The influence of electronic factors on palladium-mediated cycloisomerization: a systematic investigation of competitive 5-exo-dig versus 6-endo-dig cyclizations of sugar alkynols

Article abstract of DOI:10.1016/j.tet.2007.10.072

Pd-mediated cycloisomerization of 3-C-alkynyl-allo- and ribofuranose derivatives was investigated in detail to understand the influence of electronic factors on the regioselectivity in ring closure reaction. The reactions in general are influenced by the

Full text of DOI:10.1016/j.tet.2007.10.072

Available online at www.sciencedirect.com
Tetrahedron 64 (2008) 219e233
www.elsevier.com/locate/tet
The influence of electronic factors on palladium-mediated
cycloisomerization: a systematic investigation of competitive
5-exo-dig versus 6-endo-dig cyclizations of sugar alkynols
*
C.V. Ramana , Rosy Mallik, Rajesh G. Gonnade
National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411 008, India
Received 13 June 2007; received in revised form 1 October 2007; accepted 18 October 2007
Available online 22 October 2007
Abstract
Pd-mediated cycloisomerization of 3-C-alkynyl-allo- and ribofuranose derivatives was investigated in detail to understand the influence of
electronic factors on the regioselectivity in ring closure reaction. The reactions in general are influenced by the electronic nature of the substi-
tuent on the alkyne unit. A preference for endo-dig cyclization over exo-dig is noted, if the alkynyl substituent is not sufficiently electron with-
drawing.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Palladium; Cycloisomerization; C-Alkynyl furanose; Spiroketal; Enol ether
1. Introduction
bond triggers the dominance of 5-exo-dig over 6-endo-dig for
electronically unbiased acetylenes.6 The majority of theoretical
and experimental studies to understand 5-exo-dig versus
6-endo-dig cyclizations consider mainly the base-mediated
cyclization with hard nucleophiles,7 however, investigations
dealing with metal-catalyzed cyclizations8,10 are rare.
The pioneering work by Utimoto on the Pd-mediated cyclo-
isomerization of alkynyl diols leading to the formation of
bicyclic and spiroacetal natural products has indeed disclosed
some of the aspects related to the regiochemistry of these cy-
clizations.3g In one example it has been found that the mode of
cyclization depends upon the relative orientation of both react-
ing groups (Scheme 1) as noticed with the mercury(II)-medi-
ated cyclization reported by Schwartz and Reideker earlier.9
The participation of enolic eOH of 1,3-diketones in metal de-
pendent endo/exo selective cycloisomerization was reported
by Gulias et al.10 In this context, recently we reported a prelim-
inary investigation dealing with the influence of electronic fac-
tors on the Pd-mediated cycloisomerization reaction.11
Transition metal-mediated addition of C-and heteroatom
nucleophiles across a carbonecarbon double and/or triple bonds
is one of the most interesting and important reactions in organic
chemistry.1 The intramolecular version of this reaction falls un-
der the broad category of cycloisomerization reactions. Cyclo-
isomerization reactions are characterized by their complete
atom economy and has been recognized as an attractive tool
for delivering complex molecular diversity.2 Cycloisomeriza-
tion of alkynols is projected as a tool to synthesize oxygen-con-
taining heterocycles encompassing functionalized furan, pyran,
benzopyran, and spiroketal skeletons.3 Various transition metals
like palladium, platinum, tungsten, molybdenum, ruthenium,
rhodium, gold, and iridium have been explored as catalysts for
cycloisomerization reactions.4 The key issue is the mode of
cyclization, i.e., exo-dig versus endo-dig.5 There are several
instances in the literature which indicate that the obtuse angle
of 120ꢀe127ꢀ for the approach of a nucleophile to a triple
Herein we describe a complete compilation of our investi-
gations dealing with electronic control over the cycloisomeri-
zation of 3-C-alkynylfuranosyl derivatives (Fig. 1) using a set
of two different alkynol models (8e14 and 15e21) for
* Corresponding author. Tel.: þ91 20 25902577; fax: þ91 20 25902629.
E-mail address: vr.chepuri@ncl.res.in (C.V. Ramana).
0040-4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.10.072

220
C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
derivative 22.15 According to known procedure D-xylose was
OTBS
OTBS
MgCl
THF, 0 °C
O
O
converted to 22 in four steps with an overall yield of 42%. Ad-
dition of ethynylmagnesium chloride, prepared by exchange
with n-butylmagnesium chloride, gave 23, and of the lithiated
salts of 1-octyne and phenylacetylene (Scheme 1) gave 24 and
25, respectively. To prepare the other substrates, the Sonoga-
shira coupling16 reaction of 23 with different aryl iodides
was carried out to give compounds 26e29. The TBS group
present at O-5 of 23e29 was subsequently removed by using
TBAF/THF to give substrates 8e14.
The synthesis of the second set of cycloisomerization sub-
strates 15e21 was carried out in a similar manner from ulose
30 (Scheme 2).17 Following an established sequence for 22,
the protected alkynols 31e37 were prepared by initial addition
of alkynyl nucleophiles and Sonogashira coupling reactions of
aklynol 31. The selective hydrolysis of the 5,6-acetonide
groups of 31e37 with cat. H2SO4 in methanol gave a second
set of substrates 15e21.
rt
R
ref 15
4 steps
O
D-Xylose
O
or
O
HO
O
R
Li
O
THF, -78 °C
22
23 (R = H, 84%)
24 (R = n-hexyl, 88%)
25 (R = Ph, 81%)
OTBS
O
R
OTBS
R
O
O
I
O
8 - 14
80 - 85%
O
HO
TBAF
THF, 0 °C
Pd(PPh3)Cl2
O
HO
23
26 (R = 4-OMe, 80%)
27 (R = 4-NO2, 78%)
28 (R = 3-NO2, 76%)
29 (R = 2-NO2, 81%)
PPh3, CuI
Et3N, DMF
Scheme 1. Synthesis of 3-C-alkynyl-ribofuranose derivatives 8e14.
5-exo-dig versus 6-endo-dig mode of competitive cyclizations.
In the case of the first set of compounds 8e14, the cycloiso-
merization is expected to lead to [3.3.0] or [3.4.0]dioxabicycli-
cenol ether derivatives, whereas the formation of fused [2.2.1]
or [3.2.1]bicyclicacetal derivatives is possible from the second
set of compounds 15e21 (Fig. 1). Because these bicyclic
acetals exist in many biologically active and structurally
diverse natural products,12 the results from the present investi-
gation will be important for the strategic construction of these
molecular skeletons.13 It is pertinent to mention that the metal-
mediated cycloisomerization reactions of carbohydrate precur-
sors have been less explored and mainly confined to glycals,
exo-glycals, and related derivatives.14
2.2. Cycloisomerization of alkynols 8e14
The Pd-catalyzed cycloisomerization reactions of model
3-C-alkynyl-ribofuranose derivatives 8e14 were carried out
in the presence of PdCl2(CH3CN)2 in MeCN at room temper-
ature. The results are summarized in Scheme 3. The parent
compound 8 gave exclusively ketal 38 resulting from hydroly-
sis of the intermediate exo-enol. The structure of ketal 38 was
supported by spectral and elemental analyses. The characteris-
tic hemiketal carbon singlet appeared at d 105.6 ppm, thus
confirming the assigned structure. Cycloisomerization of alky-
nol 9 afforded the endo-product 39 exclusively, whose struc-
ture was supported by spectral and elemental analyses. For
example, a broad singlet corresponding to olefinic-H appeared
2. Results and discussion
2.1. Synthesis of cycloisomerization substrates 8e21
Two different approaches have been adopted for the synthe-
sis of the substrates 8e21. The first approach involves the
addition of HC^CeMgCl or a suitable ReC^CeLi (R:
en-C6H13 or ePh) and the second one utilizes the Sonogashira
coupling of the ethynyl Grignard product with the respective
substituted iodoarenes.
1
at much higher field (d 4.40 ppm) in the H NMR spectrum
and the olefinic carbons with substantial chemical shift differ-
ence [d 94.1 (d), 159.6 (s)] and upfield OCH2 triplet at
d 62.9 ppm in the 13C NMR spectrum of compound 39 clearly
established the presence of a dihydropyran unit. Compound 39
was found to be susceptible to hydration in CDCl3 and resulted
in the formation of hemiketal 40 as a single anomer. The
The synthesis of the requisite model 3-C-alkynyl-ribofura-
nose derivatives 8e14 was started from the known 3-ulose
HO
HO
OH
OH
O
6-endo-dig
5-exo-dig
O
O
O
O
R
O
R
R
R
R
O
HO
O
HO
Hg(II)
R =
H-
n-C4H9
n-C4H9
or Pd(II)
O
O
n-C4H9
HO
1
3
8
9
15
16
17
18
19
n-hexyl-
''
Ph-
10
11
12
n-C4H9
HO
2
4
4-MeOPh-
4-O2NPh-
O
O
O
O
O
CH3
CH3
O
CH3
M+2
3-O2NPh-
2-O2NPh-
13
14
20
21
+
5
Pd(OAc)2
PtCl2
(8:1)
(1:14)
6
7
Figure 1. Competitive 5-exo-dig and 6-endo-dig cyclizations of alkynols, some representative examples, and designed substrates for understanding the electronic
control over these cyclizations.

C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
O
221
O
O
O
O
O
R
Li
O
O
ref 17
R
D-Glucose
O
THF, −78 °C
2 steps
57%
O
or
O
O
OH
MgCl
30
31 (R = H, 63%)
32 (R = n-C6H13, 73%)
33 (R = Ph, 75%)
THF,0 °C
O
R
O
O
O
O
O
O
I
O
15 − 21
63 − 85%
0.8% H2SO4
MeOH, rt
R
O
OH
31
OH
Pd(PPh3)Cl2
PPh3, CuI
Et3N, DMF
34 (R = 4-OMe, 70%)
35 (R = 4-NO2, 91%)
36 (R = 3-NO2, 95%)
37 (R = 2-NO2, 84%)
Scheme 2. Synthesis of 3-C-alkynyl-allofuranose derivatives 15e21.
OH
O
O
O
O
O
O
Pd(CH3CN)2Cl2
CH3CN, rt
O
+
O
R
O
OH
R
O
(ppm)
OH
R
H
O
HO
H
(ppm)
--
O
O
R = H
8
9
38 (67%)
--
--
--
O
O
n-hexyl
--
39 (51%) 4.40
42 (59%) 5.18
43 (77%) 5.06
OH
OH
Ph
10
11
12
13
14
41 (29%)
--
5.51
--
38
4-MeOPh
4-O2NPh
3-O2NPh
2-O2NPh
O
O
44 (80%)
45 (64%)
47 (60%)
5.61
5.59
6.00
--
--
O
HO
n-C6H12
46 (14%) 5.37
48 (20%) 4.97
O
OH
40
Scheme 3. Cycloisomerization reactions of 3-C-alkynyl-ribofuranose derivatives 8e14.
spectral data of the resulting product 40 are in accordance with
the assigned structure and further supported by single crystal
X-ray structural analysis (Fig. 2). While the cycloisomeriza-
tion of the simple phenylalkynol 10 gave a regiomeric mixture
of exo-product 41 (29%) and the endo-product 42 (59%), only
formation of endo-product 43 was observed with methoxy-
phenyl alkynol 11. The structures of the exo-product 41 and
is found to be more shielded compared to the olefinic-H of
corresponding isomeric exo-enols (furan derivatives 41, 44,
45, 47). The single crystal X-ray structural analysis of the
exo-products 44 and 47 (Table 1) proved their structures
unambiguously.
2.3. Cycloisomerization of alkynols 15e21
1
of the endo-product 42 were proposed with the help of H
and 13C NMR analyses. For example, the characteristic furan
ring CH2 triplet of 41 (d 71.2 ppm) resonated at 9.6 ppm
downfield when compared to corresponding pyran CH2 triplet
of 41 (d 63.6 ppm) in the 13C NMR spectrum. The single crys-
tal X-ray study (Fig. 2) of the endo-product 42 unambiguously
proved its structure.
The cycloisomerizations of the regiomeric nitrophenylalky-
nols 12e14 are in general fast compared to the other alkynols
and afforded 5-exo-products exclusively or as the major prod-
ucts. From the cycloisomerization reactions of o- and m-nitro
derivatives 12 and 13, the endo-products 46 and 48, respec-
tively, could be isolated and characterized. The comparative
NMR spectral patterns of 46 and 48 with those of correspond-
ing endo-products 40, 42, and 43 confirmed their assigned
structure. Comparative chemical shifts of endo- and exo-cyclic
enolic-H are given in Scheme 3. In general the olefinic-H of
the endo-enols (in dihydropyran derivatives 42, 43, 46, 48)
The results of the PdCl2(CH3CN)2-catalyzed cycloisomeri-
zations of 3-C-alkynyl-allofuranose derivatives 15e21 are
given in Scheme 4. As indicated in Scheme 4, the cycloisome-
rization of monosubstituted alkynol 15 gave exclusively the
known [2.2.1]bicyclic acetal 49.17b In the case of n-hexyl
substituted alkynol 16 we exclusively obtained the endo-prod-
uct 50. The appearance of one of the methylene unit protons
separately as doublets at d 1.60 and 1.93 ppm with large gem-
1
inal coupling constant (14.9 Hz) in the H NMR spectrum of
50 clearly indicates that this methylene unit has no adjacent-
H coupled and thus establishes the assigned [3.2.1] bicyclic
acetal structure.18 With phenyl substituted alkynol 17, two
products 51 and 52 were isolated in 30% and 65% yields, re-
1
spectively. Considering the similarity in the H NMR spectral
pattern of 52 with 50 (two doublets at d 1.80 and 2.18 with
Jgem¼14.6 Hz), we assigned a [3.2.1] bicyclic acetal structure,
which was further confirmed by the single crystal structural

