Synthesis of diastereomeric 3-hydroxy-4-pyrrolidinyl derivatives of nucleobases

Article abstract of DOI:10.1016/j.tet.2006.11.047

The work deals with the synthesis of hydroxypyrrolidine analogs of nucleosides. Starting from the optically pure l- or d-tartaric acid, we improved the synthesis of enantiomeric trans-3,4-dihydroxypyrrolidines and elaborated a procedure for the synthesis of all possible diastereoisomers of 3-hydroxy-4-pyrrolidinyl derivatives of both purine and pyrimidine nucleobases. The prepared compounds were tested for cytostatic and antiviral properties but no significant activity was found.

Full text of DOI:10.1016/j.tet.2006.11.047

Tetrahedron 63 (2007) 1243–1253
Synthesis of diastereomeric 3-hydroxy-4-pyrrolidinyl derivatives
of nucleobases
*
ˇ
Dominik Rejman, Petr Kocalka, Milos Budesınsky, Radek Pohl and Ivan Rosenberg
ˇˇ
ꢁ
ꢀ
ꢁ
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo naꢁm. 2, 166 10 Prague 6,
Czech Republic
Received 10 July 2006; revised 31 October 2006; accepted 16 November 2006
Available online 11 December 2006
Abstract—The work deals with the synthesis of hydroxypyrrolidine analogs of nucleosides. Starting from the optically pure L- or D-tartaric
acid, we improved the synthesis of enantiomeric trans-3,4-dihydroxypyrrolidines and elaborated a procedure for the synthesis of all possible
diastereoisomers of 3-hydroxy-4-pyrrolidinyl derivatives of both purine and pyrimidine nucleobases. The prepared compounds were tested for
cytostatic and antiviral properties but no significant activity was found.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
the pyrrolidine ring and the nucleobase moiety; in this
case racemic mixtures were prepared. Richichi et al.24 de-
scribed the preparation of protected 3-hydroxypyrrolidinyl
derivatives of uracil 2c and thymine 2d by Mitsunobu
reaction of unprotected pyrimidine bases with appropriate
N-benzylpyrrolidin-3,4-diols. Recently, we published the
synthesis of 3-pyrrolidinyl derivatives of all four nucleo-
bases mimicking 20,30-dideoxynucleosides, by nucleophilic
displacement of the mesyloxy group for individual nucleo-
bases under various conditions.25,26
Sugar-modified nucleoside analogs form a large group of
potential antimetabolites.1 Thus, 1,3-oxothiolane,2 1,3-di-
oxolane,3–6 and cyclobutane7 and cyclopentane8–12 ring-con-
taining D- and L-nucleoside analogs have been synthesized
and biologically evaluated. Among these analogs, potent
compounds exhibiting remarkable antiviral and anticancer
properties have been found.13
Replacement of the sugar moiety in nucleosides by a pyrro-
lidine ring seems to be one of the promising modifications,
which could provide compounds possessing both diverse
biological activities and the possibility of further derivatiza-
tion, e.g., on the nitrogen atom of the pyrrolidine ring
(Fig. 1).
In this paper, we describe the synthesis of diastereomeric 3-
hydroxy-4-pyrrolidinyl derivatives of thymine and adenine
by nucleophilic displacement of mesyloxy group for
nucleobase.
The pyrrolidine nucleosides have attracted the attention of
several laboratories.14–26 Thus, Miyabe et al.23 reported
the total synthesis of 3-hydroxy-4-pyrrolidinyl derivatives
of uracil, thymine, and adenine 1 via construction of both
2. Results and discussion
The enantiomeric trans-3,4-dihydroxypyrrolidines 8a and
8b are known compounds and their synthesis starting from
B
B
B
B
OH
HN
R N
4
4
HN
4
HN
4
3
3
3
3
OH
4a 3R, 4S; cis; B= T
2b 3S, 4R; cis; B= A; R= H 3b 3S, 4S; trans; B= A 4b 3R, 4S; cis; B= A
2c 3R, 4S; cis; B= U; R= Bn
OH
OH
2a 3S, 4R; cis; B= T; R= H 3a 3S, 4S; trans; B= T
1a 3R, 4R; trans; B= T
1b 3R, 4R; trans; B= A
1c 3R, 4R; trans; B= U
2d 3R, 4S; cis; B= T; R= Bn
Figure 1.
Keywords: Tartaric acid; Pyrrolidine derivatives; Nucleoside analogs; Nucleobase.
