Intramolecular hydrogen abstraction reaction promoted by N-radicals in carbohydrates. Synthesis of chiral 7-oxa-2-azabicyclo[2.2.1]heptane and 8-oxa-6-azabicyclo[3.2.1]octane Ring systems

Article abstract of DOI:10.1021/jo026314h

The reaction of phenyl and benzyl amidophosphates and alkyl and benzyl carbamate derivatives of aminoalditols with (diacetoxyiodo)benzene or iodosylbenzene and iodine is a mild and selective procedure for the synthesis of chiral 7-oxa-2-azabicyclo[2.2.1]h

Full text of DOI:10.1021/jo026314h

In tr a m olecu la r Hyd r ogen Abstr a ction Rea ction P r om oted by
N-Ra d ica ls in Ca r boh yd r a tes. Syn th esis of Ch ir a l
7-Oxa -2-a za bicyclo[2.2.1]h ep ta n e a n d
8-Oxa -6-a za bicyclo[3.2.1]octa n e Rin g System s
Cosme G. Francisco, Antonio J . Herrera, and Ernesto Sua´rez*
Instituto de Productos Naturales y Agrobiologı´a del C.S.I.C., Carretera de La Esperanza 3,
38206 La Laguna, Tenerife, Spain
esuarez@ipna.csic.es
Received August 13, 2002
The reaction of phenyl and benzyl amidophosphates and alkyl and benzyl carbamate derivatives
of aminoalditols with (diacetoxyiodo)benzene or iodosylbenzene and iodine is a mild and selective
procedure for the synthesis of chiral 7-oxa-2-azabicyclo[2.2.1]heptane and 8-oxa-6-azabicyclo[3.2.1]-
octane ring systems under neutral conditions. This reaction can be considered to be an intramo-
lecular N-glycosidation that goes through an intramolecular 1,5-hydrogen abstraction promoted
by an N-amido radical followed by oxidation of the transient C-radical intermediate to an
oxycarbenium ion. This methodology proved to be useful not only as a suitable strategy for the
preparation of these bicyclic arrays but also for the selective oxidation of specific carbons of the
carbohydrate skeleton, constituting a good procedure for the synthesis of protected N,O-uloses.
The 8-oxa-6-azabicyclo[3.2.1]octane ring system forms
the characteristic framework of several physiologically
active alkaloids of the samandarine, ribasine, and zoan-
thamine types.1 On the other hand, only a few examples
of carbohydrates containing this oxa-azabicyclo ring
system in their skeleton have been described. They have
been synthesized through intramolecular nucleophilic
displacement of good leaving groups at C-6 by nitrogen
nucleophiles at the anomeric center.2 Several 7-amino-
2,7-anhydro-1,7-dideoxy-D-gulo-hept-2-ulopyranose de-
rivatives that mimic R-L-fucose and are potent inhibitors
of fucosidases have been prepared by cyclization of the
corresponding acyclic hydroxy amino ketones.3
during the TMSOTf-catalyzed reaction of methyl 1,2,3-
tri-O-acetyl-5-(acetylamino)-5-deoxy-â-D-allofuranuro-
nate with bis-siylated thymine under the conditions of a
Vorbru¨ggen coupling.5
In previous papers from this laboratory, we have
reported that N-nitroamides, N-cyanamides, and N-
phosphoramidates react with hypervalent iodine reagents
in the presence of iodine to generate N-radicals through
homolytic fragmentation of a hypothetical iodoamide
intermediate.6 The mechanism is purported to be similar
to the radical fragmentation of the hypoiodite reaction.7
Nitrogen radicals generated in this way may participate
in an intramolecular 1,5-hydrogen abstraction reaction
(IHA) from unactivated carbons, the result being the
formation of pyrrolidines. The reaction, which resembles
the Hofmann-Lo¨ffler-Freytag8 (HLF) synthesis of pyr-
rolidines, proceeds under very mild neutral conditions
compatible with the stability of the protective groups
most frequently used in synthetic organic chemistry.
Although a few examples of the HLF reaction under mild
conditions are known,9 the procedure traditionally re-
The most general approach to the 7-oxa-2-azabicyclo-
[2.2.1]heptane heterocyclic ring system implies an inter-
molecular 1,3-dipolar cycloaddition reaction.4 The only
carbohydrate possessing this heterocyclic ring system in
its skeleton is, as far as we know, a byproduct formed
* To whom correspondence should be addressed. Fax: 34-922
260135.
(1) Southon, I. W., Buckingham, J ., Eds. Dictionary of Alkaloids;
Chapman and Hall: New York, 1989 (samandarine S-00018, ribasine
R-00070, and zoanthamine Z-00019).
(4) (a) Liu, F.; Austin, D. J . Org. Lett. 2001, 3, 2273-2276. (b)
Padwa, A.; Heidelbangh, T. M.; Kuethe, J . T. J . Org. Chem. 1999, 64,
2038-2049. (c) Savinov, S.; Austin, D. J . Chem. Commun. 1999, 1813-
1814. (d) Padwa, A.; Prein, M. Tetrahedron 1998, 54, 6957-6976. (e)
Takeda, Y.; Akimoto, T.; Kyogoku, Y. Carbohydr. Res. 1982, 106, 175-
192. (f) Hamaguchi, M.; Ibata, T. Chem. Lett. 1975, 499-502. (g)
Iwakawa, M.; Yoshimura, J . Bull. Chem. Soc. J pn. 1975, 48, 610-
615.
(2) (a) Pradera, M. A.; Olano, D.; Fuentes, J . Tetrahedron Lett. 1995,
36, 8653-8656. (b) Fuentes, J .; Olano, D.; Pradera, M. A. Tetrahedron
Lett. 1999, 40, 4063-4066. (c) Lafont, D.; Wollny, A.; Boullanger, P.
Carbohydr. Res. 1998, 310, 9-16. (d) Paulsen, H.; Todt, K. Angew.
Chem., Int. Ed. Eng. 1965, 4, 592-593. (e) Paulsen, H.; Todt, K. Chem.
Ber. 1966, 99, 3450-3460. (f) Paulsen, H.; Todt, K. Chem. Ber. 1967,
100, 512-520. (g) Paulsen, H.; Todt, K. Adv. Carbohydr. Chem. 1968,
23, 115-232.
(3) (a) Beacham, A. R.; Smelt, K. H.; Biggadike, K.; Britten, C. J .;
Hackett, L.; Winchester, B. G.; Nash, R. J .; Griffiths, R. C.; Fleet, G.
