Organotransition Metal Modified Sugars, Part 10. Chromium Iminoglycosylidenes: Synthesis and Application to Photoinduced C-Glycosidation

Article abstract of DOI:10.1002/(SICI)1521-3765(19990201)5:2<691::AID-CHEM691>3.0.CO;2-E

The iminoglycosylidene complexes 3a,b, 9, and 16a,b are conveniently prepared from the sugar lactams 2a,b, 8, and 15a,b by reaction with K2Cr(CO)5 and subsequent deoxygenation with trimethylsilyl chloride (TMSCl). The Cr(CO)5-stabilized carbene moiety of the imino-D-ribo-pyranosylidene complexes 9 and 16a,b has been exploited in the photoinduced generation of ketene-like species on irradiation with UV light. These intermediates were trapped with methanol to produce the methyl 2,6-imino-D-allonates 10 and 17a,b. The C-glycosidation is β-selective and has been applied futher to the preparation of the galactosyl 2,6-imino-D-allonate 19. Solvent effects suggest that the diastereoselectivity originates in the chromium fragment, which shields the re face of the proposed ketene intermediate. - Keywords: chromium; carbene complexes; glycosides; iminosugars; photolysis

Full text of DOI:10.1002/(SICI)1521-3765(19990201)5:2<691::AID-CHEM691>3.0.CO;2-E

FULL PAPER
Organotransition Metal-Modified Sugars, Part 10=
Chromium Iminoglycosylidenes:
Synthesis and Application to Photoinduced C-Glycosidation
Karl Heinz Dötz,*[a] Markus Klumpe,[a] and Martin Nieger[b]
Dedicated to Professor Ernst Otto Fischer on the occasion of his 80th birthday
Abstract: The iminoglycosylidene com-
plexes 3a,b, 9, and 16a,b are conven-
iently prepared from the sugar lactams
2a,b, 8, and 15a,b by reaction with
K2Cr(CO)5 and subsequent deoxygena-
been exploited in the photoinduced
generation of ketene-like species on
irradiation with UV light. These inter-
mediates were trapped with methanol to
produce the methyl 2,6-imino-d-allo-
nates 10 and 17a,b. The C-glycosidation
is b-selective and has been applied
further to the preparation of the galac-
tosyl 2,6-imino-d-allonate 19. Solvent
effects suggest that the diastereoselec-
tivity originates in the chromium frag-
ment, which shields the re face of the
proposed ketene intermediate.
tion
with
trimethylsilyl
chloride
Keywords: chromium
´
carbene
(TMSCl). The Cr(CO)5-stabilized car-
bene moiety of the imino-d-ribo-pyra-
nosylidene complexes 9 and 16a,b has
complexes ´ glycosides ´ iminosu-
gars ´ photolysis
the case of lithiated or stannylated compounds. However,
some stable glycosyl complexes of various metals have been
prepared.[8] Our aim was to transfer the synthetic potential of
Introduction
Naturally occurring and synthetic iminosugars are the focus of
much attention, as they are found to be potent glycosidase
inhibitors.[1] They are therefore useful as antiviral, antidia-
betic, antimetastatic, and metabolic regulation agents.[2]
Several hundred of them have been synthesized to date by a
broad variety of approaches based mainly on ring-closing
reactions, such as intramolecular reductive amination,[3]
ˆ
Fischer-type amino carbene complexes [(CO)5Cr CR-
(NR'R'')] to iminosugar chemistry. We focused on insertion
reactions with alkynes for the construction of polycyclic
N-heterocycles,[9] and especially on the photolytic generation
of ketene equivalents, which may be trapped by imines and
oxygen or nitrogen nucleophiles to produce natural and
synthetic b-lactams, a-amino acid esters, or dipeptides.[10]
We now describe the synthesis of chromium- and tungsten-
stabilized imino-furanosylidene and -pyranosylidene com-
plexes and report the photolytic conversion of pentacarbonyl-
[iminopyranosylidene]chromium complexes to methyl[11] and
glycosyl 2,6-imino-D-aldonates. This represents the first
application of a metal-stabilized carbene moiety to the
carbon-chain elongation of iminosugars.
[4]
ˆ
amination of C C bonds, or intramolecular nucleophilic
amination.[5] However, synthetic methods for the carbon-
chain elongation/C-glycosidation of iminopyranoses are rare-
ly found in the literature,[6] and to our knowledge, there is only
one general route to the various C-glycosides of nojirimycin,
reported recently by Schmidt and co-workers.[7]
The use of organometallic chemistry in stereoselective
organic synthesis is well established, but its application to
carbohydrate chemistry is limited to a few examples, except in
Results and Discussion
[a] Prof. Dr. K. H. Dötz, Dipl.-Chem. M. Klumpe
Â
Kekule-Institut für Organische Chemie und Biochemie
der Universität Bonn
The two available synthetic pathways to amino carbene
complexes are i) the aminolysis of alkoxy carbene complexes
and ii) the Hegedus route[12] (Scheme 1), which is based on the
combination of amide or unsubstituted lactam electrophiles
with K2Cr(CO)5 as an organometalate nucleophile. Subse-
quent deoxygenation with TMSCl affords the desired amino
carbene complexes.
Gerhard-Domagk-Strasse 1, D-53121 Bonn (Germany)
Fax : (‡ 49)22-873-5813
E-mail: doetz@chemie.uni-bonn.de
[b] Dr. M. Nieger
Institut für Anorganische Chemie der Universität Bonn
Gerhard-Domagk-Strasse 1, D-53121 Bonn (Germany)
[=] Part 9: M. Klumpe, K. H. Dötz, Tetrahedron Lett. 1998, 39, 3683 ± 3684.
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K. H. Dötz et al.
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Scheme 2. Elimination of the C3-benzyloxy group in nojirilactam.
We started with the d-erythrono-1,4-lactam 1, which was
readily prepared from commercially available d-isoascorbic
acid.[16] Subsequent N-protection with either methyl iodide or
benzyl chloride resulted in the formation of the lactams 2a
and 2b, respectively (Scheme 3).
The d-ribono-1,5-lactam 8 was synthesized in 56% yield in
five steps from D-ribono-1,4-lactone, which was first protect-
ed as its 2,3-O-cyclohexylidene acetal 4 by acid (H2SO4)-
catalyzed condensation in cyclohexanone. Comparable results
have been reported for the reaction catalyzed by Amberlite
Scheme 1. Synthesis of amino carbene complexes.
‡
Although we have shown pre-
viously that aminolysis of fura-
nosylidene complexes followed
by intramolecular Mitsunobu
reaction provides a route to
both N-protected and N-un-
protected iminofuranosylidene
complexes,[13] the Hegedus pro-
cedure seems to be the method
of choice to obtain the imino-
glycosylidene complexes direct-
ly from the fully protected sug-
IR 120(H ) in benzene, but these conditions also afforded the
ar lactams.
Scheme 3. Synthesis of the sugar lactams 2a,b.
3,4-protected isomer as a side product.[17] The acetal 4 was
converted quantitatively to the tosylate 5 and then treated
with sodium azide in DMF to give the azido lactone 6.
Hydrogenation in the presence of 6 mol% palladium on
charcoal and subsequent protection of the resulting lactam 7
with methyl iodide produced the desired d-ribono-1,5-lactam
8 in an overall yield of 49% (Scheme 4).
A similar reaction sequence was used in the preparation of
lactams 15a and 15b. The azido derivative 13[19] was obtained
from the tosylated ribono-1,4-lactone 12 (synthesized by a
modified Mitchell reaction) in a yield of 88% after purifica-
tion. (Isolation of highly pure 13 is vital to the success of the
subsequent palladium-catalyzed hydrogenation.) Attempts to
perform this step from the crude azide as reported [20] were
unseccessful in our hands. Finally, the sugar lactam 14 was
treated with either methyl iodide or benzyl chloride to afford
the fully N- and O-protected d-ribono-1,5-lactams 15a
and 15b in overall yields of 52% (15a) and 44% (15b)
(Scheme 4).
Synthesis of iminoglycosylidene complexes: The pentacar-
bonyl chromate dianion is not only a potent nucleophile, but is
also a strong base. Consequently, earlier studies with perben-
zylated nojirilactam[14] had indicated that the benzyloxy group
at C-3 tends to undergo easy elimination, initiated by proton
abstraction at C-2[15] (Scheme 2). To avoid this undesired
reaction we turned our attention to the synthesis of sugar
lactams with an acetal protecting group at positions 2 and 3.
Abstract in German: Die Iminoglycosylidenkomplexe 3a,b, 9
und 16a,b können leicht aus den Zuckerlactamen 2a,b, 8 und
15a,b durch Reaktion mit K2Cr(CO)5 und nachfolgender
Deoxygenierung durch Chlortrimethylsilan dargestellt werden.
Die Pentacarbonylchrom-stabilisierte Carbenfunktionalität in
den Imino-d-ribo-pyranosyliden-Komplexen 9 und 16a,b
wurde durch Bestrahlung mit UV-Licht für die photoinduzierte
Generierung von ketenähnlichen Spezies ausgenutzt, welche
durch Methanol unter Bildung der 2,6-Imino-d-allonsäureme-
thylester 10 und 17a,b abgefangen wurden. Die C-Glycosidie-
rung verläuft b-selektiv und wurde auf die Darstellung des
Galactosyl-2,6-imino-d-allonates 19 übertragen. Lösungsmit-
teleffekte wiesen darauf hin, daû die Diastereoselektivitäten
durch das Chromfragment gesteuert werden, welches die re-
Seite des angenommenen Ketenintermediates abschirmt.
The sugar lactams 2a,b, 8, and 15a,b were converted to the
iminoglycosylidene complexes 3a ± c, 9, and 16a,b by an
efficient general procedure.[12] Cr(CO)6 was allowed to react
with a suspension of C8K in THF at 788C to produce
K2Cr(CO)5. Addition of a solution of the appropriate lactam
in THF, followed by the introduction of TMSCl, formed the
carbene complexes 3a,b and 16a,b in good yield, but the
692
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Chromium-Modified Sugars
691±699
Scheme 5. Conversion of sugar lactams to the iminoglycosylidene com-
plexes 3a ± c and 9, 16a,b.
Scheme 4. Synthesis of the sugar lactams 8 and 15a,b.
preparation of the cyclohexylidene acetal 9 was less efficient.