222
C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
Figure 2. ORTEP structures of (a) compound 40, (b) compound 42, (c) compound 44, and (d) compound 47.
analysis (Fig. 3, Table 1). The appearance of the enolic-H at
1
d 5.49 ppm in the H NMR spectrum of minor product 51
general terminal alkynes prefer exo-mode of approach of the
incoming nucleophile in intra- and intermolecular nucleophilic
addition reactions.1,19 Though the formation of the endo-prod-
uct from the alkynols 9 and 16 contrasts with the results
obtained in the cyclization of 1, the relative inductive effects
of the n-hexyl and the densely oxygenated furanose ring
explain this. In case of aryl-substituted alkynols 10e14 and
17e21, it is evident from the results obtained that a competi-
tive balance between ꢁI effect of the furanose ring and þM
effect of the aryl substituents is operational. These studies re-
veal that the presence of a þM substituent (eOMe in our case)
on the aromatic ring in general enforces a 6-endo-dig while
ꢁM group (eNO2 in our case) favored 5-exo-dig modes of
clearly indicated its exo-cyclic nature. The cycloisomerization
of p- and o-nitrophenyl substituted alkynols 19 and 21 gave
exclusively exo-cyclic products 54 and 57, respectively; how-
ever, m-nitro derivative 20 gave small amounts of [3.2.1] bicy-
clic acetal 56 along with the exo-cyclic product 55. These
results are comparable with the results we obtained for the
ribose derivatives 8e14.
From the results obtained with alkynols 8e21, it is evident
that the regioselectivity of ring closure depends upon the na-
ture of the substituents on alkyne. The formation of exclusive
5-exo-products from parent alkynols 8 and 15 is expected. In
Table 1
Crystal data for compounds 40, 42, 44, 47, 52, and 5320e22
Crystal data
40
42
44
47
52
53
Formula
Mr
C
16H28O6
C16H18O5
290.30
C16H17NO7
335.31
C16H17NO7
335.31
C17H20O6
320.33
0.75ꢂ0.43ꢂ0.37
Monoclinic
P21
9.003(3)
6.838(2)
12.987(4)
90
C18H22O7
350.36
316.38
0.92ꢂ0.08ꢂ0.06
Orthorhombic
P212121
5.460(3)
10.235(5)
30.624(14)
90
Crystal size, mm
Crystal system
Space group
0.73ꢂ0.36ꢂ0.14
Monoclinic
C2
18.566(7)
6.108(2)
12.932(5)
90
0.56ꢂ0.16ꢂ0.04
Monoclinic
P21
5.6459(19)
8.098(3)
17.191(6)
90
0.43ꢂ0.41ꢂ0.25
Monoclinic
P21
5.6601(6)
9.8552(11)
13.9858(15)
90
0.77ꢂ0.56ꢂ0.41
Orthorhombic
P212121
5.946(2)
14.795(5)
19.346(7)
90
˚
a [A]
˚
b [A]
˚
c [A]
a [ꢀ]
b [ꢀ]
g [ꢀ]
90
90
99.458(6)
90
91.759(6)
90
93.574(2)
90
97.972(5)
90
90
90
3
˚
V [A ]
1711.4(13)
4
688
1446.5(10)
4
616
785.6(5)
2
352
778.63(15)
2
352
791.8(4)
2
340
1702.0(10)
4
744
Z
F(000)
D calcd [g cmꢁ3
]
1.228
0.093
1.333
0.099
1.417
0.112
1.430
0.113
1.344
0.102
1.367
0.105
m [mmꢁ1
]
Absorption correction
min/Tmax
Multi-scan
0.9033/0.9945
15,902
3000
Multi-scan
0.9310/0.9858
5227
Multi-scan
0.9396/0.9951
5763
Multi-scan
0.9532/0.9716
3981
Multi-scan
0.9274/0.9638
5633
Multi-scan
0.9233/0.9581
12,270
T
Reflns. collected
Unique reflns.
Observed reflns.
No. of parameters
R1 [I>2s(I )]
WR2
2498
2327
2776
2402
2451
2340
2583
2455
2958
2865
2768
210
196
0.0309
263
0.0364
242
0.0307
215
237
0.0311
0.0771
0.1407
0.0849
0.1435
1.272
0.0339
0.0881
0.0357
0.0898
1.036
0.0759
0.0340
0.0665
0.0450
0.0763
0.0323
0.0776
0.0320
R1 (all data)
WR2 (all data)
Goodness-of-fit
Drmax, Drmin (e A
0.0777
1.068
0.0710
1.076
0.0777
1.055
0.0782
1.076
ꢁ3
˚
)
þ0.226, ꢁ0.161
þ0.135, ꢁ0.112
þ0.130, ꢁ0.087
þ0.116, ꢁ0.140
þ0.159, ꢁ0.159
þ0.111, ꢁ0.176

C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
223
HO
HO
HO
O
O
O
O
O
O
Pd(CH3CN)2Cl2
O
O
O
O
O
O
O
O
R
CH3CN
rt, 3 − 10h
O
OH
OH
O
OH
O
R
HO
H
R
(ppm)
--
--
R = H
n
--
--
49 (87%)
15
--
hexyl
50 (55%)
52 (65%)
53 (82%)
--
16
17
18
19
20
21
--
--
--
--
--
--
51 (30%)
--
5.49
--
Ph
p-MeOPh
p-O2NPh
54 (87%)
55 (65%)
57 (72%)
5.52
5.53
6.00
m-O2NPh
o-O2NPh
56 (18%)
--
Scheme 4. Cycloisomerization reactions of 3-C-alkynyl-allofuranose derivatives 15e21.
cyclization. However, the directional influence of the þM
OH
group is strong when it is positioned para to the alkyne.
Thus, an electronic control exists over the mode of cycliza-
tion in Pd-mediated cycloisomerization. The information is
significant when compared to the base-mediated cycloisomeri-
zation reactions. Recently, base-mediated cycloisomerization
of sugar derived alkynols was dealt with in detail by Vasella
and co-workers,14a,b who reported that these cycloisomeriza-
tions in general prefer either 5- or 6-exo-dig mode of cycliza-
tion and in case if the exo-mode of ring closure is disfavored
due to ring strain, isomerization to the allenes is preferred over
an alkynol cycloisomerization. Earlier, Padwa’s group7c,d had
extensively investigated the base-induced cycloisomerization
of several (phenylethyny1)aryl-substituted alcohols modulat-
ing one of the phenyl ring substituents (Fig. 4).
O
O
R
5-exo-dig
workup H+
R
R
R = H, OMe,
= NO2
R = CHO
= CO2Et
Figure 4. Cycloisomerization of (phenylethynyl)benzyl alcohols.
followed by an acid-catalyzed rearrangement. Along similar
lines, Hiroya et al.7a concluded that the regioselectivity in
base-mediated cycloisomerization reactions is not influenced
by the electronic nature of the functional group on the triple
bond, but by steric congestion.
It has been concluded that 5-exo-dig mode of cyclization
was exclusively independent of the nature of the aryl substit-
uent. Though they could isolate exclusively the 6-endo product
in case of substrates bearing a carbonyl group in the ortho
position of the aromatic ring, it was shown that these apparent
6-endo cyclizations are the consequence of a 5-exo cyclization
3. Conclusions
In summary, electronic control over the 5-exo-dig versus
6-endo-dig modes of cyclizations in Pd-mediated cycloisome-
rization reaction has been studied in detail. 3-C-Alkynyl-allo-
and ribofuranose derivatives with systematic variation of
functional groups at the opposite side of alkyne were employed
to understand the competitive balance between inductive effect
of furanose ring and mesomeric effect of aryl substituent. A
preference for endo-dig cyclization over exo-dig is observed,
if the aryl substituent is not sufficiently electron withdrawing.
At the outset of these studies, a simple access to highly func-
tionalized tetrahydrofuran fused bicyclic acetals and enol ether
derivatives was needed and this has been achieved using easily
accessible sugar derived alkynols and Pd-mediated coupling
and cyclization reactions.
4. Experimental
4.1. General methods
Air and/or moisture sensitive reactions were carried out in
anhydrous solvents under an atmosphere of argon in oven-
dried glassware. All anhydrous solvents were distilled prior
to use: THF and diethyl ether from Na and benzophenone,
Figure 3. ORTEP structures of (a) compound 52 and (b) compound 53.

224
C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
CH2Cl2 and CH3CN from CaH2, MeOH from Mg cake. Com-
mercial reagents were used without purification. Column chro-
matography was carried out by using Spectrochem silica gel
(60e120 mesh). Specific optical rotations [a]D are measured
at 25 ꢀC and given in 10ꢁ1 deg cm2 gꢁ1. Infrared spectra
were recorded in CHCl3 and are reported in wave number
(cmꢁ1). 1H and 13C NMR chemical shifts are reported in parts
per million downfield from tetramethylsilane and coupling
constants (J ) are reported in hertz (Hz). The following abbre-
viations are used to designate signal multiplicity: s¼singlet,
d¼doublet, t¼triplet, q¼quartet, m¼multiplet, br¼broad.
(t, J¼6.9 Hz, 3H), 0.89 (s, 9H), 1.24e1.32 (m, 5H), 1.35 (s,
3H), 1.43e1.53 (m, 3H), 1.57 (s, 3H), 2.21 (t, J¼7.0 Hz,
2H), 2.91 (s, 1H), 3.91e3.94 (m, 3H), 4.47 (d, J¼3.6 Hz,
1H), 5.79 (d, J¼3.6 Hz, 1H). 13C NMR (75 MHz) d: ꢁ5.7
(q), ꢁ5.5 (q), 13.7 (q), 18.0 (s), 18.4 (t), 22.2 (t), 25.6 (q,
3C), 26.4 (q), 26.5 (q), 28.1 (t), 28.2 (t), 31.0 (t), 63.0 (t),
75.0 (s), 76.8 (s), 81.8 (d), 84.1 (d), 88.3 (s), 103.9 (d),
112.7 (s). Anal. Calcd for C22H40O5Si: C, 64.04; H 9.77.
Found: C, 64.15; H, 10.01.
4.1.3. 1,2-O-Isopropylidene-5-O-(tert-butyldimethylsilyl)-
3-C-phenylethynyl-a-D-ribofuranose (25)
4.1.1. 1,2-O-Isopropylidene-5-O-(tert-butyldimethylsilyl)-
3-C-ethynyl-a-D-ribofuranose (23)
To a solution of phenylacetylene (400 mg, 3.9 mmol) in
THF (20 mL) at ꢁ78 ꢀC, n-BuLi (2 mL, 3.13 mmol, 1.6 M
in hexane) was added dropwise. After 1 h, a solution of com-
pound 22 (790 mg, 2.6 mmol) in THF (10 mL) was added and
stirring continued for 3 h at ꢁ78 ꢀC. The reaction was
quenched by adding saturated NH4Cl solution, diluted with
water, and extracted with ethyl acetate. The combined organic
layers were dried over Na2SO4 and concentrated. The residue
was purified on silica gel (10% ethyl acetate in light petro-
leum) to afford 25 (920 mg, 81%) as a syrup. [a]D 2.5 (c
1.5, CHCl3). IR (CHCl3): n 3459, 2929, 2856, 1599, 1492,
Mg (1.11 g, 46.3 mmol) was flame dried in a two neck R.B.
flask fitted with a reflux condenser and cooled to room temper-
ature in argon atmosphere. Dry THF (30 mL) was introduced
followed by a few crystals of iodine. Half of the total volume
of n-BuCl (4.84 mL, 46.3 mmol) was added and the contents
were refluxed till the generation of Grignard reagent. Heating
was removed and rest of n-BuCl was added. Stirring was con-
tinued at room temperature till all the magnesium was con-
sumed. Then the reaction mixture was cooled to 0 ꢀC and
acetylene gas was bubbled into it for 15 min. Ketone 22
(3.5 g, 11.6 mmol) in THF (20 mL) was added at 0 ꢀC and
stirred for 30 min. The reaction was quenched with saturated
NH4Cl solution, diluted with water, and extracted with ethyl
acetate. The combined organic layers were dried over
Na2SO4, concentrated and purified on silica gel (10% ethyl ace-
tate in light petroleum) to give 23 (3.2 g, 84%) as a colorless
oil. [a]D 10.5 (c 1, CHCl3). IR (CHCl3): n 3306, 3019, 2931,
1463, 1383, 1254, 1099, 1035, 1001, 880, 836, 690 cmꢁ1
.
1H NMR (200 MHz, CDCl3) d: 0.09 (s, 3H), 0.10 (s, 3H),
0.90 (s, 9H), 1.38 (s, 3H), 1.62 (s, 3H), 3.14 (s, 1H), 3.99e
4.12 (m, 3H), 4.65 (d, J¼3.6 Hz, 1H), 5.89 (d, J¼3.6 Hz,
1H), 7.29e7.35 (m, 3H), 7.40e7.45 (m, 2H). 13C NMR
(75 MHz) d: ꢁ5.5 (q), ꢁ5.3 (q), 18.2 (s), 25.9 (q, 3C), 26.7
(q, 2C), 63.1 (t), 76.0 (s), 81.7 (d), 84.2 (d), 85.7 (s), 87.8
(s), 104.3 (d), 113.4 (s), 121.9 (s), 128.2 (d, 2C), 128.8 (d),
131.8 (d, 2C). Anal. Calcd for C22H32O5Si: C, 65.31; H,
7.97. Found: C, 65.59; H, 7.80.
1
2401, 1514, 1459, 1376, 1163, 1092, 1012 cmꢁ1. H NMR
(200 MHz, CDCl3) d: 0.08 (s, 3H), 0.09 (s, 3H), 0.89 (s,
9H), 1.36 (s, 3H), 1.58 (s, 3H), 2.54 (s, 1H), 3.05 (br s, 1H),
3.91e3.98 (m, 3H), 4.55 (d, J¼3.66 Hz, 1H), 5.82 (d,
J¼3.66 Hz, 1H). 13C NMR (50 MHz) d: ꢁ5.63 (q), ꢁ5.45
(q), 18.11 (s), 25.75 (q, 3C), 26.46 (q), 26.57 (q), 62.68 (t),
75.13 (s), 76.00 (d), 80.43 (s), 80.92 (d), 83.71 (d), 103.98
(d), 113.24 (s). MALDI-TOF (MS): calcd for C16H28O5SiNa:
351.16, found: 351.14. Anal. Calcd for C16H28O5Si: C, 58.5;
H 8.59. Found: C, 58.2; H, 8.11.
4.1.4. 1,2-O-Isopropylidene-5-O-(tert-butyldimethylsilyl)-
3-C-(4-methoxyphenylethynyl)-a-D-ribofuranose (26)
4-Iodoanisole (267 mg, 1.14 mmol) was taken in a mixture
of Et3N and DMF (2:1) (5 mL). To this CuI (14 mg,
0.076 mmol), PPh3 (20 mg, 0.076 mmol), and Pd(PPh3)2Cl2
(53 mg, 0.076 mmol) were added followed by alkyne
(250 mg, 0.76 mmol). Argon was flushed several times and
stirred for 2.5 h. After completion, the reaction mixture was
diluted with ethyl acetate and the organic layer was washed
with water, brine, dried over Na2SO4, and concentrated. Puri-
fication of the residue by column chromatography (2:8,
EtOAc/light petroleum) afforded 26 (265 mg, 80%) as a white
spongy mass. [a]D 5.1 (c 1, CHCl3). IR (CHCl3): n 3394, 3019,
4.1.2. 1,2-O-Isopropylidene-5-O-(tert-butyldimethylsilyl)-
3-C-(oct-1-ynyl)-a-D-ribofuranose (24)
To a solution of 1-octyne (273 mg, 2.5 mmol) in THF
(10 mL) at ꢁ78 ꢀC, n-BuLi (1.25 mL, 2 mmol, 1.6 M in hex-
ane) was added dropwise. After 1 h, a solution of compound
22 (500 mg, 1.7 mmol) in THF (8 mL) was added and stirring
was continued for 6 h at ꢁ78 ꢀC. The reaction mixture was
quenched with saturated NH4Cl solution and the aqueous
phase was extracted with ethyl acetate. The combined organic
layers were dried over Na2SO4, concentrated, and purified by
chromatography (10% ethyl acetate in light petroleum) to give
24 (600 mg, 88%) as a syrup. [a]D 9.7 (c 0.9, CHCl3). IR
(CHCl3): n 3537, 3019, 2930, 2857, 2242, 1463, 1375, 1361,
1607, 1510, 1124, 757, 668 cmꢁ1 1H NMR (200 MHz,
.
CDCl3) d: 0.09 (s, 6H), 0.90 (s, 9H), 1.37 (s, 3H), 1.61 (s,
3H), 3.08 (s, 1H), 3.80 (s, 3H), 3.96e4.1 (m, 3H), 4.62 (d,
J¼3.7 Hz, 1H), 5.87 (d, J¼3.7 Hz, 1H), 6.81 (d, J¼8.9 Hz,
2H), 7.34 (d, J¼8.9 Hz, 2H). 13C NMR (75 MHz) d: ꢁ5.4
(q), ꢁ5.2 (q), 18.4 (s), 25.9 (q, 3C), 26.8 (q), 26.9 (q), 55.2
(q), 63.1 (t), 76.1 (s), 81.4 (d), 84.1 (s), 84.2 (d), 87.9 (s),
104.4 (d), 113.4 (s), 113.9 (s), 113.9 (d, 2C), 133.3 (d, 2C),
160.0 (s). MALDI-TOF (MS): calcd for C23H34O6SiNa:
1256, 1217, 1164, 1083, 1007, 873, 838, 667 cmꢁ1 1H
.
NMR (200 MHz, CDCl3) d: 0.07 (s, 3H), 0.08 (s, 3H), 0.87