W. J . Tetrahedron Lett. 1998, 39, 151-154. (b) Smelt, K. H.; Harrison,
A. J .; Biggadike, K.; Mu¨ller, M.; Prout, K.; Watkin, D. J .; Fleet, G. W.
J . Tetrahedron Lett. 1998, 39, 151-154. For another related example
see: (c) Farr, R. A.; Holland, A. K.; Huber, E. W.; Peet, N. P.;
Weintraub, P. M. Tetrahedron 1994, 50, 1033-1044.
(5) Garner, P.; Park, J . M. J . Org. Chem. 1990, 55, 3772-3787.
(6) (a) Dorta, R. L.; Francisco, C. G.; Sua´rez, E. J . Chem. Soc., Chem.
Commun. 1989, 1168-1169. (b) Armas, P.; Francisco, C. G.; Herna´n-
dez, R.; Salazar, J . A.; Sua´rez, E. J . Chem. Soc., Perkin Trans. 1 1988,
3255-3265. (c) Carrau, R.; Herna´ndez, R.; Sua´rez, E.; Betancor, C. J .
Chem. Soc., Perkin Trans. 1 1987, 937-943.
(7) Courtneidge, J . L.; Lusztyk, J .; Page´, D.Tetrahedron Lett. 1994,
35, 1003-1006.
10.1021/jo026314h CCC: $25.00 © 2003 American Chemical Society
Published on Web 01/14/2003
1012
J . Org. Chem. 2003, 68, 1012-1017

Intramolecular Hydrogen Abstraction Reaction
SCHEME 1
SCHEME 2. Su bstr a tes for th e
7-Oxa -2-a za bicyclo[2.2.1]h ep ta n e Ser iesa
quires strong acid concentrations, which severely limits
its use for the synthesis of complex or sensitive molecules.
To our knowledge, the only precedent of the IHA
reaction triggered by amidyl radicals, generated from the
photolysis of N-iodocarboxamides, is described as giving
γ-butyrolactones.10 A study of the radical amidation onto
aromatic rings using sulfonamides and hypervalent
iodine reagents has recently been published.11
With these results in mind, we decided to study the
N-radical-promoted IHA from carbons where the radical
abstraction could be favored by electron-donor groups.
In these systems the C-radical initially formed could be
subsequently oxidized by an excess of reagent to an
oxycarbenium ion, as described in Scheme 1. Intramo-
lecular nucleophilic cyclization of the amide group to this
oxycarbenium ion intermediate could give rise to an oxa-
azabicyclic system. As shown in the scheme, nucleophilic
species present in the medium can also be competitively
trapped by the oxycarbenium ion.
In this paper we describe a convenient synthesis of
carbohydrate derivatives of chiral 7-oxa-2-azabicyclo-
[2.2.1]heptane and 8-oxa-6-azabicyclo[3.2.1]octane ring
systems using this protocol.12
P r ep a r a tion of Su bstr a tes a n d Discu ssion . The
synthesis of the starting amine derivatives proceeded
a
Reagents: (a) ZnN6‚2Py, Ph3P, DIAD, MePh, rt; (b) (i) H2, Pd/C
(5%), EtOAc, rt, ap; (ii) (PhO)2P(O)Cl, TEA, CH2Cl2, rt; (c) (i) MsCl,
Py, rt, 20 min; (ii) NaN3, DMF, 80 °C, 30 min, 99%; (d) H2, Pd/C
(5%), di-tert-butyl dicarbonate, EtOAc, rt, ap, 5 h, 90%.
according to the following: The furanose amides 3, 6, 9,
and 10 were synthesized from the corresponding alcohols
1,13 4,14 and 715 by Mitsunobu azidation16 and subsequent
reduction, followed by treatment of the resulting amine
with the corresponding protective group reagent (Scheme
2). On the other hand, the pyranose amides were pre-
pared from the corresponding heptonitriles 11,17 13,17c,18
15,19 and 2020 obtained, in turn, by cyanoglycosidation.21
LAH reduction of the nitriles and appropriate protection
of the resulting amines afforded the desired amide
(8) Recent reviews: (a) Feray, L.; Kuznetsov, N.; Renaud, P. In
Radicals in Organic Synthesis; Renaud, P.; Sibi, M. P., Eds.; Wiley-
VCH: Weinheim, 2001; Vol. 2, pp 254-256. (b) Stella, L. In Radicals
in Organic Synthesis; Renaud, P.; Sibi, M. P., Eds.; Wiley-VCH:
Weinheim, 2001; Vol. 2, pp 409-426. (c) Majetich, G.; Wheless, K.
Tetrahedron 1995, 51, 7095-7129; Early reviews: (d) Mackiewicz, P.;
Furstoss, R. Tetrahedron 1978, 34, 3241-3260. (e) Neale, R. S.
Synthesis 1971, 1-15. (f) Schonberg, A. Preparative Organic Photo-
chemistry; Springer-Verlag: West Berlin, 1968; p 242. (g) Wolff, M. E.
Chem. Rev. 1963, 63, 55-64.
(9) (a) Nikishin, G. I.; Troyansky, E. I. Tetrahedron Lett. 1985, 26,
3743-3744. (b) Baldwin, S. W.; Doll, R. J .; Gross, P. M. Tetrahedron
Lett. 1979, 3275-3278. (c) Kimura, M.; Ban, Y. Synthesis 1976, 201-
204. For an example under reductive conditions, see: (d) Kim, S.; Yeon,
K. M.; Yoon, K. S. Tetrahedron Lett. 1997, 38, 3919-3922.
(10) Barton, D. H. R.; Beckwith, A. L. J .; Goosen, A. J . Chem. Soc.
1965, 181-190. For an example giving lactams, see: Herna´ndez, R.;
Medina, M. C.; Salazar, J . A.; Sua´rez, E. Tetrahedron Lett. 1987, 28,
2533-2536.
(13) Ohrui, H.; J ones, G. H.; Moffatt, J . G.; Maddox, M. L.;
Christensen, A. T.; Byram, S. K. J . Am. Chem. Soc. 1975, 97, 4602-
4613.
(14) McDevitt, J . P.; Lansbury, P. T. J . Am. Chem. Soc. 1996, 118,
3818-3828.
(15) Fre´chou, C.; Dheilly, L.; Beaupe`re, D.; Uzan, R.; Demailly, G.