In this case, formation of the tetrahedral intermediate
(Scheme 1) may be hampered by the enhanced steric hin-
drance of the acetal protecting group in 8 compared with that
in 15. The complexes are easily separated from the graphite
precipitate by chromatography on a short silica column. An
analogous procedure can be applied to the generation of
pentacarbonyl tungsten-stabilized complexes as demonstrat-
ed for 3c in Scheme 5.
Figure 1. Molecular structure of complex 3a. Thermal ellipsoids are drawn
at the 50% probability level. Selected distances [pm] and angles [8]: Cr± C1
208.93(14), C1 ± N1 130.59(19), C1 ± C2 152.78(19), C2 ± C3 153.28(19),
C3 ± C4 151.0(2), C4 ± N 147.89(19); Cr-C1-N1 132.20(10), Cr-C1-C2
122.14(9), N-C1-C2 105.63(11), C1-N-C5 127.70(12), C1-N-C4 117.17(12),
C8-N-C4 115.12(12).
The molecular structures of complexes 3a and 3c exhibit
similar 4T3 and 2T3 conformations in the solid state (Figures 1
4
and 2), whereas 16a adopts a S2 conformation (Figure 3). In
Synthesis of methyl and glycosyl 2,6-iminoaldonates: In 1982,
McGuire and Hegedus discovered that irradiation of chromi-
um carbene complexes into the metal-to-ligand charge trans-
fer (MLCT) band (350 ± 450 nm) resulted in the insertion of a
CO ligand into the metal ± carbene bond to generate short-
lived alkoxy- or amino-substituted metal-bound ketenes.[10a]
This process is proposed to be reversible with regeneration of
the carbene complex (unless a reactive substrate is present),
and has been applied to a series of acyclic and cyclic amino
carbene complexes.[22] We speculated whether this method-
ology could be exploited in a novel route to iminosugar
C-glycosides. Complexes 9 and 16a,b were dissolved in
these three compounds the carbene carbon atom C1 is sp2-
hybridized and therefore coplanar with its nearest neighbors.
In addition, the pronounced double-bond character of the
C1 ± N bond is indicated by the significantly short bond
lengths (3a: 130.59, 3c: 131.0, 16a: 130.8 pm), combined with
a planar arrangement at the nitrogen atom, which reflects the
peculiar bonding of the metal-carbene fragment. In contrast
bond lengths of 132.6 pm and 136.0 pm (together with a
distinct pyramidalization at nitrogen) are reported for nojir-
ilactam[21a] and for d-gluconhydroximo-1,5-lactam,[21b] respec-
tively.
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K. H. Dötz et al.
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Figure 2. Molecular structure of complex 3c. Thermal ellipsoids are drawn
at the 30% probability level. Selected distances [pm] and angles [8]: W± C1
221.5(5), C1 ± N1 131.0(8), C1 ± C2 151.7(9), C2 ± C3 152.9(9), C3 ± C4
150.6(11), C4 ± N 148.0(8); W-C1-N1 131.9(5), W-C1-C2 121.9(4), N-C1-C2
106.1(5), C1-N-C5 127.7(5), C1-N-C4 116.6(5), C8-N-C4 115.7(6).
Scheme 6. Photoinduced synthesis of the methyl 2,6-imino-d-allonates 10
and 17a,b.
tonation by the alcohol, which occurs from the generally less
congested opposite face. In order to verify this hypothesis we
replaced methanol by the more efficiently coordinating
CH3CN. This solvent is expected to complete successfully
with the ketene for the Cr(CO)4 fragment prior to the
addition of the alcohol. Irradiation of a solution of 16a and
methanol (1.0 equiv) in THF led again to the formation of the
single d-allo isomer 17a in 65% yield. However, the
diastereoselectivity decreased significantly when the reaction
was run under identical conditions but with CH3CN as the
solvent. The 1H NMR spectrum of the residue, obtained after
oxidative workup, contained signals which could be assigned
to three products: imino d-allonate 17a and its diastereomer
in an approximate ratio of 2:1 (confirmed by GC-MS
analysis), and lactam 15a, which is formed by oxidation of
the unconverted starting material 16a.
In contrast, the increasing steric demand of the alcohol
substrate has no influence on the stereocontrol of the
C-glycosidation. The reaction of 16a with galactose derivative
18 (1.1 equiv)[23] in THF is highly diastereoselective, even
though it was considerably slower and gave only a 25% yield
of the galactosyl 2,6-imino-d-allonate 19 after five days of
irradiation (Scheme 7).
Figure 3. Molecular structure of complex 16a. Thermal ellipsoids are
drawn at the 50% probability level. Selected distances [pm] and angles [8]:
Cr± C1 210.66(14), C1 ± N1 130.8(2), C1 ± C2 154.6(2), C2 ± C3 155.0(2),
C3 ± C4 151.0(2), C4 ± C5 152.3(2), C5 ± N 148.86(16); Cr-C1-N1 130.57(10),
Cr-C1-C2 116.67(10), N-C1-C2 112.68(12), C1-N-C6 124.37(12), C1-N-C5
123.44 (12), C6-N-C5 112.18(11).
methanol and irradiated with a 125 W mercury lamp at room
temperature. The reaction afforded the methyl 2,6-iminoald-
onates 10 and 17a,b within five days in moderate-to-fair yields
after oxidative and chromatographic workup (see Experi-
mental Section and Scheme 6).
Despite our use of various protecting groups with different
steric demands, we isolated only a single diastereomer with d-
allo configuration, as established by NOE experiments within
Conclusion
1
the accuracy of H NMR spectroscopy in combination with
GC-MS analysis or HPLC. No alternative 2,6-imino-d-altro-
nate isomer was detected. We suppose that the stereocontrol
in favor of the b-C-glycosidation products 10 and 17a,b arises
from the coordination of the chromium carbonyl fragment to
the re face of the sugar ketene intermediate, which is
generated upon photolysis of the chromium iminoglycosyli-
dene precursor. This would explain the stereoselective pro-
We have shown that iminoglycosylidene complexes of chro-
mium are readily synthesized from sugar lactams in good
yields. The metal-stabilized carbene moiety in iminopyran-
osylidene complexes can be exploited in a photoinduced
carbon-chain elongation. We propose that the chromium
carbonyl fragment in the iminopyranosylidene complexes not
only mediates the generation of ketene equivalents, but also
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Chromium-Modified Sugars
691±699
Table 1. Crystallographic data and summary of data collection and refinement of
3a, 3c and 16a.
3a
3c
16a
formula
Mr
C13H13NO7Cr
347.24
C13H13NO7W
479.09
C15H17NO8Cr
391.30
crystal system
space group
a [Š]
orthorhombic
P212121 (no.19)
7.7241(2)
12.6238(4)
16.1620(5)
1575.92(8)
4
orthorhombic
P212121 (no.19)
7.7210(1)
13.1660(3)
16.3970(3)
1666.83(5)
4
orthorhombic
P212121 (no.19)
8.9292(3)
10.0482(3)
20.2145(4)
1813.69(4)
4
b [Š]
c [Š]
V [Š3]
Z
crystal size [mm3]
0.10 Â 0.20 Â 0.50
0.20 Â 0.40 Â 0.50
0.10 Â 0.15 Â 0.25
3
1calcd [g cm
]
1.46
1.91
1.43
1
m [mm
F(000)
]
0.76
712
6.96
912
0.67
808
diffractometer
radiation
l [Š]
T [K]
max 2q [8]
index range
Nonius Kappa-CCD
MoKa
0.71073
123(2)
56.6
9 ꢀ h ꢀ 9
16 ꢀ k ꢀ 16
19 ꢀ hl ꢀ 19
72437
MoKa
MoKa
0.71073
123(2)
0.71073
293(2)
56.4
7 ꢀ h ꢀ 7
15 ꢀ k ꢀ 15
19 ꢀ l ꢀ 19
22653
56.6
10 ꢀ h ꢀ 10
12 ꢀ k ꢀ 12
22 ꢀ l ꢀ 22
27662
Scheme 7. Photoinduced synthesis of the galactosyl 2,6-imino-d-
allonate 19.
no. of data
controls the stereochemical course of the reaction with
alcohols. This may be the result of the coordination of
the metal fragment to the zwitterion opposite the acetal
protection group. The importance of metal coordination
to the ketene intermediate is demonstrated by the fact
that the diastereoselectivity of C-glycosidation decreases
significantly if methanol is replaced by the better
coordinating CH3CN.
This reaction provides a novel, complementary, and
highly diastereoselective pathway to 2,6-iminoaldonic
acid derivatives[3±5] and a straightforward, yet unconven-
tional, approach to allo-configured iminosugars.[19, 24]
no. of unique data
Rint
no. of data with
I > 2s(I)
3607
0.029
3185
0.058
3890
0.033
3343
201
3533
201
3491
231
parameters
absolute structure
parameter x
R(F) for I > 2s(I)
0.01(1)
0.023
0.02(2)
0.027
0.068
1.11
0.01(1)
0.025
0.065
wR2(F2 ) for all data 0.059
goodn. of fit on F 2
1.04
1.06
largest diff. peak
3
and hole e Š
0.26/ 0.26
1.20/ 0.81
0.22/ 0.26
graphic Data Centre as supplementary publication no. CCDC-102572 (3a),
CCDC-102573 (3c), CCDC-102574 (16a). Copies of the data can be
obtained free of charge on application to CCDC, 12 Union Road,
Cambridge CB21EZ, UK (Fax: (‡ 44)1223-336-033; e-mail: depos-
it@ccdc.cam.ac.uk).
Experimental Section
All solvents were dried by standard procedures and then saturated with
argon. Organic products were purified by chromatography carried out at
room temperature on silica gel (Merck 60, 0.062 ± 0.200 nm). Chromato-
N-Methyl-4-amino-4-deoxy-2,3-O-isopropylidene-d-erythronolactam (2a):
A solution of lactam 1[16] (3.97 g, 25.3 mmol) in DMF (25 mL) was cooled to
08C. NaH (0.85 g, 35.4 mmol) was added and the mixture was stirred at
258C for 1.5 h. After addition of CH3I (12.6 mL, 202.4 mmol), the solution
was stirred for a further 8 h. The solvent was then evaporated and the
residue was purified by chromatography (eluent CH2Cl2/CH3OH, 5:1).
