), 4.56 (1H, dd, J2,3 2.7 Hz, J3,4 7.5 Hz, H-3),
5.02 (1H, dq, J5,6 6.7, 1.9 Hz, H-5); dC (125 MHz, CDCl3):
16.0 (q, Me), 24.1 (q, Me2C), 26.0 (q, Me2C), 69.2, 73.1,
73.9, 75.5 (4 · d, C-2, C-3, C-4, C-5), 110.1 (s, CMe2),
170.9 (s, C-1); m/z (CI; NH3): 220 (M+NH4þ, 100%),
203 (M+H+, 18%), (Found: C, 53.55; H, 7.13; C9H14O5
requires C, 53.44; H, 6.98).
4.3. 2-Trifluoromethanesulfonyl-3,4-O-isopropylidene-L-
fucono-1,5-lactone 8 and methyl 2,5-anhydro-6-deoxy-
3,4-O-isopropylidene-L-talonate 10
yield) as a white solid: mp 105–108 ꢁC (ethyl acetate);
22
½aꢂD ¼ ꢀ84:5 (c 2.2, H2O, 1 h); [lit. mp 110–111 ꢁC (ethyl
21
acetate); ½aꢂD ¼ ꢀ90 ! ꢀ68 (c 0.2, H2O, equil. over
3,4-O-Isopropylidene-L-fucono-1,5-lactone
7
(3.31 g,
24 h)]; mmax (KBr)/cmꢀ1: 3403 (br, OH); dH (500 MHz,
CD3OD): 1.25 (3H, d, J5,6 6.7 Hz, CH3a), 1.33, 1.47 (6H,
2 · s, (CH3)2Ca), 1.33 (3H, d, J5,6 6.7 Hz, CH3b), 1.34,
1.49 (6H, 2 · s, (CH3)2Cb), 3.35 (1H, app t, J 7.6 Hz, H-
2b), 3.61 (1H, dd, J1,2 3.6 Hz, J2,3 7.1 Hz, H-2a), 3.94
(1H, dq, J4,5 2.2 Hz, J5,6 6.7 Hz, H-5b), 3.97 (1H, dd, J3,4
5.4 Hz, J2,3 7.4 Hz, H-3b), 4.04 (1H, dd, J4,5 2.2 Hz, J3,4
5.4 Hz, H-4b), 4.08 (1H, dd, J4,5 2.4 Hz, J3,4 5.8 Hz,
H-4a), 4.18 (1H, dd, J3,4 5.8 Hz, J2,3 7.1 Hz, H-3a), 4.35
(1H, dq, J4,5 2.4 Hz, J5,6 6.7 Hz, H-5a), 4.39 (1H, d, J1,2
8.2 Hz, H-1b), 5.01 (1H, d, J1,2 3.6 Hz, H-1a); dC
(125 MHz, CD3OD): 16.7 (q, CH3a), 16.9 (q, CH3b), 26.3
(q, (CH3)2Ca), 26.6 (q, (CH3)2Cb), 28.3 (q, (CH3)2Ca),
28.5 (q, (CH3)2Cb), 64.3, 69.9, 71.2, 75.5, 77.2, 77.5, 77.8,
80.9 (8 · d, C-2a, C-3a, C-4a, C-5a, C-2b, C-3b, C-4b, C-
16.38 mmol) was dissolved in dry dichloromethane
(100 ml) under N2 and the solution cooled to ꢀ30 ꢁC.
Dry pyridine (4 ml, 49.14 mmol, 3 equiv) was added
followed by the dropwise addition of triflic anhydride
(41 ml, 24.57 mmol, 1.5 equiv) over 5 min. The solution
was stirred at ꢀ20 ꢁC under N2. After 20 min, TLC (ethyl
acetate/hexane 1:2) showed some starting material as still
remaining. Some more triflic anhydride (1 ml, 0.4 equiv)
was added to complete the reaction. The reaction was
quenched by the addition of five drops of water. The solu-
tion was filtered through a Celite plug topped with magne-
sium sulfate and eluted with dichloromethane. The organic
extracts were combined and dried (magnesium sulfate). The
solvent was removed in vacuo and coevaporated with tolu-
ene to afford the crude 2-trifluoromethanesulfonyl-3,4-O-
21
5b), 93.4 (d, C-1a), 97.5 (d, C-1b), 109.8 (s, C(CH3)2a),
isopropylidene-L-fucono-1,5-lactone 8 as an oil: ½aꢂD ¼
þ
110.5 (s, C(CH3)2b); m/z (CI, NH3): 222 (M+NH4
,
ꢀ64:3 (c 1.11, CHCl3); mmax (film)/cmꢀ1: 1766 (C@O); dH
(200 MHz, CDCl3): 1.38, 1.44 (3H, s, (CH3)2C), 1.52 (3H,
d, J5,6 6.6 Hz, CH3), 4.46 (1H, dd, J4,5 1.6 Hz, J3,4
7.2 Hz, H-4), 4.72 (1H, dd, J2,3 2.4 Hz, J3,4 7.2 Hz, H-3),
4.81 (1H, dq, J5,6 6.6, 1.6 Hz, H-5), 5.14 (1H, d,
J = 2.7 Hz, H-2); dC (50 MHz, CDCl3): 16.1 (q, CH3),
23.9 (q, (CH3)2C), 25.7 (q, (CH3)2C), 73.4, 73.7, 74.3,
77.1 (4 · d, C-2, C-3, C-4, C-5), 111.6 (s, (CH3)2C), 162.1
(s, C-1); m/z (CI; NH3): 352 (M+NH4þ, 100%).
18%), 204 (M+NH4þꢀH2O, 100%), 187 (M+H+ꢀH2O,
37%); (Found: C, 52.73; H, 8.15; C9H16O5 requires C,
52.93; H, 7.90).