Tetrahedron Lett. 1992, 33, 5067-5070.
(16) Viand, M. C.; Rollin, P. Synthesis 1990, 130-132.
(17) Obtained as a byproduct during the hydrogenolysis of 5,7-di-
O-acetyl-2,6-anhydro-3,4-dideoxy-D-arabino-hept-3-enonitrile. (a) De
las Heras, F. G.; San-Felix, A. S.; Ferna´ndez-Resa, P. Tetrahedron
1983, 39, 1617-1620. (b) Grikiewicz, G.; BeMiller, J . N.; Carbohydr.
Res. 1982, 108, 229-236. (c) Overkleeft, H. S.; Verhelst, S. H. L.;
Pieterman, E.; Meeuwenoord, N. J .; Overhand, M.; Cohen, L. H.; Marel,
G. A.; Boom, J . H. Tetrahedron Lett. 1999, 40, 4103-4106.
(18) Raadt, A.; Griengl, H.; Klempier, N.; Stu¨tz, A. E. J . Org. Chem.
1993, 58, 3179-3184.
(19) Utimoto, K.; Wakabayashi, Y.; Horiie, T.; Inoue, M.; Shish-
iyama, Y.; Obayashi, M.; Nozaki, H. Tetrahedron 1983, 39, 967-973.
(20) Bols, M.; Binderup, L.; Hansen, J .; Rasmussen, P. J . Med.
Chem. 1992, 35, 2768-2771. Chassagne, D.; Crouzet, J .; Bayonove,
C. L.; Baumes, R. L. J . Agric. Food Chem. 1998, 46, 4352-4357.
(21) Levy, D. E.; Tang, C. The Chemistry of C-Glycosides; Pergamon
Press: Oxford, 1995; pp 30-42.
(11) Togo, H.; Hoshina, Y.; Muraki, T.; Nakayama, H.; Yokoyama,
M. J . Org. Chem. 1998, 63, 5193-5200.
(12) For a preliminary account of this work, see: Francisco, C. G.;
Herrera, A. J .; Sua´rez, E. Tetrahedron: Asymmetry 2000, 11, 3879-
3882.
J . Org. Chem, Vol. 68, No. 3, 2003 1013

Francisco et al.
TABLE 1. Syn th esis of Hom och ir a l
SCHEME 3. Su bstr a tes for th e
7-Oxa -2-a za bicyclo[2.2.1]h ep ta n e System a
8-Oxa -6-a za bicyclo[3.2.1]octa n e Ser iesa
a
Reagents: (a) (i) LAH, THF, reflux, 30 min; (ii) (BnO)2P(O)Cl,
TEA, CHCl3, rt, 1.5 h, 54%; (b) (i) LAH, THF, rt, (ii) (PhO)2P(O)Cl,
TEA, CHCl3, rt; (c) (i) LAH, THF, reflux, 1 h, (ii) dibenzyl
dicarbonate, TEA, THF, 57%; (d) (i) LAH, THF, rt, 1 h, (ii) di-tert-
butyl dicarbonate, DMF, rt, 1.5 h, 49%; (e) ZnN6‚2Py, Ph3P, DIAD,
MePh, rt, 30 h, 65%.
a
All reactions were performed at room temperature under
nitrogen containing iodosylbenzene (2 mmol) and iodine per mmol
of substrate in the solvent specified in the Experimental Section
and under irradiation with two 80 W tungsten-filament lamps.
derivatives 12, 14, 16, and 21-23 (Scheme 3). The
phosphoramidate 19 was prepared accordingly by azida-
tion-reduction of the known alcohol 17.13 These poly-
functionalized amides were synthesized to delineate the
influence of the substituents in the IHA reaction.
We elected phenyl and benzyl amidophosphates and
alkyl and benzyl carbamates derivatives not only to avoid
the oxidation of the amine groups during the formation
of the iodoamide, but also because they will exert a
control on the stability of the N-radical during the IHA
reaction. Furthermore, the regeneration of the disubsti-
tuted amine at the end of the process should be possible,
since they are suitable amino-protecting groups.
The synthesis of homochiral 7-oxa-2-azabicyclo[2.2.1]-
heptane systems from C-glycoside derivatives of carbo-
hydrates in furanose form are shown in Table 1. The
reactions were accomplished in two ways: from a phos-
phoramidate group at the side chain of a D-ribo, sub-
strates 3 and 6 (Table 1, entries 1 and 2), or by placing
the amide group on a tether attached to the C-1 of
D-mannofuranose derivatives 9 and 10 (Table 1, entries
3 and 4). In both cases, we avoided the interaction with
the neighboring protective ring, and the IHA reaction
with iodosylbenzene and iodine proceeded smoothly to
give azabicycles 24-27 in good to excellent yields (Table
1, entries 1-4). The structures were confirmed by 1H and
13C NMR spectra (DEPT, COSY, and HMBC experi-
ments), revealing in all cases a selective abstraction of
the shown proton.
Solid NaHCO3 was added. c At reflux temperature, irradiation
was omitted.
b
when further modification of the molecule is required
(entry 2). In preliminary experiments some hydrolysis
of the acid-sensitive 1,2-isopropylidene group of the di-
O-isopropylidene-D-mannofuranoses 9 and 10 was ob-
served, probably autocatalyzed by the acidity of the amide
groups. This could be avoided by adding an equimolecular
amount of solid NaHCO3 to the reaction mixture (Table
1, entries 3 and 4). The conformational rigidity that the
[3.3.1]bicycle confers to the starting materials seems to
play a critical role in the IHA reaction. Attempts to
perform the reaction on a more flexible structure such
as 4,7-anhydro-1,2,3,8-tetradeoxy-8-[(diphenoxyphospho-
ryl)amino]-5,6-di-O-methyl-D-altro-octitol (A) were unsuc-
cessful.22
The results obtained during the synthesis of the 8-oxa-
6-azabicyclo[3.2.1]octane ring system are summarized in
(22) The reaction of A with DIB/I2 or PhIO/I2 under different
conditions gave a complex mixture. Hydrogen abstraction from other
positions (e.g. 5) and radical â-fragmentation reactions could possibly
compete.