Colorless crystals of 2a (2.89 g, 66%) were obtained after distillation at
1008C (5  10 2 mbar). M.p. 86 ± 878C; Rf ˆ 0.80 (CH2Cl2/CH3OH, 5:1);
graphic workup of organometallic products was carried out between
5
and 128C with dry solvents on degassed silica gel (Merck 60, 0.062 ±
0.200 nm). TLC: Merck plates, silica gel 60F254. HPLC: Chiracel OD
(4.6 Â 250 mm), Eurospher (16 Â 250 mm). UV irradiation was performed
with a high-pressure mercury lamp, Philips TPK125, combined with a
transformer DEMA HPK125. 1H and 13C NMR (298 K): Bruker DRX 500,
AM 400. Chemical shifts refer to those of residual solvent signals based on
d(TMS) ˆ 0.00 ppm, coupling constants J are given in Hz. FTIR: Nicolet
550. MS-EI: Kratos Analytical MS50. GC-MS: Hewlett ± Packard 5890
Series-II-Gas-Chromatograph, column HP-5 MS (30m  0.2 cm), 5972
Series-Mass Selective Detector. Elemental analysis: Heraeus CHN-Rapid
and Elementar Analysensysteme GmbH Vario EL. Optical rotations:
Perkin ± Elmer Polarimeter 341, 1 mL cell, 208C, 589 nm. Melting points:
Büchi SMP 20, uncorrected. X-ray crystal structure analysis: Nonius Kappa
CCD.
‡
‡
MS (70 eV, EI): m/z (%): 171 ([M] , 6.4), 156 ([M CH3] , 100), 128
‡
([M CH3 CO] , 7.8), 114 (6.4), 96 (60); HR-MS: C8H13NO3: calcd
171.0895; found 171.0905; IR (KBr): nÄ ˆ 1693 cm 1; C8H13NO3 (171.19):
calcd C 56.13, H 7.65, N 8.18; found C 55.76, H 7.57, N 8.10; 1H NMR
(500 MHz, CD3OD): d ˆ 1.27 (s, 3H; CH3), 1.28 (s, 3H; CH3), 2.76 (s, 3H;
2
3
2
NCH3), 3.34 (dd, J4/4' ˆ 11.72, J4/3 ˆ 0.39, 1H; H-4), 3.58 (dd, J4'/4 ˆ 11.72,
3J4'/3 ˆ 4.87, 1H; H-4'), 4.56 (d, J2/3 ˆ 5.96, 1H; H-2), 4.67 (pt, 1H; H-3);
3
13C NMR (125 MHz, CD3OD): d ˆ 26.1, 27.6 (2C, CH3), 30.3 (1C, NCH3),
54.4 (1C, C-4), 74.1, 79.5 (2C, C-2, C-3), 113.5 (1C, Me2C), 173.8 (1C, C-1).
X-ray structural analysis of 3a, 3c, and 16a: The structures were solved by
direct methods (SHELXS-97).[25] The non-hydrogen atoms were refined
anisotropically on F 2 (SHELXL-97).[26] Hydrogen atoms were refined
isotropically with a riding model. An extinction correction (3a, 3c, and
N-Benzyl-4-amino-4-deoxy-2,3-O-isopropylidene-d-erythronolactam (2b):
As described in the previous procedure, treatment of 1 (0.91 g, 5.8 mmol)
with NaH (0.19 g, 8.1 mmol) and benzyl chloride (2.7 mL, 23.2 mmol) in
DMF (10 mL) yielded 2b as colorless needles (1.02 g, 71%) after
chromatographic workup (eluent CH2Cl2/CH3OH, 20:1) and distillation
at 1008C (5  10 2 mbar). M.p. 89 ± 908C; Rf ˆ 0.54 (CH2Cl2/CH3OH, 20:1);
16a) and an empirical absorption correction were applied (3c: Tmax/min
0.47906/0.35685). The absolute configuration is determined by refining
Flackꢁs x parameter.[27] Further details are given in Table 1.
ˆ
‡
‡
MS (70 eV, EI): m/z (%): 247 ([M] , 17.8), 232 ([M CH3] , 6.4), 189
‡
Crystallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge Crystallo-
([M Me2CO] , 4.2), 172 (68.5), 132 (5.7), 91 (100), 65 (12.1); HR-MS:
C14H17NO3 calcd 247.1028; found 247.1202; IR (KBr): nÄ ˆ 1685 cm 1; [a]D
ˆ
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K. H. Dötz et al.
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‡7.3 (c ˆ 0.994, CH3OH). C14H17NO3 (247.29): calcd C 68.00, H 6.93, N
5.66; found C 67.98, H 6.86, N 5.37; 1H NMR (500 MHz, C6D6): d ˆ 1.23 (s,
3H; CH3), 1.42 (s, 3H; CH3), 2.69 (dd, 2J4'/4 ˆ 11.22, 3J4'/3 ˆ 4.96, 1H; H-4'),
2.96 (d, 2J4/4' ˆ 11.22, 1H; H-4), 4.00 (pt, 1H; H-3), 4.20 (d, 2J ˆ 14.60, 1H;
57.96, H 7.58, N 6.02; 1H NMR (500 MHz, [D6]DMSO): d ˆ 1.28 ± 1.38 (m,
2
2H; C6H10), 1.45 ± 1.58 (m, 8H; C6H10), 2.91 (m, 1H; H-5'), 3.17 (t, J5/5'
ˆ
3
3J5/4 ˆ 10.43, 1H; H-5), 3.86 (m, 1H; H-4), 4.26 (d, J2/3 ˆ 6.36, 1H; H-2),
2
4.35 (m, 1H; H-3), 5.19 (d, JOH/4 ˆ 5.06, 1H; OH), 7.61 (d, 2J ˆ 3.97, 1H;
PhCH2), 4.25 (d, 2J ˆ 14.60, 1H; PhCH2), 4.31 (d, J2/3 ˆ 6.06, 1H; H-2),
NH); 13C NMR (125 MHz, [D6]DMSO): d ˆ 23.5, 23.7, 24.7, 34.7, 36.2 (5C,
C6H10), 41.5 (1C, C-5), 64.8, 73.5, 75.6 (3C, C-2, C-3, C-4), 109.8 (1C, Cspiro),
168.3 (1C, C-1).
3
7.05 ± 7.14 (m, 5H; H-aryl); 13C NMR (125 MHz, C6D6): d ˆ 25.8, 27.3 (2C,
CH3), 46.4 (1C, CH2Ph), 49.6 (1C, C-4), 72.3, 77.9 (2C, C-3, C-2), 111.9 (1C,
Me2C), 127.7, 128.4, 128.8 (5C, aryl-C), 136.5 (1C, Cipso), 170.0 (1C, C-1).
N-Methyl-5-amino-2,3-O-cyclohexylidene-5-deoxy-4-O-methyl-d-ribono-
1,5-lactam (8): Lactam 7 (909 mg, 4.0 mmol) was dissolved in DMF (50 mL)
and cooled to 08C. NaH (249 mg, 10.4 mmol) was added, and the mixture
was stirred at 258C for 1.5 h. After addition of CH3I (4.0 mL, 64.0 mmol),
the solution was stirred for a further 8 h. The solvent was then evaporated
and the residue was purified by chromatography (eluent CH2Cl2/CH3OH,
10:1). Further purification was achieved by distillation at 1208C (5 Â
2,3-O-Cyclohexylidene-d-ribono-1,4-lactone (4): d-Ribono-1,4-lactone was
protected by treatment with cyclohexanone (50 mL) and concentrated
H2SO4 (5 drops) over 20 h at 258C. The solvent was then evaporated in
vacuo at 45 ± 608C in the presence of solid NaHCO3 (0.5 g). Chromatog-
raphy of the residue (eluent EtOAc/PE, 2:1) gave 4 as a white solid (6.48 g,
56%). M.p. 120 ± 1218C; Rf ˆ 0.42 (EtOAc/PE, 2:1); MS (70 eV, EI): m/z
‡
‡
‡
(%): 228 ([M] , 96.0), 199 ([M
H
CO] , 21.4), 185 ([M ‡ H CO2] ,
10 2 mbar) to give
8
as
a
colorless syrup (950 mg, 93%). Rf ˆ 0.60
‡
100), 169 (3.2), 99 (4.2), 85 (10), 55 (53.5); HR-MS: C11H16O5: calcd
(CH2Cl2/CH3OH, 10:1); MS (70 eV, EI): m/z (%): 255 ([M] , 43.5), 226
228.0997; found 228.0993; IR (KBr): nÄ ˆ 3465, 1780 cm 1; [a]D
ˆ
53.18
([M
H
CO] , 27.8), 212 ([M H2CNCH3] , 100), 140 (58.3), 98 (17.1),
‡
‡
(c ˆ 1.440, CHCl3). C11H16O5 (228.24): calcd C 57.89, H 7.07; found C 57.63,
71 (17.8), 55 (31.4); HR-MS: C13H21NO4: calcd 255.1470; found 255.1468;
H 6.96; 1H NMR (500 MHz, CDCl3): d ˆ 1.33 ± 1.40 (m, 2H; C6H10), 1.50 ±
IR (film): nÄ ˆ 1662 cm
;
1H NMR (500 MHz, C6D6): d ˆ 1.12 ± 1.24 (m,
1
2
3
1.67 (m, 8H; C6H10), 2.61 (b, 1H; OH), 3.77 (dd, J5/5' ˆ 12.32, J5/4 ˆ 1.69,
2H; C6H10), 1.49 ± 1.71 (m, 8H; C6H10), 2.53 (dddd, 2J5/5' ˆ 11.33, 3J5/4 ˆ 4.67,
2
3
3
5
3
1H; H-5), 3.96 (dd, J5'/5 ˆ 12.32, J5'/4 ˆ 2.28, 1H; H-5'), 4.61 (pt, J4/5
ꢁ
3J5/3 ˆ 1.39, J5/2 ˆ 0.50, 1H; H-5), 2.57 (s, 3H; NCH3), 2.75 (dddd, J4/5'
ˆ
3J4/5' ꢁ 1.98, 1H; H-4), 4.74 (d, 3J3/2 ˆ 5.67, 1H; H-3), 4.81 (d, 3J2/3 ˆ 5.67, 1H;
H-2); 13C NMR (125 MHz, CDCl3): d ˆ 23.6, 23.7, 24.7, 34.8, 36.2 (5C,
C6H10), 61.8 (1C, C-5), 75.2, 77.7, 82.9 (3C, C-2, C-3, C-4), 113.8 (1C, Cspiro),
175.3 (1C, C-1).