4.2. 3,4-O-Isopropylidene-L-fucono-1,5-lactone 7
Barium carbonate (20.3 g, 102.9 mmol, 3 equiv) was added
to a solution of 3,4-O-isopropylidene-L-fucose 6 (7.0 g,
34.3 mmol) in distilled water (100 ml) under vigorous
stirring. The resulting suspension was cooled to 0 ꢁC and
bromine (6.2 ml, 120.1 mmol, 3.5 equiv) was added by
Crude triflate 8 was dissolved in 1% HCl in methanol
(20 ml) under N2 and the solution stirred at room temper-

Y. Ble´riot et al. / Tetrahedron: Asymmetry 17 (2006) 2276–2286
2281
ature. After 16 h, TLC (ethyl acetate/hexane 1:1) showed
no starting material and two new products (Rf 0.8 and Rf
0.4). The reaction mixture was diluted with ethyl acetate
(20 ml) and neutralized with an excess of sodium bicarbon-
ate. The solution was filtered through a Celite pad eluted
with ethyl acetate and then concentrated in vacuo. The
resulting oil was dissolved in an acetone/2,2-dimethoxypro-
pane solution (9:1, 150 ml) and camphorsulfonic acid
(33 mg) was added. The solution was stirred under N2 for
6 h by which time TLC (ethyl acetate/hexane 1:1) showed
one main product (Rf 0.8). The solution was neutralized
with an excess of sodium bicarbonate. The solution was fil-
tered through a Celite pad eluted with ethyl acetate and
then concentrated in vacuo. The residue was partitioned
between CHCl3 (100 ml) and water (100 ml). The aqueous
layer was extracted with CHCl3 (2 · 100 ml). The organic
extracts were combined, dried (magnesium sulfate) and
the solvent removed under reduced pressure. Purification
by flash chromatography (ethyl acetate/hexane 1:4 then
1:3 then 1:2) afforded methyl 2,5-anhydro-6-deoxy-3,4-O-
solved in carbon tetrachloride (4 ml) under N2. N-
Bromosuccinimide (127 mg, 0.716 mmol, 1.3 equiv) and
benzoyl peroxide (5 mg) were added under N2. The solu-
tion was degassed three times and air replaced with N2.
The suspension was plunged into an oil bath at 80 ꢁC
and stirred for 25 min when TLC (ethyl acetate/hexane
1:2) showed a new product (Rf 0.7) and a trace of starting
material (Rf 0.25). The flask was plunged in an ice bath.
The solution was filtered and the sinta funnel eluted with
carbon tetrachloride. The solvent was removed under re-
duced pressure to give the crude bromoester 11, which
was dissolved in dry DMF (3 ml) under N2, and sodium
azide (107 mg, 1.64 mmol) was added. The solution was
stirred for 12 h under N2. The solvent was removed under
reduced pressure and coevaporated with toluene
(3 · 20 ml). The residue was preadsorbed on silica and
purified by flash chromatography (ethyl acetate/hexane
1:5) to afford a mixture of azidoesters 12a and 12b
(77 mg, 0.303 mmol) in 55% yield and in a 9:1 ratio from
10.
isopropylidene-L-talonate 10 (2.741 g, 75% yield) as a
22
colourless oil: ½aꢂD ¼ ꢀ33:8 (c 1.95, CHCl3); mmax (film)/
4.4.3. Method 3. Methyl 2,5-anhydro-6-deoxy-3,4-O-
isopropylidene-L-galactonate 15 (1 g, 4.63 mmol) was
dissolved in carbon tetrachloride under N2. N-Bromo-
succinimide (1.071 g, 6.02 mmol, 1.3 equiv) and benzoyl
peroxide (10 mg) were added under N2. The solution was
degassed three times and air replaced with N2. The suspen-
sion was plunged into an oil bath at 80 ꢁC and stirred for
25 min when TLC (ethyl acetate/hexane 1:2) showed a
new product (Rf 0.7) and a trace of starting material (Rf
0.25). The flask was plunged in an ice bath. The solution
was filtered and the sinta funnel eluted with carbon tetra-
chloride. The solvent was removed under reduced pressure
to give the crude bromoester 11, which was dissolved in dry
DMF (10 ml) under N2, and sodium azide (391 mg,
1.3 equiv) then added. The solution was stirred for 16 h
under N2. The solvent was removed under reduced pressure
and coevaporated with toluene (3 · 20 ml). The residue was
preadsorbed on silica and purified by flash chromato-
graphy (ethyl acetate/hexane 1:5) to afford a mixture of
cmꢀ1: 1754 (C@O); dH (500 MHz, CDCl3): 1.35, 1.51
(6H, 2 · s, (CH3)2C), 1.36 (3H, d, J5,6 6.3 Hz, CH3), 3.76
(3H, s, CH3O2C), 4.14 (1H, dq, J5,6 6.3 Hz, J5,4 3.6 Hz,
H-5), 4.54 (1H, s, H-2), 4.58 (1H, dd, J4,5 3.6 Hz, J4,3
6.0 Hz, H-4), 4.97 (1H, d, J3,4 6.0 Hz, H-3); dC
(125 MHz, CDCl3): 13.7 (q, CH3), 25.1 (q, (CH3)2C),
26.2 (q, (CH3)2C), 52.2 (q, CH3O2C), 78.4, 81.9, 82.5,
84.6 (4 · d, C-2, C-3, C-4, C-5), 112.9 (s, (CH3)2C), 171.1
(s, C-1); m/z (CI; NH3): 234 (M+NH4þ, 100%), 217
(M+H+, 35%); (Found: C, 55.79; H, 7.17; C10H16O5
requires C, 55.53; H, 7.46).
4.4. Methyl 2,5-anhydro-2-bromo-6-deoxy-3,4-O-isoprop-
ylidene-L-galactonate 11, methyl 2,5-anhydro-2-azido-6-
deoxy-3,4-O-isopropylidene-L-talonate 12a and methyl
2,5-anhydro-2-azido-6-deoxy-3,4-O-isopropylidene-
L-galactonate 12b
methyl
ene-L-talonate 12a and methyl 2,5-anhydro-2-azido-
6-deoxy-3,4-O-isopropylidene-L-galactonate 12b as
colourless oil in a 10:1 ratio (891 mg, 74% yield). Careful
chromatography enabled to obtain pure samples of both
azidoesters.