The use of a carbonate to protect the cis-diol did not
change the cyclization yield and this should be convenient
1014 J . Org. Chem., Vol. 68, No. 3, 2003

Intramolecular Hydrogen Abstraction Reaction
TABLE 2. Syn th esis of Hom och ir a l
8-Oxa -6-a za bicyclo[3.2.1]octa n e System a
stereochemistry at C-5, we could not find a plausible
explanation other than steric interference between the
bulky diphenyl phosphoramidate group and the vicinal
syn R-methyl ether.
The 8-oxa-6-azabicyclo[3.2.1]octane ring system can
also be obtained from the C-glycoxyl derivatives of
L-rhamnose 21-23 (Table 2, entries 5-7). The IHA
reaction proceeded this time on the â-side of the molecule
through a chairlike six-membered transition state to give
the L-altro-hept-2-ulopyranose derivatives 32-34. The
1
carbohydrate ring was in a more stable C4 chair confor-
mation. This allowed the required approach between the
N-radical and the hydrogen at C-6 for the IHA reaction
to take place.
It is clear from the above examples and previous work
of this group23 that this reagent system is very tolerant
of the common carbohydrate protective groups and that
this modified HLF reaction provides a suitable strategy
for the synthesis of these sensitive N,O-protected ulose
derivatives. Other notable features of this one-step
methodology in comparison with the traditional HLF
reaction are the following: (a) The unstable iodoamide
intermediates are generated in situ. (b) The iodoamide
homolysis proceeds thermally at low temperature (20-
40 °C) or by irradiation with visible light, ultraviolet light
being unnecessary.
Exp er im en ta l Section
Gen er a l Meth od s. Melting points were determined with
a hot-stage apparatus. Optical rotations were measured at the
sodium line at ambient temperature in CHCl3 solutions unless
otherwise stated. IR spectra were obtained as a thin film
smeared onto NaCl plates. NMR spectra were determined at
500 MHz for 1H and 125.7 MHz for 13C in CDCl3, 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) was 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.
“Usual workup” means aqueous treatment, extraction with
CH2Cl2, washing with 10% aqueous sodium thiosulfate, drying
with Na2SO4, filtration, and evaporation in vacuo. All reactions
involving air- or moisture-sensitive materials were carried out
under a nitrogen atmosphere. The spray reagent for TLC
analysis was 0.5% vanillin in H2SO4-EtOH (4:1) and further
heating until development of color.
a
All reactions were performed at room temperature under
nitrogen containing iodine in CH2Cl2 and under irradiation with
two 80 W tungsten-filament lamps. Method A, PhIO was used.
Method B, DIB was used. At reflux temperature, irradiation was
b
omitted.
Table 2. The reactions of the first four examples proceed
on the R-side of the molecule with the carbohydrate ring
in its more stable C1 chair conformation, which allows
4
a 1,3-diaxial relationship between the phosphoramidate
tether at C-6 and the hydrogen atom at C-2 (Table 2,
entries 1-4). In preliminary studies, observations were
made that the use of (diacetoxyiodo)benzene (DIB) re-
duced the oxa-azabicyclo yield as a consequence of the
external nucleophilic competition of the acetyl group. In
the reaction of compound 14 with DIB (method B), under
the conditions shown in entry 2, after 1.75 h of reaction,
the desired anhydro 29 (68%) was accompanied by minor
amounts (5%) of 2-O-acetyl-4,5,7-trideoxy-7-[(diphenoxy-
phosphoryl)amino]-1,3-di-O-methyl-D-threo-hept-2-ulopy-
ranose. Notwithstanding, when the reaction was stopped
at earlier stages (45 min), the above-mentioned 2-acetate,
coming from external nucleophilic attack, was the prin-
cipal product of the reaction (65%). Without a doubt, the
tertiary acetate formed initially is transformed over time
into the bicycle by acid-catalyzed cyclization under the
reaction conditions.
Meth yl 3,7-An h yd r o-2,7-d id eoxy-7-[(d ip h en oxyp h os-
p h or yl)a m in o]-4,5-O-isop r op ylid en e-D-r ibo-h ep t -3-u lo-
fu r a n oson a te (24). A solution of the amide 3 (25.5 mg, 0.053
mmol) in a mixture of CH2Cl2-cyclohexane (1:1) (3 mL)
containing iodosylbenzene (22 mg, 0.106 mmol) and iodine (15
mg, 0.064 mmol) was irradiated with two 80 W tungsten-
filament lamps at room temperature under nitrogen for 80
min. The usual workup followed by column chromatography
(hexanes-EtOAc, 85:15) afforded the anhydrosugar 24 (19 mg,
0.04 mmol, 75%) as a colorless oil: [R]D -46.5 (c ) 0.97); IR
1
2988, 2950, 1747, 1591, 1488, 1191 cm-1; H NMR 1.19 (3H,
s), 1.40 (3H, s), 3.06 (1H, dd, J ) 3.0, 8.1 Hz), 3.20 (1H, d, J
) 16.1 Hz), 3.33 (1H, dddd, J ) 3.7, 3.7, 3.7, 4.0 Hz), 3.44 (1H,
d, J ) 16.5 Hz), 3.56 (3H, s), 4.23 (1H, d, J ) 5.2 Hz), 4.37
The much lower yield obtained for the D-gluco anhydro
derivative 30 (Table 2, entry 3) when compared with the
D-manno analogue 31 (entry 4) was somewhat surprising.
Although it is presumably due to the difference of the
(23) (a) Francisco, C. G.; Herrera, A. J .; Sua´rez, E. J . Org. Chem.
2002, 67, 7439-7445. (b) Francisco, C. G.; Freire, R.; Herrera, A. J .;
Pe´rez-Mart´ın, I.; Sua´rez, E. Org. Lett. 2002, 4, 1959-1961. (c)
Gonza´lez, C. G.; Kennedy, A. R.; Leo´n, E. I.; Riesco-Fagundo, C.;
Sua´rez, E. Angew. Chem., Int. Ed. 2001, 40, 2326-2327.
J . Org. Chem, Vol. 68, No. 3, 2003 1015

Francisco et al.
(1H, d, J ) 5.5 Hz), 4.61 (1H, d, J ) 5.2 Hz), 7.1-7.34 (10H,
(C); MS (EI) m/z (rel intensity) 371 (M+, 6), 356 (1), 300 (12);
HRMS calcd for C18H29NO7 371.1943853, found 371.190636.