10.13, 3J4/5 ˆ 4.67, 3J4/3 ˆ 2.69, 4J4/2 ˆ 0.55, 1H; H-4), 2.98 (s, 3H; OCH3), 3.43
(dd, 2J5'/5 ˆ 11.33, 3J5'/4 ˆ 10.13, 1H; H-5'), 4.15 (m, 1H; H-3), 4.28 (d, 3J2/3
ˆ
6.16, 1H; H-2); 13C NMR (125 MHz, C6D6): d ˆ 24.0, 24.1, 25.2 (3C, C6H10),
34.3 (1C, NCH3), 35.2, 36.8 (2C, C6H10), 46.9 (1C, C-5), 56.2 (1C, OCH3),
72.8 (1C, C-3), 73.9 (1C, C-4), 74.6 (1C, C-2), 111.1 (1C, Cspiro), 166.5 (1C,
C-1).
2,3-O-Cyclohexylidene-5-O-p-toluenesulfonyl-D-ribono-1,4-lactone (5): p-
Toluenesulfonyl chloride (8.0 g, 42.0 mmol) was added to a solution of the
acetal 4 (3.5 g, 21.0 mmol) in cold pyridine (20 mL, 208C) in one portion.
After the mixture had been kept for 20 h at 288C, water (2.0 mL) was
added, and the solution was then poured slowly into ice water (500 mL)
with vigorous stirring. The crystals formed were collected, dried, and
purified chromatographically (eluent EtOAc/PE, 2:1) to furnish the
tosylate 5 as a colorless liquid (8.0 g, 100%). Rf ˆ 0.87 (EtOAc/PE, 2:1);
2,3-O-Isopropylidene-5-O-p-toluenesulfonyl-d-ribono-1,4-lactone
(12):
2,3-O-Isopropylidene-d-ribono-1,4-lactone 11[18] (6.03 g, 32.0 mmol) was
dissolved in cold pyridine (30 mL, 208C) and p-toluenesulfonyl chloride
(12.22 g, 64.0 mmol) was introduced to the solution in one portion. The
solution was left at 288C for 20 h. Water (2 mL) was then added (2 mL),
and the solution was poured into ice water (2400 mL). The crystals formed
were filtered and dried in vacuo to give the tosylate 12 as a slightly yellow
solid (9.24 g, 84%). M.p. 110 ± 1148C; MS (70 eV, EI): m/z (%): 327 ([M
‡
‡
MS (70 eV, EI): m/z (%): 382 ([M ], 35.6), 353 ([M HCO] , 23.7), 339
‡
‡
‡
([M ‡ H CO2] , 100), 155 ([C7H7O2S] , 23.7), 139 ([C7H7OS] , 8.4), 91
‡
‡
‡
‡
([C7H7] , 25.4), 55 (35.3); HR-MS: C18H22O7S: calcd 382.1086; found
CH3] , 100), 172 ([p-TosOH] , 2.5), 155 ([M
H
p-TosOMe] , 64.4), 127
382.1091; IR (film): nÄ ˆ 1795, 1733 cm 1; H NMR (500 MHz, C6D6): d ˆ
(45.7), 85 (59.3), 68 (45.7), 59 (9.3); HR-MS: C14H15O7S (M CH3): calcd
1
1.08 ± 1.17 (m, 2H; C6H10), 1.27 ± 1.63 (m, 8H; C6H10), 1.81 (s, 3H; PhCH3),
327.0538; found 327.0541; IR (KBr): nÄ ˆ 1786 cm 1; [a]D
ˆ
16.8 (c ˆ 2.51,
2
2
2
3
3.53 (dd, J5/5' ˆ 11.22, J5/4 ˆ 2.08, 1H; H-5), 3.58 (dd, J5'/5 ˆ 11.22, J5'/4
ˆ
acetone); C15H18O7S (342.36): calcd C 52.62, H 5.30, S 9.36; found C 52.60,
3
3
3
2.58, 1H; H-5'), 4.00 (pt, J4/5 ꢁ J4/5' ꢁ 2.28, 1H; H-4), 4.16 (d, J3/2 ˆ 5.66,
1H; H-3), 4.60 (d, 3J2/3 ˆ 5.66, 1H; H-2), 6.70 (d, 3J ˆ 8.54, 2H; H-aryl), 7.61
(d, 3J ˆ 8.54, 2H; H-aryl); 13C NMR (125 MHz, C6D6): d ˆ 21.1 (1C,
PhCH3), 23.9, 24.0, 24.9, 35.0, 36.5 (5C, C6H10), 68.2 (1C, C-5), 74.9, 77.1,
78.7 (3C, C-2, C-3, C-4), 114.1 (1C, Cspiro), 128.0, 130.1, 132.4 (5C, aryl-C),
145.2 (1C, Cipso), 172.7 (1C, C-1).
H 5.33, S 9.18; 1H NMR (500 MHz, CDCl3): d ˆ 1.35 (s, 3H; CH3), 1.43 (s,
2
3
3H; CH3), 2.44 (s, 3H; PhCH3), 4.15 (dd, J5/5' ˆ 11.13, J5/4 ˆ 2.43, 1H;
2
3
3
3
H-5), 4.31 (dd, J5'/5 ˆ 11.13, J5'/4 ˆ 1.89, 1H; H-5'), 4.65 (pt, J4/5 ꢁ J4/5'
ꢁ
2.14, 1H; H-4), 4.72 (d, 3J3/2 ˆ 5.56, 1H; H-3), 4.75 (d, 3J2/3 ˆ 5.56, 1H; H-2),
7.35 (d, 3J ˆ 8.44, 2H; H-aryl), 7.72 (d, 3J ˆ 8.44, 2H; H-aryl); 13C NMR
(125 MHz, CDCl3): d ˆ 21.6 (1C, PhCH3), 25.4 (1C, CH3), 26.6 (1C, CH3),
68.2 (1C, C-5), 74.9, 77.3, 78.9 (3C, C-4, C-3, C-2), 113.8 (1C, Me2C), 127.9,
130.2, 131.4 (5C, aryl-C), 145.8 (1C, Cipso), 173.0 (1C, C-1).
5-Azido-2,3-O-cyclohexylidene-5-deoxy-d-ribono-1,4-lactone (6): Sodium
azide (1.07 g, 16.5 mmol) was added to a solution of 5 (1.96 g, 5.0 mmol) in
DMF (50 mL) and the suspension was warmed to 1008C for 6 h. After
evaporation of the solvent in vacuo at 408C, the residue was taken up in
water (40 mL) and extracted with Et2O (6 Â 50 mL). The combined extracts
were dried over MgSO4 and then concentrated to give white needles of the
azido lactone 6 (1.26 g, 100%). M.p. 80 ± 818C; MS (70 eV, EI): m/z (%):
5-Azido-5-deoxy-2,3-O-isopropylidene-d-ribono-1,4-lactone (13): A sus-
pension of tosylate 12 (9.00 g, 26.2 mmol) and sodium azide (5.12 g,
78.8 mmol) in DMF (150 mL) was heated for 6 h at 1008C. After
evaporation of the solvent, the residue was taken up in water (200 mL)
and extracted with Et2O (7 Â 200 mL). The combined extracts were dried
over MgSO4 and evaporated. The residue was then purified by column
chromatography (eluent Et2O/PE/CH3OH, 15:5:1). The azido lactone 13
was obtained as yellowish needles (4.95 g, 88%). M.p. 398C; Rf ˆ 0.58
‡
‡
‡
253 ([M] , 20), 224 ([M
H
CO] , 19.2), 210 ([M HN3] , 38.5), 196
([224 N2], 2.1), 182 ([210 CO], 7.8), 55 (100); HR-MS: C11H15N3O4:
1
calcd 253.1062; found 253.1067; IR (KBr): nÄ ˆ 2112, 1784 cm 1; H NMR
‡
(500 MHz, CDCl3): d ˆ 1.33 ± 1.39 (m, 2H; C6H10), 1.48 ± 1.67 (m, 8H;
(Et2O/PE/CH3OH, 15:5:1); MS (70 eV, EI): m/z (%): 214 ([M ‡ H] , 0.7),
2
3
2
‡
‡
C6H10), 3.63 (dd, J5/5' ˆ 13.21, J5/4 ˆ 2.28, 1H; H-5), 3.75 (dd, J5'/5 ˆ 13.21,
198 ([M CH3] , 100), 170 ([M HN3] , 12.1), 129 (12.8), 112 (2.8), 100
(10.0), 85 (25.7), 59 (52.1), 55 (26.4); HR-MS: C8H11N3O4 (M CH3): calcd
198.0514; found 198.0513; IR (KBr): nÄ ˆ 2115, 1787 cm 1; [a]D ˆ ‡15.0
(c ˆ 1.001, CHCl3); C8H11N3O4 (213.19): calcd C 45.07, H 5.20, N 19.71;
found C 45.13, H 5.19, N 19.26; 1H NMR (500 MHz, CDCl3): d ˆ 1.35 (s,
3J5'/4 ˆ 3.17, 1H; H-5'), 4.59 (d, J3/2 ˆ 5.77, 1H; H-3), 4.64 (pt, J4/5 ꢁ J4/5'
ꢁ
3
3
3
2.73, 1H; H-4), 4.81 (d, 3J2/3 ˆ 5.77, 1H; H-2); 13C NMR (125 MHz, CDCl3):
d ˆ 23.6, 23.7, 24.6, 34.8, 36.2 (5C, C6H10), 52.4 (1C, C-5), 74.7, 77.5, 80.1
(3C, C-2, C-3, C-4), 114.3 (1C, Cspiro), 173.5 (1C, C-1).
2
3
3H; CH3), 1.44 (s, 3H; CH3), 3.64 (dd, J5/5' ˆ 13.21, J5/4 ˆ 1.89, 1H; H-5),
3.76 (dd, 2J5'/5 ˆ 13.21, 3J5'/4 ˆ 2.89, 1H; H-5'), 4.60 (d, 3J3/2 ˆ 5.66, 1H; H-3),
4.63 (m, 1H; H-4), 4.82 (d, 3J2/3 ˆ 5.66; H-2); 13C NMR (125 MHz, CDCl3):
d ˆ 25.3 (1C, CH3), 26.5 (1C, CH3), 52.3 (1C, C-5), 75.0, 77.9, 79.9 (3C, C-4,
C-3, C-2), 113.5 (1C, Me2C), 173.3 (1C, C-1).
