Fragmentation of carbohydrate anomeric alkoxy radicals. Synthesis of polyhydroxy piperidines and pyrrolidines related to carbohydrates

Article abstract of DOI:10.1021/jo0057452

Imino sugars of the piperidine and pyrrolidine types can be specifically obtained when protected 5-amino-5-deoxyfuranopentoses, 5-amino-5-deoxyfuranohexoses, 6-amino-6-deoxyfuranohexoses, and 6-amino-6-deoxypyranohexoses undergo a tandem alkoxy radical β-fragmentation-intramolecular cyclization reaction. The reaction is promoted by the system: iodosylbenzene - iodine under mild conditions. The tert-butoxycarbonyl, benzyloxycarbonyl, and diphenylphosphinoyl radicals have been studied as amino-protecting groups. Using this methodology, polyhydroxylated pyrrolidines of the D-erythrofuranoses 34 and 35, D-threofuranose 36, L-xylofuranose 42, and D-arabinofuranose 43 series and polyhydroxylated piperidines of the D-arabinopyranose type 37 and 38 were obtained.

Full text of DOI:10.1021/jo0057452

J . Org. Chem. 2001, 66, 1861-1866
1861
F r a gm en ta tion of Ca r boh yd r a te An om er ic Alk oxy Ra d ica ls.
Syn th esis of P olyh yd r oxy P ip er id in es a n d P yr r olid in es Rela ted to
Ca r boh yd r a tes
Cosme G. Francisco, Raimundo Freire, Concepcio´n C. Gonza´lez, Elisa I. Leo´n,
Concepcio´n Riesco-Fagundo, and Ernesto Sua´rez*
Instituto de Productos Naturales y Agrobiologı´a del CSIC, Carretera de La Esperanza 3,
38206-La Laguna, Tenerife, Spain
esuarez@ipna.csic.es
Received November 27, 2000
Imino sugars of the piperidine and pyrrolidine types can be specifically obtained when protected
5-amino-5-deoxyfuranopentoses, 5-amino-5-deoxyfuranohexoses, 6-amino-6-deoxyfuranohexoses, and
6-amino-6-deoxypyranohexoses undergo a tandem alkoxy radical â-fragmentation-intramolecular
cyclization reaction. The reaction is promoted by the system: iodosylbenzene-iodine under mild
conditions. The tert-butoxycarbonyl, benzyloxycarbonyl, and diphenylphosphinoyl radicals have been
studied as amino-protecting groups. Using this methodology, polyhydroxylated pyrrolidines of the
D-erythrofuranoses 34 and 35, D-threofuranose 36, L-xylofuranose 42, and D-arabinofuranose 43
series and polyhydroxylated piperidines of the D-arabinopyranose type 37 and 38 were obtained.
The synthesis of sugar-mimic glycosidase inhibitors
has recently received considerable attention from organic
chemists.1 These polyhydroxylated piperidines and pyr-
rolidines, structurally related to cyclic carbohydrates, the
so-called azasugars,2 in which the ring oxygen has been
replaced by a basic nitrogen atom, bind specifically to the
active sites of the enzyme by mimicking the correspond-
ing carbohydrate. Since glycosidases are involved in
many types of important biological processes, some of
these substances have a promising therapeutic potential
as antiviral and anticancer agents and in the treatment
of diabetes.3 The study of the â-fragmentation reaction
of anomeric alkoxy radicals of carbohydrates using hy-
pervalent iodine reagents has engaged the attention of
our laboratory for several years.4 The application of this
protocol allows us to obtain carbohydrates with one
carbon less and it is therefore useful for descending the
aldose series and for the preparation of chiral synthons.4a
The synthesis of cyclic aldoses4b and ketoses4c in furanose
and pyranose form as well as alduronic acid lactones4d,f
and aldonitriles4e can also be accomplished using this
methodology.
(1) For reviews see, inter alia: (a) Driguez, H.; Thiem, J . Topics in
Current Chemistry; Springer: Berlin, Germany, 1997; Vol. 187, pp
157-186. (b) Depezay, J .-C. In Carbohydrate mimics: Concepts and
Methods; Chapleur, Y., Ed.; Wiley-VCH Publishers: Weinheim, 1998;
pp 307-326. (c) Ganem, B. Acc. Chem. Res. 1996, 29, 340-347. (d)
Sears, P.; Wong, C.-H. Angew. Chem., Int. Ed. 1999, 38, 2300-2324.
(e) Heightman, T. D.; Vasella, A. T. Angew. Chem., Int. Ed. 1999, 38,
750-770. (f) Bols, M. Acc. Chem. Res. 1998, 31, 1-8. For recent
references, see, inter alia: (g) Hansen, A.; Tagmose, T. M.; Bols, M.
Tetrahedron 1997, 53, 697-706. (h) Cipolla, L.; Lay, L.; Nicostra, F.;
Pangrazio, C.; Panza, L. Tetrahedron 1995, 51, 4679-4690. (i) Poitout,
L.; Lemerrer, Y.; Depezay, J . C. Tetrahedron Lett. 1996, 37, 1609-
1612. (j) Henderson, I.; Laslo, K.; Wong, C.-H. Tetrahedron Lett. 1994,
35, 359-362. (k) Takaoka, Y.; Kajimoto, T.; Wong, C.-H. J . Org. Chem.
1993, 58, 4809-4812. (l) Dondoni, A.; Merino, P.; Perrone, D. Tetra-
hedron 1993, 49, 2939-2958. (m) Furneaux, R. H.; Tyler, P. C.;
Whitehouse, L. A. Tetrahedron Lett. 1993, 34, 3613-3616. (n) Fair-
banks, A. J .; Carpenter, N. C.; Fleet, G. W. J .; Ramsden, N. G.; Cenci
de Bello, I.; Winchester, B. G.; Al-Daher, S. S.; Nagahashi, G.
Tetrahedron. 1992, 48, 3365-3376. (o) Straub, A.; Effenberger, F.;
Fischer, P. J . Org. Chem. 1990, 55, 3926-3932. (p) Fleet, G. W. J .;
Ramsden, N. G.; Witty, D. R. Tetrahedron Lett. 1988, 29, 2871-2874.
(2) Although frequently used, the term azasugar is not recommended
for this type of compounds (Nomenclature of Carbohydrates, IUPAC,
Rule 2-Carb-34.1).
(3) (a) Asano, N.; Nash, R. J .; Molyneux, R. J .; Fleet, G. W. J .