* Corresponding author. Tel.: +420 220 183 381; fax: +420 220 183 578; e-mail: ivan@uochb.cas.cz
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.11.047

1244
D. Rejman et al. / Tetrahedron 63 (2007) 1243–1253
Table 1. Conditions for dimethoxytritylation of 7a to 9 (Scheme 2)
L- and D-tartaric acids (5a and 5b, respectively) was de-
scribed in the literature many times.27–35 We prepared 8a
and 8b from the appropriate tartaric acids via corresponding
2,5-diones 6a and 6b, the preparation of which was recently
improved.26 In short, the monobenzylammonium salt of tar-
taric acid prepared in aqueous methanol was refluxed, after
evaporation of solvents, in xylene in the Dean–Stark appara-
tus for 8 h. A clear, homogenous solution was obtained
within several minutes of heating. Xylene was evaporated
in vacuo and the crude material was crystallized from hot
ethanol to yield the products 6a and 6b in w90% yield
(Scheme 1). The reduction of benzyl imides 6a and 6b
to benzylpyrrolidines 7a and 7b, respectively, proceeded
smoothly by treatment with diborane generated in situ
from NaBH4 and iodine in THF.36 Desalting of N-benzyl-
3-pyrrolidinols 7a and 7b on Dowex 50W (H+) followed
by removal of N-benzyl group using catalytic hydrogenation
afforded pure 3-pyrrolidinols 8a and 8b, respectively.
Conditions (rt, 16 h)
Yield, %
DMTrCl (1.5 equiv)/pyridine
56
54
46
44
36
25
25
DMTrCl (1.5 equiv)/DCM/DMAP (1.5 equiv)
DMTrCl (1.5 equiv)/THF/NaH (1 equiv)/ꢀ78 ꢁC
DMTrCl (1.5 equiv)/DBU (1.5 equiv)/(no solvent)
DMTrCl (1.5 equiv)/pyridine/DBU (1.5 equiv)
DMTrCl (1.5 equiv)/DCM/DBU (1.5 equiv)
DMTrCl (2 equiv)/THF/AgNO3 (1.5 equiv)
of 9 was fast and nearly quantitative using an excess of mesyl
chloride. The mesyl derivative 10 was subjected to the reac-
tion with the cesium salt of adenine in DMSO at elevated
temperature. However, the reaction did not proceed via
SN2-substitution mechanism exclusively, so that a diastereo-
meric mixture of products 11 and 12, together with the 7-N-
substituted adenine isomer 13, were obtained in a low yield.
Attempts at tuning the reaction conditions (e.g., the use of
DMF and variable amount of sodium hydride) to improve
either the yield or at least the product distribution failed.
The structure of compounds 11–13 was unambiguously
confirmed using a combination of NMR techniques
(H,H-COSY, H,C-HSQC and H,C-HMBC). The relativecon-
figuration of 11 and 12 at chiral carbons C-3 and C-4 was
checked by ROESY, whereby NOE contacts between H-8
from adenine and particular protons from the pyrrolidine
ring served as the proof of the configuration.
Having prepared N-benzyl derivative 7, we first attempted to
use it for the protection of one hydroxyl of the trans diol
moiety (Scheme 2). Thus, 7a was dimethoxytritylated under
various conditions with the aim of increasing the yield of the
monosubstituted product 9 (Table 1). As both the hydroxyl
groups in 7a are equally reactive, it is difficult in this
case to obtain nearly quantitative yield as it is in the case
of non-equivalent hydroxyls (e.g., dimethoxytritylation of
primary hydroxyl in the presence of secondary one in
nucleosides).
We concluded that the presence of the tertiary amine moiety
possessing a free electron pair on pyrrolidine nitrogen atom
is likely to be the main factor influencing the epimerization
of the C-3 atom of 10 during nucleophilic displacement of
the mesyloxy group. The pyrrolidine nitrogen atom could in-
teract with a C-3 carbocation (or with some kind of SN2 tran-
sition state intermediate) via a free electron pair giving rise
to two hypothetical chiral intermediates A and B (Fig. 2),
which can be attacked on the C-3 atom by adenine as a nucle-
ophile either from the cis or trans position with respect to
the dimethoxytrityloxy substituent, providing a mixture of
As is obvious from Table 1, the best yield of the dimethoxy-
trityl derivative 9 was obtained in the first two cases, using
pyridine and DCM as solvents. The use of dimethoxytrityl
group offers several advantages: (i) it is stable under nucleo-
philic displacement (alkaline conditions), (ii) the reagent for
its introduction (DMTrCl) possesses sufficient reactivity,
(iii) the group is bulky enough to react preferentially with
only one hydroxyl, and (iv) its removal is accomplished
under mild acidic conditions. The subsequent mesylation
O
4
O
OH
OH
OH
OH
OH
OH
OH
OH
HO
HO
5
3
2
(ii)
(i)
4
3
5
2
5
2
(iii)
4
3
4
3
1
Bn N
1
HN
1
Bn N
2
1
O
O
5a 2S, 3S; trans
5b 2R, 3R; trans
6a 2S, 3S; trans
6b 3R, 4R; trans
7a 3R, 4R; trans
7b 3S, 4S; trans
8a 3R, 4R; trans
8b 3S, 4S; trans
Scheme 1. (i) (1) BnNH2, methanol; (2) xylene, reflux; (ii) NaBH4, I2, THF; (iii) H2, Pd/C, ethanol.