Anal. Calcd for C18H29NO7: C, 58.20; H, 7.87; N, 3.77. Found:
C, 58.35; H, 7.81; N, 3.72.
m); 13C NMR 25.3 (CH3), 25.8 (CH3), 33.1 (CH2), 47.2 (CH2),
3
51.6 (CH3), 78.7 (CH, J CP ) 6.1 Hz), 81.1 (CH), 83.8 (CH),
2
95.9 (C, J CP ) 8.8 Hz), 112.4 (C), 120.1 (4 × CH), 125.7 (2 ×
CH), 129.7 (4 × CH), 150.7 (2 × C), 168.7 (C); MS (EI) m/z
(rel intensity) 475 (M+, 24), 460 (3), 417 (98), 324 (100); HRMS
calcd for C23H26NO8P 475.1395896, found 475.13797. Anal.
Calcd for C23H26NO8P: C, 58.10; H, 5.51; N, 2.95. Found: C,
58.04; H, 5.62; N, 3.01.
2,7-An h yd r o-7-{[bis(ben zyloxy)p h osp h or yl]a m in o}-1-
O-(ter t-bu tyldim eth yl)silyl-3,4,5,7-tetr a deoxy-â-D-glycer o-
h ep -2-u lop yr a n ose (28). A solution of the amide 12 (20 mg,
0.038 mmol) in dry CH2Cl2 (3 mL) containing iodosylbenzene
(17.5 mg, 0.076 mmol), iodine (10 mg, 0.038 mmol), and solid
NaHCO3 (20 mg) was heated at reflux temperature under
nitrogen for 100 min. The usual workup followed by column
chromatography (hexanes-EtOAc, 70:30) afforded the anhy-
drosugar 28 (13 mg, 0.025 mmol, 66%) as a colorless oil: [R]D
1,2,3,8-Tetr a d eoxy-8-[(d ip h en oxyp h osp h or yl)a m in o]-
5,6-O-oxom eth ylen e-D-r ibo-oct-4-u lofu r a n ose (25). A solu-
tion of the amide 6 (165 mg, 0.38 mmol) in dry CH2Cl2 (7 mL)
containing iodosylbenzene (168 mg, 0.76 mmol) and iodine (97
mg, 0.38 mmol) was irradiated with two 80 W tungsten-
filament lamps at room temperature under nitrogen for 1.75
h. The usual workup followed by Chromatotron chromatogra-
phy (hexanes-EtOAc, 80:20f70:30) afforded the anhydro-
sugar 25 (120 mg, 0.28 mmol, 74%) as a colorless oil: [R]D +10
(c ) 0.58); IR 3055, 2966, 1814, 1487, 1160 cm-1; 1H NMR 0.90
(3H, t, J ) 7.3 Hz), 1.46 (2H, m), 2.09 (1H, ddd, J ) 5.3, 10.7,
15.5 Hz), 2.39 (1H, ddd, J ) 4.8, 10.7, 15.3 Hz), 3.31 (1H, dd,
J ) 3.4, 9.0 Hz), 3.41 (1H, dd, J ) 4.3, 9.0 Hz), 4.62 (1H, d, J
) 6.0 Hz), 4.69 (1H, d, J ) 6.0 Hz), 4.79 (1H, d, J ) 4.4 Hz),
7.22 (6H, m), 7.35 (4H, m); 13C NMR 13.3 (CH3), 15.2 (CH2),
1
-17 (c ) 1.1); IR 2927, 1462, 1017 cm-1; H NMR (200 MHz)
0.04 (6H, s), 0.87 (9H, s), 1.38-1.92 (6H, m), 3.30 (2H, m), 3.84
(1H, d, J ) 11.1 Hz), 4.08 (1H, d, J ) 11.1 Hz), 4.98-5.08
(4H, m), 7.32 (10H, br s); 13C NMR (50.3 MHz) -5.1 (CH3),
-5.4 (CH3), 16.3 (CH2), 18.5 (C), 26.0 (3 × CH3), 28.6 (CH2),
2
30.7 (CH2), 50.7 (CH2, J CP ) 4.3 Hz), 66.4 (CH2), 67.7 (CH2,
2J CP ) 5.5 Hz), 68.0 (CH2, 2J CP ) 5.5 Hz), 74.2 (CH, 3J CP ) 8.8
2
Hz), 96.7 (C, J CP ) 10.1 Hz), 127.6 (4 × CH), 128.2 (2 × CH),
128.5 (4 × CH), 136.5 (2 × C); MS (EI) m/z (rel intensity) 517
(M+, <1), 502 (<1), 484 (1), 460 (17), 91 (100); HRMS calcd
for C27H40NO5PSi 517.2413207, found 517.241501. Anal. Calcd
for C27H40NO5PSi: C, 62.64; H, 7.79; N, 2.71. Found: C, 62.45;
H, 7.81; N, 2.75.
3
27.8 (CH2), 47.1 (CH2), 78.0 (CH, J CP ) 6.1 Hz), 79.3 (CH),
2
80.8 (CH), 98.1 (C, J CP ) 9.2 Hz), 119.1 (2 × CH), 119.3 (2 ×
CH), 124.8 (2 × CH), 129.1 (2 × CH), 129.2 (2 × CH), 149.4
(C), 149.5 (C), 153.0 (C); MS (EI) m/z (rel intensity) 431
(M+, 41), 387 (53), 345 (39); HRMS calcd for C21H22NO7P
431.1133771, found 431.113914. Anal. Calcd for C21H22NO7P:
C, 58.47; H, 5.14; N, 3.25. Found: C, 58.66; H, 5.22; N, 3.33.
2,7-An h yd r o-4,5,7-tr id eoxy-7-[(d ip h en oxyp h osp h or yl)-
am in o]-1,3-di-O-m eth yl-â-D-th r eo-h ept-2-u lopyr an ose (29).
A solution of the amide 14 (80 mg, 0.19 mmol) in dry CH2Cl2
(5 mL) containing (diacetoxyiodo)benzene (DIB) (92 mg, 0.285
mmol) and iodine (48 mg, 0.19 mmol) was irradiated with two
80 W tungsten-filament lamps at room temperature under
nitrogen for 110 min. The usual workup followed by column
chromatography (hexanes-EtOAc, 60:40) afforded the anhy-
drosugar 29 (54 mg, 0.13 mmol, 68%) and 2-O-acetyl-4,5,7-
trideoxy-7-[(diphenoxyphosphoryl)amino]-1,3-di-O-methyl-D-
threo-hept-2-ulopyranose (4 mg, 0.01 mmol, 5%). Compound
29: colorless oil; [R]D -27.6 (c ) 0.21); IR 3066, 2945, 1591,
3,7-An h ydr o-7-deoxy-7-[(diph en oxyph osph or yl)am in o]-
1,2:4,5-di-O-isopr opyliden e-D-a llo-h ept-3-u lofu r an ose (26)
A solution of the amide 9 (15 mg, 0.03 mmol) in a mixture of
CH2Cl2-cyclohexane (1:1) (3 mL) containing iodosylbenzene
(13 mg, 0.06 mmol), iodine (9 mg, 0.036 mmol), and solid
NaHCO3 (15 mg) was irradiated with two 80 W tungsten-
filament lamps at room temperature under nitrogen for 1 h.