Tetrahedron: Asymmetry 2000, 11, 1645-1680. (b) Hughes, A. B.;
Rudge, A. J . Nat. Prod. Rep. 1994, 11, 135-162. (c) Look, G. C.; Fotsch,
C. H.; Wong, C.-H. Acc. Chem. Res. 1993, 26, 182-190. (d) Winchester,
B.; Fleet, G. W. J . Glycobiology 1992, 2, 199-210. (e) van den Broek,
L. A. G. M.; Vermaas, D. L.; Heskamp, B. M.; van Boeckel, C. A. A.;
Tan, M. C. A. A.; Bolscher, J . G. M.; Ploegh, H. L.; van Kemenade, F.
J .; de Goede, R. E. Y.; Miedema, F. Recl. Trav. Chim. Pays-Bas 1993,
112, 82-94. (f) Fleet, G. W. J .; Karpas, A.; Dwek, R. A.; Fellows, L. E.;
Tyms, A. S.; Petursson, S.; Namgoong, S. K.; Ramsden, N. G.; Smith,
P. W.; Son, J . C.; Wilson, F.; Witty, D. R.; J acob, G. S.; Rademacher,
T. M. FEBS Lett. 1988, 237, 128-132.
In Scheme 1 we depict the basic features of our
strategy directed toward the synthesis of imino-sugars
within the context of a research program devoted to the
study of the alkoxy radical â-fragmentation reaction
(ARF). This methodology relies on the initial formation
of an alkoxy anomeric radical (I) originated by the action
of the hypervalent iodine reagent in the presence of
iodine, presumably through an alkyl hypoiodite inter-
mediate.5 Subsequently, the alkoxy radical undergoes a
fragmentation of the C1-C2 bond and gives rise to a C2
radical (II) that is afterward oxidized by an excess of
reagent to the oxycarbenium ion (III). The intramolecular
nucleophilic cyclization of the amine derivative affords
the required sugar derivative. A similar protocol using
alcohols as nucleophiles has previously been reported by
(4) (a) Armas, P.; Francisco, C. G.; Sua´rez, E. Angew. Chem., Int.
Ed. Engl. 1992, 31, 772-774. (b) Armas, P.; Francisco, C. G.; Sua´rez,
E. J . Am. Chem. Soc. 1993, 115, 8865-8866. (c) Armas, P.; Francisco,
C. G.; Sua´rez, E. Tetrahedron Lett. 1993, 34, 7331-7334. (d) Francisco,
C. G.; Gonza´lez, C. C.; Sua´rez, E. Tetrahedron Lett. 1996, 37, 1687-
1690. (e) Herna´ndez, R.; Leo´n, E. I.; Moreno, P.; Sua´rez, E. J . Org.
Chem. 1997, 62, 8974-8975. (f) Francisco, C. G.; Gonza´lez, C. C.;
Sua´rez, E. J . Org. Chem. 1998, 63, 2099-2109. (g) Francisco, C. G.;
Leo´n, E. I.; Moreno, P.; Sua´rez, E. Tetrahedron: Asymmetry 1998, 9,
2975-2978. (h) Francisco, C. G.; Gonza´lez, C. C.; Sua´rez, E. J . Org.
Chem. 1998, 63, 8092-8093. (i) Mart´ın. A.; Rodr´ıguez, M. S.; Sua´rez,
E. Tetrahedron Lett. 1999, 40, 7525-7528.
(5) Courtneidge, J . L.; Lusztyk, J .; Page´, D. Tetrahedron Lett. 1994,
35, 1003-1006.
10.1021/jo0057452 CCC: $20.00 © 2001 American Chemical Society
Published on Web 01/31/2001

1862 J . Org. Chem., Vol. 66, No. 5, 2001
Francisco et al.
Sch em e 1
Sch em e 2. Syn th esis of Su bstr a tes fr om P en tose
Ser iesa
this research group for the specific synthesis of furanose
or pyranose forms of cyclic aldoses and ketoses.4b,c This
methodology has also been applied to an approach to the
synthesis of (+)-preussin.6
Resu lts a n d Discu ssion
Herein, we report on an extension of the ARF meth-
odology that is particularly effective for the synthesis of
five- and six-membered imino-sugars under mild condi-
tions that are compatible in many cases with the stability
of the protective groups most widely used in carbohydrate
chemistry. In a previous communication, we described
the preliminary results obtained,7 and we now report full
details of these experiments and their extension to a
number of new models. To test the scope of the reaction,
we have prepared substrates from both the pentose and
hexose series of carbohydrates as depicted in Schemes 2
and 3.
a
Key: (a) PivCl, Py, 0 °C to room temperature, 52 h, 89%; (b)
TBAF, THF, rt, 1 h, 92%; (c) ZnN6‚2Py, PPh3, DIAD, toluene, rt,
24-63 h, 65-93%; (d) H2, Pd/C, Boc2O, EtOAc, rt, 20 h, 83%; (e)
NaOMe, MeOH, 0-40 °C, 1-4 h, 52-84%; (f) Bu3SnH, AIBN,
PhH, reflux, 1.5 h, then diphenyl chlorophosphate, TEA, rt, 21 h,
91%; (g) H2, Pd(OH)2/C, EtOAc, rt, 20 h, 90%; (h) H2, Pd/C, EtOAc,
rt, 20 h, then benzyl chloroformate, NaHCO3, 0 °C to rt, 1 h, 62%.
subsequent treatment with di-tert-butyl dicarbonate gave
the N-Boc-D-gluco derivative 17. The anomeric benzyl
ether was then hydrogenolyzed with Pd(OH)2/C to give
the intended substrate 18 (Scheme 3).
Su bstr a tes fr om P en tose Ser ies. The 5-amino-5-
deoxy-D-ribo derivatives 6 and 10 were synthesized
starting from 2,3-O-isopropylidene-D-ribofuranose8 using
well-established methods (Scheme 2). The azides 4 and
8 were prepared directly from the respective primary
alcohols using zinc azide-pyridine complex under Mit-
sunobu substitution conditions.9 Reduction of the azides
and protection of the resulting amines with di-tert-butyl
dicarbonate10 and diphenyl chlorophosphate11 gave after
deprotection of the anomeric alcohols the required sub-
strates 6 and 10, respectively. The D-lyxose derivative
14 was prepared from benzoyl 5-azido-5-deoxy-2,3-O-
isopropylidene-D-lyxofuranoside (12),12 after reduction of
the azide, reaction of the obtained amine with benzyl
chloroformate, and deprotection of the anomeric alcohol
(Scheme 2).