(i)
(ii)
OH
OMs
8a
Bn
N
Bn
N
3
4
4
3
ODMTr
ODMTr
9
10
(iii)
(iii)
(iii)
N
N
N
NH2
NH2
N9
N7
N
N
Bn
N
Bn N
Bn
N
4
4
4
3
N
N
N
N
3
3
N
+
+
H2N
ODMTr
ODMTr
ODMTr
13
11
12
Scheme 2. (i) DMTrCl, pyridine; (ii) MsCl, DMAP, DCM; (iii) adenine, Cs2CO3, DMSO.

D. Rejman et al. / Tetrahedron 63 (2007) 1243–1253
1245
Adenine
configuration, were obtained by deprotection using 20%
TFA in DCM. Again, the relative configurations of the free
nucleosides were assigned by ROESY spectra.
A
B
4
3
+
3
+
Adenine
OR
N
OR
N
4
All the steps involved in the series of reactions were simple
and gave very good yields. The only difficulty encountered
was with the purification of 4-nitrobenzoate 18 after Mitsu-
nobu reaction. Residual diisopropyl-hydrazinodicarboxylate
was completely removed at the level of mesyl derivative 20
using silica gel chromatography carefully (elution with a
linear gradient of toluene in petroleum ether followed by a
slow linear gradient of ethyl acetate in toluene).
11
12
Figure 2. Possible explanation of epimerization (see also Scheme 2).
diastereoisomers 11 and 12. The formation of a quaternary
aziridine derivative as an intermediate does not seem to be
plausible.
In order to overcome the problem with participation of the
free electron pair of basic pyrrolidine nitrogen atom during
the nucleophilic displacement of mesyloxy group in 10 for
nucleobase, we exchanged the N-benzyl protecting group of
pyrrolidine nitrogen atom for a N-butyloxycarbonyl group,
which made the nitrogen atom non-basic due to delocaliza-
tion of the electron pair. The N-benzyl group of compounds
7a and 7b was removed by a catalytic reduction under hydro-
gen and the unprotected 3,4-dihydroxypyrrolidines 8a and
8b were transformed into N-Boc derivatives 14a and 14b,
respectively (Scheme 3). It should be noted that the starting
N-benzylpyrrolidine 7 had to be passed through silica gel
before the hydrogenation step, to avoid poisoning of the
palladium catalyst by unidentified impurities.
The cytostatic activity of analogs 1a,b, 2a,b, 3a,b, and 4a,b
was examined with L1210, L929, and HeLa S3 cell lines.
The antiviral activity was evaluated against (i) HSV-1,
HSV-2, vaccinia virus, VSV, and HSV-1 TK- KOS ACVr
in HEL cell cultures, (ii) VSV, coxsackie virus B4 in HeLa
cell cultures, and (iii) parainfluenza virus, rheovirus-1, sind-
bis virus, coxsackie virus B4, and Punta Toro virus in Vero
cell cultures. No significant activity was found.
3. Conclusions
We reported the synthesis of novel nucleoside mimics, eight
diastereoisomeric 3-hydroxy-4-pyrrolidinyl derivatives of
adenine and thymine 1a,b, 2a,b, 3a,b, and 4a,b by a direct
nucleophilic displacement of mesyloxy group in 16a,b and
19a,b for nucleobases. We improved the synthesis of key
enantiomeric trans-1-N-benzyl-3,4-dihydroxypyrrolidines
8a and 8b to obtain reproducibly high yields of these com-
pounds. We found that the N-benzyl protecting group in
mesyloxy derivative 10 participated in the nucleophilic dis-
placement of mesyloxy group for the adenine moiety and
that, therefore, this reaction proceeded with epimerization.
The prepared compounds 1–4 offer further possibility for
derivatization at the pyrrolidine nitrogen atom, thus provid-
ing the chance to prepare other types of structurally diverse
compounds, e.g., phosphonate pyrrolidine nucleotides, and
consequently, enlarge the area of potentially biologically
active compounds. This makes these compounds interesting,
Dimethoxytritylation of the 3-hydroxy group of 14 with di-
methoxytrityl chloride in pyridine provided 70% yield of
compound 15, which was mesylated to give the trans mesyl
derivative 16. To obtain cis mesylate 20, the configuration
on carbon C-3 was inverted using Mitsunobu reaction with
4-nitrobenzoic acid. The ester 18 was treated with metha-
nolic ammonia to remove the 4-nitrobenzoyl group, and sub-
sequent mesylation of 19 provided the cis mesyl derivative