The usual workup followed by column chromatography
(hexanes-EtOAc, 70:30) afforded the anhydrosugar 26 (14.5
mg, 0.029 mmol, 96%) as a crystalline solid: mp 136-137 °C
(from n-pentane-EtOAc); [R]D -37.5 (c ) 0.31); IR 2986, 1593,
1489, 1198 cm-1; 1H NMR 1.16 (3H, s), 1.28 (3H, s), 1.33 (3H,
s), 1.39 (3H, s), 3.10 (1H, dd, J ) 3.0, 8.2 Hz), 3.20 (1H, ddd,
J ) 4.0, 8.3, 11.8 Hz), 4.12 (2H, d, J ) 6.9 Hz), 4.20 (1H, d, J
) 5.2 Hz), 4.32 (1H, d, J ) 5.6 Hz), 4.63 (1H, d, J ) 3.9 Hz),
5.03 (1H, dd, J ) 7.1, 7.1 Hz), 7.10-7.35 (10H, m); 13C NMR
24.8 (CH3), 25.5 (CH3), 25.5 (CH3), 26.0 (CH3), 47.1 (CH2), 66.1
1488 cm-1 1H NMR (200 MHz) 1.58 (1H, m), 1.61 (1H, m),
;
1.89 (1H, m), 2.02 (1H, m), 3.29 (3H, s), 3.37 (3H, s), 3.37 (1H,
d, J ) 6.7 Hz), 3.51 (1H, dd, J ) 5.6, 9.6 Hz), 3.58 (1H, dd, J
) 7.0, 7.0 Hz), 3.74 (1H, d, J ) 10.3 Hz), 4.5 (1H, s), 4.19 (1H,
d, J ) 10.3 Hz), 7.1-7.32 (10H, m); 13C NMR 22.3 (CH2), 28.9
(CH2), 50.7 (CH2), 56.4 (CH3), 59.1 (CH3), 71.6 (CH2), 73.5 (CH,
2
3J CP ) 8.5 Hz), 77.3 (CH), 96.9 (C, J CP ) 10.5 Hz), 120.3 (4 ×
CH), 124.4 (2 × CH), 129.3 (4 × CH), 137.7 (2 × C); MS (EI)
m/z (rel intensity) 419 (M+, 83), 404 (70); HRMS calcd for
C
C
21H26NO6P 419.1497614, found 419.147217. Anal. Calcd for
21H26NO6P: C, 60,14; H, 6,25; N, 3,34. Found: C, 60.11; H,
3
(CH2), 71.7 (CH), 78.8 (CH, J CP ) 7.6 Hz), 81.2 (CH), 83.1
(CH), 97.6 (C, 2J CP ) 11.4 Hz), 108.3 (C), 112.3 (C), 120.1 (2 ×
CH), 120.3 (2 × CH), 124.8 (CH), 125.1 (CH), 129.3 (2 × CH),
129.6 (2 × CH), 150.7 (2 × C); MS (EI) m/z (rel intensity) 503
(M+, 38), 488 (22), 445 (9); HRMS calcd for C25H30NO8P
503.170888, found 503.173279. Anal. Calcd for C25H30NO8P:
C, 59.64; H, 6.01; N, 2.78. Found: C, 59.98; H, 6.23; N, 2.46.
6.42; N, 3.53. Acetylated compound: colorless oil; 1H NMR (200
MHz) 1.31 (1H, m), 1.55-2.0 (3H, m), 1.99 (3H, s), 3.05 (1H,
m), 3.16 (1H, m), 3.33 (3H, s), 3.33 (3H, s), 3.41 (1H, m), 3.68
(1H, m), 3.76 (1H, d, J ) 9.9 Hz), 3.99 (1H, d, J ) 9.9 Hz); 13
NMR (50.3 MHz) 20.9 (CH2), 21.3 (CH2), 21.9 (CH3), 45.8 (CH2),
57.3 (CH3), 59.3 (CH3), 70.2 (CH2), 71.6 (CH, J CP ) 6.1 Hz),
C
3
72.4 (CH), 103.2 (C), 120.3 (4 × CH), 124.8 (2 × CH), 129.6 (4
× CH), 135.3 (2 × C), 168.6 (C); MS (EI) m/z (rel intensity)
420 (M+ - C3H7O, 8), 406 (6); HRMS calcd for C20H23NO7P
420.1212017, found 420.127136. Anal. Calcd for C23H30NO8P:
C, 57.62; H, 6.31; N, 2.92. Found: C, 57.83; H, 6.42; N, 3.01.
When, under the same conditions, the reaction was interrupted
after 50 min, the acetyl derivative was the major product (65%)
with only 11% of the anhydrosugar 29.
2,7-An h ydr o-7-deoxy-7-[(diph en oxyph osph or yl)am in o]-
1,3,4,5-tetr a -O-m eth yl-â-D-id o-h ep t-2-u lop yr a n ose (30). A
solution of the amide 16 (57 mg, 0.118 mmol) in dry CH2Cl2
(6 mL) containing iodosylbenzene (116 mg, 0.53 mmol) and
iodine (30 mg, 0.118 mmol) was irradiated with two 80 W
tungsten-filament lamps at room temperature under nitrogen
for 7 h. The usual workup followed by Chromatotron chroma-
tography (hexanes-EtOAc, 60:40) afforded the anhydrosugar
30 (25 mg, 0.052 mmol, 44%) as a colorless oil: [R]D -14 (c )
3,7-An h yd r o-7-d eoxy-7-[(ter t-bu toxyca r bon yl)a m in o]-
1,2:4,5-di-O-isopr opyliden e-D-a llo-h ept-3-u lofu r an ose (27).