The 6-amino-6-deoxy-D-manno derivative 25 was ob-
tained starting from benzoyl 2,3-O-isopropylidene-R-D-
mannofuranoside (19) which was selectively silylated at
the more reactive 6-hydroxyl with t-BuMe2SiCl in the
presence of imidazole. The secondary hydroxyl was
protected as its methyl ether, and the tert-butyldimeth-
ylsilyl ether at C6 hydrolyzed to give alcohol 22. This
time, azide grouping was introduced by mesylation of the
primary alcohol to provide the crude mesylate, which was
then treated with NaN3 in DMF to give azide 23.
Subsequent in situ hydrogenation-protection of the azide
afforded, after removal of the anomeric benzoyl ester with
NaOMe, N-Boc-D-manno derivative 25 (Scheme 3). The
preparation of 5-amino-5-deoxy-L-gulo model 28 was also
started with compound 20. The 5-azide grouping was
introduced by triflation of the secondary alcohol and SN2
displacement with sodium azide. One-pot hydrogena-
tion-protection of the azide with a tert-butoxycarbonyl
group afforded, after hydrolysis of the anomeric ester,
the required N-Boc-L-gulo substrate 28. The N-Boc-D-
manno analogue 33 was also synthesized starting from
compound 20 by a double inversion of configuration at
C5. The stereochemistry of the 5-hydroxyl was first
inverted using Mitsunobu13 conditions to give after
Su bstr a tes fr om Hexose Ser ies. The reduction of the
azide 16, obtained from the known benzyl 2,3,4-tri-O-
methyl-â-D-glucopyranoside (15),4f with Bu3SnH and
(6) Armas, P.; Garcia-Tellado, F.; Marrero-Tellado, J . J .; Robles, J .
Tetrahedron Lett. 1998, 39, 131-134.
(7) Francisco, C. G.; Freire, R.; Gonza´lez, C. C.; Sua´rez, E. Tetra-
hedron: Asymmetry 1997, 8, 1971-1974.
(8) Kaskar, B.; Heise, G. L.; Michalak, R. S.; Vishnuvajjala, B. R.
Synthesis 1990, 1031-1032. Duvoid, T.; Francis, G. W.; Papaioannou,
D. Tetrahedron Lett. 1995, 36, 3153-3156.
(9) Viand, M. C.; Rollin, P. Synthesis 1990, 130-132.
(10) Saito, S.; Nakajima, H.; Inaba, M.; Moriwake, T. Tetrahedron
Lett. 1989, 30, 837-838.
(11) Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic
Synthesis, 2nd ed.; J ohn Wiley & Sons: New York, 1991; p 376.
(12) Ichikawa, Y.; Igarashi, Y. Tetrahedron Lett. 1995, 36, 4585-
4586.
(13) (a) Mitsunobu, O. Synthesis 1981, 1-28. (b) Hughes, D. L. Org.
React. 1992, 42, 335-656.

Fragmentation of Carbohydrate Anomeric Alkoxy Radicals
J . Org. Chem., Vol. 66, No. 5, 2001 1863
Ta ble 1. Syn th esis of Im in o Su ga r s Usin g a n Alk oxy
Ra d ica l F r a gm en ta tion Rea ction a
Sch em e 3. Syn th esis of Su bstr a tes fr om Hexose
Ser iesa
a
Key: (a) ZnN6‚2Py, PPh3, DIAD, toluene, rt, 48 h, 75%; (b)
Bu3SnH, AIBN, PhH, reflux, 1.5 h, then (Boc)2O, TEA, DMF, 40
°C to rt, 2 h, 97%; (c) H2, Pd(OH)2/C, EtOH, rt, 4 h, 92%; (d)
TBDMSCl, imidazole, DMF, rt, 30 min, 91%; (e) MeI, Ag2O,
acetone, rt, 24 h, 93%; (f) PPTS, MeOH, rt, 20 h, 99%; (g) mesyl
chloride, Py, 0 °C, 30 min, 99% then NaN3, DMF, rt, 3-6 h, 85%;
(h) H2, Pd/C, Boc2O, EtOAc, rt, 1-20 h, 79-99%; (i) NaOMe,
MeOH, rt, 0.5-2 h, 89-98%; (j) (i) triflic anhydride, Py, CH2Cl2,
0 °C, 30 min, 90%; (ii) NaN3, DMF, rt, 2 h, 87%; (k) DIAD, PPh3,
CF3CO2H, THF, 0 °C f rt, 16 h, 61%; (l) MeOH, NaHCO3, rt, 30
min, 85%.
a
b
The reactions were performed in dry CH2Cl2 at rt. mmol of
iodosylbenzene and iodine per mmol of substrate. c Compound 40
d
(42%) is also obtained. Compound 44 (33%) is also obtained.
e CCl4 was used as solvent.
good yield. The H and 13C NMR spectra of this N-Boc
1
hydrolysis of the trifluoroacetate ester intermediate the
alcohol 30, which was then mesylated and treated with
NaN3 with overall retention of configuration. The 5-azide-
5-deoxy-D-manno 31 obtained was transformed into the
N-Boc-protected amine 33 using the protocol described
above for the preparation of compound 28.
As can be observed in Table 1, our procedure was
applied to carbohydrates of the pentose and hexose series
in pyranose or furanose form with the object of obtaining
polyhydroxylated substances with pyrrolidine or piperi-
dine skeletons. We therefore undertook a systematic
investigation of this reaction, focusing on the scope and
stereochemical course of the process.
derivative appear at room temperature as a mixture of
two conformers due to the restricted rotation of the
nitrogen-carbon bond of the carbamate group. To over-
come this situation, NMR spectra were run at 75 °C. At
this temperature, the spectra are consistent with the
proposed structure. The phosphoramidate 10 was syn-
thesized starting with the same ribofuranoside to inves-
tigate the influence of the amine protecting group in the
cyclization reaction. In this case, the reaction behaved
analogously and compound 35 was obtained in similar
yield (entry 2). The NMR spectra of this substance
showed a complex pattern because of the presence of long-
range coupling between the phosphorus atom and certain
carbons and hydrogens of the molecule.
When the reaction was performed with the N-Boc-
protected 5-amino-5-deoxy-D-ribo derivative 6 using io-
dosylbenzene and iodine as oxidizing system under the
conditions shown in Table 1 (entry 1), the 4-amino-4-
deoxy-D-erythrofuranose derivative 34 was obtained in
The reaction does not seem to be dependent on the
stereochemistry at C2 or C3 since the N-Cbz-protected
5-amino-5-deoxy-D-lyxofuranose derivative 14, which re-
quired a sterically more crowded transition state for the

1864 J . Org. Chem., Vol. 66, No. 5, 2001
Francisco et al.