20. The obtained mesylates 16 and 20 were used for the
nucleosidation reaction with the cesium or potassium salt
of adenine or thymine in DMSO. The nucleosidation reac-
tions led in both cases to a good yield of the desired adenine
derivatives and to a moderate yield of the desired thymine
ones. Final compounds 1a,b and 3a,b with trans configura-
tion, as well as compounds 4a,b and 2a,b with cis
OMs
B
(iv)
OH
OH
BocN
BocN
BocN
BocN
4
(i)
(ii)
(iii)
(v)
2a 3S, 4R; cis; B= T
2b 3S, 4R; cis; B= A
8a
3
OH
14a 3R, 4R; trans
(vi)
ODMTr
ODMTr
ODMTr
15a 3R, 4R; trans 16a 3R, 4R; trans
17a 3R, 4S; cis; B= T
17b 3R, 4S; cis; B= A
B
OPNB
(vii)
OH
(iii)
OMs
BocN
BocN
BocN
BocN
(iv)
(v)
1a 3R, 4R; trans; B= T
1b 3R, 4R; trans; B= A
ODMTr
21a 3R, 4R; trans; B= T
21b 3R, 4R; trans; B= A
ODMTr
18a 3S, 4R; cis
ODMTr
19a 3R, 4S; cis
ODMTr
20a 3S, 4R; cis
(v)
(v)
(iii)
(iv)
(ii)
4a 3R, 4S; cis; B= T
4b 3R, 4S; cis; B= A
17c 3S, 4R; cis; B= T
16b 3S, 4S; trans
20b 3R, 4S; cis
14b 3S, 4S; trans
15b 3S, 4S; trans
19b 3S, 4R; cis
17d 3S, 4R; cis; B= A
(i)
(vi)
8b
(vii)
(iii)
(iv)
21c 3S, 4S; trans; B= T
21d 3S, 4S; trans; B= A
3a 3S, 4S; trans; B= T
3b 3S, 4S; trans; B= A
18b 3R, 4S; cis
Scheme 3. (i) Boc2O, NaHCO3, dioxane, water; (ii) DMTrCl, pyridine; (iii) MsCl, DMAP, DCM; (iv) adenine or thymine, Cs2CO3 or K2CO3, DMSO; (v) 20%
TFA/DCM; (vi) Ph3P, PNBA, DIAD, THF; (vii) NH3/methanol.

1246
D. Rejman et al. / Tetrahedron 63 (2007) 1243–1253
although no significant cytostatic and antiviral activities
of the prepared compounds were observed.
d6): 1.77 (d, 3H, JCH ;6 ¼ 1:2, CH3-5), 2.63 (dd, 1H,
3
0
0
0
Jgem¼11.3, J2 b,3 ¼5.1, H-2 b), 2.75 (dd, 1H, Jgem¼11.7,
0
0
0
0
00
J5 b,4 ¼5.7, H-5 b), 3.08 (dd, 1H, Jgem¼11.3, J2 a,3 ¼6.2,
H-20a), 3.19 (dd, 1H, Jgem¼11.7, J5 a,4 ¼8.1, H-5 a), 4.16
0
0 0
0
0
0
0 0
4. Experimental
4.1. General
(dt, 1H, J3 ,2 ¼6.2, 5.1, J3 ,4 ¼4.5, H-3 ), 4.52 (ddd, 1H,
0
0
0
0
J4 ,5 ¼8.1, 5.7, J4 ,3 ¼4.5, H-4 ), 7.52 (q, 1H, J6;CH ¼ 1:2,
3
H-6). 13C NMR (125.8 MHz, DMSO-d6): 12.31 (CH3-5),
49.73 (CH2-50), 53.63 (CH2-20), 64.11 (CH-40), 75.58
(CH-30), 109.24 (C-5), 138.81 (CH-6), 151.27 (C-2),
164.05 (C-4).
Unless stated otherwise, all used solvents were anhydrous.
Final products were lyophilized from water, and dried over
phosphorus pentoxide at 50–70 ꢁC and 13 Pa. TLC was per-
formed on silica gel pre-coated aluminum plates Silica gel/
TLC-cards, UV 254 (Fluka), and the compounds were de-
tected by UV light (254 nm), by heating (detection of di-
methoxytrityl group; orange color), by spraying with 1%
solution of ninhydrin to visualize amines, and by spraying
with 1% solution of 4-(4-nitrobenzyl)pyridine in ethanol fol-
lowed by heating and treating with gaseous ammonia (blue
color of mono- and diesters of phosphonic acid). Preparative
column chromatography was carried out on silica gel (40–
60 mm, Fluka) neutralized with triethylamine (1 mL/100 g),
and elution was performed at the flow rate of 40 mL/min.
The following solvent systems were used for TLC and pre-
parativechromatography: toluene/ethyl acetate 1:1 (T); chlo-
roform/ethanol 9:1 (C1); ethyl acetate/acetone/ethanol/water
6:1:1:0.5 (H3); ethyl acetate/acetone/ethanol/water 4:1:1:1
(H1). The concentrations of solvent systems are stated invol-
ume percents (%, v/v). Analytical RP-HPLC was performed
on LC5000 Liquid Chromatograph (INGOS-PIKRON, CR)
using Luna C18 (2) column (4.6ꢂ150 mm) at the flow rate
of 1 mL/min by a gradient elution of methanol in 0.1 M
TEAA, pH 7.5 (A¼0.1 M TEAA, B¼0.1 M TEAA in 50%
aqueous methanol, C¼methanol). Mass spectra were re-
corded on ZAB-EQ (VG Analytical) instrument, using
FAB (ionization with Xe, accelerating voltage 8 kV). Gly-
cerol and thioglycerol were used as matrices. NMR spectra
4.1.2. (3R,4R)-4-(Adenin-9-yl)-3-hydroxypyrrolidine
(1b). Compound 1b was prepared from 21b (7.7 g,
12.4 mmol) using the same procedure as for the compound
1a in 84% yield (2.3 g) in the form of a white amorphous
solid.