2,5-anhydro-2-azido-6-deoxy-3,4-O-isopropylid-
4.4.1. Method 1. Methyl 2,5-anhydro-6-deoxy-3,4-O-iso-
propylidene-L-talonate 10 (115 mg, 0.53 mmol) was dis-
solved in anhydrous THF under N2. The solution was
cooled to ꢀ70 ꢁC and LiN(TMS)2 (1.33 ml, 1.33 mmol,
1 M solution in THF) was added over 3 min and the reac-
tion mixture then stirred for 5 min. The reaction was then
quenched with CBr4 and stirred for 40 min. The reaction
mixture was then diluted with CH2Cl2 (20 ml), and washed
with water (20 ml). The organic layer was dried over
MgSO4, and the solvent evaporated. The crude bromoester
11 was dissolved in dry DMF (2 ml) under N2 and sodium
azide (38 mg, 0.58 mmol) was added. The solution was stir-
red for 16 h under N2. The solvent was removed under re-
duced pressure and coevaporated with toluene (3 · 20 ml).
The residue was preadsorbed on silica and purified by flash
chromatography (ethyl acetate/hexane 1:5) to afford a mix-
ture of azidoesters 12 (49 mg, 0.191 mmol) in 36% yield
from 11.
a
4.5. Methyl 2,5-anhydro-2-bromo-6-deoxy-3,4-O-isopropyl-
idene-L-galactonate 11
21
½aꢂD ¼ ꢀ199:0 (c 1.60, CHCl3); mmax (film)/cmꢀ1: 1763
(C@O); dH (500 MHz, CDCl3): 1.33, 1.41 (6H, 2 · s,
(CH3)2C), 1.47 (3H, d, J5,6 6.5 Hz, CH3), 3.92 (3H, s,
CH3O2C), 4.44 (1H, dq, J5,6 6.5 Hz, J5,4 3.9 Hz, H-5),
4.78 (1H, dd, J4,5 3.9 Hz, J4,3 5.7 Hz, H-4), 5.31 (1H, d,
J3,4 5.7 Hz, H-3); dC (50 MHz, CDCl3): 12.4 (q, CH3),
25.2 (q, (CH3)2C), 25.8 (q, (CH3)2C), 53.4 (q, CH3O2C),
79.6, 80.8, 90.6 (3 · d, C-3, C-4, C-5), 99.6 (s, C-2), 113.6
(s, (CH3)2C), 165.1 (s, C-1); m/z (CI; NH3): 312
(M+NH4þ, 100%), 314 (M+NH4þ, 100%), 232 (95%);
(Found: C, 40.15; H, 4.94; C10H15O5Br requires C, 40.70;
H, 5.12).
4.4.2. Method 2. Methyl 2,5-anhydro-6-deoxy-3,4-O-iso-
propylidene-L-talonate 10 (119 mg, 0.551 mmol) was dis-

2282
Y. Ble´riot et al. / Tetrahedron: Asymmetry 17 (2006) 2276–2286
4.6. Methyl 2,5-anhydro-2-azido-6-deoxy-3,4-O-isopropyl-
idene-L-talonate 12a
1.05 (3H, d, J5,6 6.5 Hz, CH3), 1.00, 1.29 (6H, 2 · s,
(CH3)2C), 3.11 (1H, dq, J4,5 1.7 Hz, J5,6 6.5 Hz, H-5),
3.20 (1H, dd, J3,4 7.7 Hz, J4,5 1.7 Hz, H-4), 3.35 (1H, br,
OH), 3.59 (1H, br, H-2), 4.10 (1H, dd, J3,4 7.7 Hz, J2,3
3.5 Hz, H-3); dC (50 MHz, CDCl3): 15.5 (q, CH3), 24.3,
25.8 (2 · q, (CH3)2C), 68.5, 73.3, 74.8, 75.3 (4 · d, C-2,
C-3, C-4, C-5), 110.8 (s, C(CH3)2), 172.4 (s, C@O); m/z
(CI, NH3): 220 (M+NH4þ, 100%), 203 (MH+, 90%), 210
(100%); (Found: C, 53.41; H, 7.16; C9H14O5 requires C,
53.44; H, 6.98).
22
½aꢂD ¼ ꢀ35:3 (c 1.23, CHCl3); mmax (film)/cmꢀ1: 2130 (N3),
1744 (C@O); dH (500 MHz, CDCl3): 1.39 (3H, d, J5,6
6.4 Hz, CH3), 1.38, 1.60 (6H, 2 · s, (CH3)2C), 3.83 (s,
CH3O2C), 4.13 (1H, dq, J4,5 4.0 Hz, J5,6 6.4 Hz, H-5),
4.69 (1H, dd, J3,4 5.9 Hz, J4,5 4.0 Hz, H-4), 4.98 (1H, d,
J3,4 5.9 Hz, H-3); dH (125 MHz, CDCl3): 13.6 (q, CH3),
24.6, 25.3 (2 · q, (CH3)2C), 53.2 (q, CH3O2C), 76.4, 81.2,
83.6 (3 · d, C-3, C-4, C-5), 94.4 (s, C-2), 113.7 (s,
C(CH3)2), 168.0 (s, C@O); m/z per (CI, NH3): 275
(M+NH4þ, 25%), 232 (M+NH4þꢀCH3CO, 74%), 210
(100%); (Found: C, 46.88; H, 5.89; N, 16.97; C10H15O5N3
requires C, 46.69; H, 5.88; N, 16.33); (HRMS: Found:
232.1032; Calcd for MH+ꢀN2: 230.1028).
4.9. 2-Trifluoromethanesulfonyl-3,4-O-isopropylidene-L-
talono-1,5-lactone 14
3,4-O-Isopropylidene-L-talono-1,5-lactone 13 (1.86 g,
9.2 mmol) was dissolved in dry dichloromethane (30 ml)
under N2 and the solution cooled to ꢀ40 ꢁC. Dry pyridine
(1.49 ml, 18.4 mmol, 2 equiv) was added followed by drop-
wise addition of triflic anhydride (1.86 ml, 11.0 mmol,
1.2 equiv) over 5 min. The solution was stirred at ꢀ30 ꢁC
under N2. After 40 min, TLC (ethyl acetate/hexane 1:1)
showed no starting material. The reaction was quenched
by addition of three drops of water. The solution was fil-
tered through a Celite pad topped with magnesium sulfate
and eluted with dichloromethane. The organic layer was
concentrated in vacuo and coevaporated with toluene.