Sch em e 4a
cyclization step, gave rise to the D-threofuranose deriva-
tive 36 also in a similar yield (entry 3).
For the sake of completeness, this methodology was
also extended to the synthesis of imino-sugars of the
pentose series in pyranose form, through a 1,6-coupling
cyclization reaction. The N-Boc-protected 6-amino-6-
deoxy-D-glucopyranose derivative 18 was transformed
into the 5-amino-5-deoxy-D-arabinopyranose derivative
37 under the conditions shown in Table 1 (entry 4). The
proposed stereochemistry at C1 was based on the small
coupling constant observed between the H1 and H2
protons (3.5 Hz) in the 1H NMR spectrum, which preclude
a trans-diaxial relationship between them and is clearly
indicative of the â-orientation of the C1-substituent. The
observed correlation of the anomeric methoxyl group with
the â-proton at C5 in a ROESY experiment in combina-
tion with COSY, DEPT and HMQC spectra, to assign
carbons and protons, not only confirms the proposed
stereochemistry at the anomeric carbon but also suggests
a
Key: (a) PhIO, I2, CH2Cl2, rt, 1 h; (b) MeOH, HCl, rt, 1 h.
inhibitors of a range of R-glucosidases and R-mannosi-
dases.17 In the first case, the reaction proceeded smoothly
and the 4-amino-4-deoxy-L-xylofuranose 42 was formed
in good yield (entry 6). No products were detected that
derived from deprotection of the 1,2-isopropylidene group.
However, during the reaction of compound 33, partial
cleavage of the 1,2-isopropylidene group took place and
the expected 4-amino-4-deoxy-D-arabinofuranose 43 was
only obtained in 28% yield (entry 7), the principal
compound being the interesting azetidine derivative 44
(33%) (Scheme 4). On the basis of spectroscopic evidence,
the 2-hydroxyazetidine 44 would exist predominantly in
the thermodynamically stable cyclic form as a hemiac-
etal.18 The reaction of 44 with MeOH/HCl simultaneously
removed the tert-butyldimethylsilyl ether and the formyl
group and introduced the methyl group at the anomeric
center to afford methyl 3-amino-3-deoxy-â-D-erythroox-
etoside 45. The assignment of the stereochemistry of the
methoxyl group at C1 was made on the basis of the
coupling constant between H1 and H2 (found ∼0 Hz,
calcd 1.5 Hz).14 The lability of the 1,2-isopropylidene in
the D-arabino derivative 43 compared to its L-xylo 42
counterpart may be due to steric hindrance between one
of the methyls of the protecting group and the tether at
C4 in the transition state of the cyclization step.
1
a C4 conformation for the piperidine ring. Furthermore,
the observed coupling constants are in accord with those
1
calculated over a C4-minimized structure using the MMX
force field.14
To test the possibility of exploiting this procedure to
prepare imino-pentoses in pyranose form starting from
conveniently functionalized furanohexoses, we synthe-
sized 6-amino-6-deoxy-D-mannofuranose derivative 25. In
this case, however, results were only partially satisfactory
from the synthetic point of view. In fact, the expected
piperidine derivative 38 was formed only as a minor
product (15%), the principal compound being the pyrro-
lidine derivative 40 obtained in 42% yield (entry 5). The
structure of compound 40 was further confirmed by
converting it into the methyl erythrofuranoside derivative
1
41, using MeOH/HCl. The H and 13C NMR spectra of
this compound at room temperature correspond to a
clearly defined mixture of two rotamers in a ratio of 1:1.
The observed null value for the coupling constant be-
tween H1 and H2 is in complete accord with a â-config-
uration for the methoxyl group at C1. We first expected
the tandem fragmentation-cyclization reaction to pro-
ceed in good yield to give 38, but the sensitive 1,2-
isopropylidene was hydrolyzed by the iodine15 present in
the reaction medium to afford 1,2-diol 39 (Scheme 4).
This compound could not be isolated because was oxidized
in situ with an excess of iodosylbenzene and subsequently
transformed into 40. This assumption turned out to be
partially incorrect. Inasmuch as the pure compound 38
seems to be stable under the reaction conditions (iodo-
sylbenzene/iodine at room temperature for 5 h) and the
hydrolysis of the isopropylidene has had to occur at an
earlier stage before the cyclization step.
The diastereoisomeric 5-amino-5-deoxy-L-gulofuranose
28 and 5-amino-5-deoxy-D-mannofuranose 33 were pre-
pared in order to check the validity of this method in the
synthesis of imino-sugars with a pentofuranoses struc-
ture. This type of compounds are directly related with
the polyhydroxylated pyrrolidines: nectrisine, 4-epi-
nectrisine, DAB-1, and LAB-1,16 which are powerful
Derivatives of 4-amino-4-deoxy-L-xylofuranose and
4-amino-4-deoxy-D-arabinofuranose have recently been
synthesized by Kitahara et al.16a starting from D-(-)-
diethyl tartrate, as intermediates in their synthesis of
nectrisine and 4-epi-nectrisine.
In conclusion, this two-step tandem procedure allows,
under mild conditions, the synthesis of polyhydroxy
pyrrolidines and piperidines corresponding to carbohy-
drates of the tetroses and pentoses series. In this latter
series, the preparation of the five- or six-membered
heterocycles can be specifically achieved only by changing
the relative position of the amine group.
(16) (a) Kim, Y. J .; Takatsuki, A.; Kogoshi, N.; Kitahara, T.
Tetrahedron 1999, 55, 8353-8364. (b) Kim, Y. J .; Kido, M.; Bando,
M.; Kitahara, T. Tetrahedron 1997, 53, 7501-7508. (c) Chen, S. H.;
Danishefsky, S. J . Tetrahedron Lett. 1990, 31, 2229-2232. (d) Kayakiri,
H.; Nakamura, K.; Takase, S.; Setoi, H.; Uchida, I.; Terano, H.;
Hashimoto, M.; Tada, T.; Koda, S. Chem. Pharm. Bull. 1991, 39, 2807.
(17) (a) Furukawa, J .; Okuda, S.; Saito, K.; Hatanaka, S. I. Phy-
tochemistry 1985, 24, 593-594. (b) Nash, R. J .; Bell, E. A.; Williams,
J . M. Phytochemistry 1985, 24, 1620-1622. (c) Fleet, G. W. J .; Nicholas,
S. I.; Smith, P. W.; Evans, S. V.; Fellows, L. E.; Nash, R. J . Tetrahedron
Lett. 1985, 26, 3127-3130. (d) Shibata, T.; Nakayama, O.; Tsurumi,
Y.; Okuhara, M.; Terano, H.; Kohsaka, M. J . Antibiot. 1988, 41, 296.