HRMS for C9H12N6O (M+H)+ calcd: 221.1151, found:
221.1151. [a]D20 ꢀ18.7 (c 0.171, H2O); nmax (KBr) 3455
(m), 3410 (m, br, sh), 3360 (m, sh), 3336 (s), 3325 (s, sh),
3267 (m), 3210 (s), 1658 (vs), 1637 (s, sh), 1608 (s), 1573
(m), 1506 (w), 1479 (m), 1414 (m), 1374 (w), 1330 (m),
1311 (m), 1296 (w), 1256 (m), 1225 (w), 797 (w), 653
1
(m), 538 (w). H NMR (500 MHz, DMSO-d6): 2.72 (dd,
0
0
0
1H, Jgem¼11.6, J2 b,3 ¼4.5, H-2 b), 3.05 (dd, 1H, Jgem¼11.7,
0
0
0
0
00
J5 b,4 ¼5.3, H-5 b), 3.25 (dd, 1H, Jgem¼11.6, J2 a,3 ¼6.2,
H-20a), 3.35 (dd, 1H, Jgem¼11.7, J5 a,4 ¼7.3, H-5 a), 4.42
0
0 0
0
0
0
00
(dt, 1H, J3 ,2 ¼6.2, 4.5, J3 ,4 ¼3.8, H-3 ), 4.65 (ddd, 1H,
0
0
0
0
J4 ,5 ¼7.3, 5.3, J4 ,3 ¼3.8, H-4 ), 7.17 (br s, 2H, NH2), 8.13
(s, 1H, H-2), 8.17 (s, 1H, H-8). 13C NMR (125.8 MHz,
DMSO-d6): 50.98 (CH2-50), 53.89 (CH2-20), 63.23 (CH-
40), 76.49 (CH-30), 119.14 (C-5), 139.70 (CH-8), 149.51
(C-4), 152.36 (CH-2), 156.16 (C-6).
4.1.3. (3S,4R)-3-Hydroxy-4-(thymin-1-yl)-pyrrolidine
(2a). Compound 2a was prepared from 17c (3.7 g,
6 mmol) using the same procedure as for the compound 1a
in 73% yield (1 g) in the form of a white amorphous solid.
were measured on Bruker Avance 400 (1H at 400 MHz, 13
C
at 100.6 MHz), Bruker Avance 500, and Varian Unity 500
(1H at 500 MHz, 13C at 125.8 MHz) spectrometers. Chemi-
cal shifts (in parts per million, d scale) were referenced to
TMS as internal standard; coupling constants (J) are given
in Hertz. Complete assignment of protons and carbons was
achieved by analysis of correlated homonuclear 2D-COSY
and heteronuclear 1H–13C HSQC and 1H–13C HMBC spec-
tra. Relative configuration was checked using DPFGSE-
NOE and 2D-ROESY techniques.
HRMS for C9H12N6O (M+H)+ calcd: 212.1035, found:
221.1013. [a]D20 +73.6 (c 0.324, H2O); nmax (KBr) 3393
(m), 3317 (m), 1696 (vs, br), 1665 (vs), 1643 (m, sh),
1489 (m), 1468 (m), 1444 (m), 1394 (m), 1375 (w), 1295
1
(m), 1271 (m), 1076 (w), 1060 (m), 767 (m), 763 (m). H
NMR (400 MHz, DMSO-d6): 1.76 (d, 3H, JCH ;6 ¼ 1:2,
3
0
0
0
0
CH3-5), 2.69 (dd, 1H, Jgem¼12.0, J2 b,3 ¼3.0, H-2 b),
0
0
0
2.94 (dd, 1H, Jgem¼11.5, J5 b,4 ¼8.0, H-5 b), 3.01 (dd, 1H,
0
0
4.1.1. (3R,4R)-3-Hydroxy-4-(thymin-1-yl)-pyrrolidine
(1a). Compound 21a (3.2 g, 5.2 mmol) was treated with
a 20% solution of TFA in DCM (50 mL) containing 1% of
water overnight. The reaction mixture was concentrated in
vacuo, water was added, and the solution was applied onto
a column of Dowex 50W in H+ cycle (100 mL). The resin
was washed with water (300 mL) and the desired compound
1a was obtained after elution with 3% aqueous ammonia,
concentration, and lyophilization from water in 68% yield
(0.8 g) in the form of a white amorphous solid.