The resulting solid was preadsorbed on silica. Purification
by flash chromatography (ethyl acetate/hexane 1:2 then
1:1) afforded 2-trifluoromethanesulfonyl-3,4-O-isopropyl-
4.7. Methyl 2,5-anhydro-2-azido-6-deoxy-3,4-O-isopropyl-
idene-L-galactonate 12b
mmax (film)/cmꢀ1: 1766 (C@O), 2116 (N3); dH (500 MHz,
CDCl3): 1.32, 1.44 (6H, 2 · s, (CH3)2C), 1.46 (3H, d, J5,6
6.4 Hz, CH3), 3.89 (3H, s, CH3O2C), 4.27 (1H, dq, J5,6
6.4 Hz, J5,4 3.5 Hz, H-5), 4.63 (1H, d, J3,4 5.7 Hz, H-3),
4.68 (1H, dd, J4,5 3.5 Hz, J4,3 5.7 Hz, H-4); dC (125 MHz,
CDCl3): 13.2 (q, CH3), 25.2 (q, (CH3)2C), 25.8 (q,
(CH3)2C), 53.1 (q, CH3O2C), 78.3, 80.9, 86.6 (3 · d, C-3,
C-4, C-5), 98.7 (s, C-2), 113.8 (s, (CH3)2C), 165.5 (s, C-1).
4.8. 3,4-O-Isopropylidene-L-talono-1,5-lactone 13
idene-talono-1,5-lactone 14 (2.648 g, 86% yield) as a white
23
solid: mp 142–145 ꢁC; ½aꢂD ¼ ꢀ56:9 (c 0.91, CHCl3); mmax
3,4-O-Isopropylidene-L-fucono-1,5-lactone 7 (2.2 g, 10.89
mmol) was dissolved in dry dichloromethane under N2
and the solution was cooled to ꢀ30 ꢁC. Dry pyridine
(2.65 ml, 32.67 mmol, 3 equiv) was added followed by the
dropwise addition of triflic anhydride (2.2 ml, 13.7 mmol,
1.2 equiv). The solution was stirred at ꢀ20 ꢁC under N2.
After 20 min, TLC (ethyl acetate/hexane 1:2) showed some
starting material remaining. Some more triflic anhydride
(1.1 ml, 0.6 equiv) was added to complete the reaction.
The reaction was quenched by the addition of a few drops
of water. The solution was filtered through a Celite pad
topped with magnesium sulfate and eluted with dichloro-
methane. The solvent was removed in vacuo and coevapo-
rated with toluene. The crude triflate 8 was then dissolved
in dry DMF (20 ml) under N2 and sodium trifluoroacetate
(4.477 g, 32.67 mmol, 3 equiv) was added. The solution was
stirred at 70 ꢁC for 43 h. The reaction mixture was then
diluted with dry methanol (4 ml) and stirred under N2
for 18 h at room temperature. The solvent was removed
under reduced pressure and coevaporated with toluene
(4 · 20 ml) to give a yellow oil, which was dissolved in ethyl
acetate (80 ml) and washed with brine (80 ml). The aqueous
layer was extracted with ethyl acetate (2 · 80 ml). The
organic extracts were combined, dried (magnesium sulfate)
and the solution concentrated in vacuo to afford a yellow
oil, which was preadsorbed on silica. Purification by flash
chromatography (ethyl acetate/hexane 2:3 then 1:1 then
ethyl acetate) afforded 3,4-O-isopropylidene-L-talono-1,5-
(film)/cmꢀ1: 1777 (C@O); dH (500 MHz, CDCl3): 1.40,
1.50 (6H, 2 · s, (CH3)2C), 1.50 (3H, d, J5,6 6.4 Hz, CH3),
4.43 (1H, dq, J4,5 1.7 Hz, J5,6 6.4 Hz, H-5), 4.50 (1H, dd,
J3,4 7.7 Hz, J4,5 1.7 Hz, H-4), 4.88 (1H, dd, J3,4 7.7 Hz,
J2,3 3.3 Hz, H-3), 3.59 (1H, d, J2,3 3.3 Hz, H-2); dC
(125 MHz, CDCl3): 15.6 (q, CH3), 24.5, 25.8 (2 · q,
(CH3)2C), 73.7, 73.8, 75.6, 78.9 (4 · d, C-2, C-3, C-4, C-
5), 112.2 (s, C(CH3)2), 162.7 (s, C@O); m/z (CI, NH3):
352 (M+NH4þ, 100%); (Found: C, 35.86; H, 3.86;
C10H13O7SF3 requires C, 35.93; H, 3.92).
4.10. Methyl 2,5-anhydro-6-deoxy-3,4-O-isopropylidene-L-
galactonate 15
3,4-O-Isopropylidene-L-talono-1,5-lactone 13 (1.38 g,
6.83 mmol) was dissolved in dry dichloromethane (50 ml)
under N2 and the solution was cooled to ꢀ25 ꢁC. Dry pyr-
idine (1.65 ml, 20.5 mmol, 3 equiv) was added followed by
the dropwise addition of triflic anhydride (1.38 ml,
8.2 mmol, 1.2 equiv) over 3 min. The solution was stirred
at ꢀ20 ꢁC under N2. After 20 min, TLC (ethyl acetate/hex-
ane 1:1) showed some starting material remaining. Some
more triflic anhydride (0.5 ml, 0.4 equiv) was added to
complete the reaction. After 50 min, the reaction was
quenched by the addition of 4 drops of water. The solution
was filtered through a Celite pad topped with magnesium
sulfate and eluted with dichloromethane. The solvent was
removed in vacuo and coevaporated with toluene. The
crude triflate 14 was dissolved in 3% HCl in methanol
(20 ml) under N2 and the solution was stirred at room tem-
perature. After 64 h, TLC (ethyl acetate/hexane 1:1)
lactone 13 (1.38 g, 63% yield) as a white solid: mp 144–
21
145 ꢁC; ½aꢂD ¼ ꢀ105:4 (c 0.74, CHCl3); mmax (film)/cmꢀ1
:
3401 (br, OH), 1746 (C@O); dH (500 MHz, benzene-d6):

Y. Ble´riot et al. / Tetrahedron: Asymmetry 17 (2006) 2276–2286
2283
showed a trace of starting material. The solution was then
stirred at 55 ꢁC for 8 h. The reaction mixture was diluted
with ethyl acetate (20 ml) and neutralized with sodium
bicarbonate. The solution was filtered through a Celite
pad eluted with ethyl acetate and concentrated in vacuo
to afford an oil, which was preadsorbed on silica. Purifica-
tion by flash chromatography (ethyl acetate/hexane 1:2
then 1:1 then ethyl acetate) afforded methyl 2,5-anhydro-
1.48 mmol,
1.3 equiv)
and
1-hydroxybenzotriazole
(300 mg, 1.48 mmol, 1.3 equiv) were added at 0 ꢁC. The
white suspension was sonicated and stirred for 15 min at
0 ꢁC and then allowed to warm up to room temperature
and stirred for a further 30 min at room temperature.