C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
225
457.2, found: 457.1. Anal. Calcd for C23H34O6Si: C, 63.56; H
7.89. Found: C, 63.15; H, 8.01.
0.89 (s, 9H), 1.38 (s, 3H), 1.60 (s, 3H), 3.2 (s, 1H), 3.99e
4.09 (m, 3H), 4.68 (d, J¼3.66 Hz, 1H), 5.93 (d, J¼3.66 Hz,
1H), 7.44e7.63 (m, 3H), 8.04e8.08 (m, 1H). 13C NMR
(75 MHz) d: ꢁ5.6 (q), ꢁ5.4 (q), 18.2 (s), 25.8 (q, 3C), 26.6 (q),
26.7 (q), 62.9 (t), 76.2 (s), 81.4 (d), 82.9 (s), 83.8 (d), 93.6 (s),
104.3 (d), 113.4 (s), 117.2 (s), 124.7 (d), 129.3 (d), 132.8 (d),
134.7 (d), 149.7 (s). MALDI-TOF (MS): calcd for C22H31NO7-
SiNa: 472.18, found: 472.06. Anal. Calcd for C22H31NO7Si: C,
58.5; H, 8.59; N, 3.12. Found: C, 58.6; H, 8.29; N, 3.14.
4.1.5. 1,2-O-Isopropylidene-5-O-(tert-butyldimethylsilyl)-
3-C-(4-nitrophenylethynyl)-a-D-ribofuranose (27)
To a solution of 4-nitroiodobenzene (341 mg, 1.37 mmol) in
2:1 mixture of Et3N/DMF (5 mL) were added CuI (17 mg,
0.09 mmol), PPh3 (24 mg, 0.09 mmol), and Pd(PPh3)2Cl2
(64 mg, 0.09 mmol) followed by alkyne 23 (300 mg,
0.913 mmol). The reaction mixture was flushed with argon
and stirring was continued for 3 h at 25 ꢀC. Following usual
work-up procedure and purification by column chromatogra-
phy (2:8, EtOAc/light petroleum) gave 27 (321 mg, 78%) as
a yellow oil. [a]D 1.3 (c 0.8, CHCl3). IR (CHCl3): n 3523,
4.1.8. 1,2-O-Isopropylidene-3-C-ethynyl-a-D-ribofuranose (8)
A solution of 23 (140 mg, 0.42 mmol) in THF (2 mL) was
treated with TBAF (0.5 mL, 0.5 mmol, 1 M in THF) at 0 ꢀC
and stirred for 1 h. The reaction mixture was quenched with
saturated NH4Cl solution and partitioned between ethyl ace-
tate and water. The aqueous layer was extracted with ethyl
acetate and the combined organic layers were dried over
Na2SO4 and concentrated. The residue was purified on silica
gel by eluting with 50% ethyl acetate in light petroleum to ob-
tain 8 (75 mg, 82%) as a colorless sticky mass. [a]D 36.7 (c 1,
CHCl3). IR (CHCl3): n 3305, 3019, 2401, 1519, 1377, 1163,
3020, 2931, 2400, 1595, 1523, 1471, 1346, 1096, 838 cmꢁ1
.
1H NMR (200 MHz, CDCl3) d: 0.09 (s, 6H), 0.90 (s, 9H),
1.39 (s, 3H), 1.62 (s, 3H), 3.21 (s, 1H), 3.97e4.12 (m, 1H),
4.66 (d, J¼3.66 Hz, 2H), 5.89 (d, J¼3.66 Hz, 2H), 7.58 (d,
J¼8.97 Hz, 2H), 8.20 (d, J¼8.97 Hz, 2H). 13C NMR
(75 MHz) d: ꢁ5.5 (q), ꢁ5.3 (q), 18.3 (s), 25.9 (q, 3C), 26.6
(q), 26.8 (q), 62.9 (t), 76.2 (s), 81.2 (d), 83.8 (d), 85.7 (s),
91.0 (s), 104.3 (d), 113.7 (s), 123.6 (d, 2C), 128.5 (s), 132.5
(d, 2C), 147.5 (s). MALDI-TOF (MS): calcd for C22H31NO7-
SiNa: 472.18, found: 472.28. Anal. Calcd for C22H31NO7Si:
C, 58.78; H 6.95; N, 3.12. Found: C, 58.99; H, 6.77; N, 3.14.
1019 cmꢁ1 1H NMR (200 MHz, CDCl3) d: 1.35 (s, 3H),
.
1.57 (s, 3H), 2.43 (br s, 1H), 2.59 (s, 1H), 3.29 (br s, 1H),
3.89e3.98 (m, 3H), 4.51 (d, J¼3.7 Hz, 1H), 5.84 (d, J¼
3.7 Hz, 1H). 13C NMR (50 MHz) d: 26.5 (q), 26.7 (q), 61.8
(t), 74.7 (s), 76.8 (d), 79.9 (s), 81.5 (d), 83.8 (d), 103.9 (d),
113.5 (s). MALDI-TOF (MS): calcd for C10H14O5Na:
237.07, found: 237.09. Anal. Calcd for C10H14O5Si: C,
56.07; H, 6.59. Found: C, 56.19; H, 6.47.
4.1.6. 1,2-O-Isopropylidene-5-O-(tert-butyldimethylsilyl)-3-
C-(3-nitrophenylethynyl)-a-D-ribofuranose (28)
Following a similar procedure as described above, the cou-
pling of 3-nitroiodobenzene (295 mg, 1.19 mmol) and alkyne
23 (260 mg, 0.79 mmol) using CuI (15 mg, 0.079 mmol),
PPh3 (21 mg, 0.079 mmol), and Pd(PPh3)2Cl2 (55 mg,
0.079 mmol) afforded 28 (270 mg, 76%) as a colorless oil.
[a]D 2.03 (c 1, CHCl3). IR (CHCl3): n 3450, 2931, 1533,
4.1.9. 1,2-O-Isopropylidene-3-C-oct-1-ynyl-a-D-
ribofuranose (9)
A solution of 24 (1 g, 2.4 mmol) in THF (25 mL) and
TBAF (2.9 mL, 2.9 mmol, 1 M solution in THF) was stirred
at 0 ꢀC for 1 h. Usual workup followed by purification over sil-
ica gel (40% ethyl acetate in light petroleum) gave 9 (600 mg,
83%) as a syrup. [a]D 41 (c 0.5, CHCl3). IR (CHCl3): n 3460,
3019, 2934, 2860, 2240, 1456, 1377, 1163, 1078, 1008, 873,
1472, 1352, 1258, 1102, 838 cmꢁ1 1H NMR (200 MHz,
.
CDCl3) d: 0.10 (s, 6H), 0.9 (s, 9H), 1.39 (s, 3H), 1.62 (s, 3H),
3.2 (s, 1H), 3.98e4.12 (m, 3H), 4.66 (d, J¼3.68 Hz, 1H),
5.89 (d, J¼3.68 Hz, 1H), 7.51 (t, J¼8 Hz, 1H), 7.72 (dt,
J¼1.35, 7.7 Hz, 1H), 8.2 (ddd, J¼1.1, 2.3, 8.23 Hz, 1H),
8.26e8.28 (m, 1H). 13C NMR (75 MHz) d: ꢁ5.5 (q), ꢁ5.3
(q), 18.3 (s), 25.8 (q, 3C), 26.6 (q), 26.7 (q), 62.9 (t), 76.1 (s),
81.2 (d), 83.8 (d), 85.2 (s), 88.6 (s), 104.3 (d), 113.6 (s),
123.6 (s), 123.6 (d), 126.6 (d), 129.4 (d), 137.3 (d), 148.1 (s).
MALDI-TOF (MS): calcd for C22H31NO7SiNa: 472.18, found:
472.17. Anal. Calcd for C22H31NO7Si: C, 58.78; H 6.95; N,
3.12. Found: C, 58.83; H, 6.75; N, 3.10.
1
668 cmꢁ1. H NMR (200 MHz, CDCl3) d: 0.87 (t, J¼6.9 Hz,
3H), 1.20e1.31 (m, 6H), 1.34 (s, 3H), 1.43e1.50 (m, 2H),
1.56 (s, 3H), 2.20 (t, J¼7.0 Hz, 2H), 3.0 (br s, 1H), 3.82e
3.95 (m, 3H), 4.44 (d, J¼3.7 Hz, 1H), 5.81 (d, J¼3.7 Hz,
1H). 13C NMR (125 MHz) d: 13.7 (q), 18.3 (t), 22.2 (t),
26.3 (q), 26.4 (q), 28.0 (t), 28.2 (t), 30.9 (t), 61.7 (t), 74.5
(s), 76.0 (s), 81.6 (d), 84.0 (d), 88.9 (s), 103.6 (d), 112.9 (s).
MALDI-TOF (MS): calcd for C16H26O5Na: 321.17, found:
321.15. Anal. Calcd for C16H26O5: C, 64.41; H, 8.78. Found:
C, 64.55; H, 8.61.
4.1.7. 1,2-O-Isopropylidene-5-O-(tert-butyldimethylsilyl)-3-
C-(2-nitrophenylethynyl)-a-D-ribofuranose (29)
Coupling of 2-nitro-iodobenzene (568 mg, 2.28 mmol) and
alkyne 23 (500 mg, 1.52 mmol) was carried out by using CuI
(29 mg, 0.152 mmol), PPh3 (40 mg, 0.152 mmol), and
Pd(PPh3)2Cl2 (107 mg, 0.152 mmol) to procure 29 (555 mg,
81%) after column chromatography (2:8, EtOAc/light petro-
leum) as a pale yellow oil. [a]D 1.2 (c 1.0, CHCl3). IR
(CHCl3): n 3526, 3020, 2956, 2410, 1530, 1471, 1346, 1216,
4.1.10. 1,2-O-Isopropylidene-3-C-phenylethynyl-a-D-
ribofuranose (10)
A solution of 25 (1.125 g, 2.8 mmol) in THF (25 mL) was
treated with TBAF (3.3 mL, 3.3 mmol. 1 M in THF) at 0 ꢀC
and stirred for 1 h. Usual workup and purification by column
chromatography (50% ethyl acetate in light petroleum) gave
10 (646 mg, 80%) as a colorless solid. Mp¼112 ꢀC. [a]D
50.5 (c 1, CHCl3). IR (CHCl3): n 3436, 2924, 2852, 1612,
1097 cmꢁ1 1H NMR (200 MHz, CDCl3) d: 0.08 (s, 6H),
.