Jgem¼11.5, J2 a,3 ¼8.0, H-2 a), 3.08 (dd, 1H, Jgem¼12.0,
0
0
0
0
0
0
0 0
J5 a,4 ¼5.6, H-5 a), 4.11 (td, 1H, J3 ,4 ¼6.1, J3 ,2 ¼5.6, 3.0,
H-30), 4.68 (td, 1H, J4 ,5 ¼8.0, J4 ,3 ¼6.1, H-4 ), 5.07 (br,
0
0
0
0
1H, OH), 7.48 (q, 1H, JCH ;6 ¼ 1:2, H-6). 13C NMR
3
(100.6 MHz, DMSO-d6): 12.37 (CH3-5), 48.13 (CH2-50),
54.55 (CH2-20), 57.14 (CH-40), 69.19 (CH-30), 107.01
(C-5), 140.53 (CH-6), 151.71 (C-2), 164.10 (C-4).
4.1.4. (3S,4R)-4-(Adenin-9-yl)-3-hydroxypyrrolidine
(2b). Compound 2b was prepared from 17d (6 g,
9.6 mmol) using the same procedure as for the compound
1a in 75% yield (1.6 g) in the form of a white amorphous
solid.
HRMS for C9H13N3O3 (M+H)+ calcd: 212.1035, found:
212.1043. nmax (KBr) 3387 (m, br, sh), 3342 (s), 3160 (w,
br), 1684 (vs, br), 1664 (vs, sh), 1642 (s, sh), 1492 (m),
1466 (m), 1441 (m), 1400 (m), 1388 (m), 1375 (m), 1284
HRMS for C9H12N6O (M+H)+ calcd: 221.1151, found:
1
(m), 1272 (m, sh), 765 (m). H NMR (500 MHz, DMSO-
221.1013. [a]D20 +91.2 (c 0.339, H2O); nmax (KBr) 3433

D. Rejman et al. / Tetrahedron 63 (2007) 1243–1253
1247
(m, br, sh), 3319 (s), 3266 (s), 3177 (s, br), 1644 (vs, br),
1600 (vs), 1575 (s), 1505 (w), 1475 (s), 1415 (s), 1370
(m), 1331 (m), 1301 (m), 1254 (m), 1220 (m), 1081 (m,
and concentrated in vacuo. The obtained solid material
was co-evaporated with ethanol (2ꢂ200 mL) to remove
traces of xylene and refluxed in ethanol (1000 mL) for
5 min. The suspension was cooled, crystals were filtered
off, washed with ethanol (3ꢂ100 mL) and dried to yield
242.2 g (73%) of compound 6a. Combined filtrates were
concentrated to a volume of 500 mL. Charcoal (50 g) was
added and the suspension was refluxed for 5 min and then
filtered through CeliteÒ. The filtration cake was washed
with hot ethanol (100 mL) and combined filtrates were left
aside to crystallize. The crystallization of mother liquor
was repeated three times to obtain an additional 66.4 g
(20%) of compound 6a. The total yield of 6a was 308.6 g
(93%).
1
sh), 1067 (m, br), 798 (m), 649 (m), 536 (w). H NMR
(400 MHz, DMSO-d6): 2.79 (dd, 1H, Jgem¼11.9,
0
0
0
0
00
J2 b,3 ¼3.3, H-2 b), 3.17 (dd, 1H, Jgem¼11.1, J5 b,4 ¼8.4,
H-50b), 3.21 (dd, 1H, Jgem¼11.9, J2 a,3 ¼5.6, H-2 a), 3.23
0
0
0
0
0
(dd, 1H, Jgem¼11.1, J5 a,4 ¼8.2, H-5 a), 4.21 (dt, 1H,
0
0
0
0
0
0
0
J3 ,4 ¼5.8, J3 ,2 ¼5.6, 3.3, H-3 ), 4.81 (dt, 1H, J4 ,5 ¼8.4,
0
0
0
8.2, J4 ,3 ¼5.8, H-4 ), 5.09 (br, 1H, OH), 7.16 (br s, 2H,
NH2), 8.13 (s, 1H, H-2), 8.14 (s, 1H, H-8). 13C NMR
(100.6 MHz, DMSO-d6): 49.58 (CH2-50), 54.52 (CH2-20),
57.04 (CH-40), 69.83 (CH-30), 118.49 (C-5), 140.85 (CH-
8), 150.19 (C-4), 152.28 (CH-2), 156.05 (C-6).
4.1.5. (3S,4S)-3-Hydroxy-4-(thymin-1-yl)-pyrrolidine
(3a). Compound 3a was prepared from 21c (2.9 g,
4.7 mmol) using the same procedure as for the compound
1a in 75% yield (0.7 g) in the form of a white amorphous
solid.
Mp 194–197 ꢁC. HRMS for C11H12N1O4 (M+H)+ calcd:
222.0766, found: 222.0769. H NMR (500 MHz, DMSO-
1
d6): 4.38 (d, 2H, J¼4.9, OCH), 4.53 and 4.58 (2ꢂd,
2ꢂ1H, Jgem¼15.0, NCH2), 6.29 (d, 2H, J¼4.9, OH), 7.24
(m, 2H, H-m-Ph), 7.27 (m, 1H, H-p-Ph), 7.33 (m, 2H, H-o-
Ph). 13C NMR (125.8 MHz, DMSO-d6): 41.31 (NCH2),
74.65 (OCH), 127.64, 127.67 and 128.69 (CH-Ph), 136.13
(C-i-Ph), 174.71 (CO).