A solution of the amide 10 (30 mg, 0.08 mmol) in dry CH2Cl2
(3 mL) containing iodosylbenzene (35 mg, 0.16 mmol), iodine
(20 mg, 0.08 mmol), and solid NaHCO3 (30 mg) was heated at
reflux temperature under nitrogen for 10 h. The usual workup
followed by column chromatography (hexanes-EtOAc, 75:25)
afforded the anhydrosugar 27 (25 mg, 0.067 mmol, 84%) as a
crystalline solid: mp 90-91.5 °C (from n-hexanes-EtOAc);
[R]D -59.5 (c ) 0.36, CCl4); IR 2981, 2937, 1694, 1403, 1255,
1210, 1165, 1088 cm-1; 1H NMR 1.26 (3H, s), 1.39 (3H, s), 1.41
(3H, s), 1.43 (3H, s), 1.48 (9H, s), 3.09 (1H, br d, J ) 8.2 Hz),
3.36 (1H, dd, J ) 4.2, 9.6 Hz), 4.13 (2H, d, J ) 6.8 Hz), 4.31
(1H, br s), 4.41 (1H, br s), 4.56 (1H, d, J ) 4.2 Hz), 4.90 (1H,
br s); 13C NMR 25.1 (CH3), 25.6 (CH3), 25.9 (CH3), 26.0 (CH3),
28.3 (3 × CH3), 46.8 (CH2), 66.4 (CH2), 72.1 (CH), 78.0 (CH),
81.5 (2 × CH), 81.7 (C), 95.8 (C), 108.5 (C), 112.6 (C), 155.8
1016 J . Org. Chem., Vol. 68, No. 3, 2003

Intramolecular Hydrogen Abstraction Reaction
0.34); IR 3069, 2933, 1592, 1488, 1106 cm-1; 1H NMR 3.29 (1H,
dd, J ) 8.0, 8.0 Hz), 3.37 (1H, dd, J ) 4.4, 8.3 Hz), 3.38 (3H,
s), 3.39 (1H, d, J ) 7.8 Hz), 3.44 (3H, s), 3.45 (1H, m), 3.49
(3H, s), 3.50 (3H, s), 3.60 (1H, dd, J ) 1.9, 10.8 Hz), 3.62 (1H,
d, J ) 10.4 Hz), 4.24 (1H, d, J ) 10.4 Hz), 4.49 (1H, dd, J )
5.1, 5.1 Hz), 7.13-7.34 (10H, m); 13C NMR 46.3 (CH2), 57.8
(CH3), 58.4 (CH3), 59.2 (CH3), 59.8 (CH3), 70.6 (CH2), 72.3 (CH,
C22H28NO7P: C, 58.79; H, 6.28; N, 3.12. Found: C, 58.99; H,
6.22; N, 2.95.
2,7-An h yd r o-7-{[(b en zyloxy)ca r b on yl]a m in o}-1,7-d i-
deoxy-3,4,5-tr i-O-m eth yl-â-L-a ltr o-h ept-2-u lopyr an ose (33).
A solution of the amide 22 (190 mg, 0.538 mmol) in dry CH2-
Cl2 (10 mL) containing DIB (313 mg, 0.97 mmol) and iodine
(137 mg, 0.54 mmol) was irradiated with two 80 W tungsten-
filament lamps at room temperature under nitrogen for 8 h.
The usual workup followed by Chromatotron chromatography
(hexanes-EtOAc, 70:30 f 60:40) afforded the anhydrosugar
33 (155 mg, 0.441 mmol, 82%) as a colorless oil: [R]D +94 (c )
2
3J CP ) 8.6 Hz), 80.4 (CH), 82.9 (CH), 83.2 (CH), 95.4 (C, J CP
) 11.2 Hz), 119.1 (2 × CH), 119.6 (2 × CH), 123.8 (CH), 123.9
(CH), 128.6 (2 × CH), 128.8 (2 × CH), 150.0 (C), 150.4 (C);
MS (EI) m/z (rel intensity) 479 (M+, 4), 464 (4), 448 (29); HRMS
calcd for C23H30NO8P 479.170888, found 479.164001. Anal.
Calcd for C23H30NO8P: C, 57.62; H, 6.31; N, 2.92. Found: C,
57.72; H, 6.29; N, 3.00.
1
1.38); IR 2923, 2952, 1723, 1112 cm-1; H NMR (60 °C) 1.79
(3H, br s), 3.23 (1H, d, J ) 10.4 Hz), 3.28 (1H, dd, J ) 4.2, 8.8
Hz), 3.33 (1H, d, J ) 8.8 Hz), 3.47 (3H, s), 3.52 (3H, s), 3.54
(1H, m), 3.56 (3H, s), 3.67 (1H, dd, J ) 6.9, 10.4 Hz), 4.52 (1H,
dd, J ) 2.1, 6.9 Hz), 5.10 (1H, d, J ) 12.5 Hz), 5.18 (1H, d, J
) 12.5 Hz), 7.29-7.38 (5H, m); 13C NMR (60 °C) 20.4 (CH3),
47.8 (CH2), 57.9 (CH3), 58.0 (CH3), 61.1 (CH3), 66.9 (CH2), 71.8
(CH), 77.8 (CH), 80.4 (CH), 86.0 (CH), 93.9 (C), 127.7 (2 × CH),
127.7 (CH), 128.3 (2 × CH), 136.7 (C), 156.5 (C); MS (EI) m/z
(rel intensity) 351 (M+, 2), 336 (2), 320 (72), 91 (100); HRMS
calcd for C18H25NO6 351.1681728, found 351.168671. Anal.
Calcd for C18H25NO6: C, 61.52; H, 7.17; N, 3.99. Found: C,
61.40; H, 7.37; N, 4.01.
2,7-An h yd r o-7-[(ter t-bu toxyca r bon yl)a m in o]-1,7-d id e-
oxy-3,4,5-tr i-O-m eth yl-â-L-a ltr o-h ep t-2-u lop yr a n ose (34).