226
C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
1489, 1384, 1083, 1061, 1019, 879, 691 cmꢁ1
.
1H NMR
3H), 1.61 (s, 3H), 2.9 (br s, 2H), 3.98e4.09 (m, 3H), 4.63
(d, J¼3.7 Hz, 1H), 5.93 (d, J¼3.7 Hz, 1H), 7.51 (t,
J¼8.0 Hz, 1H), 7.74 (dt, J¼1.4, 7.8 Hz, 1H), 8.19 (ddd,
J¼1.15, 2.18, 8.3 Hz, 1H), 8.28 (t, J¼1.9 Hz, 1H). 13C NMR
(75 MHz) d: 25.7 (q), 25.9 (q), 61.2 (t), 74.7 (s), 81.4 (d),
83.47 (d), 84.2 (s), 88.1 (s), 95.3 (s), 103.4 (d), 112.4 (s),
122.8 (d), 125.7 (d), 129.0 (d), 136.8 (d), 147.4 (s). MALDI-
TOF (MS): calcd for C16H17NO7Na: 358.09, found: 358.1.
Anal. Calcd for C16H17NO7: C, 57.31; H 5.11; N, 4.18. Found:
C, 57.35; H, 5.19; N, 4.15.
(200 MHz, CDCl3) d: 1.40 (s, 3H), 1.62 (s, 3H), 2.98 (s,
1H), 3.93e4.15 (complex AB, 3H), 4.63 (d, J¼3.7 Hz,1H),
5.93 (d, J¼3.7 Hz, 1H), 7.30e7.36 (m, 3H), 7.42e7.47 (m,
2H). 13C NMR (50 MHz) d: 26.5 (q), 26.7 (q), 62.0 (t), 75.2
(s), 82.0 (d), 84.0 (d), 84.8 (s), 88.2 (s), 103.9 (d), 113.3 (s),
121.4 (s), 128.2 (d, 2C), 128.9 (d), 131.8 (d, 2C). MALDI-
TOF (MS): calcd for C16H18O5Na: 313.11, found: 313.10.
Anal. Calcd for C16H18O5: C, 66.19; H, 6.25. Found: C,
65.96; H, 6.35.
4.1.11. 1,2-O-Isopropylidene-3-C-(4-methoxyphenyl-
ethynyl)-a-D-ribofuranose (11)
4.1.14. 1,2-O-Isopropylidene-3-C-(2-nitrophenylethynyl)-
a-D-ribofuranose (14)
A solution of 26 (200 mg, 0.46 mmol) and 1 M TBAF in
THF (0.6 mL, 0.6 mmol) in THF (10 mL) was stirred at
0 ꢀC for 4 h. Usual workup and purification of the crude prod-
uct by column chromatography (1:1, EtOAc/light petroleum)
gave 11 (125 mg, 85%) as a colorless oil. [a]D 36.1 (c 1.2,
CHCl3). IR (CHCl3): n 3397, 3020, 2395, 1211, 1421, 1037,
A solution of 29 (300 mg, 0.667 mmol) in THF (10 mL)
was cooled to 0 ꢀC. TBAF (1 M) in THF (0.8 mL, 0.8 mmol)
was added dropwise and stirring continued for 2 h. After com-
pletion, the reaction mixture was treated with saturated NH4Cl
solution and extracted with EtOAc. The combined organic
layers were dried over Na2SO4, concentrated, and purified by
column chromatography (1:1, EtOAc/light petroleum) to obtain
14 (185 mg, 83%) as a colorless oil. [a]D 36.7 (c 1, CHCl3). IR
(CHCl3): n 3427, 3020, 1609, 1473, 1377, 1346, 1164, 1047,
1
926 cmꢁ1. H NMR (200 MHz, CDCl3) d: 1.39 (s, 3H), 1.6
(s, 3H), 3.0 (s, 1H), 3.8 (s, 3H), 4.04 (br s, 3H), 4.62 (d,
J¼3.75 Hz, 1H), 5.93 (d, J¼3.75 Hz, 1H), 6.83 (d,
J¼8.9 Hz, 2H), 7.37 (d, J¼8.9 Hz, 2H). 13C NMR (75 MHz)
d: 26.6 (q), 26.8 (q), 55.3 (q), 62.3 (t), 75.3 (s), 82.2 (d),
83.12 (s), 84.1 (d), 88.7 (s), 104.2 (d), 113.4 (s), 113.5 (s),
114.0 (d, 2C), 133.5 (d, 2C), 160.2 (s). MALDI-TOF (MS):
calcd for C17H20O6Na: 343.12, found: 343.18. Anal. Calcd
for C17H20O6: C, 63.74; H 6.29. Found: C, 63.51; H, 6.47.
1
872 cmꢁ1. H NMR (200 MHz, CDCl3) d: 1.38 (s, 3H), 1.60
(s, 3H), 2.28 (br s, 1H), 3.34 (s, 1H), 3.99e4.09 (m, 3H),
4.67 (d, J¼3.7 Hz, 1H), 5.96 (d, J¼3.7 Hz, 1H), 7.45e7.68
(m, 3H), 8.07 (br d, J¼8.1 Hz, 1H). 13C NMR (75 MHz) d:
26.6 (q), 26.8 (q), 62.0 (t), 75.6 (s), 82.2 (d), 83.5 (s), 83.9
(d), 92.9 (s), 104.2 (d), 113.6 (s), 117.1 (s), 124.8 (d), 129.5
(d), 133.0 (d), 135.0 (d), 149.7 (s). MALDI-TOF (MS): calcd
for C16H17NO7Na: 358.09, found: 357.99. Anal. Calcd for
C16H17NO7: C, 57.31; H 5.11; N, 4.18. Found: C, 57.15; H,
4.98; N, 4.35.
4.1.12. 1,2-O-Isopropylidene-3-C-(4-nitrophenylethynyl)-
a-D-ribofuranose (12)
Following the procedure as described, treatment of 27
(250 mg, 0.556 mmol) with 1 M TBAF in THF (0.66 mL,
0.66 mmol) followed by usual workup and purification by col-
umn chromatography (1:1, EtOAc/light petroleum) gave 12
(158 g, 85%) as a colorless oil. [a]D 51.6 (c 1, CHCl3). IR
4.1.15. 1,2:5,6-Di-O-isopropylidene-3-C-ethynyl-a-D-
allofuranose (31)
As described for compound 23, at 0 ꢀC to a solution of
ketone 30 (5 g, 19.35 mmol) in THF (25 mL) was added ethynyl
MgCl [generated from Mg (1.86 g, 77.43 mmol) and n-BuCl
(8.1 mL, 77.4 mmol)] and stirred for 30 min. Usual workup
and purification by column chromatography (10% ethyl ace-
tate in light petroleum) gave 31 (3.5 g, 63%). [a]D 7.9 (c 2.5,
(CHCl3): n 3423, 2917, 1665, 1591, 1377, 1342, 858 cmꢁ1
.
1H NMR (200 MHz, CDCl3) d: 1.4 (s, 3H), 1.61 (s, 3H), 3.2
(s, 1H), 4.01e4.11 (m, 3H), 4.64 (d, J¼3.71 Hz, 1H), 5.95
(d, J¼3.71 Hz, 1H), 7.61 (d, J¼8.78 Hz, 2H), 8.18 (d,
J¼8.78 Hz, 2H). 13C NMR (75 MHz) d: 26.4 (q), 26.8 (q),
62.1 (t), 75.4 (s), 82.2 (d), 83.7 (d), 86.3 (s), 89.8 (s), 104.1
(d), 113.8 (s), 123.6 (d, 2C), 128.2 (s), 132.7 (d, 2C), 147.7
(s). MALDI-TOF (MS): calcd for C16H17NO7Na: 358.09,
found: 358.10. Anal. Calcd for C16H17NO7: C, 57.31; H,
5.11; N, 4.18. Found: C, 57.28; H, 5.17; N, 4.23.
1
CHCl3) [lit.17b [a]D21 9.5 (c 1, CHCl3)]. H NMR (400 MHz,
CDCl3) d: 1.35 (s, 6H), 1.44 (s, 3H), 1.58 (s, 3H), 2.64 (s,
1H), 3.09 (s, 1H), 3.82 (d, J¼8.2 Hz, 1H), 4.0 (dd, J¼4.6,
8.8 Hz, 1H), 4.12 (dd, J¼6.2, 8.8 Hz, 1H), 4.4 (ddd, J¼5.6,
6.1, 8.2 Hz, 1H), 4.58 (d, J¼3.5 Hz, 1H), 5.78 (d,
J¼3.5 Hz, 1H). 13C NMR (50 MHz) d: 25.1 (q), 26.5 (q),
26.6 (q, 2C), 66.8 (t), 74.6 (d), 75.6 (s), 76.8 (s), 76.8 (d),
80.9 (d), 84.1 (d), 103.9 (d), 109.4 (s), 113.2 (s). Anal. Calcd
for C14H20O6: C, 59.14; H 7.09. Found: C, 59.03; H, 7.14.
4.1.13. 1,2-O-Isopropylidene-3-C-(3-nitrophenylethynyl)-
a-D-ribofuranose (13)
A solution of 28 (210 mg, 0.47 mmol) and 1 M TBAF
(0.56 mL, 0.56 mmol) in THF (10 mL) was stirred for 2 h at
0 ꢀC. After completion, the reaction mixture was worked up
as described above and the crude product was purified by col-
umn chromatography (1:1, EtOAc/light petroleum) to obtain
13 (126 mg, 80%) as a colorless oil. [a]D ꢁ1.7 (c 1.5,
CHCl3). IR (CHCl3): n 3466, 3078, 2923, 1531, 1459, 1354,
4.1.16. 1,2:5,6-Di-O-isopropylidene-3-C-(oct-1-ynyl)-a-D-
allofuranose (32)
Compound 32 was prepared by treating the ketone 30 (1 g,
3.9 mmol) with lithium salt of 1-octyne prepared from 1-
octyne (640 mg, 5.8 mmol) and n-BuLi (2.9 mL, 4.6 mmol,
1.6 M in hexane) stirring at ꢁ78 ꢀC for 5 h followed by usual
1050, 884 cmꢁ1 1H NMR (200 MHz, CDCl3) d: 1.39 (s,
.

C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
227
workup. The resulting residue was purified by silica gel chro-
matography (20% ethyl acetate in light petroleum) to afford 32
(1.04 g, 73%) as thick syrup. [a]D 6.7 (c 1.6, CHCl3). 1H NMR
(200 MHz, CDCl3) d: 0.87 (t, J¼6.7 Hz, 3H), 1.24e1.30 (m,
6H), 1.34 (s, 6H), 1.43 (s, 3H), 1.48e1.51 (m, 2H), 1.57 (s,
3H,), 2.23 (t, J¼7.0 Hz, 2H), 3.82 (d, J¼7.6 Hz, 1H), 3.99
(dd, J¼5.1, 8.6 Hz, 1H), 4.09 (dd, J¼6.2, 8.6 Hz, 1H), 4.36
(ddd, J¼5.1, 6.2, 7.6 Hz, 1H), 4.51 (d, J¼3.6 Hz, 1H), 5.75
(d, J¼3.6 Hz, 1H). 13C NMR (75 MHz) d: 14.0 (q), 18.7 (t),
22.5 (t), 25.2 (q), 26.7 (q, 3C), 28.3 (t), 28.4 (t), 31.2 (t),
66.8 (t), 74.9 (d), 75.7 (s), 77.8 (s), 81.2 (d), 84.4 (d), 89.7
(s), 104.0 (d), 109.3 (s), 113.4 (s). Anal. Calcd for
C20H32O6: C, 65.19; H, 8.75. Found: C, 65.30; H, 8.78.
calcd for C21H26O7Na: 413.16, found: 413.22. Anal. Calcd
for C21H26O7: C, 64.60; H, 6.71. Found: C, 64.43; H, 6.90.
4.1.19. 1,2:5,6-Di-O-isopropylidene-3-C-(4-nitrophenyl-
ethynyl)-a-D-allofuranose (35)
To a solution of 4-nitroiodobenzene (328 mg, 1.3 mmol) in
Et3N/DMF (6 mL, 2:1) were successively added CuI (33 mg,
0.176 mmol), PPh3 (23 mg, 0.088 mmol), Pd(PPh3)2Cl2
(62 mg, 0.088 mmol), and alkyne 31 (250 mg, 0.88 mmol).
The reaction mixture was flushed with argon for 30 min and
the stirring continued for 5 h. After usual workup, the residue
was chromatographed on silica gel (40% ethyl acetate in light
petroleum) to procure 35 (324 mg, 91%) as a syrup. [a]D
ꢁ20.5 (c 1.5, CHCl3). IR (CHCl3): n 3447, 3020, 1596,
4.1.17. 1,2:5,6-Di-O-isopropylidene-3-C-phenylethynyl-a-
D-allofuranose (33)
1523, 1384, 1347, 1071, 855, 669 cmꢁ1 1H NMR
.
(200 MHz, CDCl3) d: 1.37 (s, 3H), 1.39 (s, 3H), 1.47 (s,
3H), 1.62 (s, 3H), 3.22 (s, 1H), 3.92 (d, J¼8.1 Hz, 1H), 4.05
(dd, J¼4.8, 8.8 Hz, 1H), 4.15 (dd, J¼6.1, 8.8 Hz, 1H), 4.43
(ddd, J¼4.8, 6.1, 8.1 Hz, 1H), 4.70 (d, J¼3.6 Hz, 1H), 5.87
(d, J¼3.6 Hz, 1H), 7.61 (br d, J¼8.9 Hz, 2H), 8.20 (br d,
J¼8.9 Hz, 2H). 13C NMR (50 MHz) d: 25.1 (q), 26.6 (q,
2C), 26.7 (q), 67.0 (t), 74.8 (d), 76.4 (s), 81.0 (d), 83.8 (d),
86.4 (s), 90.8 (s), 104.0 (d), 109.7 (s), 113.8 (s), 123.5 (d,
2C), 128.2 (s), 132.6 (d, 2C), 147.5 (s). MALDI-TOF (MS):
calcd for C20H23O8NNa: 428.13, found: 428.17. Anal. Calcd
for C20H23O8N: C, 59.25; H, 5.72; N, 3.46. Found: C,
59.55; H, 5.69; N, 3.48.
Compound 33 was prepared by treating the ketone 30 (1 g,
3.9 mmol) with lithium salt of phenylacetylene prepared from
phenylacetylene (593 mg, 5.8 mmol) and n-BuLi (2.9 mL,
4.6 mmol, 1.6 M in hexane) at ꢁ78 ꢀC for 1 h followed by
usual workup and purification on silica gel column (20% ethyl
acetate in light petroleum) gave 33 (1.05 g, 75%). [a]2D5 ꢁ8.4
(c 0.4, CHCl3). IR (CHCl3): n 3684, 3543, 3019, 2992, 2938,
1
2230, 1599, 1520, 1069, 1042, 873, 841, 625 cmꢁ1. H NMR
(200 MHz, CDCl3) d: 1.37 (s, 3H), 1.38 (s, 3H), 1.46 (s, 3H),
1.61 (s, 3H), 3.11 (s, 1H), 3.93 (d, J¼7.6 Hz, 1H), 4.06 (dd, J¼
5.2, 8.7 Hz, 1H), 4.15 (dd, J¼6.1, 8.7 Hz, 1H), 4.47 (ddd,
J¼5.2, 6.1, 7.6 Hz, 1H), 4.67 (d, J¼3.6 Hz, 1H), 5.85 (d, J¼
3.6 Hz, 1H), 7.29e7.35 (m, 3H), 7.42e7.47 (m, 2H). 13C
NMR (75 MHz) d: 25.1 (q), 26.5 (q, 2C), 26.6 (q), 66.7 (t),
74.8 (d), 76.1 (s), 81.5 (d), 84.1 (d), 85.7 (s), 88.4 (s), 104.1
(d), 109.3 (s), 113.5 (s), 121.6 (s), 128.2 (d, 2C), 128.8 (d),
131.7 (d, 2C). Anal. Calcd for C20H24O6: C, 66.65; H, 6.71.
Found: C, 66.45; H, 6.43.
4.1.20. 1,2:5,6-Di-O-isopropylidene-3-C-(3-nitrophenyl-
ethynyl)-a-D-allofuranose (36)
Preparation of 36 was carried out by treating 31 (260 mg,
0.91 mmol) with 3-nitroiodobenzene (341 mg, 1.37 mmol),
CuI (35 mg, 0.18 mmol), PPh3 (24 mg, 0.09 mmol), and
Pd(PPh3)2Cl2 (63 mg, 0.09 mmol) and stirring the contents
for 5 h followed by usual workup and chromatographic purifi-
cation (30% ethyl acetate in light petroleum) to obtain 36
(352 mg, 95%) as a liquid. [a]D ꢁ14.0 (c 1, CHCl3). IR
(CHCl3): n 3537, 3020, 2992, 1534, 1455, 1384, 1354, 1164,
4.1.18. 1,2:5,6-Di-O-isopropylidene-3-C-(4-methoxy-
phenylethynyl)-a-D-allofuranose (34)
A solution of alkyne 31 (0.5 g, 1.76 mmol), p-iodoanisole
(620 mg, 2.64 mmol), Et3N (10 mL), CuI (67 mg,
0.35 mmol), PPh3 (46 mg, 0.17 mmol), and Pd(PPh3)2Cl2
(123 mg, 0.17 mmol) in DMF (5 mL) was flushed with argon
for 30 min and stirred for 10 h. The reaction mixture was di-
luted with ethyl acetate, washed with water, brine, dried
over Na2SO4, and concentrated. The residue was purified on
silica gel column (30% ethyl acetate in light petroleum) to ob-
tain 34 (481 mg, 70%) as a solid. Mp¼120 ꢀC. [a]D ꢁ7.1 (c 1,
CHCl3). IR (CHCl3): n 3437, 3019, 2936, 1606, 1511, 1384,
1
1071, 928, 841, 623 cmꢁ1. H NMR (200 MHz, CDCl3) d:
1.37 (s, 3H), 1.38 (s, 3H), 1.47 (s, 3H), 1.61 (s, 3H), 3.21 (s,
1H), 3.91 (d, J¼8.0 Hz, 1H), 4.05 (dd, J¼4.8, 8.7 Hz, 1H),
4.15 (dd, J¼6.1, 8.7 Hz, 1H), 4.44 (ddd, J¼4.8, 6.1, 8.0 Hz,
1H), 4.69 (d, J¼3.6 Hz, 1H), 5.86 (d, J¼3.6 Hz, 1H), 7.52 (t,
J¼8.1 Hz, 1H), 7.75 (dt, J¼1.3, 7.7 Hz, 1H), 8.20 (ddd,
J¼1.1, 2.3, 8.2 Hz, 1H), 8.09 (br t, J¼1.8 Hz, 1H). 13C NMR
(50 MHz) d: 25.1 (q), 26.5 (q, 2C), 26.6 (q), 66.9 (t), 74.8 (d),
76.2 (s), 81.0 (d), 83.9 (d), 85.8 (s), 88.4 (s), 104.0 (d), 109.6
(s), 113.7 (s), 123.3 (s), 123.6 (d), 126.5 (d), 129.4 (d), 137.3
(d), 147.9 (s). MALDI-TOF (MS): calcd for C20H23O8NNa:
428.13, found: 428.17. Anal. Calcd for C20H23O8N: C, 59.25;
H, 5.72; N, 3.46. Found: C, 58.98; H, 5.46; N, 3.18.
1216, 1070, 1034, 834, 668 cmꢁ1 1H NMR (200 MHz,
.
CDCl3) d: 1.37 (s, 6H), 1.46 (s, 3H), 1.61 (s, 3H), 3.13 (s,
1H), 3.80 (s, 3H), 3.96 (d, J¼7.5 Hz, 1H), 4.07 (dd, J¼5.2,
8.7 Hz, 1H), 4.15 (dd, J¼6.1, 8.7 Hz, 1H), 4.49 (br ddd,
J¼5.2, 6.1, 7.6 Hz, 1H), 4.67 (d, J¼3.4 Hz, 1H), 5.86 (d,
J¼3.4 Hz, 1H), 6.83 (d, J¼8.9 Hz, 2H), 7.37 (d, J¼8.9 Hz,
2H). 13C NMR (125 MHz) d: 25.1 (q), 26.6 (q), 26.7 (q,
2C), 55.3 (q), 66.9 (t), 74.9 (d), 76.2 (s), 81.4 (d), 84.1 (d),
84.2 (s), 88.8 (s), 104.2 (d), 109.5 (s), 113.6 (s), 113.7 (s),
114.0 (d, 2C), 133.3 (d, 2C), 160.1 (s). MALDI-TOF (MS):
4.1.21. 1,2:5,6-Di-O-isopropylidene-3-C-(4-nitrophenyl-
ethynyl)-a-D-allofuranose (37)
The preparation of 37 was carried out by treating 31
(250 mg, 0.88 mmol) with 2-nitroiodobenzene (326 mg,
1.3 mmol), CuI (33 mg, 0.176 mmol), PPh3 (23 mg,