Methyl 2-amino-2,5-anhydro-6-deoxy-3,4-O-isopropylid-
ene-L-talonate 16a and methyl 2-amino-2,5-anhydro-6-
deoxy-3,4-O-isopropylidene-L-galactonate 16b (265 mg,
1.14 mmol) were dissolved in dry DMF (5 ml) under N2
and then added dropwise to the suspension stirred at room
temperature. After 18 h, TLC (ethyl acetate/hexane 1:1)
showed a trace of starting material and three new spots.
The solvent was removed under reduced pressure and
coevaporated with toluene to give a white solid, which
was preadsorbed on silica. Purification by flash chromatog-
raphy (ethyl acetate/hexane 1:1 then ethyl acetate) afforded
methyl N-2-(benzyloxycarbonylglycylamino)-2,5-anhydro-
6-deoxy-3,4-O-isopropylidene-L-galactonate 15 (1.069 g,
22
74% yield) as a colourless oil: ½aꢂD ¼ ꢀ53:9 (c 1.21, CHCl3);
mmax (film)/cmꢀ1: 1766 (C@O); dH (500 MHz, benz-
ene-d6): 0.74 (3H, d, J5,6 6.8 Hz, CH3), 1.14, 1.48 (6H,
2 · s, (CH3)2C), 3.43 (3H, s, CH3O2C), 3.89 (1H, dd, J4,5
2.2 Hz, J4,3 6.2 Hz, H-4), 4.28 (1H, d, J2,3 5 Hz, H-2),
4.39 (1H, dq, J5,6 6.3 Hz, J5,4 2.2 Hz, H-5), 4.51 (1H, app
t, J 5.6 Hz, H-3); dC (125 MHz, CDCl3): 16.9 (q, CH3),
25.2, 26.2 (2 · q, (CH3)2C), 52.1 (q, CH3O2C), 79.3, 80.4,
81.7, 85.5 (4 · d, C-2, C-3, C-4, C-5), 113.7 (s, C(CH3)2),
168.7 (s, C-1); m/z (CI; NH3): 234 (M+NH4þ, 100%),
217 (MH+, 55%), 201 (22%); (Found: C, 55.36; H, 7.74;
C10H16O5 requires C, 55.53; H, 7.46).
3,4-O-isopropylidene-6-deoxy-L-talonate
17
(85 mg,
0.201 mmol, 17% yield) as a white solid: mp 94–96 ꢁC
22
(ethyl acetate/hexane); ½aꢂD ¼ ꢀ3:2 (c 1.19, CHCl3); mmax
(film)/cmꢀ1: 3399 (NH), 2937 (NH), 1733 (C@O), 1697
(C@O); dH (500 MHz, CDCl3): 1.37 (3H, d, J5,6 6.5 Hz,
CH3), 1.37, 1.51 (6H, 2 · s, (CH3)2C), 3.78 (s, CH3O2C),
3.96 (2H, m, NHCH2C@O), 4.32 (1H, dq, J4,5 3.5 Hz,
J5,6 6.5 Hz, H-5), 4.62 (1H, dd, J3,4 5.8 Hz, J4,5 3.5 Hz,
H-4), 4.76 (1H, d, J3,4 5.8 Hz, H-3), 5.14 (2H, s, CH2Ph),
5.33 (1H, br, NH), 7.20 (1H, br, NH), 7.32–7.38 (5H, m,
ArH); dC (125 MHz, CDCl3): 13.6 (q, CH3), 25.0, 25.8
(2 · q, (CH3)2C), 44.4 (t, NHCH2C@O), 53.1 (q, CH3O2C),
67.2 (t, CH2Ph), 75.9, 81.3, 83.8 (3 · d, C-3, C-4, C-5), 88.2
(s, C-2), 113.8 (s, C(CH3)2), 128.1, 128.2, 128.6 (3 · d,
Pho,m,p), 136.1 (s, Phipso), 156.2 (s, C@O), 168.3 (s, C@O),
169.5 (s, C@O); m/z (APCI+): 423 (MH+, 100%); (Found:
C, 56.79; H, 6.30; N, 6.63; C20H26O8N2 requires C, 56.87;
H, 6.20; N, 6.63).
4.11. Methyl 2-amino-2,5-anhydro-6-deoxy-3,4-O-isopropyl-
idene-L-talonate 16a and methyl 2-amino-2,5-anhydro-6-
deoxy-3,4-O-isopropylidene-L-galactonate 16b
Methyl 2,5-anhydro-2-azido-6-deoxy-3,4-O-isopropylid-
ene-L-talonate 12a (222 mg, 0.863 mmol) was dissolved in
HPLC grade methanol (10 ml). Palladium black (52 mg)
was added. The solution was degassed three times and air
was replaced by H2. The solution was stirred at room tem-
perature under an atmosphere of H2. After 19 h, TLC
(ethyl acetate/hexane 1:2) showed no trace of starting
material (Rf 0.7) and a new product (Rf 0.3). The solution
was filtered through a Celite plug eluted with methanol
(50 ml). The solvent was removed under reduced pressure
to give an oil. Purification by flash chromatography (ethyl
acetate/hexane 1:2) afforded a mixture of methyl 2-amino-
2,5-anhydro-6-deoxy-3,4-O-isopropylidene-L-talonate 16a
and methyl 2-amino-2,5-anhydro-6-deoxy-3,4-O-isopropyl-
idene-L-galactonate 16b (143 mg, 72% yield) as a colourless
oil.