(18) Chelucci, G.; Saba, A. Tetrahedron: Asymmetry 1997, 8, 699-
702.
(14) MMX force field as implemented in PCMODEL (v. 4.0), Serena
Software, Bloomington, IN, 47402-3076.
(15) Although deprotection of isopropylidene derivatives has never
been observed under the reaction conditions, iodine is a mild Lewis
acid that has been used for the formation and cleavage of acetals. (a)
Kartha, K. P. R. Tetrahedron Lett. 1986, 27, 3415-3416. (b) Szarek,
W. A.; Zamojski, A.; Tiwari, K. N.; Ison, E. R. Tetrahedron Lett. 1986,
27, 3827-3830.

Fragmentation of Carbohydrate Anomeric Alkoxy Radicals
J . Org. Chem., Vol. 66, No. 5, 2001 1865
(19), 316 (100), 315 (47), 251 (15), 233 (7); HRMS calcd for
Exp er im en ta l Section
C20H22NO7P 419.1134, found 419.1145. Anal. Calcd for C20H22
-
Gen er a l Meth od s. Melting points were determined with
a hot-stage apparatus and are uncorrected. Optical rotations
were measured at the sodium line at ambient temperature in
CHCl3 solutions. IR spectra were recorded in CCl4 solutions
unless otherwise stated. NMR spectra were determined at 500
MHz for 1H and 125.7 MHz for 13C in CDCl3 at 26 °C unless
otherwise stated, in the presence of TMS as internal standard.
Mass spectra were determined at 70 eV. Merck silica gel 60
PF (0.063-0.2 mm) were used for column chromatography.
Circular layers of 1 mm of Merck silica gel 60 PF254 were used
on a Chromatotron for centrifugally assisted chromatography.
Commercially available reagents and solvents were analytical
grade or were purified by standard procedures prior to use.19
All reactions involving air- or moisture-sensitive materials
were carried out under a nitrogen atmosphere. The spray
reagents for TLC analysis were conducted with 0.5% vanillin
in H2SO4-EtOH (4:1) and further heating until development
of color.
Gen er a l P r oced u r e for th e Alk oxy Ra d ica l F r a gm en -
ta tion Rea ction . To a solution of the amine derivative (1
mmol) in CH2Cl2 (35 mL) were added freshly prepared iodo-
sylbenzene20 (1.6-3 mmol) and I2 (0.2-1.2 mmol), and the
reaction was stirred at room temperature for 1-21 h. The
reaction mixture was then poured into aqueous 10% Na2S2O3
and extracted with CH2Cl2. The organic layer was then washed
with brine, dried (Na2SO4), and concentrated under reduced
pressure. The obtained residue was purified by chromatogra-
phy under the conditions specified in each case.
NO7P: C, 57.28; H, 5.29; N, 3.34. Found: C, 57.44; H, 5.46;
N, 3.25.
4-(N-Ben zyloxyca r b on yl)a m in o-4-d eoxy-3-O-for m yl-
1,2-O-isop r op ylid en e-â-D-th r eofu r a n ose (36). Following
the general procedure, compound 14 (42 mg, 0.13 mmol) in
dry CH2Cl2 (7 mL) containing iodosylbenzene (75 mg, 0.34
mmol) and I2 (41 mg, 0.16 mmol) was stirred at room
temperature for 2 h. Chromatotron chromatography (hexanes-
EtOAc, 80:20 f 70:30) of the residue afforded compound 36
(30 mg, 0.09 mmol, 70%) as a crystalline solid (two rotamers
in a ratio of 1:1): mp 72-74 °C (from ether-n-hexane); [R]D
+68 (c ) 0.540); IR 1736, 1723 cm-1 1H NMR (75 °C) 1.34
;
(3H, s), 1.45 (3H, s), 3.75 (1H, dd, J ) 3.9, 13.0 Hz), 3.82 (1H,
d, J ) 13.0 Hz), 4.56 (1H, d, J ) 4.5 Hz), 5.17 (1H, d, J ) 12.7
Hz), 5.21 (1H, d, J ) 12.7 Hz), 5.24 (1H, d, J ) 3.9 Hz), 6.03
(1H, brs), 7.27-7.39 (5H, m), 7.98 (1H, s); 13C NMR (75 °C)
25.8 (CH3), 26.8 (CH3), 49.6 (CH2), 67.2 (CH2), 74.3 (CH), 82.3
(CH), 88.8 (CH), 112.3 (C), 127.7 (2 × CH), 127.8 (CH), 128.3
(2 × CH), 136.0 (C), 154.2 (C), 159.0 (CH); MS (rel intensity)
321 (M+, 13), 306 (6), 263 (9), 219 (11), 214 (8), 174 (13), 156
(10); HRMS calcd for C16H19NO6 321.1212, found 321.1216.
Anal. Calcd for C16H19NO6: C, 59.81; H, 5.96; N, 4.36. Found:
C, 59.74; H, 6.05; N, 4.30.
Meth yl 5-(N-ter t-Bu toxyca r bon yl)a m in o-5-d eoxy-4-O-
for m yl-2,3-d i-O-m eth yl-â-D-a r a bin op yr a n osid e (37). Fol-
lowing the general procedure, compound 18 (34 mg, 0.106
mmol) in dry CH2Cl2 (5 mL) containing iodosylbenzene (73 mg,
0.33 mmol) and I2 (32 mg, 0.13 mmol) was stirred at room
temperature for 1 h. Chromatotron chromatography (hexanes-
EtOAc, 95:5) of the residue afforded compound 37 (23 mg,
0.072 mmol, 68%) as a syrup (two rotamers in a ratio of 3:2):
4-(ter t-Bu toxyca r bon yl)a m in o-4-d eoxy-3-O-for m yl-1,2-
O-isop r op ylid en e-r-D-er yth r ofu r a n ose (34). Following the
general procedure, compound 6 (50 mg, 0.17 mmol) in CH2Cl2
(6 mL) containing iodosylbenzene (93.5 mg, 0.43 mmol) and I2
(43 mg, 0.17 mmol) was stirred at room temperature for 21 h.