228
C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
0.088 mmol), and Pd(PPh3)2Cl2 (62 mg, 0.088 mmol) in Et3N/
DMF (6 mL, 2:1) as described earlier for 5 h. The residue was
chromatographed on silica gel (20% ethyl acetate in light pe-
troleum) to afford 37 (300 mg, 84%) as a colorless oil. [a]D
ꢁ16.1 (c 1.9, CHCl3). IR (CHCl3): n 3437, 3020, 1530,
for C17H28O6Na: 351.18, found: 351.17. Anal. Calcd for
C17H28O6: C, 62.17; H, 8.59. Found: C, 62.15; H, 8.36.
4.1.24. 1,2-O-Isopropylidene-3-C-phenylethynyl-a-D-
allofuranose (17)
1385, 1352, 1084, 1029, 929, 668 cmꢁ1
.
1H NMR
A solution of 33 (500 mg, 1.4 mmol) in MeOH (20 mL)
and dil H2SO4 (5 mL, 0.8% in water) was stirred at 25 ꢀC
for 15 h, quenched with NaHCO3, and concentrated. The res-
idue was partitioned between ethyl acetate and water and the
aqueous layer was extracted with ethyl acetate. The combined
organic phase was dried over Na2SO4, concentrated, and puri-
fied by column chromatography (80% ethyl acetate in light
petroleum) to obtain 17 (312 mg, 70%) as white solid.
Mp¼126 ꢀC. [a]D 40.1 (c 1, CHCl3). IR (CHCl3): n 3468,
(200 MHz, CDCl3) d: 1.37 (s, 3H), 1.39 (s, 3H), 1.47 (s,
3H), 1.61 (s, 3H), 3.22 (s, 1H), 3.9 (d, J¼8.2 Hz, 1H), 4.02
(br dd, J¼4.9, 8.8 Hz, 1H), 4.12 (br dd, J¼6.1, 8.8 Hz, 1H),
4.44e4.54 (m, 1H), 4.72 (d, J¼3.6 Hz, 1H), 5.89 (d,
J¼3.6 Hz, 1H), 7.47e7.69 (m, 3H), 8.1 (d, J¼8.0 Hz, 1H).
13C NMR (50 MHz) d: 25.0 (q), 26.6 (q), 26.7 (q, 2C), 67.1
(t), 74.8 (d), 76.5 (s), 81.2 (d), 83.6 (s), 84.0 (d), 93.6 (s),
104.1 (d), 109.5 (s), 113.6 (s), 117.1 (s), 124.7 (d), 129.4
(d), 132.8 (d), 134.8 (d), 149.6 (s). MALDI-TOF (MS): calcd
for C20H23NO8Na: 428.13, found: 428.17. Anal. Calcd for
C20H23NO8: C, 59.25; H, 5.72; N, 3.46. Found: C, 59.01; H,
5.61; N, 3.28.
1
3019, 1385, 1039, 929, 874, 669 cmꢁ1. H NMR (200 MHz,
CDCl3) d: 1.35 (s, 3H), 1.59 (s, 3H), 3.37 (br s, 3H), 3.73
(dd, J¼4.9, 11.8 Hz, 1H), 3.87 (dd, J¼3.1, 11.8 Hz, 1H),
3.96 (d, J¼8.6 Hz, 1H), 4.15 (ddd, J¼3.1, 4.9, 8.3 Hz, 1H),
4.66 (d, J¼3.6 Hz, 1H), 5.84 (d, J¼3.7 Hz, 1H), 7.28e7.32
(m, 3H), 7.42e7.47 (m, 2H). 13C NMR (50 MHz) d: 26.6
(q, 2C), 64.0 (t), 71.8 (d), 76.6 (s), 79.6 (d), 84.1 (d),
85.4 (s), 88.8 (s), 103.9 (d), 113.7 (s), 121.4 (s), 128.4 (d,
2C), 129.0 (d), 132.0 (d, 2C). MALDI-TOF (MS): calcd
for C17H20O6Na: 343.13, found: 343.09. Anal. Calcd for
C17H20O6: C, 63.74; H, 6.29. Found: C, 63.74; H, 6.05.
4.1.22. 1,2-O-Isopropylidene-3-C-ethynyl-a-D-
allofuranose (15)
Compound 31 (170 mg, 0.6 mmol) and 0.8% H2SO4 (1 mL)
in MeOH (4 mL) were stirred for 12 h. The reaction mixture
was neutralized with NaHCO3 and extracted with ethyl ace-
tate. The combined organic phase was washed with brine,
dried over Na2SO4, and concentrated. The residue was purified
by silica gel chromatography (90% ethyl acetate in light petro-
leum) to give 15 (100 mg, 68%) as colorless thick liquid. [a]D
53.8 (c 1, CHCl3). IR (CHCl3): n 3445, 3251, 3020, 2941,
4.1.25. 1,2-O-Isopropylidene-3-C-(4-methoxyphenyl-
ethynyl)-a-D-allofuranose (18)
Compound 34 (100 mg, 0.26 mmol) and 0.8% H2SO4
(1 mL) in MeOH (4 mL) were stirred for 12 h, neutralized
with NaHCO3, and worked up as usual to give a residue which
was purified on silica gel (80% ethyl acetate in light petro-
leum) to afford 18 (72 mg, 80%) as a white solid. Mp¼116 ꢀC.
[a]D 42.3 (c 1, CHCl3). IR (CHCl3): n 3404, 3019, 1606, 1511,
1603, 1386, 1166, 1107, 1072, 1017, 874, 669 cmꢁ1 1H
.
NMR (200 MHz, D2O) d: 1.39 (s, 3H), 1.58 (s, 3H), 3.63
(dd, J¼5.9, 12.0 Hz, 1H), 3.8 (dd, J¼2.7, 12.0 Hz, 1H), 3.91
(d, J¼8.6 Hz, 1H), 4.04 (ddd, J¼2.7, 5.8, 8.5 Hz, 1H), 4.75
(d, J¼3.7 Hz, 1H), 5.93 (d, J¼3.7 Hz, 1H). 13C NMR
(50 MHz, D2O) d: 27.3 (q, 2C), 65.2 (t), 72.7 (d), 77.2 (s),
80.4 (d), 85.9 (d), 105.1 (d), 115.9 (s). MALDI-TOF (MS):
calcd for C11H16O6Na: 267.084, found: 267.09. Anal. Calcd
for C11H16O6: C, 54.09; H, 6.60. Found: C, 54.34; H, 6.47.
1
1250, 1106, 1035, 930, 874, 834 cmꢁ1. H NMR (200 MHz,
CDCl3) d: 1.35 (s, 3H), 1.58 (s, 3H), 3.10 (br s, 2H), 3.72e
3.78 (m, 2H), 3.77 (s, 3H), 3.83 (br s, 1H), 3.91 (d,
J¼8.6 Hz, 1H), 4.07e4.17 (m, 1H), 4.62 (d, J¼3.6 Hz, 1H),
5.81 (d, J¼3.6 Hz, 1H), 6.79 (d, J¼8.8 Hz, 2H), 7.37 (d,
J¼8.8 Hz, 2H). 13C NMR (50 MHz, CDCl3) d: 26.7 (q, 2C),
55.2 (q), 64.0 (t), 71.8 (d), 76.7 (s), 79.6 (d), 84.1 (s), 84.2
(d), 88.8 (s), 103.9 (d), 113.6 (s, 2C), 114.0 (d, 2C), 133.5
(d, 2C), 160.2 (s). MALDI-TOF (MS): calcd for
C18H22O7Na: 373.13, found: 373.14. Anal. Calcd for
C18H22O7: C, 61.71; H, 6.33. Found: C, 61.55; H, 6.27.
4.1.23. 1,2-O-Isopropylidene-3-C-(oct-1-nyl)-a-D-
allofuranose (16)
Compound 16 was prepared by treating 32 (500 mg,
1.4 mmol) with 0.8% H2SO4 (5 mL) for 15 h followed by
usual workup. The residue was chromatographed on silica
gel (80% ethyl acetate in light petroleum) to obtain 16
(352 mg, 79%) as a solid. Mp¼76 ꢀC. [a]D 31.8 (c 1.3,
CHCl3). IR (CHCl3): n 3400, 3019, 2933, 1644, 1428, 1377,
4.1.26. 1,2-O-Isopropylidene-3-C-(4-nitrophenylethynyl)-
a-D-allofuranose (19)
1163, 1076, 1045, 1007, 929, 872, 668 cmꢁ1
.
1H NMR
Compound 19 (75% yield) was prepared by adopting sim-
ilar reaction condition as reported for 31. Mp¼139 ꢀC. [a]D
36.9 (c 1, CH3OH). IR (CHCl3): n 3419, 3020, 1594, 1522,
(200 MHz, CDCl3) d: 0.87 (t, J¼6.8 Hz, 3H), 1.28e1.32 (m,
6H), 1.35 (s, 3H), 1.45e1.52 (m, 2H), 1.57 (s, 3H), 2.24 (t,
J¼7.0 Hz, 2H), 2.57 (br s, 1H), 2.96 (d, J¼4 Hz, 1H), 3.47
(s, 1H), 3.69e3.9 (m, 3H), 4.0e4.10 (m, 1H), 4.51 (d,
J¼3.6 Hz, 1H), 5.77 (d, J¼3.6 Hz, 1H). 13C NMR (75 MHz)
d: 13.9 (q), 18.7 (t), 22.4 (t), 26.6 (q, 2C), 28.4 (t), 28.5 (t),
31.2 (t), 63.9 (t), 71.8 (d), 76.2 (s), 76.8 (s), 79.6 (d), 84.4
(d), 90.2 (s), 103.9 (d), 113.5 (s). MALDI-TOF (MS): calcd
1
1377, 1346, 1020, 929, 855, 669 cmꢁ1. H NMR (200 MHz,
CDCl3/DMSO-d6) d: 1.30 (s, 3H), 1.53 (s, 3H), 3.49 (br s, 1H),
3.62 (br d, J¼10.7 Hz, 1H), 3.79 (br d, J¼10.7 Hz, 1H), 3.93
(br d, J¼8.9 Hz, 1H), 3.98e4.08 (m, 2H), 4.50 (s, 1H), 4.62
(d, J¼3.6 Hz, 1H), 5.78 (d, J¼3.6 Hz, 1H), 7.55 (br d,
J¼8.4 Hz, 2H), 8.10 (br d, J¼8.4 Hz, 2H). 13C NMR