Further elution afforded methyl N-2-(benzyloxycarbonyl-
glycylamino)-2,5-anhydro-3,4-O-isopropylidene-6-deoxy-L-
galactonate 18 (333 mg, 0.789 mmol, 69% yield) as a white
22
solid: mp 191–193 ꢁC (ethyl acetate/hexane); ½aꢂD ¼ ꢀ49:0
(c 0.42, CHCl3); mmax (film)/cmꢀ1: 3330 (NH), 2951 (NH),
1740 (C@O), 1687 (C@O); dH (500 MHz, CDCl3): 1.36
(3H, d, J5,6 6.4 Hz, CH3), 1.30, 1.45 (6H, 2 · s, (CH3)2C),
3.81 (s, CH3O2C), 3.86 (2H, m, NHCH2C@O), 4.26 (1H,
dq, J4,5 3.6 Hz, J5,6 6.4 Hz, H-5), 4.69 (1H, app t, J3,4
5.7 Hz, J4,5 3.6 Hz, H-4), 4.90 (1H, d, J3,4 5.7 Hz, H-3),
5.13 (2H, s, CH2Ph), 5.53 (1H, br, NH), 7.29 (1H, br,
NH), 7.31–7.40 (5H, m, ArH); dC (125 MHz, CDCl3):
13.3 (q, CH3), 25.0, 25.5 (2 · q, (CH3)2C), 44.4 (t,
NHCH2C@O), 52.8 (q, CH3O2C), 67.1 (t, CH2Ph), 77.1,
81.6, 87.2 (3 · d, C-3, C-4, C-5), 92.3 (s, C-2), 113.7
(s, C(CH3)2), 128.1, 128.4, 128.7 (3 · d, Pho,m,p), 136.4 (s,
Phipso), 157.1 (s, C@O), 168.0 (s, C@O), 170.0 (s, C@O);
m/z (APCI+): 423 (MH+, 53%), 215 (MꢀZ-Gly, 100%);
(Found: C, 56.76; H, 6.29; N, 6.55; C20H26O8N2 requires
C, 56.87; H, 6.20; N, 6.63).
23
Data for the major epimer: ½aꢂD ¼ ꢀ27:7 (c 0.95, CHCl3);
mmax (film)/cmꢀ1: 1737 (C@O), 3401 (NH2); dH (500 MHz,
CDCl3): 1.27 (3H, d, J5,6 6.3 Hz, CH3), 1.36, 1.52 (6H,
2 · s, (CH3)2C), 2.45 (2H, br, NH2), 3.77 (3H, s, CH3O2C),
3.85 (1H, dq, J5,6 6.3 Hz, J5,4 3.8 Hz, H-5), 4.64 (1H, dd, J4,5
3.8 Hz, J4,3 6.0 Hz, H-4), 4.88 (1H, d, J3,4 6.0 Hz, H-3); dC
(125 MHz, CDCl3): 13.8 (q, CH3), 24.7 (q, (CH3)2C), 26.0
(q, (CH3)2C), 52.4 (q, CH3O2C), 74.4, 81.6, 81.8 (3 · d,
C-3, C-4, C-5), 92.1 (s, C-2), 112.3 (s, (CH3)2C), 169.3 (s,
C-1); m/z (APCI+): 232 (MH+, 82%), 215 (100%); (HRMS:
Found: 232.1184; Calcd for MH+: 232.1184).
4.12. Methyl N-2-(benzyloxycarbonylglycylamino)-2,5-
anhydro-3,4-O-isopropylidene-6-deoxy-L-talonate 17 and
methyl N-2-(benzyloxycarbonylglycylamino)-2,5-anhydro-
3,4-O-isopropylidene-6-deoxy-L-galactonate 18
4.13. (2S,3R,4R,5R)-3,4-O-Isopropylidene-2-methyl-6,9-
diaza-1-oxaspiro-[4.5]-decane-7,10-dione 19
DCC (305 mg, 1.48 mmol, 1.3 equiv) was suspended in
Methyl N-2-(benzyloxycarbonylglycylamino)-2,5-anhydro-
dry DMF (10 ml) at 0 ꢁC under N2. Z-Glycine (310 mg,
3,4-O-isopropylidene-6-deoxy-L-talonate
17
(85 mg,

2284
Y. Ble´riot et al. / Tetrahedron: Asymmetry 17 (2006) 2276–2286
0.20 mmol) was dissolved in HPLC methanol (10 ml).
Palladium black (30 mg) was then added. The suspension was
degassed three times and air replaced with H2. The solution
was stirred at room temperature under an H2 atmosphere.
After 24 h, the suspension was filtered through Celite,
which was eluted with methanol. The solvent was removed
under reduced pressure and the residue dried on the vac-
uum line for 2 h. The residue was then dissolved in dry
THF (5 ml) under N2. Potassium tert-butoxide (28 mg,
0.25 mmol) was added and the solution stirred at room
temperature. After 24 h, TLC (ethyl acetate) showed a
major spot (Rf 0.45). The reaction mixture was pread-
sorbed on silica. Purification by flash chromatography
(ethyl acetate/hexane 1:1 then ethyl acetate) afforded
(2S,3R,4R,5R)-3,4-O-isopropylidene-2-methyl-6,9-diaza-1-
oxaspiro-[4.5]-decane-7,10-dione 19 (36 mg, 70% yield) as a
(2 · q, (CH3)2C), 45.4 (t, NHCH2C@O), 78.5, 82.5, 89.6
(3 · d, C-3, C-4, C-5), 92.2 (s, C-2), 114.8 (s, C(CH3)2),
167.3 (s, C@O), 169.4 (s, C@O); m/z (APCI+): 257
(MH+, 100%), 183 (57%), 115 (42%); (Found: C, 51.66;
H, 6.48; N, 10.79; C11H16O5N2 requires C, 51.56; H,
6.29; N, 10.93).