HRMS for C9H13N3O3 (M+H)+ calcd: 212.1035, found:
1
212.1041. [a]D20 +53.2 (c 0.348, H2O). H NMR and 13C
NMR spectra were identical to those of compound 1a.
4.1.10. (3R,4R)-1-N-Benzyl-3,4-dihydroxypyrrolidin-2,6-
dione (6b). Compound 6b was prepared from (3R,4R)-tarta-
ric acid (225.1 g, 1.5 mol) using the same procedure as for
the compound 6a. The total yield of 6b was 298.5 g (90%).
4.1.6. (3S,4S)-4-(Adenin-9-yl)-3-hydroxypyrrolidine
(3b). Compound 3b was prepared from 21d (3.5 g,
6.1 mmol) using the same procedure as for the compound
1a in 78% yield (1 g) in the form of a white amorphous solid.
Mp 196–198 ꢁC. HRMS for C11H12N1O4 (M+H)+ calcd:
222.0766, found: 222.0765. 1H NMR and 13C NMR spectra
were identical to those of compound 6a.
HRMS for C9H12N6O (M+H)+ calcd: 221.1151, found:
1
221.1154. [a]D20 +53.3 (c 0.176, H2O). H NMR and 13C
NMR spectra were identical to those of compound 1b.
4.1.11. (3R,4R)-1-N-Benzyl-3,4-dihydroxypyrrolidine
(7a). A solution of iodine (95.2 g, 375 mmol) in THF
(450 mL) was added dropwise to a vigorously stirred ice
bath cooled suspension of NaBH4 (28.4 g, 750 mmol) in a
solution of 6a (33.2 g, 150 mmol) in THF (700 mL) under
argon atmosphere. The reaction mixture was stirred at rt
overnight, then cooled to 0 ꢁC, and the excess of NaBH4
was decomposed with 3 M HCl (143 mL) (note: intensive
gas evolution occurred). The reaction mixture was concen-
trated in vacuo, filtered through CeliteÒ, the cake was
washed with acetone, and the filtrate was evaporated. The
oily residue was deionized on Dowex 50W (H+, 1.5 L).
Crude material was purified on a silica gel column using
a linear gradient of system H1 in ethyl acetate yielding
27.2 g (94%) of yellowish crystals of compound 7a.
4.1.7. (3R,4S)-3-Hydroxy-4-(thymin-1-yl)-pyrrolidine
(4a). Compound 3a was prepared from 17a (0.34 g,
0.56 mmol) using the same procedure as for the compound
1a in 88% yield (104 mg, 0.5 mmol) in the form of a white
amorphous solid.
HRMS for C9H13N3O3 (M+H)+ calcd: 212.1035, found:
1
212.1032. [a]D20 ꢀ101.0 (c 0.302, H2O); H NMR and 13C
NMR spectra were identical to those of compound 2a.
4.1.8. (3R,4S)-4-(Adenin-9-yl)-3-hydroxypyrrolidine
(4b). Compound 4b was prepared from 17b (3.1 g,
5 mmol) using the same procedure as for the compound 1a
in 54% yield (0.6 g) in the form of a white amorphous solid.
HRMS for C9H12N6O (M+H)+ calcd: 221.1151, found:
Mp 86–89 ꢁC. HRMS for C11H16N1O2 (M+H)+ calcd:
194.1181, found: 194.1186. H NMR (500 MHz, DMSO-
1
1
221.1143. [a]D20 ꢀ53.5 (c 0.213, H2O). H NMR and 13C
NMR spectra were identical to those of compound 2b.
d6): 2.30 (dd, 2H, Jgem¼9.5, Jvic¼4.5, CHbHaN), 2.74 (dd,
2H, Jgem¼9.5, Jvic¼5.9, CHaHbN), 3.46 and 3.57 (2ꢂd,
2ꢂ1H, Jgem¼13.1, CH2-Ph), 3.84 (br t, 2H, J¼5.9, 4.5,
OCH), 4.84 (br s, 2H, OH), 7.20–7.35 (m, 5H, Ph). 13C
NMR (125.8 MHz, DMSO-d6): 60.14 (CH2-Ph), 60.99
(NCH2), 77.81 (OCH), 126.92, 128.32 and 128.71 (CH-
Ph), 139.23 (C-i-Ph).
4.1.9. (3S,4S)-1-N-Benzyl-3,4-dihydroxypyrrolidin-2,6-
dione (6a). Benzylamine (160.7 mL, 1.5 mol) was slowly
added to a stirred suspension of (3S,4S)-tartaric acid
(225.1 g, 1.5 mol) in 50% aqueous methanol (300 mL).
The resulting mixture was heated at 50 ꢁC until a clear solu-
tion was obtained. The viscous solution was concentrated on
rotary evaporator, xylene (4 L) was added, and the reaction
mixture was refluxed in a Dean–Stark apparatus in oil bath
at 190 ꢁC for 8 h. During that period, additional xylene
(2ꢂ500 mL) was added. The resulting solution was cooled
4.1.12. (3S,4S)-1-N-Benzyl-3,4-dihydroxypyrrolidine
(7b). Compound 7b was prepared from 6b (33.2 g,
150 mmol) using the same procedure as for the compound
7a in 93% (26.9 g) yield.