5-Amino-2,3-O-cyclohexylidene-5-deoxy-d-ribono-1,5-lactam (7): Azido
lactone 6 (1.26 g, 5.0 mmol) was dissolved in methanol (100 mL) and
hydrogenated in the presence of palladium on charcoal (6 mol%) at 1.5 bar
H2 and 258C. After 2 h, the catalyst was filtered through a short column
filled with silica gel. Evaporation of the solvent yielded the lactam 7 as a
‡
white solid (1.07 g, 94%). M.p. 2028C; MS (70 eV, EI): m/z (%): 227 ([M] ,
5-Amino-5-deoxy-2,3-O-isopropylidene-d-ribono-1,5-lactam (14): Azido
lactone 13 (4.95 g, 23.0 mmol) was hydrogenated in methanol (250 mL)
in the presence of palladium on charcoal (6 mol%) at 1.0 bar H2 and 258C.
After 2.5 h, the catalyst was filtered through a short column filled with silica
gel. The filtrate was concentrated to a sticky foam, which was triturated
‡
‡
31.4), 198 ([M
H
CO] , 22.8), 184 ([M HNCO] , 100), 171 (2.1), 130
(3.5), 112 (10.0), 84 (6.4), 55 (57.1); HR-MS: C11H17NO4: calcd 227.1157;
found 227.1158; IR (KBr): nÄ ˆ 3412, 3257, 1656 cm 1; [a]D ˆ ‡14.9 (c ˆ
0.705, CH3OH); C11H17NO4 (227.26): calcd C 58.14, H 7.54, N 6.16; found C
696
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0502-0696 $ 17.50+.50/0
Chem. Eur. J. 1999, 5, No. 2

Chromium-Modified Sugars
691±699
with a mixture of acetone/Et2O (1:1, 100 mL) with vigorous stirring to
induce precipitation of the product. After filtration, the residue obtained
was concentrated again and the procedure was repeated (acetone/Et2O, 1:1,
30 mL) to give the lactam 14 as a white solid (2.93 g, 67%). M.p. 139 ±
appropriate lactam (2a,b, 8, or 15a,b; 1.0 equiv in THF) was added by
syringe. The mixture was kept for 0.5 h at 788C, 1.5 h at 58C, and then
cooled again to 788C. TMSCl (3.1 equiv) was added in one portion and
the reaction mixture was stirred for 0.5 h. Neutral Al2O3 was used to adsorb
the product, and the solvent was then removed under reduced pressure.
The resulting dry powder was eluted on a silica gel column (eluent Et2O/
PE/CH3OH, 15:5:1 for 3a ± c, 9, 16a; Et2O/PE/CH3OH, 15:10:1 for 16b).
‡
‡
1408C. MS (70 eV, EI): m/z (%): 188 ([M ‡ H] , 0.6), 172 ([M CH3] ,
‡
‡
100), 144 ([M HNCO] , 6.4), 130 ([M ‡ H Me2CO] , 32.8), 112 (9.6),
‡
101 (10.7), 84 (23.9), 73 (19.6), 59 ([Me2COH] , 46.7); HR-MS: C7H10NO4
(M CH3): calcd 172.0609; found 172.0610; IR (KBr): nÄ ˆ 3529, 3427, 3290,
1664, 1633 cm 1; [a]D ˆ ‡22.6 (c ˆ 1.030, CHCl3); C8H13NO4 (187.19): calcd
Pentacarbonyl[1,4-dideoxy-2,3-O-isopropylidene-1,4-(methylimino)-d-
erythro-furanosylidene]chromium (3a): Compound 3a (2.36 mmol,
820 mg, 78%) was isolated as an orange solid by reaction of graphite
(634 mg, 52.8 mmol), potassium (258 mg, 6.6 mmol), and Cr(CO)6 (726 mg,
3.3 mmol) with 2a (513 mg, 3.0 mmol) and TMSCl (1.17 mL, 9.3 mmol) in
THF (15 mL) (see general procedure above). M.p. 878C (decomp); Rf ˆ
C 51.33, H 7.00, N 7.48; found C 51.08, H 6.86, N 7.28; 1H NMR (500 MHz,
2
[D6]DMSO): d ˆ 1.28 (s, 3H; CH3), 1.32 (s, 3H; CH3), 2.92 (dpt, J5'/5
ˆ
11.42, 3J5'/4 ꢁ J5'/NH ꢁ 4.6, 1H; H-5'), 3.17 (dd, 2J5/5' ˆ 11.42, 3J5/4 ˆ 11.13, 1H;
3
3
3
3
3
H-5), 3.87 (dddd, J4/5 ˆ11.13, J4/OH ˆ 5.15, J4/5' ˆ 4.77, J4/3 ˆ 2.59, 1H;
3
3
3
H-4), 4.25 (d, J2/3 ˆ 6.35, 1H; H-2), 4.35 (dd, J3/2 ˆ 6.35, J3/4 ˆ 2.59, 1H;
‡
0.58 (Et2O/PE/CH3OH, 15:5:1); MS (70 eV, EI): m/z (%): 347 ([M] , 10.0),
3
3
H-3), 5.20 (d, JOH/4 ˆ 5.15, 1H; OH), 7.63 (d, JNH/5' ꢁ 4.6, 1H; NH);
13C NMR (125 MHz, [D6]DMSO): d ˆ 25.4 (1C, CH3), 26.8 (1C, CH3), 41.5
(1C, C-5), 64.7, 73.8, 75.9 (3C, C-4, C-3, C-2), 109.3 (1C, Me2C), 168.1 (1C,
C-1).
‡
‡
‡
332 ([M CH3] , 5.0), 319 ([M CO] , 5.0), 291 ([M 2CO] , 2.1), 263
‡
‡
‡
([M 3CO] , 3.2), 235 ([M 4CO] , 21.6), 207 ([M 5CO] , 100), 192
‡
ˆ ˆ
([207 CH3], 15.3), 149 ([207 Me2CO], 20.2), 93 ([H3CN C Cr] , 20.7);
HR-MS: C13H1352CrNO7: calcd 347.0097; found 347.0098; IR (PE): nÄ ˆ 2058,
1978, 1940, 1930 cm 1; [a]D
ˆ
61 (c ˆ 0.278, Et2O); C13H13CrNO7 (347.24):
N-Methyl-5-amino-5-deoxy-2,3-O-isopropylidene-4-O-methyl-d-ribono-
1,5-lactam (15a): As in the procedure reported for 8, reaction of 14 (1.49 g,
8.0 mmol) with NaH (0.50 g, 20.8 mmol) and CH3I (8.0 mL, 128.0 mmol) in
DMF (100 mL) yielded the lactam 15a as a colorless solid (1.53 g, 88%)
after chromatographic workup (eluent CH2Cl2/CH3OH, 10:1) and distil-
lation at 1208C (5  10 2 mbar). M.p. 658C; Rf ˆ 0.56 (CH2Cl2/CH3OH,
calcd C 44.97, H 3.77, N 4.03; found C 44.98, H 3.79, N 3.90; 1H NMR
(500 MHz, CD3OD): d ˆ 1.23 (s, 3H; CH3), 1.28 (s, 3H; CH3), 3.60 (s, 3H;
NCH3), 3.88 (d, 2J4/4' ˆ 13.91, 1H; H-4), 4.02 (ddd, 2J4'/4 ˆ 13.91, 3J4'/3 ˆ 4.96,
4J4'/2 ˆ 0.70, 1H; H-4'), 4.60 (pt, J ꢁ 5.2, 1H; H-3), 5.13 (dd, J2/3 ˆ 5.57,
3
4J2/4' ˆ 0.70, 1H; H-2); 13C NMR (100 MHz, CD3OD): d ˆ 26.2, 27.7 (2C,
CH3), 43.3 (1C, NCH3), 69.5 (1C, C-4), 75.9 (1C, C-3), 100.2 (1C, C-2),
112.8 (1C, Me2C), 219.5 (4C, COcis), 224.7 (1C, COtrans), 265.1 (1C, C-1).
‡
‡
10:1); MS (70 eV, EI): m/z (%): 215 ([M] , 7.1), 200 ([M CH3] , 100), 182
‡
‡
([M CH3OH] , 14.2), 172 ([200 CO], 5.7), 158 ([M CH3NCO] ,
31.4), 140( [172 CH3OH], 23.5), 71 ([H2CNCH3CO] , 34.2), 58
‡
Pentacarbonyl[1,4-(benzylimino)-1,4-dideoxy-2,3-O-isopropylidene-d-
erythro-furanosylidene]chromium (3b): Compound 3b (1.00 mmol,
424 mg, 67%) was obtained as a red-orange solid by reaction of graphite
(317 mg, 26.4 mmol), potassium (129 mg, 3.3 mmol), and Cr(CO)6 (363 mg,
1.6 mmol) with 2b (371 mg, 1.5 mmol) and TMSCl (0.59 mL, 4.6 mmol) in
THF (8 mL), as described for compound 3a. M.p. 145 ± 1468C; Rf ˆ 0.40
‡
([Me2CO] , 27.1); HR-MS: C9H14NO4 (M CH3): calcd 200.0922; found
200.0922; IR (KBr): nÄ ˆ 1660 cm 1. [a]D
ˆ
3.6 (c ˆ 1.006, CH3OH);
C10H17NO4 (215.24): calcd C 55.80, H 7.96, N 6.51; found C 55.81, H 7.97, N
6.33; 1H NMR (500 MHz, C6D6): d ˆ 1.27 (s, 3H; CH3), 1.41 (s, 3H; CH3),
2.59 (dd, 2J5'/5 ˆ 11.63, 3J5'/4 ˆ 4.67, 1H; H-5'), 2.61 (s, 3H; NCH3), 2.82 (ddd,
3J4/5 ˆ 10.00, 3J4/5' ˆ 4.67, 3J4/3 ˆ 2.69, 1H; H-4), 3.03 (s, 3H; OCH3), 3.44 (dd,
‡
(Et2O/PE/CH3OH, 15:5:1); MS (70 eV, EI): m/z (%): 423 ([M] , 4.1), 408
2J5/5' ˆ 11.63, J5/4 ˆ 10.00, 1H; H-5), 4.15 (dd, J3/2 ˆ 6.16, J3/4 ˆ 2.69, 1H;
3
3
3
‡
‡
‡
([M CH3] , 0.9), 395 ([M CO] , 2.0), 339 ([M 3CO] , 21.6), 311
H-3), 4.31 (d, J2/3 ˆ6.16, 1H; H-2); 13C NMR (125 MHz, C6D6): d ˆ 25.3
3
‡
‡
([M 4CO] , 7.5), 283 ([M 5CO] , 40.0), 268 ([283 CH3], 7.5), 225
(1C, CH3), 26.8 (1C, CH3), 34.6 (1C, NCH3), 46.9 (1C, C-5), 56.2 (1C,
OCH3), 73.0 (1C, C-3), 73.8 (1C, C-4), 74.9 (1C, C-2), 110.3 (1C, Me2C),
166.3 (1C, C-1).