C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
229
(50 MHz, CDCl3) d: 26.2 (q), 26.3 (q), 63.8 (t), 71.7 (d), 76.4
(s), 79.0 (d), 83.8 (d), 85.5 (s), 91.8 (s), 103.5 (d), 113.3 (s),
123.1 (d, 2C), 128.4 (s), 132.4 (d, 2C), 147.0 (s). MALDI-
TOF (MS): calcd for C17H19NO8Na: 388.10, found: 388.11.
Anal. Calcd for C17H19NO8: C, 55.89; H, 5.24; N, 3.83.
Found: C, 56.08; H, 5.37; N, 3.62.
1.48 (s, 3H), 1.57 (s, 3H), 2.51 (s, 1H), 3.01 (s, 1H), 4.02
(dd, J¼1.64, 10.48 Hz, 1H), 4.19 (dd, J¼5.05, 10.48 Hz,
1H), 4.43 (m, 1H), 4.51 (d, J¼3.79 Hz, 1H), 5.89 (d,
J¼3.79 Hz, 1H). 13C NMR (75 MHz, CDCl3) d: 21.8 (q),
26.9 (q), 27.2 (q), 70.8 (t), 78.9 (d), 86.6 (d), 89.3 (s), 105.6
(s), 108.1 (d), 112.4 (s). MALDI-TOF (MS): calcd for
C10H16O6Na: 255.08, found: 255.12. Anal. Calcd for
C10H16O6: C, 51.72; H 6.94. Found: C, 51.79; H, 7.13.
4.1.27. 1,2-O-Isopropylidene-3-C-(3-nitrophenylethynyl)-
a-D-allofuranose (20)
Following a similar procedure reported for the deprotection
of 31, triol 20 (347 mg, 77%) was obtained by deprotection of
36 (500 mg, 1.23 mmol). [a]D 35.7 (c 1, MeOH). IR (CHCl3):
n 3433, 3020, 2935, 1533, 1385, 1164, 1353, 1084, 1040, 929,
4.1.30. Pd-mediated cyclization of 9
A solution of 9 (200 mg, 0.67 mmol) and PdCl2(CH3CN)2
(17 mg, 0.067 mmol) in dry CH3CN (6 mL) was stirred under
argon for 32 h. Usual workup followed by chromatographic
purification (30% ethyl acetate in light petroleum) gave 39
(51 mg, 51%) and unreacted 9 (100 mg).
1
872, 624 cmꢁ1. H NMR (200 MHz, CDCl3) d: 1.40 (s, 3H),
1.62 (s, 3H), 2.70 (br s, 1H), 3.57 (br s, 1H), 3.79 (dd,
J¼4.8, 11.5 Hz, 1H), 3.93 (dd, J¼3.3, 11.5 Hz, 1H), 3.97 (d,
J¼8.0 Hz, 1H), 4.14e4.22 (m, 1H), 4.71 (d, J¼3.6 Hz, 1H),
5.91 (d, J¼3.6 Hz, 1H), 7.53 (t, J¼8.0 Hz, 1H), 7.78 (dt,
J¼1.4, 7.7 Hz, 1H), 8.21 (ddd, J¼1.1, 2.3, 8.3 Hz, 1H), 8.31
(br t, J¼1.9 Hz, 1H). 13C NMR (75 MHz, CDCl3) d: 26.0
(q), 26.1 (q), 63.5 (t), 71.4 (d), 76.1 (s), 78.8 (d), 83.7 (d),
84.7 (s), 89.2 (s), 103.2 (d), 112.8 (s), 122.8 (d), 123.2 (s),
126.0 (d), 129.0 (d), 137.1 (d), 147.4 (s). MALDI-TOF
(MS): calcd for C17H19NO8Na: 388.10, found: 388.09. Anal.
Calcd for C17H19NO8: C, 55.89; H, 5.24; N, 3.83. Found: C,
55.90; H, 5.43; N, 3.57.
1,2-O-Isopropylidene-3-C-(20-hydroxy-oct-1-enyl)-20,5-an-
hydro-a-D-ribofuranose (39): [a]D 35.2 (c 0.25, CHCl3). IR
(CHCl3): n 3381, 3019, 2930, 1376, 1163, 1124, 1066,
1
668 cmꢁ1. H NMR (200 MHz, CDCl3) d: 0.87 (t, J¼6.8 Hz,
3H), 1.26e1.28 (m, 6H), 1.36 (s, 3H), 1.42e1.57 (m, 2H),
1.57 (s, 3H), 2.05 (t, J¼7.2 Hz, 2H), 2.86 (s, 1H), 3.83 (br
dd, J¼0.8, 12.3 Hz, 1H), 3.90e3.91 (m, 1H), 4.19 (d,
J¼3.6 Hz, 1H), 4.33 (br dd, J¼1.6, 12.3 Hz, 1H), 4.40 (br s,
1H), 5.70 (d, J¼3.6 Hz, 1H). 13C NMR (125 MHz) d: 13.9
(t), 22.4 (t), 26.3 (t), 26.6 (q), 26.9 (q), 28.6 (t), 31.4 (t),
34.0 (t), 62.9 (t), 71.1 (s), 76.6 (d), 83.4 (d), 94.1 (d), 104.0
(d), 112.6 (s), 159.6 (s). MALDI-TOF (MS): calcd for
C16H26O5Na: 321.17, found: 321.18. Anal. Calcd for
C16H26O5: C, 64.41; H, 8.78. Found: C, 64.65; H, 8.60.
4.1.28. 1,2-O-Isopropylidene-3-C-(2-nitrophenylethynyl)-
a-D-allofuranose (21)
Compound 21 (73%) was prepared by adopting similar re-
action condition as reported for 31. [a]D 26.0 (c 1, MeOH). IR
(CHCl3): n 3401, 2924, 1610, 1527, 1384, 1217, 1084, 1030,
4.1.31. 1,2-O-Isopropylidene-3-C-(20-oxooctyl)-a-D-
ribofuranose-(20-C,5-O)-hemiketal (40)
1
930 cmꢁ1. H NMR (200 MHz, CDCl3) d: 1.39 (s, 3H), 1.6
[a]D ꢁ3.7 (c 0.4, CHCl3). IR (CHCl3): n 3516, 3019, 2930,
1422, 1376, 1105, 1051, 1005, 877 cmꢁ1. 1H NMR (500 MHz,
CDCl3) d: 0.85 (t, J¼6.6 Hz, 3H), 1.23e1.29 (m, 6H), 1.32
(s, 3H), 1.35e1.42 (m, 2H), 1.51 (d, J¼14.1 Hz, 1H), 1.54 (s,
3H), 1.56e1.59 (m, 2H), 1.77 (d, J¼14.1 Hz, 1H), 3.66 (s,
1H), 3.91 (d, J¼13.8 Hz, 1H), 4.05 (d, J¼3.7 Hz, 1H), 4.11
(dd, J¼2.2, 14.0 Hz, 1H), 4.16 (br s, 1H), 5.74 (d, J¼3.7 Hz,
1H). 13C NMR (125 MHz, CDCl3) d: 14.1 (q), 22.6 (t), 22.7
(t), 26.4 (q), 26.5 (q), 29.5 (t), 31.8 (t), 36.8 (t), 41.6 (t),
57.3 (t), 74.0 (d), 74.6 (s), 82.6 (d), 95.5 (s), 103.6 (d),
112.7 (s). MALDI-TOF (MS): calcd for C16H28O6Na:
339.18, found: 339.18. Anal. Calcd for C16H28O6: C, 60.74;
H, 8.98. Found: C, 60.32; H, 9.02.
(s, 3H), 2.47 (br s, 1H), 3.06 (br s, 1H), 3.76 (dd, J¼4.8,
11.7 Hz, 1H), 3.91 (dd, J¼3.2, 11.7 Hz, 1H), 4.01 (d,
J¼8.2 Hz, 1H), 4.20 (ddd, J¼3.2, 4.8, 8.2 Hz, 1H), 4.74 (d,
J¼3.6 Hz, 1H), 5.93 (d, J¼3.6 Hz, 1H), 7.50 (ddd, J¼1.8,
7.3, 8.0 Hz, 1H), 7.61 (dt, J¼1.5, 7.5 Hz, 1H), 7.69 (dd,
J¼1.8, 7.6 Hz, 1H), 8.08 (dd, J¼1.3, 8.0 Hz, 1H). 13C NMR
(75 MHz) d: 26.6 (q, 2C), 64.1 (t), 71.8 (d), 76.7 (s), 79.8
(d), 83.5 (s), 84.1 (d), 94.1 (s), 104.0 (d), 113.7 (s), 117.2
(s), 124.6 (d), 129.4 (d), 133.0 (d), 135.1 (d), 149.6 (s).
MALDI-TOF (MS): calcd for C17H19NO8Na: 388.10, found:
388.09. Anal. Calcd for C17H19NO8: C, 55.89; H, 5.24; N,
3.83. Found: C, 55.80; H, 5.33; N, 3.74.
4.1.29. Pd-mediated cyclization of 8
4.1.32. Pd-mediated cyclization of 10
A solution of 8 (60 mg, 0.28 mmol) and PdCl2(CH3CN)2
(7 mg, 0.028 mmol) in dry CH3CN (4 mL) under argon atmo-
sphere was stirred at 25 ꢀC for 1 h. The crude product was
purified by column chromatography on silica gel (30% ethyl
acetate in light petroleum) to obtain 38 (44 mg, 67%) as a
colorless liquid.
The reaction of 10 (100 mg, 0.34 mmol) and PdCl2-
(CH3CN)2 (9 mg, 0.034 mmol) in dry CH3CN (6 mL) was
carried out as described earlier for 48 h at 25 ꢀC followed
by chromatography on silica (10% ethyl acetate in light petro-
leum) to obtain 41 (29 mg, 29%) as a colorless oil.
1,2-O-Isopropylidene-3-C-(10-hydroxy-20-phenyl-Z-vinyl)-
10,5-anhydro-a-D-ribofuranose (41): [a]D 21.3 (c 0.3, CHCl3).
IR (CHCl3): n 3393, 3020, 1495, 1385, 1165, 1143, 1083,
1,2-O-Isopropylidene-3-C-(10-acetyl)-a-D-ribofuranose-(10-
C,5-O)-hemiketal (38): [a]D 56.7 (c 0.75, CHCl3). IR
(CHCl3): n 3466, 3019, 2991, 1456, 1384, 1165, 1087,
1
1060, 1011, 978, 876 cmꢁ1. H NMR (500 MHz, CDCl3) d:
1025 cmꢁ1
.
1H NMR (200 MHz, CDCl3) d: 1.39 (s, 3H),
1.42 (s, 3H), 1.62 (s, 3H), 3.15 (s, 1H), 4.35 (dd, J¼2.7,