4.15. (2S,3R,4R,5R)-3,4-O-Isopropylidene-2-methyl-6,8-
diaza-1-oxaspiro-[4.4]-nonane-7,9-dione 21
Methyl 2-amino-2,5-anhydro-6-deoxy-3,4-O-isopropylid-
ene-L-talonate 15a and methyl 2-amino-2,5-anhydro-6-
deoxy-3,4-O-isopropylidene-L-galactonate 15b (143 mg,
0.619 mmol) were dissolved in glacial acetic acid (5 ml).
Potassium cyanate (150 mg, 1.85 mmol, 3 equiv) was added
to the solution, which was stirred at 65 ꢁC under N2. After
4 h, TLC (ethyl acetate/hexane) showed no starting material
(Rf 0.65) and a new spot (Rf 0.75). The solvent was removed
in vacuo and coevaporated with toluene (3 · 5 ml). The
residue was preadsorbed on silica. Purification by flash chro-
matography (ethyl acetate/hexane 1:2 then 1:1 then ethyl
acetate) afforded (2S,3R,4R,5R)-3,4-O-isopropylidene-
white solid: mp 203–205 ꢁC (ethyl acetate/hexane);
22
½aꢂD ¼ ꢀ56:1 (c 0.51, CHCl3); mmax (KBr)/cmꢀ1: 3436
(NH), 1697 (C@O), 1787 (C@O); dH (500 MHz, CDCl3):
1.33 (3H, d, J5,6 6.4 Hz, CH3), 1.44, 1.60 (6H, 2 · s,
0
(CH3)2C), 3.95 (1H, dd, JNH,7 4.2 Hz, J7 ;7 17.4 Hz, H-7),
4.20 (1H, dq, J4,5 3.7 Hz, J5,6 6.4 Hz, H-5), 4.27 (1H, d,
J7;7 17.4 Hz, H-70), 4.81 (1H, dd, J3,4 5.9 Hz, J4,5 3.7 Hz,
2-methyl-6,8-diaza-1-oxaspiro-[4.4]-nonane-7,9-dione 21
0
22
H-4), 5.02 (1H, d, J3,4 5.9 Hz, H-3), 6.07 (1H, br, NH),
6.84 (1H, br, NH); dC (125 MHz, CDCl3): 13.5 (q, CH3),
24.6, 26.0 (2 · q, (CH3)2C), 44.9 (t, NHCH2C@O), 75.5,
80.5, 81.9 (3 · d, C-3, C-4, C-5), 86.2 (s, C-2), 113.2 (s,
C(CH3)2), 165.0 (s, C@O), 166.0 (s, C@O); m/z (APCI+):
257 (MH+, 100%), 156 (57%); (HRMS; Found: 257.1134;
Calcd for MH+: 257.1137).
(111 mg, 74% yield) as a foam: ½aꢂD ¼ ꢀ72:6 (c 0.58, CHCl3);
m
max (film)/cmꢀ1: 3272 (NH), 1790 (C@O), 1739 (C@O); dH
(500 MHz, CDCl3): 1.32 (3H, d, J5,6 6.4 Hz, CH3), 1.37, 1.53
(6H, 2 · s, (CH3)2C), 4.50 (1H, dq, J4,5 3.4 Hz, J5,6 6.4 Hz,
H-5), 4.74–4.78 (2H, m, H-3 and H-4), 6.22 (1H, br, NH),
8.49 (1H, br, NH); dC (125 MHz, CDCl3): 13.5 (q, CH3),
24.6, 26.0 (2 · q, (CH3)2C), 75.0, 80.2, 81.6 (3 · d, C-3,
C-4, C-5), 91.6 (s, C-2), 113.6 (s, C(CH3)2), 155.2 (s,
C@O), 172.5 (s, C@O); m/z (electrospray, ꢀve): 241
(MꢀHꢀ, 100%); (Found: C, 49.41; H, 5.76; N, 11.03;
C11H16O5N2 requires C, 49.58; H, 5.83; N, 11.26).
4.14. (2S,3R,4R,5S)-3,4-O-Isopropylidene-2-methyl-6,9-
diaza-1-oxaspiro-[4.5]-decane-7,10-dione 20
Methyl N-2-(benzyloxycarbonylglycylamino)-2,5-anhydro-
3,4-O-isopropylidene-6-deoxy-L-galactonate 18 (333 mg,
0.789 mmol) was dissolved in HPLC methanol (25 ml).
Palladium black (102 mg) was added. The suspension was
degassed three times and air replaced with H2. The solution
was stirred at room temperature under H2 atmosphere.