([283 Me2CO], 11.7), 172 (27.5), 157 (20.0), 133 ([283 C7H8], 28.3), 91
([C7H7] , 100); HR-MS: C19H1752CrNO7: calcd 423.0410; found 423.0407;
‡
IR (PE): nÄ ˆ 2058, 1977, 1940, 1931 cm 1; [a]D
ˆ
91 (c ˆ 0.29, Et2O);
C19H17CrNO7 (423.34): calcd C 53.91, H 4.05, N 3.31; found C 53.58, H 4.21,
N 3.03; 1H NMR (500 MHz, CD3COCD3): d ˆ 1.36 (s, 3H; CH3), 1.41 (s,
3H; CH3), 3.82 (d, 2J4/4' ˆ 13.81, 1H; H-4), 4.06 (dd, 2J4'/4 ˆ 13.81, 3J4'/3 ˆ 4.76,
1H; H-4'), 4.79 (pt, J ꢁ 5.1, 1H; H-3), 5.26 (d, 2J ˆ 14.90, 1H; PhCH2), 5.43
(d, 3J2/3 ˆ 5.47, 1H; H-2), 5.55 (d, 2J ˆ 14.90, 1H; PhCH2), 7.36 ± 7.45 (m, 5H;
H-aryl); 13C NMR (125 MHz, CD3COCD3): d ˆ 25.9, 27.4 (2C, CH3), 59.5
(1C, PhCH2), 65.8 (1C, C-4), 75.0 (1C, C-3), 99.3 (1C, C-2), 112.0 (1C,
Me2C), 218.7 (4C, COcis), 224.2 (1C, COtrans), 266.0 (1C, C-1).
N-Benzyl-5-amino-4-O-benzyl-5-deoxy-2,3-O-isopropylidene-d-ribono-
1,5-lactam (15b): As in the procedure reported for 8, reaction of 14 (1.49 g,
8.0 mmol) with NaH (0.50 g, 20.8 mmol) and benzyl chloride (7.4 mL,
64.0 mmol) in DMF (100 mL) yielded the lactam 15b as a colorless solid
(2.23 g, 75%) after chromatographic workup (eluent CH2Cl2/CH3OH,
20:1). M.p. 99 ± 1008C; Rf ˆ 0.50 (CH2Cl2/CH3OH, 20:1); MS (70 eV, EI):
‡
‡
m/z (%): 367 ([M] , 16.9), 309 ([M Me2CO] , 3.3), 280 ([309
H
CO],
‡
6.7), 261 ([M PhCHO] , 8.4), 218 ([309 C7H7], 11.8), 203 ([309
‡
PhCHO], 11.8), 174 ([280 PhCHO], 11.0), 91 ([C7H7] , 100); HR-MS:
Pentacarbonyl[1,4-dideoxy-2,3-O-isopropylidene-1,4-(methylimino)-d-
erythro-furanosylidene]tungsten (3c): Compound 3c (1.82 mmol, 872 mg,
72%) was obtained as an orange solid by reaction of graphite (538 mg,
44.8 mmol), potassium (219 mg, 5.6 mmol), and W(CO)6 (985 mg,
2.8 mmol) with 2a (436 mg, 2.5 mmol) and TMSCl (0.99 mL, 7.9 mmol) in
THF (15 mL), as described for compound 3a. M.p. 1048C; Rf ˆ 0.41 (Et2O/
1
C22H25NO4: calcd 367.1783; found 367.1783; IR (KBr): nÄ ˆ 1660 cm
;
[a]D ˆ ‡34.6 (c ˆ 1.006, CH3OH). C22H25NO4 (367.44): calcd C 71.91, H
6.86, N 3.81; found C 71.83, H 6.76, N 3.58; 1H NMR (500 MHz, C6D6/
2
TMS): d ˆ 1.31 (s, 3H; CH3), 1.46 (s, 3H; CH3), 2.87 (ddd, J5'/5 ˆ 11.63,
3J5'/4 ˆ 4.27, J5'/3 ˆ 1.29, 1H; H-5'), 3.28 (ddd, J4/5 ˆ 9.63, J4/5' ˆ 4.27, J4/3
ˆ2.68, 1H; H-4), 3.55 (dd, 2J5/5' ˆ 11.63, 3J5/4 ˆ9.63, 1H; H-5), 4.23 (d, 2J ˆ
11.82, 1H; PhCH2), 4.25 (ddd, 3J3/2 ˆ 6.56, 3J3/4 ˆ 2.68, 4J3/5' ˆ 1.29, 1H; H-3),
4.34 (d, 2J ˆ 14.61, 1H; PhCH2), 4.35 (d, 2J ˆ 11.82, 1H; PhCH2), 4.45 (d,
4
3
3
3
‡
PE/CH3OH, 15:5:1); MS (70 eV, EI): m/z (%): 479 ([M] , 2.1), 464 ([M
‡
‡
‡
CH3] , 2.5), 451 ([M CO] , 8.4), 423 ([M 2CO] , 20.1), 408 ([464
‡
2CO], 5.0), 395 ([M 3CO] , 2.5), 380 ([464 3CO], 8.4), 367 ([M
3J2/3 ˆ 6.56, 1H; H-2), 4.55 (d, J ˆ 14.61, 1H; PhCH2), 7.11 ± 7.29 (m, 10H;
2
‡
‡
4CO] , 3.3), 352 ([464 4CO], 3.3), 339 ([M 5CO] , 3.3), 324 ([464
5CO], 6.7), 309 ([367 Me2CO], 39.4), 281 ([339 Me2CO], 53.7), 253
(12.6), 82 (100); HR-MS: C13H13NO7182W: calcd 477.0174; found 477.0166;
H-aryl); 13C NMR (125 MHz, C6D6/TMS): d ˆ 25.2, 26.7 (2C, CH3), 44.6
(1C, PhCH2N), 50.4 (1C, C-5), 70.9 (1C, PhCH2O), 72.4 (1C, C-3), 73.8
(1C, C-4), 75.2 (1C, C-2), 110.5 (1C, Me2C), 127.6, 127.7, 127.8, 128.5, 128.6,
128.7 (10C, aryl-C), 137.3, 138.4 (2C, Cipso), 166.3 (1C, C-1).
IR (PE): nÄ ˆ 2065, 1975, 1940, 1928 cm 1; [a]D
ˆ
51 (c ˆ 0.250, Et2O);
C13H13NO7W (479.09): calcd C 32.59, H 2.73, N 2.92; found C 32.64, H 2.78,
1
N 2.80; H NMR (500 MHz, CD3OD): d ˆ 1.24 (s, 3H; CH3), 1.28 (s, 3H;
General procedure for preparation of the iminoglycosylidene complexes
3a ± c, 9, and 16a,b: In order to prepare C8K, graphite (17.6 equiv) was
stirred in vacuo for 20 min at 1658C. Potassium (2.2 equiv) was then added
under a flow of argon, and the mixture was kept at 1658C for 1.5 h to
complete the formation of C8K. The laminate was cooled to 258C and then
suspended in freshly distilled THF (the volume used was that required for a
0.15 ± 0.3m solution of the pentacarbonyl metalate). The suspension was
cooled to 788C, and either Cr(CO)6 or W(CO)6 (1.1 equiv) was added.
The reaction mixture was stirred for 0.5 h at 788C and then kept between
10 and 58C until no more carbon monoxide was evolved (approx-
imately 1.5 ± 2 h). The solution was cooled again to 788C, and the
CH3), 3.53 (s, 3H; NCH3), 3.88 (d, 2J4'/4 ˆ 14.01, 1H; H-4'), 4.01 (dd, 2J4/4'
ˆ
14.01, 3J4/3 ˆ 4.77, 1H; H-4), 4.62 (pt, J ꢁ 5.2, 1H; H-3), 5.12 (d, 3J2/3 ˆ 5.46,
1H; H-2); 13C NMR (125 MHz, CD3OD): d ˆ 26.0, 27.5 (2C, CH3), 44.8
(1C, NCH3), 68.3 (1C, C-4), 76.1 (1C, C-3), 100.9 (1C, C-2), 112.5 (1C,
Me2C), 199.3 (4C, COcis), 204.0 (1C, COtrans), 247.0 (1C, C-1).