230
C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
10.4 Hz, 1H), 4.43 (d, J¼10.4 Hz, 1H), 4.46 (d, J¼2.7 Hz,
1H), 4.62 (d, J¼3.8 Hz, 1H), 5.51 (s, 1H), 5.88 (d,
J¼3.8 Hz, 1H), 7.13 (t, J¼7.3 Hz, 1H), 7.27 (t, J¼7.7 Hz,
2H), 7.57 (d, J¼7.7 Hz, 2H). 13C NMR (125 MHz) d: 27.1
(q), 27.3 (q), 73.2 (t), 83.2 (d), 83.8 (d), 87.1 (s), 103.3 (d),
105.8 (d), 113.2 (s), 126.3 (d), 128.3 (2d, 4C), 135.2 (s),
155.7 (s). MALDI-TOF (MS): calcd for C16H18O5Na:
313.11, found: 313.14. Anal. Calcd for C16H18O5: C, 66.19;
H, 6.25. Found: C, 66.10; H, 6.47.
[a]D 42.9 (c 1, CHCl3). IR (CHCl3): n 3458, 3019, 1674,
1592, 1508, 1344, 1257, 1150, 1060, 878 cmꢁ1 1H NMR
.
(200 MHz, CDCl3) d: 1.43 (s, 3H), 1.63 (s, 3H), 3.34 (s, 1H),
4.40e4.56 (m, 3H), 4.62 (d, J¼3.87 Hz, 1H), 5.61 (s, 1H),
5.91 (d, J¼3.87 Hz, 1H), 7.70 (d, J¼8.95 Hz, 2H), 8.14 (d,
J¼8.95 Hz, 2H). 13C NMR (75 MHz) d: 26.9 (q), 27.1 (q),
74.2 (t), 82.7 (d), 83.2 (d), 87.5 (s), 101.3 (d), 105.7 (d),
113.5 (s), 123.7 (d, 2C), 128.4 (d, 2C), 142.1 (s), 145.4 (s),
159.8 (s). MALDI-TOF (MS): calcd for C16H17NO7Na:
358.09, found: 358.15. Anal. Calcd for C16H17NO7: C, 57.3;
H, 5.11; N, 4.18. Found: C, 57.9; H, 5.24; N, 4.006.
Further elution with 20% ethyl acetate in light petroleum
gave 42 (59 mg, 59%) as white solid.
1,2-O-Isopropylidene-3-C-(20-hydroxy-20-phenyl-Z-vinyl)-
20,5-anhydro-a-D-ribofuranose (42): mp¼103 ꢀC. [a]D ꢁ58.2
(c 0.3, CHCl3). IR (CHCl3): n 3531, 3019, 2928, 1451,
1384, 1164, 1116, 1087, 1056, 1009, 895, 874, 693, 668,
4.1.35. Pd-mediated cyclization of 13
Alkyne 13 (50 mg, 0.15 mmol) and PdCl2(CH3CN)2 (4 mg,
0.015 mmol) were taken in CH3CN (5 mL) and stirred under
argon for 12 h. After completion of reaction the reaction mix-
ture was concentrated and purified by column chromatography
(30% ethyl acetate in light petroleum) to obtain 45 (32 mg,
64%) as yellow syrup.
1
623 cmꢁ1. H NMR (200 MHz, CDCl3) d: 1.37 (s, 3H), 1.60
(s, 3H), 3.05 (s, 1H), 4.02 (br s, 1H), 4.05 (s, 1H), 4.32 (d,
J¼3.6 Hz, 1H), 4.54 (br d, J¼12.2 Hz, 1H), 5.18 (s, 1H),
5.74 (d, J¼3.6 Hz, 1H), 7.31e7.32 (m, 3H), 7.58e7.60 (m,
2H). 13C NMR (125 MHz) d: 26.8 (q), 27.1 (q), 63.6 (t),
71.7 (s), 77.4 (d), 83.5 (d), 95.1 (d), 104.2 (d), 112.8 (s),
125.2 (d, 2C), 128.2 (d, 2C), 129.2 (d), 134.3 (s), 155.5 (s).
MALDI-TOF (MS): calcd for C16H18O5Na: 313.11, found:
313.11. Anal. Calcd for C16H18O5: C, 66.19; H, 6.25. Found:
C, 66.40; H, 6.23.
1,2-O-Isopropylidene-3-C-[10-hydroxy-20-(3-nitro-phenyl)-
Z-vinyl]-10,5-anhydro-a-D-ribofuranose (45): [a]D 16.4 (c 1.8,
CHCl3). IR (CHCl3): n 3502, 3021, 2991, 1673, 1528, 1459,
1376, 1351, 1165, 1085, 1012, 876 cmꢁ1. 1H NMR (400 MHz,
CDCl3) d: 1.42 (s, 3H), 1.62 (s, 3H), 3.32 (s, 1H), 4.42 (dd,
J¼2.8, 10.5 Hz, 1H), 4.50 (m, 2H), 4.62 (d, J¼3.8 Hz, 1H),
5.59 (s, 1H), 5.91 (d, J¼3.8 Hz, 1H), 7.42 (t, J¼8.0 Hz,
1H), 7.84 (d, J¼7.8 Hz, 1H), 7.98 (ddd, J¼0.78, 2.01,
8.17 Hz, 1H), 8.46 (s, 1H). 13C NMR (100 MHz) d: 26.9
(q), 27.0 (q), 73.9 (t), 82.8 (d), 83.4 (d), 87.3 (s), 100.9 (d),
105.7 (d), 113.4 (s), 120.7 (d), 122.6 (d), 128.9 (d), 133.8
(d), 136.9 (s), 148.4 (s), 158.4 (s). MALDI-TOF (MS): calcd
for C16H17NO7Na: 358.09, found: 358.15. Anal. Calcd for
C16H17NO7: C, 57.31; H 5.11; N, 4.18. Found: C, 57.22; H,
5.03; N, 4.09.
4.1.33. Pd-mediated cyclization of 11
Alkyne 11 (130 mg, 0.406 mmol) was taken in CH3CN in
argon atmosphere. PdCl2(CH3CN)2 (10 mg, 0.04 mmol) was
added to it. After completion of reaction the reaction mixture
was concentrated and purified by column chromatography
(4:6, EtOAc/hexane). The product 43 was obtained as white
crystalline solid (0.100 g, 77%).
1,2-O-Isopropylidene-3-C-[20-hydroxy-20-(4-methoxy-phe-
nyl)-Z-vinyl]-20,5-anhydro-a-D-ribofuranose (43): mp¼
110.8 ꢀC. [a]D ꢁ77.16 (c 1, CHCl3). IR (CHCl3): n 3480,
2989, 1651, 1455, 1249, 1056, 898 cmꢁ1. 1H NMR (200 MHz,
CDCl3) d: 1.37 (s, 3H), 1.59 (s, 3H), 3.02 (s, 1H), 3.80 (s, 3H),
4.02e4.05 (m, 2H), 4.31 (d, J¼3.66 Hz, 1H), 4.53 (ddd,
J¼0.68, 2.1, 12.48 Hz, 1H), 5.06 (d, J¼1.86 Hz, 1H), 5.75
(d, J¼3.66 Hz, 1H), 6.83 (d, J¼8.9 Hz, 2H), 7.51 (d,
J¼8.9 Hz, 2H). 13C NMR (75 MHz) d: 26.76 (q), 27.00 (q),
55.18 (q), 63.48 (t), 71.72 (d), 77.32 (d), 83.49 (d), 93.32
(d), 104.22 (d), 112.79 (s), 113.47 (d, 2C), 126.57 (d, 2C),
126.83 (s), 155.24 (s), 160.35 (s). MALDI-TOF (MS): calcd
for C17H20O6Na: 343.12, found: 343.18. Anal. Calcd for
C17H20O6: C, 63.74; H, 6.29. Found: C, 64.03; H, 6.47.
Further elution (35% ethyl acetate in light petroleum) gave
46 (7 mg, 14%) as a colorless oil.
1,2-O-Isopropylidene-3-C-[20-hydroxy-20-(3-nitro-phenyl)-
Z-vinyl]-20,5-anhydro-a-D-ribofuranose (46): [a]D ꢁ41.5 (c
0.5, CHCl3). IR (CHCl3): n 3478, 3019, 2927, 2855, 1654,
1533, 1451, 1350, 1118, 1057, 1020, 874 cmꢁ1 1H NMR
.
(400 MHz, CDCl3) d: 1.40 (s, 3H), 1.62 (s, 3H), 3.14 (s,
1H), 4.09e4.12 (m, 2H), 4.39 (d, J¼3.65 Hz, 1H), 4.62 (br
d, J¼12.5 Hz, 1H), 5.37 (s, 1H), 5.80 (d, J¼3.65 Hz, 1H),
7.52 (t, J¼8.03 Hz, 1H), 7.93 (d, J¼7.9 Hz, 1H), 8.19 (d,
J¼8.0 Hz, 1H), 8.48 (s, 1H). 13C NMR (100 MHz) d: 26.8
(q), 26.9 (q), 63.9 (t), 71.5 (s), 77.2 (d), 83.1 (d), 97.4 (d),
104.2 (d), 113.1 (s), 120.3 (d), 123.8 (d), 129.3 (d), 130.9
(d), 136.0 (s), 148.4 (s), 153.2 (s). MALDI-TOF (MS): calcd
for C16H17NO7Na: 358.09, found: 358.12. Anal. Calcd for
C16H17NO7: C, 57.31; H 5.11; N, 4.18. Found: C, 57.19; H,
4.91; N, 3.98.
4.1.34. Pd-mediated cyclization of 12
A
solution of alkyne 12 (50 mg, 0.15 mmol) and
PdCl2(CH3CN)2 (4 mg, 0.015 mmol) in CH3CN (6 mL) was
stirred under argon atmosphere at 25 ꢀC for 12 h. After com-
pletion of reaction the reaction mixture was concentrated
and purified by column chromatography (4:6, EtOAc/light pe-
troleum) to afford 44 (40 mg, 80%) as yellow crystalline solid.
1,2-O-Isopropylidene-3-C-[10-hydroxy-20-(4-nitro-phenyl)-
Z-vinyl]-10,5-anhydro-a-D-ribofuranose (44): mp¼220.4 ꢀC.
4.1.36. Pd-mediated cyclization of 14
A
solution of alkyne 14 (50 mg, 0.15 mmol) and
PdCl2(CH3CN)2 (4 mg, 0.015 mmol) in CH3CN (5 mL) was
stirred under argon atmosphere for 12 h. After completion of

C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
231
reaction, the reaction mixture was concentrated and purified
by column chromatography (40% ethyl acetate in light
petroleum) to obtain 47 (30 mg, 60%) as yellow crystalline
solid.
4.1.38. Pd-mediated cyclization of 16
Compound 50 was prepared as described earlier treating
16 (200 mg, 0.61 mmol) and PdCl2(CH3CN)2 (15 mg,
0.061 mmol) in dry CH3CN (10 mL) under argon at 25 ꢀC
for 24 h, followed by chromatography on silica gel (30% ethyl
acetate in light petroleum) to obtain 50 (50 mg, 55%) based on
recovered 16 (110 mg).
1,2-O-Isopropylidene-3-C-[10-hydroxy-20-(2-nitro-phenyl)-
Z-vinyl]-10,5-anhydro-a-D-ribofuranose (47): mp¼163.4 ꢀC.
[a]D 17.4 (c 1.5, CHCl3). IR (CHCl3): n 3401, 3020, 1605,
1522, 1423, 1347, 1165, 1086, 1018 cmꢁ1
.
1H NMR
1,2-O-Isopropylidene-3-C-(20-oxooctyl)-a-D-allofuranose-
(20-C,5-O,6-O)-ketal (50): [a]D ꢁ1.2 (c 0.8, CHCl3). IR
(CHCl3): n 3406, 3019, 2957, 2927, 1495, 1457, 1384, 1164,
(200 MHz, CDCl3) d: 1.37 (s, 3H), 1.56 (s, 3H), 3.22 (s, 1H),
4.35 (d, J¼2.4 Hz, 1H), 4.36 (s, 1H), 4.41 (d, J¼2.4 Hz, 1H),
4.59 (d, J¼3.86 Hz, 1H), 5.84 (d, J¼3.86 Hz, 1H), 6.02 (s,
1H), 7.18 (ddd, J¼1.4, 7.44, 8.18 Hz, 1H), 7.45 (ddd, J¼1.3,
7.6, 8.3 Hz, 1H), 7.8 (dd, J¼1.39, 8.21 Hz, 1H), 8.1 (dd,
J¼1.37, 8.08 Hz, 1H). 13C NMR (75 MHz) d: 27.0 (q), 27.1
(q), 73.9 (t), 82.7 (d), 83.3 (d), 87.4 (s), 96.5 (d), 105.7 (d),
113.4 (s), 124.5 (d), 126.5 (d), 129.6 (s), 130.6 (d), 132.4
(d), 147.4 (s), 159.2 (s). MALDI-TOF (MS): calcd for
C16H17NO7Na: 358.09, found: 358.10. Anal. Calcd for
C16H17NO7: C, 57.31; H, 5.11; N, 4.18. Found: C, 57.43; H,
5.25; N, 4.92.
1
1100, 1081, 1050, 695 cmꢁ1. H NMR (500 MHz, CDCl3) d:
0.86 (t, J¼6.7 Hz, 3H), 1.23e1.31 (m, 6H), 1.35 (s, 3H),
1.39e1.44 (m, 2H), 1.57 (s, 3H), 1.60 (d, J¼14.5 Hz, 1H),
1.69e1.72 (m, 2H), 1.93 (d, J¼14.5 Hz, 1H), 3.05 (br s,
1H), 3.75 (s, 1H), 3.80 (dd, J¼5.7, 7.1 Hz, 1H), 4.09 (d,
J¼3.7 Hz, 1H), 4.17 (d, J¼7.2 Hz, 1H), 4.67 (br d,
J¼5.2 Hz, 1H), 5.85 (d, J¼3.7 Hz, 1H). 13C NMR
(125 MHz) d: 14.1 (q), 22.5 (t), 22.6 (t), 26.7 (q), 26.9 (t),
29.4 (d), 31.7 (t), 37.2 (t), 40.9 (t), 65.5 (t), 73.8 (d), 75.0
(s), 78.1 (d), 84.0 (d), 104.0 (d), 107.0 (s), 112.8 (s).
MALDI-TOF (MS): calcd for C17H28O6Na: 351.18, found:
351.19. Anal. Calcd for C17H28O8: C, 62.17; H, 8.59. Found:
C, 62.46; H, 8.71.
Further elution (35% ethyl acetate in light petroleum) gave
48 (10 mg, 20%) as colorless oil.
1,2-O-Isopropylidene-3-C-[20-hydroxy-20-(2-nitro-phenyl)-
Z-vinyl]-20,5-anhydro-a-D-ribofuranose (46): [a]D 95.8 (c 0.8,
CHCl3). IR (CHCl3): n 3493, 3020, 2928, 1663, 1609, 1449,
4.1.39. Pd-mediated cyclization of 17
1
1357, 1100, 999, 897 cmꢁ1. H NMR (400 MHz, CDCl3) d:
Compound 17 (100 mg, 0.31 mmol) and PdCl2(CH3CN)2
(8 mg, 0.031 mmol) in dry CH3CN (6 mL) were stirred under
argon for 7 h at 25 ꢀC. The reaction mixture was concentrated
and purified on silica gel (10% ethyl acetate in light petro-
leum) to obtain 51 (30 mg, 30%) as colorless oil and 52
(65 mg, 65%) as yellow solid.
1.40 (s, 3H), 1.61 (s, 3H), 3.01 (s, 1H), 3.99 (br d,
J¼12.0 Hz, 1H), 4.04e4.08 (m, 1H), 4.32 (d, J¼3.7 Hz, 1H),
4.43 (dd, J¼1.0, 12.3 Hz, 1H), 4.97 (d, J¼1.76 Hz, 1H), 5.85
(d, J¼3.7 Hz, 1H), 7.44e7.57 (m, 3H), 7.82 (m, 1H). 13C
NMR (100 MHz) d: 26.9 (q), 27.1 (q), 64.6 (t), 71.6 (s),
77.8 (d), 83.2 (d), 100.1 (d), 104.3 (d), 113.0 (s), 124.2 (d),
129.9 (d), 130.3 (d), 130.5 (s), 132.2 (d), 148.9 (s), 154.2
(s). MALDI-TOF (MS): calcd for C16H17NO7Na: 358.09,
found: 358.04. Anal. Calcd for C16H17NO7: C, 57.31; H,
5.11; N, 4.18. Found: C, 57.51; H, 4.95; N, 4.30.
1,2-O-Isopropylidene-3-C-(10-hydroxy-20-phenyl-Z-vinyl)-
10,5-anhydro-a-D-allofuranose (51): [a]D 24.9 (c 1.3, CHCl3).
IR (CHCl3): n 3415, 2928, 2854, 1751, 1671, 1599, 1494,
1449, 1375, 1083, 1023, 872, 696 cmꢁ1. H NMR (200 MHz,
1
CDCl3) d: 1.40 (s, 3H), 1.62 (s, 3H), 3.82 (dd, J¼4.4, 12.1 Hz,
1H), 3.90 (dd, J¼3.9, 12.1 Hz, 1H), 4.22 (br s, 1H), 4.46
(s, 1H), 4.60 (t, J¼4.2 Hz, 1H), 4.63 (d, J¼3.7 Hz, 1H), 5.49
(s, 1H), 5.84 (d, J¼3.7 Hz, 1H), 7.10e7.17 (m, 1H), 7.25e
7.32 (m, 2H), 7.55e7.59 (m, 2H). 13C NMR (75 MHz) d:
27.1 (q), 27.3 (q), 62.6 (t), 83.8 (d), 85.6 (d), 86.1 (d), 86.7
(s), 102.7 (d), 105.8 (d), 113.5 (s), 126.3 (d), 128.2 (d),
128.3 (d, 3C), 135.3 (s), 156.8 (s). MALDI-TOF (MS): calcd
for C17H20O6Na: 343.13, found: 343.11. Anal. Calcd for
C17H20O6: C, 63.74; H, 6.29. Found: C, 64.01; H, 6.54.
1,2-O-Isopropylidene-3-C-(20-oxo-20-phenylethyl)-a-D-allo-
furanose-(20-C,5-O,6-O)-ketal (52): mp¼123 ꢀC. [a]D ꢁ2.2
(c 1, CHCl3). IR (CHCl3): n 3515, 2986, 2899, 1450, 1384,
4.1.37. Pd-mediated cyclization of 15
A solution of 15 (50 mg, 0.21 mmol) and PdCl2(CH3CN)2
(5 mg, 0.02 mmol) in CH3CN (4 mL) was stirred at 25 ꢀC
for 10 h under argon atmosphere. The reaction mixture was
concentrated and chromatographed on silica gel (40% ethyl
acetate in light petroleum) to obtain 49 (44 mg, 87%) as
a solid.
1,2-O-Isopropylidene-[3-C,5-O,6-O(methylmethylidyne)]-
a-D-allofuranose (49): mp¼159 ꢀC. [a]D ꢁ40.1 (c 1, CHCl3)
[lit.17d [a]2D1 ꢁ34.4 (c 0.9, CHCl3)]. IR (CHCl3): n 3491,
2995, 2942, 1456, 1378, 1239, 1216, 1160, 1100, 1009,
1374, 1053, 1011, 890, 872, 700 cmꢁ1. H NMR (200 MHz,
1
1
936 cmꢁ1. H NMR (200 MHz, CDCl3) d: 1.40 (s, 3H), 1.56
CDCl3) d: 1.29 (s, 3H), 1.52 (s, 3H), 1.80 (d, J¼14.6 Hz,
1H), 2.18 (d, J¼14.6 Hz, 1H), 3.08 (br s, 1H), 3.76 (s, 1H),
3.89 (br dd, J¼5.2, 7.3 Hz, 1H), 4.03 (d, J¼3.6 Hz, 1H),
4.26 (d, J¼7.3 Hz, 1H), 4.79 (d, J¼5.2 Hz, 1H), 5.82 (d,
J¼3.6 Hz, 1H), 7.22e7.30 (m, 3H), 7.46e7.50 (m, 2H). 13C
NMR (75 MHz) d: 26.7 (q), 27.0 (q), 43.3 (t), 65.6 (t), 74.3
(d), 75.2 (s), 78.1 (d), 84.1 (d), 104.2 (d), 106.2 (s), 112.9
(s), 125.1 (d, 2C), 128.2 (d, 2C), 128.5 (d), 139.9 (s).
(s, 6H), 3.19 (s, 1H), 3.60e3.69 (m, 2H), 4.16 (s, 1H), 4.32
(d, J¼3.9 Hz, 1H), 4.50 (br d, J¼3.0 Hz, 1H), 5.86 (d,
J¼3.9 Hz, 1H). 13C NMR (75 MHz, CDCl3) d: 13.4 (q),
27.4 (q, 2C), 64.9 (t), 81.6 (d), 81.9 (d), 88.0 (s), 88.7 (d),
107.1 (d), 107.6 (s), 114.0 (s). MALDI-TOF (MS): calcd for
C11H16O6Na: 267.08, found: 267.10. Anal. Calcd for
C11H16O6: C, 54.09; H, 6.60. Found: C, 53.88; H, 6.69.