A solution of the amide 23 (244 mg, 0.76 mmol) in dry CH2Cl2
(2 mL) containing DIB (492 mg, 1.53 mmol) and iodine (145
mg, 0.57 mmol) was irradiated with two 80 W tungsten-
filament lamps at room temperature under nitrogen for 85
min. The usual workup followed by column chromatography
(hexanes-EtOAc, 25:75) afforded the anhydrosugar 34 (210
mg, 0.66 mmol, 87%) as a colorless oil: [R]D +100 (c ) 0.8); IR
2977, 1714, 1682, 1402, 1114 cm-1; 1H NMR 1.45 (9H, s), 1.73
(3H, s), 3.16 (1H, m), 3.24 (1H, m), 3.28 (1H, d, J ) 8.6 Hz),
3.44 (3H, s), 3.50 (3H, s), 3.51 (1H, m), 3.54 (3H, s), 3.60 (1H,
dd, J ) 7.2, 10.4 Hz), 4.51 (1H, br d, J ) 7.0 Hz); 13C NMR
21.1 (CH3), 28.3 (3 × CH3), 47.5 (CH2), 57.8 (2 × CH3), 58.0
(CH3), 61.1 (CH), 71.2 (CH), 77.7 (CH), 80.0 (CH), 81.1 (C),
85.9 (CH), 93.4 (C), 150.7 (C); MS (EI) m/z (rel intensity) 317
(M+, 1), 286 (15); HRMS calcd for C15H27NO6 317.183822, found
317.183006. Anal. Calcd for C15H27NO6: C, 56.76; H, 8.57; N,
4.41. Found: C, 56.38; H, 8.93; N, 4.42.
2,7-An h ydr o-7-deoxy-7-[(diph en oxyph osph or yl)am in o]-
1,3,4,5-tetr a -O-m eth yl-â-D-a ltr o-h ep t-2-u lop yr a n ose (31).
A solution of the amide 19 (25 mg, 0.052 mmol) in dry CH2Cl2
(5 mL) containing iodosylbenzene (22 mg, 0.104 mmol) and
iodine (13 mg, 0.052 mmol) was irradiated with two 80 W
tungsten-filament lamps at room temperature under nitrogen
for 40 min. The usual workup followed by column chromatog-
raphy (hexanes-EtOAc, 25:75) afforded the anhydrosugar 31
(20 mg, 0.04 mmol, 80%) as a colorless oil: [R]D -66.5 (c )
1.71); IR 3075, 2979, 2932, 2891, 2824, 1592, 1455, 1287, 1195,
1126 cm-1; 1H NMR 3.16 (1H, br d, J ) 9.1 Hz), 3.34 (1H, dd,
J ) 4.1, 8.6 Hz), 3.37 (6H, s), 3.48 (3H, s), 3.49 (1H, dd, J )
2.5, 4.1 Hz), 3.53 (3H, s), 3.57 (1H, d, J ) 8.6 Hz), 3.61 (1H,
ddd, J ) 2.0, 6.6, 9.1 Hz), 3.85 (1H, d, J ) 10.2 Hz), 4.13 (1H,
d, J ) 10.2 Hz), 4.71 (1H, br d, J ) 6.6 Hz); 13C NMR 47.2
(CH2), 56.9 (CH3), 57.4 (CH3), 58.3 (CH3), 59.7 (CH3), 69.8
3
(CH2), 72.1 (CH, J CP ) 9.1 Hz), 76.7 (CH), 79.0 (CH), 80.9
2
(CH), 96.1 (C, J CP ) 9.1 Hz), 119.3 (2 × CH), 119.5 (2 × CH),
123.9 (2 × CH), 128.7 (2 × CH), 128.8 (2 × CH), 150.1 (C),
150.3 (C); MS (EI) m/z (rel intensity) 479 (M+, 5), 464 (7), 448
(60), 416 (4); HRMS calcd for C23H30NO8P 479.170888, found
479.168571. Anal. Calcd for C23H30NO8P: C, 57.62; H, 6.31;
N, 2.92. Found: C, 57.72; H, 6.42; N, 2.94.
2,7-An h yd r o-1,7-d id eoxy-7-[(d ip h en oxyp h osp h or yl)-
a m in o]-3,4,5-t r i-O-m et h yl-â-L-a ltr o-h ep t -2-u lop yr a n ose
(32). A solution of the amide 21 (52 mg, 0.115 mmol) in dry
CH2Cl2 (2.5 mL) containing DIB (50 mg, 0.15 mmol) and iodine
(30 mg, 0.115 mmol) was irradiated with two 80 W tungsten-
filament lamps at room temperature under nitrogen for 75
min. The usual workup followed by column chromatography
(n-hexanes-EtOAc, 50:50) afforded the anhydrosugar 32 (34
mg, 0.08 mmol, 69%) as a crystalline solid: mp 101-102 °C
(from n-hexane-CH2Cl2); [R]D +87.5 (c ) 0.64); IR 2935, 2829,
1592, 1489, 1195 cm-1; 1H NMR 1.77 (3H, s), 3.11 (1H, d, J )
9.1 Hz), 3.24 (1H, dd, J ) 4.0, 8.8 Hz), 3.28 (1H, d, J ) 8.8
Hz), 3.34 (3H, s), 3.45 (1H, dd, J ) 2.6, 4.0 Hz), 3.48 (3H, s),
3.52 (3H, s), 3.58 (1H, ddd, J ) 2.7, 6.4, 9.0 Hz), 4.59 (1H, d,
J ) 6.6 Hz), 7.1-7.3 (10H, m); 13C NMR 21.1 (CH3), 48.2 (CH2),
Ack n ow led gm en t. This work was supported by the
Investigation Programs no. BQU2000-0650 and
BQU2001-1665 of the Direccio´n General de Investiga-
cio´n Cient´ıfica y Te´cnica, Spain. A.J .H. thanks the
Ministerio de Educacio´n y Ciencia, Spain for fellowships.
Su p p or tin g In for m a tion Ava ila ble: A complete descrip-
tion of experimental details and characterization data for
compounds 2, 3, 5, 6, 8-10, 12-14, 16, and 18-23. This
material is available free of charge via the Internet at
http://pubs.acs.org.
3
58.1 (CH3), 58.2 (CH3), 60.9 (CH3), 72.6 (CH, J CP ) 8.4 Hz),
77.7 (CH), 79.8 (CH), 85.6 (CH), 96.1 (C, 2J CP ) 9.4 Hz), 119.9
(CH), 120.1 (CH), 124.6 (2 × CH), 124.7 (2 × CH), 129.4 (2 ×
CH), 129.5 (2 × CH), 150.8 (C), 151.0 (C); MS (EI) m/z (rel
intensity) 449 (M+, 2), 434 (15), 418 (99); HRMS calcd for
C
22H28NO7P 449.1603247, found 449.160004. Anal. Calcd for
J O026314H
J . Org. Chem, Vol. 68, No. 3, 2003 1017