Pentacarbonyl[2,3-O-cyclohexylidene-1,5-dideoxy-4-O-methyl-1,5-(meth-
ylimino)-d-ribo-pyranosylidene]chromium (9): Compound 9 (0.78 mmol,
336 mg, 21%) was obtained as an orange solid by reaction of graphite
(773 mg, 64.4 mmol), potassium (315 mg, 8.0 mmol), and Cr(CO)6 (886 mg,
4.0 mmol) with 8 (934 mg, 3.6 mmol) and TMSCl (1.43 mL, 11.3 mmol) in
Chem. Eur. J. 1999, 5, No. 2
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0502-0697 $ 17.50+.50/0
697

K. H. Dötz et al.
FULL PAPER
‡
THF (16 mL), as described for compound 3a. M.p. 958C (decomp); Rf ˆ
(Et2O/PE/CH3OH, 15:5:1); MS (70 eV, EI): m/z (%): 299 ([M] , 1.4), 240
‡
‡
0.42 (Et2O/PE/CH3OH, 15:5:1); MS (70 eV, EI): m/z (%): 431 ([M] , 0.6),
([M CO2CH3] , 100), 208 ([240 CH3OH], 1.0), 184 (10.0), 152 (2.8), 142
‡
‡
‡
403 ([M CO] , 8.2), 375 ([M 2CO] , 2.4), 319 ([M 4CO] , 16.8), 291
(35.0), 126 (2.8), 114 (8.2), 82 (5.7), 71 (14.2); HR-MS: C15H25NO5: calcd
‡
‡
1
ˆ ˆ
([M 5CO] , 100), 110 (94.1), 94 ([MeNH C Cr] , 81.5), 69 (24.3), 55
(77.3); HR-MS: C17H2152CrNO7 (M CO): calcd 403.0723; found 403.0725;
IR (PE): nÄ ˆ 2056, 1976, 1938, 1922 cm 1; [a]D ˆ ‡81.8 (c ˆ 0.592, Et2O);
C18H21CrNO8 (431.36): calcd C 50.12, H 4.91, N 3.25; found C 50.22, H 4.87,
299.1732; found 299.1741; IR (film): nÄ ˆ 1743 cm
;
1H NMR (500 MHz,
C6D6): d ˆ 1.20 ± 1.27 (m, 2H; C6H10), 1.54 ± 1.59 (m, 4H; C6H10), 1.63 ± 1.72
(m, 2H; C6H10), 1.83 ± 1.93 (m, 2H; C6H10), 2.11 (s, 3H; NCH3), 2.47 (pt,
2J6/6' ˆ 10.83, 3J6/5 ˆ 10.83, 1H; H-6), 2.76 (dd, 2J6'/6 ˆ 10.83, 3J6'/5 ˆ 5.30, 1H;
1
3
N 3.07; H NMR (500 MHz, CD3COCD3): d ˆ 1.30 ± 1.37 (m, 1H; C6H10),
H-6'), 3.04 (d, J2/3 ˆ 8.54, 1H; H-2), 3.17 (s, 3H; OCH3), 3.39 (s, 3H;
3
3
1.49 ± 1.72 (m, 8H; C6H10), 1.79 ± 1.82 (m, 1H; C6H10), 3.40 (s, 3H; OCH3),
CO2CH3), 3.58 (m, 1H; H-5), 4.27 (dd, J4/3 ˆ 4.57, J4/5 ˆ 3.87, 1H; H-4),
4.55 (dd, 3J3/2 ˆ 8.54, 3J3/4 ˆ 4.57, 1H; H-3); 13C NMR (125 MHz, C6D6): d ˆ
23.9, 24.2, 25.2, 35.7, 38.3 (5C, C6H10), 43.2 (1C, NCH3), 51.6 (1C, CO2CH3),
54.1 (1C, C-6), 55.9 (1C, OCH3), 70.9 (1C, C-2), 71.9 (1C, C-4), 74.4 (1C,
C-5), 76.2 (1C, C-3), 110.7 (1C, Cspiro), 172.0 (1C, C-1).
2
3
3.65 (dd, J5'/5 ˆ 13.61, J5'/4 ˆ 2.19, 1H; H-5'), 3.74 (m, 1H; H-4), 3.80 (dd,
2J5/5' ˆ 13.61, 3J5/4 ˆ 6.46, 1H; H-5), 3.90 (s, 3H; NCH3), 4.43 (dd, 3J3/2 ˆ 7.35,
3J3/4 ˆ 3.08, 1H; H-3), 4.88 (d, J2/3 ˆ 7.35, 1H; H-2); 13C NMR (125 MHz,
3
CD3COCD3): d ˆ 24.3, 24.7, 26.0, 34.5, 36.4 (5C, C6H10), 53.6 (1C, NCH3),
55.9 (1C, C-5), 58.2 (1C, OCH3), 72.2 (2C, C-3, C-4), 86.2 (1C, C-2), 110.3
(1C, Cspiro), 219.1 (4C, COcis), 225.0 (1C, COtrans), 264.7 (1C, C-1).
Methyl 2,6-dideoxy-3,4-O-isopropylidene-5-O-methyl-2,6-(methylimino)-
d-allonate (17a): As in the general procedure above, compound 16a
(274 mg, 0.70 mmol) was irradiated in solution in methanol (12 mL). After
oxidation and chromatographic purification (eluent Et2O/PE/CH3OH,
15:5:3), 17a was obtained as a colorless syrup (0.49 mmol, 127 mg, 70%).
Pentacarbonyl[1,5-dideoxy-2,3-O-isopropylidene-4-O-methyl-1,5-(methyl-
imino)-d-ribo-pyranosylidene]chromium
(16a):
Compound
16a
(4.32 mmol, 1.69 g, 72%) was isolated as a yellow solid by reaction of
graphite (1.26 g, 105.6 mmol), potassium (516 mg, 13.2 mmol), and
Cr(CO)6 (1.45 g, 6.6 mmol) with 15a (1.29 g, 6.0 mmol) and TMSCl
(2.35 mL, 18.6 mmol) in THF (44 mL). M.p. 1108C (decomp); Rf ˆ 0.38
‡
Rf ˆ 0.60 (Et2O/PE/CH3OH, 15:5:3); MS (70 eV, EI): m/z (%): 259 ([M] ,
‡
‡
2.4), 244 ([M CH3] , 4.7), 200 ([M CO2CH3] , 100), 184 ([244
HCO2CH3], 6.4), 142 ([200 Me2CO], 37.8), 114 (10.0), 100 (10.0), 82
(7.1), 71 (21.4); HR-MS: C12H21NO5: calcd 259.1419; found 259.1430; IR
‡
(Et2O/PE/CH3OH, 15:5:1); MS (70 eV, EI): m/z (%): 391 ([M] , 1.7), 376
‡
‡
‡
(film): nÄ ˆ 1745 cm 1; [a]D
ˆ
7 (c ˆ 0.064, Et2O); C12H21NO5 (259.30):
([M CH3] , 0.3), 363 ([M CO] , 13.7), 335 ([M 2CO] , 2.7), 307
‡
‡
‡
calcd C 55.58, H 8.16, N 5.40; found C 55.59, H 8.14, N 5.40; 1H NMR
(500 MHz, C6D6): d ˆ 1.26 (s, 3H; CH3), 1.56 (s, 3H; CH3), 2.11 (s, 3H;
NCH3), 2.46 (pt, 2J6/6' ˆ 10.72, 3J6/5 ˆ 10.72, 1H; H-6), 2.72 (dd, 2J6'/6 ˆ 10.72,
([M 3CO] , 1.0), 279 ([M 4CO] , 24.1), 251 ([M 5CO] , 100), 94
([H3CNH C Cr] , 51.6); HR-MS: C15H1752CrNO8: calcd 391.0359; found
‡
ˆ ˆ
391.0365; IR (PE): nÄ ˆ 2056, 1976, 1930 cm 1; [a]D ˆ ‡81.5 (c ˆ 0.404,
Et2O); C15H17CrNO8 (391.29): calcd C 46.04, H 4.38, N 3.58; found C 46.03,
H 4.39, N 3.40; 1H NMR (500 MHz, CD3OD): d ˆ 1.47 (s, 3H; CH3), 1.48 (s,
3H; CH3), 3.47 (s, 3H; OCH3), 3.58 (dd, 2J5/5' ˆ 13.71, 3J5/4 ˆ 2.48, 1H; H-5),
3.69 (pquin, 1H; H-4), 3.76 (dd, 2J5'/5 ˆ 13.71, 3J5'/4 ˆ 6.65, 1H; H-5'), 3.93 (s,
3J6'/5 ˆ 5.26, 1H; H-6'), 3.03 (d, J2/3 ˆ 8.44, 1H; H-2), 3.15 (s, 3H; OCH3),
3
3
3
3
3.38 (s, 3H; CO2CH3), 3.49 (ddd, J5/6 ˆ 10.72, J5/6' ˆ 5.26, J5/4 ˆ 3.87, 1H;
H-5), 4.23 (dd, 3J4/3 ˆ 4.67, 3J4/5 ˆ 3.87, 1H; H-4), 4.51 (dd, 3J3/2 ˆ 8.44, 3J3/4
ˆ
4.67, 1H; H-3); 13C NMR (125 MHz, C6D6): d ˆ 26.3, 28.3 (2C, CH3), 43.3
(1C, NCH3), 51.6 (1C, CO2CH3), 54.2 (1C, C-6), 55.9 (1C, OCH3), 70.9
(1C, C-2), 72.2 (1C, C-4), 74.5 (1C, C-5), 76.8 (1C, C-3), 109.9 (1C, Me2C),
172.5 (1C, C-1).
3
3
3
3H; NCH3), 4.39 (dd, J3/2 ˆ 7.55, J3/4 ˆ 3.27, 1H; H-3), 4.94 (d, J2/3 ˆ 7.55,
1H; H-2); 13C NMR (125 MHz, CD3OD): d ˆ 24.4, 26.1 (2C, CH3), 53.5
(1C, NCH3), 55.6 (1C, C-5), 58.2 (1C, OCH3), 72.7 (1C, C-3), 72.9 (1C,
C-4), 86.9 (1C, C-2), 110.1 (1C, Me2C), 219.6 (4C, COcis), 225.4 (1C,
COtrans), 266.9 (1C, C-1).