232
C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
MALDI-TOF (MS): calcd for C17H20O6Na: 343.13, found:
343.12. Anal. Calcd for C17H20O6: C, 63.74; H, 6.29. Found:
C, 63.99; H, 6.48.
3H), 1.61 (s, 3H), 3.03 (br s, 1H), 3.88 (dd, J¼3.8, 12.0 Hz, 1H),
4.0 (br dd, J¼3.4, 12.0 Hz, 1H), 4.50 (s, 1H), 4.51 (s, 1H), 4.64
(d, J¼3.7 Hz, 1H), 4.69 (t, J¼3.8 Hz, 1H), 5.53 (s, 1H), 5.84 (d,
J¼3.7 Hz, 1H), 7.39 (t, J¼8.0 Hz, 1H), 7.79 (dt, J¼1.3, 7.8 Hz,
1H), 7.92 (ddd, J¼1.0, 2.3, 8.2 Hz, 1H), 8.42 (t, J¼1.9 Hz, 1H).
13C NMR (50 MHz, CDCl3) d: 26.9 (q), 27.2 (q), 62.5 (t), 83.5
(d), 85.3 (d), 86.7 (d), 86.8 (s), 100.1 (d), 105.6 (d), 113.8 (s),
120.6 (d), 122.6 (d), 129.0 (d), 133.8 (d), 137.0 (s), 148.3 (s),
159.7 (s). MALDI-TOF (MS): calcd for C17H19NO8Na: 388.10,
found: 388.09. Anal. Calcd for C17H19NO8: C, 55.89; H, 5.24;
N, 3.83. Found: C, 55.85; H, 5.43; N, 3.87.
4.1.40. Pd-mediated cyclization of 18
A solution of 18 (50 mg, 0.14 mmol) and PdCl2(CH3CN)2
(4 mg, 0.014 mmol) in dry CH3CN (4 mL) was stirred at
25 ꢀC for 3 h and concentrated. The residue was purified on
silica gel (50% ethyl acetate in light petroleum) to give 53
(41 mg, 82%) as white solid.
1,2-O-Isopropylidene-3-C-[20-oxo-20-(4-methoxyphenyl)-
ethyl]-a-D-allofuranose-(20-C,5-O,6-O)-ketal (53): mp¼168 ꢀC.
[a]D 2.6 (c 1.25, CHCl3). IR (CHCl3): n 3019, 1516, 1249, 1177,
1,2-O-Isopropylidene-3-C-[20-oxo-20-(3-nitrophenyl)-ethyl]-
a-D-allofuranose-(20-C,5-O,6-O)-ketal (56): [a]D 3.7 (c 0.8,
CHCl3). IR (CHCl3): n 3400, 3020, 1533, 1385, 1352, 1165,
1
1084, 1052, 873, 802, 669 cmꢁ1. H NMR (200 MHz, CDCl3)
1
d: 1.37 (s, 3H), 1.60 (s, 3H), 1.89 (d, J¼14.6 Hz, 1H), 2.27
(d, J¼14.6 Hz, 1H), 3.17 (s, 1H), 3.79 (s, 3H), 3.84 (br s,
1H), 3.98 (dd, J¼5.7, 7.2 Hz, 1H), 4.13 (br d, J¼3.7 Hz, 1H),
4.33 (dd, J¼0.8, 7.2 Hz, 1H), 4.87 (br d, J¼5.4 Hz, 1H), 5.91
(d, J¼3.7 Hz, 1H), 6.87 (br d, J¼8.9 Hz, 2H), 7.48 (br d,
J¼8.9 Hz, 2H). 13C NMR (50 MHz, CDCl3) d: 26.7 (q), 26.9
(q), 43.0 (t), 55.2 (q), 65.6 (t), 74.2 (d), 75.2 (s), 77.9 (d),
83.8 (d), 104.0 (d), 106.1 (s), 112.9 (s), 113.5 (d, 2C), 126.4
(d, 2C), 132.1 (s), 159.7 (s). MALDI-TOF (MS): calcd for
C18H22O7Na: 373.13, found: 373.11. Anal. Calcd for
C18H22O7: C, 61.71; H, 6.33. Found: C, 61.77; H, 6.22.
1084, 1053, 992, 890 cmꢁ1. H NMR (500 MHz, CDCl3) d:
1.39 (s, 3H), 1.61 (s, 3H), 1.90 (d, J¼14.6 Hz, 1H), 2.28 (d,
J¼14.6 Hz, 1H), 3.18 (s, 1H), 3.85 (s, 1H), 4.01 (dd, J¼5.9,
7.0 Hz, 1H), 4.15 (d, J¼3.7 Hz, 1H), 4.40 (d, J¼7.3 Hz,
1H), 4.92 (d, J¼5.4 Hz, 1H), 5.94 (d, J¼3.7 Hz, 1H), 7.55
(t, J¼8.1 Hz, 1H), 7.91 (d, J¼7.8 Hz, 1H), 8.21 (dd, J¼1.2,
8.1 Hz, 1H), 8.47 (br t, J¼1.8 Hz, 1H). 13C NMR
(125 MHz, CDCl3) d: 26.8 (q), 26.9 (q), 43.0 (t), 65.9 (t),
74.5 (d), 75.2 (s), 77.9 (d), 83.7 (d), 104.2 (d), 105.3 (s),
113.1 (s), 120.8 (d), 123.6 (d), 129.3 (d), 131.4 (d), 141.9
(s), 148.3 (s). MALDI-TOF (MS): calcd for C17H19NO8Na:
388.10, found: 388.08. Anal. Calcd for C17H19NO8: C,
55.89; H, 5.24; N, 3.83. Found: C, 56.17; H, 5.53; N, 3.48.
4.1.41. Pd-mediated cyclization of 19
Compound 19 (100 mg, 0.27 mmol) and PdCl2(CH3CN)2
(7 mg, 0.027 mmol) in dry CH3CN (4 mL) were stirred under
argon atmosphere at 25 ꢀC for 5 h and concentrated. The
residue was purified on silica gel (50% ethyl acetate in light
petroleum) to obtain 54 (87 mg, 87%) as a yellow oil.
1,2-O-Isopropylidene-3-C-[10-hydroxy-20-(4-nitro-phenyl)-
Z-vinyl]-10,5-anhydro-a-D-ribofuranose (54): [a]D 33.8 (c 1.5,
CHCl3). IR (CHCl3): n 3437, 3020, 2938, 1781, 1661, 1593,
4.1.43. Pd-mediated cyclization of 21
A solution of 21 (50 mg, 0.14 mmol) and PdCl2(CH3CN)2
(4 mg, 0.014 mmol) in dry CH3CN (4 mL) was stirred under
argon atmosphere for 5 h at 25 ꢀC. The reaction mixture was
concentrated and the residue chromatographed on silica
(30% ethyl acetate in light petroleum) to obtain 57 (36 mg,
72%) as yellow oil.
1,2-O-Isopropylidene-3-C-[10-hydroxy-20-(2-nitrophenyl)-
Z-vinyl]-10,5-anhydro-a-D-ribofuranose (57): [a]D 76.9 (c 0.5,
CHCl3). IR (CHCl3): n 3435, 3020, 1729, 1662, 1523, 1376,
1513, 1376, 1341, 1216, 1165, 1086, 1027, 861 cmꢁ1 1H
.
NMR (200 MHz, CDCl3) d: 1.40 (s, 3H), 1.61 (s, 3H), 3.14
(br s, 1H), 3.88 (dd, J¼3.7, 12.1 Hz, 1H), 4.01 (dd, J¼3.4,
12.1 Hz, 1H), 4.50 (s, 2H), 4.64 (d, J¼3.7 Hz, 1H), 4.69 (t,
J¼3.7 Hz, 1H), 5.52 (s, 1H), 5.84 (d, J¼3.7 Hz, 1H), 7.61
(d, J¼8.9 Hz, 2H), 8.01 (d, J¼8.9 Hz, 2H). 13C NMR
(50 MHz, CDCl3) d: 27.0 (q), 27.2 (q), 62.5 (t), 83.5 (d),
85.2 (d), 87.0 (s), 87.2 (d), 100.4 (d), 105.6 (d), 113.8 (s),
123.7 (d, 2C), 128.3 (d, 2C), 142.3 (s), 145.1 (s), 161.4 (d).
MALDI-TOF (MS): calcd for C17H19NO8Na: 388.10, found:
388.12. Anal. Calcd for C17H19NO8: C, 55.89; H, 5.24; N,
3.83. Found: C, 56.08; H, 5.16; N, 3.71.
1346, 1165, 1085, 1027, 873 cmꢁ1 1H NMR (200 MHz,
.
CDCl3) d: 1.42 (s, 3H), 1.62 (s, 3H), 3.88 (dd, J¼4.3,
12.1 Hz, 1H), 3.96 (dd, J¼3.8, 12.1 Hz, 1H), 4.49 (br s,
1H), 4.62 (t, J¼4.2 Hz, 1H), 4.69 (d, J¼3.7 Hz, 1H), 5.89
(d, J¼3.7 Hz, 1H), 6.0 (s, 1H), 7.27 (ddd, J¼1.4, 7.4,
8.4 Hz, 1H), 7.52 (ddd, J¼1.4, 7.6, 8.9 Hz, 1H), 7.83 (dd,
J¼1.3, 8.2 Hz, 1H), 7.99 (dd, J¼1.3, 8.0 Hz, 1H). 13C NMR
(75 MHz, CDCl3) d: 27.0 (q), 27.3 (q), 62.6 (t), 83.5 (d),
85.4 (d), 86.9 (s), 86.9 (d), 96.1 (d), 105.8 (d), 113.8 (s),
124.5 (d), 126.7 (d), 129.6 (s), 130.9 (d), 132.4 (d), 147.7
(s), 160.0 (s). MALDI-TOF (MS): calcd for C17H19NO8Na:
388.10, found: 388.11. Anal. Calcd for C17H19NO8: C,
55.89; H, 5.24; N, 3.83. Found: C, 55.91; H, 5.39; N, 3.73.
4.1.42. Pd-mediated cyclization of 20
The reaction of 20 (100 mg, 0.27 mmol) and PdCl2-
(CH3CN)2 (7 mg, 0.027 mmol) in dry CH3CN (4 mL) was car-
ried out as described earlier to procure 55 (65 mg, 65%) and
56 (18 mg, 18%).
Acknowledgements
1,2-O-Isopropylidene-3-C-[10-hydroxy-20-(3-nitro-phenyl)-Z-
vinyl]-10,5-anhydro-a-D-ribofuranose (55): [a]D 7.4 (c 1.5,
CHCl3). IR (CHCl3): n 3535, 3020, 1609, 1529, 1384, 1346,
Financial support from the University Grants Commission
(New Delhi) in the form of a research fellowship to R.M. is
gratefully acknowledged.
1
1164, 1083, 842 cmꢁ1. H NMR (200 MHz, CDCl3) d: 1.40 (s,

C.V. Ramana et al. / Tetrahedron 64 (2008) 219e233
233
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˚
l Mo Ka¼0.71073 A at T¼297(2) K. All the data were corrected for
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using SHELXS-97 and the refinement was performed by full matrix least
squares of F2 using SHELXL-97.21
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21. Sheldrick, G. M. SHELX-97 Program for Crystal Structure Solution and
Refinement; Unversity of Gottingen: Gottingen, Germany, 1997.
¨
¨
22. Only cell parameters are reported herein (Table 1); a full structural anal-
ysis will be published elsewhere. The crystallographic data have been de-
posited with the Cambridge Crystallographic Data Centre as deposition
nos. CCDC-649447 (40), CCDC-296444 (42), CCDC-649448 (44),
CCDC-649449 (47), CCDC-296445 (52), and CCDC-649450 (53). Copies
of the data can be obtained, free of charge, on application to the CCDC, 12
Union Road, Cambridge CB2 1EZ, UK [fax: þ44(1223)336033; e-mail:
deposit@ccdc.cam.ac.uk].