Chromatotron chromatography (hexanes-EtOAc, 80:20) of the
reaction residue afforded compound 34 (36 mg, 0.13 mmol,
76%) as a crystalline solid (two rotamers in a ratio of 2:3): mp
71-73 °C (from CH2Cl2); [R]D -73.3 (c ) 0.514); IR 1736, 1714
1
[R]D -92.1 (c ) 0.34); IR 1732, 1703 cm-1; H NMR 1.45 (9H,
s), 1.47 (9H, s), 3.03 (1H, d, J ) 14.7 Hz), 3.09 (1H, d, J )
14.3 Hz), 3.30 (3H, s), 3.32 (3H, s), 3.44 (3H, s), 3.45 (3H, s),
3.48 (1H, dd, J ) 6.7, 3.5 Hz), 3.50 (1H, dd, J ) 6.6, 3.5 Hz),
3.54 (3H, s), 3.56 (3H, s), 3.61 (1H, dd, J ) 10.0, 3.4 Hz), 3.64
(1H, dd, J ) 9.9, 3.3 Hz), 4.10 (1H, dd, J ) 2.6, 14.7 Hz), 4.20
(1H, dd, J ) 1.9, 14.7 Hz), 5.32 (1H, brs), 5.43 (1H, d, J ) 3.5
Hz), 5.47 (1H, brs), 5.61 (1H, d, J ) 3.5 Hz), 8.09 (1H, s), 8.11
(1H, s); 1H NMR (75 °C) 1.46 (9H, s), 3.06 (1H, d, J ) 14.8
Hz), 3.32 (3H, s), 3.43 (3H, s), 3.46 (1H, dd, J ) 9.9, 3.7 Hz),
3.53 (3H, s), 3.60 (1H, dd, J ) 9.9, 3.4 Hz), 4.11 (1H, brs), 5.33
(1H, brs), 5.53 (1H, brs), 8.06 (1H, s); 13C NMR (75 °C) 28.5 (3
× CH3), 40.8 (CH2), 55.5 (CH3), 58.3 (CH3), 58.7 (CH3), 78.1 (2
× CH), 78.5 (2 × CH), 81.0 (C), 154.8 (C), 160.0 (CH); MS (rel
intensity) 319 (M+, <1), 287 (3), 246 (2), 231 (3), 218 (5), 204
(29), 190 (2), 186 (1), 158 (11), 142 (100); HRMS calcd for
1
cm-1; H NMR (75 °C) 1.35 (3H, s), 1.48 (9H, s), 1.50 (3H, s),
3.38 (1H, dd, J ) 9.4, 10.4 Hz), 3.96 (1H, dd, J ) 7.6, 10.4
Hz), 4.75 (1H, dd, J ) 4.7, 4.6 Hz), 4.95 (1H, ddd, J ) 4.7, 9.4,
7.6 Hz), 5.85 (1H, s), 8.04 (1H, s); 13C NMR (75 °C, one
quaternary carbon missing) 26.1 (CH3), 26.6 (CH3), 28.2 (3 ×
CH3), 45.8 (CH2), 69.7 (CH), 80.8 (CH), 88.3 (CH), 112.7 (C),
153.3 (C), 159.4 (CH); MS (rel intensity) 288 (M+ + 1, 2), 272
(3), 241 (8), 230 (4), 214 (7), 185 (19), 172 (11), 170 (4), 156
(16), 128 (11), 112 (19). Anal. Calcd for C13H21NO6: C, 54.35;
H, 7.37; N, 4.88. Found: C, 54.25; H, 7.37; N, 4.89.
C
14H25NO7 319.1631, found 319.1635. Anal. Calcd for C14H25-
4-Deoxy-4-(N-d ip h en ylp h osp h in oyl)a m in o-3-O-for m yl-
1,2-O-isop r op ylid en e-r-D-er yth r ofu r a n ose (35). Following
the general procedure, compound 10 (33 mg, 0.078 mmol) in
dry CH2Cl2 (3 mL) containing iodosylbenzene (38 mg, 0.17
mmol) and I2 (24 mg, 0.09 mmol) was stirred at room
temperature for 2 h. Chromatotron chromatography (hexanes-
EtOAc, 70:30) of the residue afforded compound 35 (23.5 mg,
NO7: C, 52.65; H, 7.89; N, 4.39. Found: C, 52.56; H, 7.84; N,
4.01.
5-(ter t-Bu toxyca r bon yl)a m in o-5-d eoxy-3-O-for m yl-1,2-
O-isop r op ylid en e-4-O-m eth yl-â-D-a r a bin op yr a n ose (38).
Following the general procedure, compound 25 (46 mg, 0.14
mmol) in CH2Cl2 (5 mL) containing iodosylbenzene (92 mg,
0.42 mmol) and I2 (42 mg, 0.17 mmol) was stirred at room
temperature for 2.3 h. Silica gel flash chromatography (hex-
anes-EtOAc, 85:15 f 70:30) of the residue afforded compound
38 (7 mg, 0.021 mmol, 15%) and compound 40 (15 mg, 0.051
mmol, 42%). Compound 38 (two rotamers in a ratio of 2:1):
0.057 mmol, 72%): syrup; [R]D -25.9 (c ) 0.328); IR 1737 cm-1
;
1H NMR 1.33 (3H, s), 1.38 (3H, s), 3.35 (1H, ddd, J ) 9.7, 9.3
Hz, J P ) 2.5 Hz), 3.82-3.86 (1H, m), 4.72-4.77 (2H, m), 5.86
(1H, dd, J ) 4.3 Hz, J P ) 2.8 Hz), 7.17-7.21 (2H, m), 7.27-
1
7.37 (8H, m), 8.06 (1H s); H NMR (75 °C) 1.31 (3H, s), 1.38
oil; [R]D -51 (c ) 0.47); IR 1714 cm-1; H NMR (70 °C) 1.40
1
(3H, s), 3.34 (1H, ddd, J ) 9.4, 9.4 Hz, J P ) 2.9 Hz), 3.80-
3.84 (1H, m), 4.70-4.75 (2H, m), 5.85 (1H, dd, J ) 4.3 Hz, J P
) 2.1 Hz), 7.13-7.16 (2H, m), 7.25-7.32 (8H, m), 8.01 (1H, s);
13C NMR (75 °C) 25.8 (CH3), 26.1 (CH3), 46.4 (CH2, J P ) 3.8
Hz), 71.0 (CH, J P ) 11.4 Hz), 76.8 (CH, J P ) 9.5 Hz), 90.5
(CH, J P ) 3.8 Hz), 112.1 (C), 120.0 (2 × CH, J P ) 3.8 Hz),
120.1 (2 × CH, J P ) 5.7 Hz), 124.9 (2 × CH, J P ) 5.7 Hz),
129.5 (4 × CH, J P ) 7.6 Hz), 150.6 (2 × C, J P ) 5.7 Hz), 159.3
(CH); MS (rel intensity) 419 (M+, <1), 404 (9), 373 (37), 344
(3H, s), 1.49 (3H, s), 1.49 (9H, s), 3.19 (1H, brd, J ) 13 Hz),
3.37 (3H, s), 3.71 (1H, ddd, J ) 2.9, 2.9, 4.9 Hz), 4.15 (1H,
brd, J ) 10 Hz), 4.23 (1H, dd, J ) 6.2, 6.7 Hz), 5.10 (1H, dd,
J ) 6.7, 2.8 Hz), 6.10 (1H, brd, J ) 5.8 Hz), 8.14 (1H, s); 13C
NMR (70 °C) 26.4 (CH3), 27.8 (CH3), 28.3 (3 × CH3), 40.4 (CH2),
57.0 (CH3), 71.5 (CH), 72.8 (CH), 73.82 (CH), 81.4 (C), 81.8
(CH), 107.7 (C), 154.7 (C), 160.2 (CH); MS (rel intensity) 331
(M+, <1), 316 (3), 260 (6), 258 (3), 217 (6); HRMS calcd for
C
C
15H25NO7 331.163102, found 331.164749. Anal. Calcd for
15H25NO7: C, 54.35; H, 7.61; N, 4.23. Found: C, 54.38; H,
(19) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: New York, 1988.