After 24 h, TLC (ethyl acetate) showed only a trace
amount of starting material (Rf 0.7) and a new product
(Rf 0.0). The suspension was filtered through Celite, which
was eluted with methanol. The solvent was removed under
reduced pressure. The residue was then dissolved in dry
THF (20 ml) under N2. Potassium tert-butoxide (98 mg,
0.868 mmol) was added and the solution stirred at room
temperature. After 24 h, the reaction mixture was pread-
sorbed on silica. Purification by flash chromatography
(ethyl acetate then 10% methanol in ethyl acetate) afforded
(2S,3R,4R,5S)-3,4-O-isopropylidene-2-methyl-6,9-diaza-1-
oxaspiro-[4.5]-decane-7,10-dione 20 (148 mg, 0.578 mmol,
4.16. (2S,3R,4R,5R)-2-Methyl-6,9-diaza-1-oxaspiro-[4.5]-
decane-7,10-dione 3
(2S,3R,4R,5R)-3,4-O-Isopropylidene-2-methyl-6,9-diaza-1-
oxaspiro-[4.5]-decane-7,10-dione 19 (20 mg, 0.078 mmol)
was dissolved in water (1 ml) and trifluoroacetic acid
(1 ml). The solution was stirred at room temperature. After
90 min, TLC (5% methanol in ethyl acetate) showed no
starting material (Rf 0.7) and a new product (Rf 0.2). The
reaction mixture was concentrated in vacuo and coevapo-
rated with toluene (2 · 3 ml). The resulting solid was
preadsorbed on silica. Purification by flash chromato-
graphy (ethyl acetate then 5% methanol in ethyl acetate)
afforded (2S,3R,4R,5R)-2-methyl-6,9-diaza-1-oxaspiro-[4.5]-
decane-7,10-dione 3 (17 mg, quantitative yield) as a white
22
solid: mp 110–113 ꢁC (ethyl acetate/hexane); ½aꢂD ¼ ꢀ1:1
(c 0.43, CH3OH); mmax (KBr)/cmꢀ1: 3520 (NH, OH),
1672 (C@O); dH (500 MHz, CD3OD): 1.26 (3H, d, J5,6
6.4 Hz, CH3), 3.90 (1H, d, J 18.2 Hz, H-7), 4.02 (1H, d, J
18.2 Hz, H-70), 4.05 (1H, dd, J4,5 2.9 Hz, J3,4 4.3 Hz, H-
4), 4.15 (1H, dq, J4,5 2.9 Hz, J5,6 6.4 Hz, H-5), 4.72 (1H,
d, J3,4 4.3 Hz, H-3); dC (125 MHz, CD3OD): 15.2 (q,
CH3), 45.4 (t, NHCH2C@O), 74.0, 75.8, 79.2 (3 · d, C-3,
C-4, C-5), 89.3 (s, C-2), 168.3 (s, C@O), 169.2 (s, C@O);
m/z (APCI+): 338 (29%), 231 (18%), 217 (MH+, 100%);
HRMS (CI, NH3): Calcd for C8H13N2O5 (M+H+):
217.0824, Found 217.0820.
73% yield) as a white solid: mp 284–288 ꢁC decomposed
25
(ethyl acetate/hexane); ½aꢂD ¼ ꢀ152:1 (c 0.61, CH3OH);
mmax (KBr)/cmꢀ1: 3394 (NH), 3255 (NH), 1711 (C@O),
1686 (C@O), dH (500 MHz, CD3CN): 1.31 (3H, d, J5,6
6.3 Hz, CH3), 1.27, 1.40 (6H, 2 · s, (CH3)2C), 3.68 (1H,
0
0
dd, JNH,7 5.0 Hz, J7 ,7 17.5 Hz, H-7), 3.97 (1H, d, J7;7
17.5 Hz, H-70), 4.30 (1H, dq, J4,5 3.4 Hz, J5,6 6.3 Hz, H-
5), 4.74 (1H, dd, J3,4 5.6 Hz, J4,5 3.4 Hz, H-4), 4.83 (1H,
d, J3,4 5.6 Hz, H-3), 6.51 (1H, br, NH), 7.02 (1H, br,
NH); dC (50 MHz, CD3OD): 13.1 (q, CH3), 24.5, 25.2

Y. Ble´riot et al. / Tetrahedron: Asymmetry 17 (2006) 2276–2286
2285
4.17. (2S,3R,4R,5S)-2-Methyl-6,9-diaza-1-oxaspiro-[4.5]-
decane-7,10-dione 4
References
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was dissolved in water (1 ml) and trifluoroacetic acid
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1 h, TLC (5% methanol in ethyl acetate, double elution)
showed no starting material (Rf 0.3) and a new product
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and coevaporated with toluene (2 · 3 ml). The resulting
solid was preadsorbed on silica.
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4
(23 mg, quantitative yield) as a white solid: mp 184–
22
186 ꢁC (ethyl acetate/hexane); ½aꢂD ¼ ꢀ0:3 (c 0.41,
CH3OH); mmax (KBr)/cmꢀ1
: 3422 (NH, OH), 1675
(C@O); dH (CD3OD, 500 MHz): 1.25 (3H, d, J5,6 6.4 Hz,
CH3), 3.90 (1H, dd, J3,4 2.9 Hz, J4,5 5.8 Hz, H-4), 3.98
(2H, d, J 4.2 Hz, H-7 and H-70), 4.39 (1H, dq, J4,5
2.9 Hz, J5,6 6.4 Hz, H-5), 4.40 (1H, d, J3,4 5.8 Hz, H-3);
dC (125 MHz, D2O + dioxan): 14.3 (q, CH3), 44.6 (t,
NHCH2C@O), 74.0, 80.6, 80.8 (3 · d, C-3, C-4, C-5),
91.2 (s, C-2), 167.7 (s, C@O), 168.8 (s, C@O); m/z
(APCI+): 217 (MH+, 46%), 143 (100%); HRMS (CI,
NH3): Calcd for C8H13N2O5 (M+H+): 217.0824, Found
217.0828.
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was dissolved in water/trifluoroacetic acid (1:1, 2 ml) and
the solution was stirred at room temperature for 7 h by
which time (ethyl acetate/hexane 1:1) showed no starting
material and a new product. The solvent was removed
under reduced pressure and coevaporated with toluene
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(2S,3R,4R,5R)-2-methyl-6,8-diaza-1-oxaspiro-[4.4]-nonane-
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23
135 ꢁC; ½aꢂD ¼ ꢀ23:2 (c 0.57, CH3OH); mmax (KBr)/cmꢀ1
:
3392 (OH, NH), 1770 (C@O), 1733 (C@O); dH
(500 MHz, D2O): 1.19 (3H, d, J5,6 6.4 Hz, CH3), 4.12
(1H, dd, J3,4 3.7 Hz, J4,5 2.6 Hz, H-4), 4.25 (1H, dq, J5,6
6.4 Hz, J5,4 2.6 Hz, H-5), 4.45 (1H, d, J3,4 3.7 Hz, H-3);
dC (125 MHz, CDCl3): 14.3 (q, CH3), 72.3, 74.4, 79.4
(3 · d, C-3, C-4, C-5), 92.1 (s, C-2), 157.9 (s, C@O),
176.4 (s, C@O); m/z (electrospray, ꢀve): 201 (MꢀHꢀ,
100%); (Found: C, 41.76; H, 5.16; N, 13.75; C7H10O5N2
requires C, 41.59; H, 4.99; N, 13.86).
Acknowledgements
Michela I. Simone acknowledges the financial support pro-
vided through the European Community’s Human Poten-
tial Programme under contract HPRN-CT-2002-00173.

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