Methyl 5-O-benzyl-2,6-(benzylimino)-2,6-dideoxy-3,4-O-isopropylidene-
d-allonate (17b): As in the general procedure above, compound 16b
(380 mg, 0.70 mmol) was irradiated in solution in methanol (12 mL). After
oxidation and chromatographic purification (eluent Et2O/PE/CH3OH,
15:5:1) 17b was first obtained as a colorless syrup (0.42 mmol, 170 mg,
59%). Then compound 15b (56 mg) eluted as the product of oxidative
degradation. Rf ˆ 0.49 (Et2O/PE/CH3OH, 15:5:1); MS (70 eV, EI): m/z
Pentacarbonyl[4-O-benzyl-1,5-(benzylimino)-1,5-dideoxy-2,3-O-isopropyli-
dene-d-ribo-pyranosylidene]chromium (16b): Compound 16b (3.09 mmol,
1.68 g, 62%) was obtained as a sticky orange foam by reaction of graphite
(1.05 g, 88.0 mmol), potassium (430 mg, 11.0 mmol), and Cr(CO)6 (1.21 g,
5.5 mmol) with 15b (1.83 g, 5.0 mmol) and TMSCl (1.95 mL, 15.5 mmol) in
THF (35 mL), as described above for compound 3a. Rf ˆ 0.36 (Et2O/PE/
‡
‡
‡
(%): 411 ([M] , 4.1), 396 ([M CH3] , 20.8), 352 ([M CO2CH3] , 85.0),
305 ([396 C7H7], 6.6), 294 ([352 Me2CO], 13.3), 91 ([C7H7] , 100); HR-
‡
‡
CH3OH, 15:10:1); MS (70 eV, EI): m/z (%): 459 ([M 3CO] , 3.3), 431
‡
‡
1
([M 4CO] , 0.8), 403 ([M 5CO] , 1.2), 388 (0.7), 345 ([403 Me2CO],
MS: C24H29NO5: calcd 411.2045; found 411.2048; IR (film): nÄ ˆ 1742 cm
;
1.8), 312 ([403 C7H7], 1.8), 293 ([345 Me2CO], 2.0), 276 (3.0), 170
[a]D ˆ ‡25.8 (c ˆ 0.062, Et2O); C24H29NO5 (411.49): calcd C 70.05, H 7.10,
N 3.40; found C 69.69, H 7.19, N 3.17; 1H NMR (500 MHz, C6D6/TMS): d ˆ
1.22 (s, 3H; CH3), 1.59 (s, 3H; CH3), 2.51 (dd, 2J6/6' ˆ 10.83, 3J6/5 ˆ 10.53, 1H;
([BnNH C Cr] , 11.6), 91 ([C7H7] , 100); HR-MS: C24H2552CrNO5 (M
‡
‡
ˆ ˆ
1
3CO): calcd 459.1137; found 459.1136; IR (PE): 2056, 1977, 1934 cm
;
1H NMR (500 MHz, CD3COCD3): d ˆ 1.46 (s, 3H; CH3), 1.51 (s, 3H; CH3),
2
3
2
H-6), 2.95 (dd, J6'/6 ˆ 10.83, J6'/5 ˆ 5.26, 1H; H-6'), 3.14 (d, J ˆ 13.11, 1H;
2
3
2
3
3
3.40 (dd, J5'/5 ˆ 14.27, J5'/4 ˆ 1.94, 1H; H-5'), 3.68 (dd, J5/5' ˆ 14.27, J5/4
ˆ
PhCH2), 3.31 (s, 3H; OCH3), 3.38 (d, J2/3 ˆ 7.85, 1H; H-2), 3.63 (ddd,
3
3
3J5/6 ˆ 10.53, J5/6' ˆ 5.26, J5/4 ˆ 3.87, 1H; H-5), 3.76 (d, 2J ˆ 13.11, 1H;
3
3
5.31, 1H; H-5), 3.95 (m, 1H; H-4), 4.45 (dd, J3/2 ˆ 8.09, J3/4 ˆ 4.57, 1H;
H-3), 4.46 (d, 2J ˆ 12.16, 1H; PhCH2), 4.71 (d, 2J ˆ 12.16, 1H; PhCH2), 5.07
3
3
PhCH2), 4.19 (d, 2J ˆ 11.82, 1H; PhCH2), 4.25 (dd, J4/3 ˆ 4.87, J4/5 ˆ 3.87,
1H; H-4), 4.32 (d, 2J ˆ 11.82, 1H; PhCH2), 4.53 (dd, 3J3/2 ˆ 7.85, 3J3/4 ˆ 4.87,
1H; H-3), 7.03 ± 7.33 (m, 10H; H-aryl); 13C NMR (125 MHz, C6D6/TMS):
d ˆ 26.2, 28.3 (2C, CH3), 50.1 (1C, C-6), 51.6 (1C, CO2CH3), 59.7 (1C,
PhCH2), 69.5 (1C, C-2), 70.7 (1C, PhCH2), 73.0 (1C, C-5), 73.2 (1C, C-4),
77.0 (1C, C-3), 110.1 (1C, Me2C), 127.5, 127.6, 128.3, 128.4, 128.5, 129.3
(10C, aryl-C), 138.4, 138.8 (2C, Cipso), 172.7 (1C, C-1).
3
(d, J2/3 ˆ 8.09, 1H; H-2), 5.53 (d, 2J ˆ 14.70, 1H; PhCH2), 5.58 (d, 2J ˆ
14.70, 1H; PhCH2), 7.23 ± 7.33 (m, 8H; H-aryl), 7.39 ± 7.42 (m, 2H; H-aryl);
13C NMR (125 MHz, CD3COCD3): d ˆ 24.2, 26.0 (2C, CH3), 54.2 (1C, C-5),
68.8 (1C, PhCH2), 70.1 (1C, C-4), 72.4 (1C, PhCH2), 72.9 (1C, C-3), 86.5
(1C, C-2), 109.5 (1C, Me2C), 127.8, 128.1, 128.9, 129.0, 129.1, 129.5 (10C,
aryl-C), 134.9, 139.5 (2C, Cipso), 218.7 (4C, COcis), 224.9 (1C, COtrans), 267.5
(1C, C-1).
(6'-Deoxy-1',2':3',4'-di-O-isopropylidene-a-d-galactopyranos-6'-yl)-2,6-di-
deoxy-3,4-O-isopropylidene-5-O-methyl-2,6-(methylimino)-d-allonate
(19): A solution of 16a (274 mg, 0.70 mmol) and 1,2:3,4-di-O-isopropyli-
dene-a-d-galactopyranose 18[23] (200 mg, 0.77 mmol) in THF (6 mL) was
irradiated for five days. Oxidative workup of the reaction residue in Et2O/
PE (1:1, 40 mL) in air and subsequent chromatographic purification (eluent
Et2O/PE/CH3OH, 15:5:1) give first unconverted starting material 18
(127 mg), followed by the disaccharide 19 as a colorless syrup (0.18 mmol,
88 mg, 25%), and then the lactam 15a (83 mg). Rf ˆ 0.30 (Et2O/PE/
General procedure for the photoinduced generation of the methyl 2,6-
imino-d-allonates 10 and 17a,b: Carbene complex 9 or 16a,b and methanol
were loaded into a flame-dried Schlenk tube. The resulting solution (under
argon) was irradiated with a 125 W high-pressure mercury lamp at 258C for
five days. The solvent was evaporated and the residue was taken up in
Et2O/PE (1:1, 40 mL). Unconverted carbene complex and chromium
precipitates were oxidized by vigorous stirring in air. After filtration of the
solids and evaporation of the solvent, the crude product was purified by
column chromatography.
‡
CH3OH, 15:5:1); MS (70 eV, EI): m/z (%): 487 ([M] , 0.8), 472 ([M
‡
Methyl 3,4-O-cyclohexylidene-2,6-dideoxy-5-O-methyl-2,6-(methylimino)-
d-allonate (10): As in the general procedure above, compound 9 (164 mg,
0.38 mmol) was irradiated in solution in methanol (9 mL). After oxidation
and chromatographic purification (eluent Et2O/PE/CH3OH, 15:5:1), 10
was obtained as a colorless syrup (0.14 mmol, 43 mg, 38%). Rf ˆ 0.32
CH3] , 7.8), 414 ([472 Me2CO], 1.5), 245 (2.0), 200 (100), 142 ([200
Me2CO], 16.1); HR-MS: C23H37NO10: calcd 487.2417; found 487.2414;
[a]D
ˆ
21.3 (c ˆ 0.052, Et2O); C23H37NO10 (487.54): calcd C 56.66, H 7.65,
N 2.87; found C 56.37, H 7.56, N 2.68; 1H NMR (500 MHz, C6D6): d ˆ 1.02
(s, 3H; CH3gal), 1.10 (s, 3H; CH3gal), 1.24 (s, 3H; CH3all), 1.39 (s, 3H; CH3gal),
698
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Chem. Eur. J. 1999, 5, No. 2

Chromium-Modified Sugars
691±699
1.45 (s, 3H; CH3gal), 1.58 (s, 3H; CH3all), 2.22 (s, 3H; NCH3), 2.45 (pt,
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Ed. Engl. 1984, 23, 587 ± 608; b) W. D. Wulff in Comprehensive
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5538 ± 5540; b) L. S. Hegedus, G. de Weck, S. D'Andrea, J. Am. Chem.
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2J6/6a ˆ 10.76, 3J6/5 ˆ 10.76, 1H; H-6), 2.70 (dd, 2J6a/6 ˆ 10.76, 3J6a/5 ˆ 5.28, 1H;
H-6a), 3.09 (d, 3J2/3 ˆ 8.42, 1H; H-2), 3.12 (s, 3H; OCH3), 3.46 (ddd, 3J5/6
ˆ
3
3
3
3
10.76, J5/6a ˆ 5.28, J5/4 ˆ 3.92, 1H; H-5), 3.84 (dd, J4'/3' ˆ 7.92, J4'/5' ˆ 1.85,
1H; H-4'), 4.11 (dd, 3J2'/1' ˆ 5.09, 3J2'/3' ˆ 2.44, 1H; H-2'), 4.19 ± 4.22 (m, 2H;
H-4, H-5'), 4.42 (dd, 3J3'/4' ˆ 7.92, 3J3'/2' ˆ 2.44, 1H; H-3'), 4.51 (dd, 3J3/2 ˆ 8.42,
3J3/4 ˆ 4.70, 1H; H-3), 4.53 ± 4.56 (m, 2H; H-6', H-6a'), 5.44 (d, 3J1'/2' ˆ 5.09,
1H; H-1'); 13C NMR (125 MHz, C6D6): d ˆ 24.2 (1C, CH3gal), 24.8 (1C,
CH3gal), 26.0 (1C, CH3all), 26.1 (1C, CH3gal), 26.3 (1C, CH3gal), 28.3 (1C,
CH3all), 43.4 (1C, NCH3), 54.2 (1C, C-6), 55.9 (1C, OCH3), 64.4 (1C, C-6'),
66.6 (1C, C-4/5'), 70.7 (1C, C-2'), 70.9 (1C, C-2), 71.1 (1C, C-3'), 71.3 (1C,
C-4'), 72.4 (1C, C-4/5'), 74.6 (1C, C-5), 76.8 (1C, C-3), 96.6 (1C, C-1'), 108.4
(1C, Me2Cgal), 109.4 (1C, Me2Cgal), 109.9 (1C, Me2Call), 172.0 (1C, C-1).
Acknowledgements
Support from the Deutsche Forschungsgemeinschaft (SFB 334), the
Graduiertenkolleg (ꢁSpektroskopie isolierter und kondensierter Mole-
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Received: August 14, 1998 [F1305]
Chem. Eur. J. 1999, 5, No. 2
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