(20) Saltzman, H.; Sharefkin, J . G. Organic Syntheses; Wiley: New
York, 1973; Collect. Vol. V, pp 658-659.
7.50; N, 4.33. Compound 40 (two rotamers in a ratio of 4:1):
oil; [R]D +8.0 (c ) 0.91); IR (neat) 3420, 1731, 1699 cm-1; H
1
NMR (C6D6) (major rotamer) 1.36 (9H, s), 2.93 (3H, s), 3.35

1866 J . Org. Chem., Vol. 66, No. 5, 2001
Francisco et al.
(1H, dd, J ) 8.1, 10.5 Hz), 3.54 (1H, dd, J ) 7.1, 10.0 Hz),
3.95 (1H, ddd, J ) 3.9, 7.7, 7.7 Hz), 5.38 (1H, d, J ) 3.8 Hz),
5.55 (1H, s), 7.47 (1H, s); 13C NMR (C6D6) (major rotamer) 28.3
(3 × CH3) 47.8 (CH2), 57.8 (CH3), 73.9 (CH), 77.6 (CH), 80.5
(C) 83.9 (CH), 155.1 (C), 159.4 (CH); MS (rel intensity) 260
(M+ - H, <1), 244 (<1), 202 (1), 188 (4), 173 (5); HRMS calcd
for C11H18NO6 260.113413, found 260.121101. Anal. Calcd. for
pound 33 (83 mg, 0.191 mmol) in CCl4 (7 mL) containing
iodosylbenzene (68 mg, 0.31 mmol) and I2 (9.7 mg, 0.038 mmol)
was stirred at room temperature for 1 h. Chromatotron
chromatography (hexanes-EtOAc, 95:5 f 80:20) of the residue
afforded compound 43 (23.3 mg, 0.054 mmol, 28%) and
compound 44 (22.6 mg, 0.063 mmol, 33%). Compound 43 (two
rotamers in a ratio of 2:3): oil; [R]D -44.5 (c ) 1.13); IR (CHCl3)
1
C
11H19NO6: C, 50.56; H, 7.33; N, 5.36. Found: C, 50.21; H,
1724, 1703 cm-1; H NMR (70 °C) 0.05 (6H, s), 0.87 (9H, s),
6.98; N, 5.43.
1.39 (3H, s), 1.48 (12H, s), 3.20 (1H, d, J ) 13.4 Hz), 3.97 (1H,
m), 4.13 (1H, ddd, J ) 2.4, 1.6, 4.7 Hz), 4.20 (1H, dd, J ) 7.3,
5.9 Hz), 4.95 (1H, dd, J ) 7.3, 2.4 Hz), 6.11 (1H, brs), 8.11
(1H, s); 13C NMR (70 °C) -5.0 (CH3), -4.96 (CH3), 18.1 (C),
25.6 (3 × CH3), 26.6 (CH3), 27.9 (CH3), 28.3 (3 × CH3), 44.8
(CH2), 66.2 (CH), 71.5 (CH), 74.7 (CH), 81.3 (C), 81.9 (CH),
Met h yl 4-(ter t-Bu t oxyca r b on yl)a m in o-4-d eoxy-3-O-
m eth yl-â-D-er yth r ofu r a n osid e (41). A solution of compound
40 (15.9 mg, 0.061 mmol) in MeOH (0.5 mL) was treated with
an undetermined catalytic amount of HCl (some gas taken
with a Pasteur pipet from the headspace of a concd HCl bottle)
and stirred at room temperature for 1 h. The reaction mixture
was then poured into aqueous saturated NaHCO3 and ex-
tracted with EtOAc. Chromatotron chromatography (hexanes-
EtOAc, 80:20) of the residue afforded compound 41 (13.4 mg,
0.054 mmol, 76%) as an oil (two rotamers in a ratio of 1:1):
107.5 (C), 154.8 (C), 160.3 (C); MS (rel intensity) 416 (M+
-
CH3, <1), 358 (2), 318 (48), 316 (3), 312 (2), 300 (1); HRMS
calcd for C19H34NO7Si 416.210456, found 416.207977. Anal.
Calcd for C20H37NO7Si: C, 55.65; H, 8.64; N, 3.25 Found: C,
56.05; H, 8.26; N, 3.40. Compound 44: (two rotamers in a ratio
of 7:3): oil; [R]D -13.6 (c ) 0.36); IR (neat) 3420, 1735, 1703
cm-1; 1H NMR (major rotamer) 0.07 (3H, s), 0.08 (3H, s), 0.87
(9H, s), 1.44 (9H, s), 3.22 (1H, dd, J ) 7.1, 10.7 Hz), 3.64 (1H,
dd, J ) 6.6, 10.7 Hz), 4.56 (1H, ddd, J ) 4.1, 6.6, 6.6 Hz), 5.10
(1H, brs), 5.34 (1H, brs), 8.11 (1H, s); 13C NMR (C6D6, major
rotamer) -5.4 (CH3), -5.2 (CH3), 25.7 (3 × CH3), 28.3 (3 ×
CH3), 50.5 (CH2), 69.3 (CH), 76.6 (CH), 84.0 (CH), 159.3 (CH)
(three quaternary carbons missing); MS (rel intensity) 304 (M+
- C4H9, 1), 186 (31), 158 (12), 129 (17), 103 (100); HRMS calcd
for C12H22NO6Si 304.121641, found 304.121078. Anal. Calcd
for C16H31NO6Si: C, 53.16; H, 8.64; N, 3.87. Found: C, 53.14;
H, 8.57; N, 3.62. Treatment of 44 with MeOH/HCl under the
same conditions used for the preparation of 41 afforded methyl
3-(tert-butoxycarbonyl)amino-3-deoxy-D-erythrooxetoside (45)
(50%): oil (two rotamers in a ratio of 6:4); 1H NMR (C6D6) 1.44
(9H, s), 1.46 (9H, s), 3.25 (3H, s), 3.40 (1H, dd, J ) 7.7, 9.7
Hz), 3.44 (3H, s), 3.59 (1H, m), 3.61 (1H, dd, J ) 7.8, 9.7 Hz),
3.70 (1H, dd, J ) 10.7, 7.7 Hz), 3.84 (1H, brd, J ) 3.4 Hz),
3.94 (1H, brs), 5.05 (1H, s), 5.30 (1H, s); MS (rel intensity)
233 (M+, 14), 177 (7), 160 (26), 146 (19), 132 (25), 115 (100);
HRMS calcd for C10H19NO5 233.126323, found 233.130611.
[R]D -12.3 (c ) 0.65); IR (neat) 3450, 1705 cm-1 1H NMR
;
(C6D6) 1.38 (9H, s), 1.40 (9H, s), 2.23 (1H, brs, OH), 2.41 (1H,
brs, OH), 2.72 (3H, s), 2.77 (3H, s), 3.20 (3H, s), 3.39 (3H, s),
3.40 (1H, dd, J ) 8.1, 10.5 Hz), 3.53 (1H, dd, J ) 7.9, 10.3
Hz), 3.59 (1H, dd, J ) 7.6, 11.0 Hz), 3.63 (1H, dd, J ) 7.6,
10.5 Hz), 3.77 (1H, ddd, J ) 4.3, 7.2, 7.2 Hz), 3.84 (1H, ddd, J
) 3.8, 7.6, 7.6 Hz), 4.03 (1H, d, J ) 3.8 Hz), 4.05 (1H, d, J )
3.8 Hz), 4.41 (1H, s), 5.09 (1H, s); 13C NMR (C6D6) 28.3 (3 ×
CH3), 48.0 (CH2), 48.1 (CH2), 55.8 (CH3), 56.4 (CH3), 57.1 (CH3),
57.1 (CH3), 72.2 (CH), 73.4 (CH), 78.6 (CH), 79.4 (CH), 79.6
(C), 79.8 (C), 92.9 (CH), 93.2 (CH), 154.6 (C), 155.6 (C); MS
(rel intensity) 247 (M+, 1), 215 (4), 183 (1), 160 (3), 159 (3);
HRMS calcd for C11H21NO5 247.141973, found 247.138393.
Anal. Calcd for C11H21NO5: C, 53.42; H, 8.56; N, 5.67. Found:
C, 53.35; H, 8.65; N, 5.42.
4-(ter t-Bu toxyca r bon yl)a m in o-5-O-(ter t-bu tyld im eth -
ylsilyl)-4-d eoxy-3-O-for m yl-1,2-O-isop r op ylid en e-r-L-xy-
lofu r a n ose (42). Following the general procedure, compound
28 (105 mg, 0.24 mmol) in CH2Cl2 (9 mL) containing iodosyl-
benzene (158 mg, 0.72 mmol) and I2 (73 mg, 0.287 mmol) was
stirred at room temperature for 2 h. Chromatotron chroma-
tography (hexanes-EtOAc, 95:5) of the residue afforded
compound 42 (80 mg, 0.18 mmol, 78%) as an oil (two rotamers
in a ratio of 3:1): [R]D +30 (c ) 0.742); IR 1736, 1711 cm-1; 1H
NMR (75 °C) 0.056 (3H, s), 0.063 (3H, s), 0.91 (9H, s), 1.37
(3H, s), 1.50 (9H, s), 1.51 (3H, s), 3.76 (1H, brd, J ) 9.8 Hz),
3.84 (1H, dd, J ) 10.3, 4.9 Hz), 4.29 (1H, ddd, J ) 4.9, 2.4, 6.5
Hz), 4.68 (1H, dd, J ) 5.2, 4.8 Hz), 5.37 (1H, dd, J ) 4.8, 6.5
Hz), 5.79 (1H, d, J ) 5.2 Hz), 8.08 (1H, s); 13C NMR (75 °C)
-5.5 (2 × CH3), 18.2 (C), 25.9 (3 × CH3), 27.0 (CH3), 27.8 (CH3),
28.5 (3 × CH3), 59.1 (CH2), 60.8 (CH), 76.7 (CH), 80.9 (C), 81.6
(CH), 88.7 (CH), 113.1 (C), 153.8 (C), 159.7 (CH); MS (rel
intensity) 416 (M+ - CH3, <1), 374 (1), 358 (11), 318 (59), 274
(76); HRMS calcd for C19H34NO7Si 416.2104, found 416.2091.
Anal. Calcd for C20H37NO7Si: C, 55.65; H, 8.64; N, 3.25.
Found: C, 55.72; H, 8.71; N, 3.04.
Ack n ow led gm en t. This work was supported by the
Investigation Program No. PB96-1461 of the Direccio´n
General de Investigacio´n Cient´ıfica y Te´cnica, Spain and
Program Nos. 93/030 and 93/014 of the Direccio´n
General de Universidades e Investigacio´n del Gobierno
de Canarias. C.C.G. and C.R.-F. thank the Ministerio
de Educacio´n y Ciencia, Spain, and the Direccio´n
General de Universidades e Investigacio´n del Gobierno
de Canarias, respectively, for fellowships.
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures, physical properties, and spectroscopic data for com-
pounds 2-33. This material is available free of charge via the
Internet at http://pubs.acs.org.
4-(ter t-Bu toxyca r bon yl)a m in o-5-O-(ter t-bu tyld im eth -
ylsilyl)-4-d eoxy-3-O-for m yl-1,2-O-isop r op ylid en e-â-D-a r a -
bin ofu r a n ose (43). Following the general procedure, com-
J O0057452