1248
D. Rejman et al. / Tetrahedron 63 (2007) 1243–1253
Mp 95–98 ꢁC. HRMS for C11H16N1O2 (M+H)+ calcd:
194.1181, found: 194.1177. 1H NMR and 13C NMR spectra
were identical to those of compound 7a.
was stirred at rt for 2 h, cooled in an ice bath, and quenched
with water (10 mL). The reaction mixture was washed with
a saturated solution of sodium hydrogen carbonate. The
organic layer was dried over sodium sulfate and evaporated.
Compound 10 was obtained by chromatography on silica gel
using a linear gradient of toluene in petroleum ether
followed by a linear gradient of ethyl acetate in toluene in
83% yield (11 g) in the form of a yellowish foam.
4.1.13. (3R,4R)-3,4-Dihydroxypyrrolidine (8a). N-Benzyl-
pyrrolidine derivative 7a (29.0 g, 150 mmol) in 80% aque-
ous ethanol (900 mL) was treated with hydrogen gas
(10 psi) in the presence of 10% Pd/C (2 g) at rt for 2 d.
The catalyst was filtered off, the filtrate was concentrated
in vacuo, the residue was co-evaporated with ethanol
(2ꢂ100 mL), and dried over P2O5 (13 Pa). Compound 8a
was obtained as a yellow oil in 90% yield (13.9 g).
HRMS for C33H35NO6S (M+H)+ calcd: 574.2263, found:
574.2261. H NMR (500 MHz, DMSO-d6): 2.63 (dd, 1H,
1
Jgem¼10.2, J5b,4¼3.7, H-5b), 2.94 (d, 2H, J2,3¼7.0, 6.6,
H-2), 2.95 (dd, 1H, Jgem¼10.2, J5a,4¼6.6, H-5a), 3.69 (s, 2H,
HRMS for C4H10N1O2 (M+H)+ calcd: 104.0712, found:
104.0674. H NMR (500 MHz, DMSO-d6): 2.60 (m, 2H,
CH2-Ph), 4.40 (m, 1H, J4,3¼6.6, J4,5¼6.6, 3.7, J4,OH¼5.0,
1
0
0
0
0
0
0
00
H-4), 5.03 (q, 1H, J3 ,2 a¼J3 ,2 b¼J3 ,4 ¼6.6, H-3 ), 5.11 (d,
0
CHbHaN), 3.02 (m, 2H, CHaHbN), 3.83 (br m, 2H, OCH),
4.81 (br s, 3H, NH+OH). 13C NMR (125.8 MHz, DMSO-
d6): 52.55 (NCH2), 77.39 (OCH).
1H, JOH,4 ¼5.0, OH-4 ), 7.15 (br s, 2H, NH2), 7.24–7.37
(m, 5ꢂAr-H (N-Bn)), 8.12 (s, 1 H, H-2), 8.16 (s, 1 H,
13
H-8). C NMR (125.7 MHz, DMSO-d6): 54.89 (CH2-30),
57.10 (CH-20), 59.37 (N-CH2 (N-Bn)), 61.12 (CH2-50),
68.70 (CH-40), 118.23 (C-5), 127.08 (–CH](N–Bn)),
128.40 (2ꢂ–CH](N–Bn)), 128.59 (2ꢂ–CH](N–Bn)),
138.93 (pC](N–Bn)), 141.07 (C-8), 150.13 (C-4), 152.24
(C-2), 155.98 (C-6).
4.1.14. (3S,4S)-3,4-Dihydroxypyrrolidine (8b). Com-
pound 8b was prepared from 7b (29.0 g, 150 mmol) using
the same procedure as for the compound 8a in 92% overall
yield (14.2 g) in the form of a yellow oil.
HRMS for C4H10N1O2 (M+H)+ calcd: 104.0712, found:
4.1.17. (3R,4R)-4-(Adenin-9-yl)-1-N-benzyl-3-dimethoxy-
trityloxypyrrolidine (11), (3S,4R)-4-(adenin-9-yl)-1-N-
benzyl-3-dimethoxytrityloxypyrrolidine (12), and
(3R,4R)-4-adenin-7-yl-1-N-benzyl-3-dimethoxytrityloxy-
pyrrolidine (13). A mixture of 10 (7 g, 12.2 mmol) and
adenine (3.3 g, 25 mmol) was co-evaporated with toluene
(2ꢂ20 mL), DMF (2ꢂ20 mL), and suspended in DMF
(120 mL). Cs2CO3 (8 g, 25 mmol) was added, and the reac-
tion mixture was stirred at 110 ꢁC for 4 d. DMF was evapo-
rated and the crude material was purified on a silica gel
column using a linear gradient of ethyl acetate in toluene fol-
lowed by a linear gradient of ethanol in ethyl acetate. Com-
pounds 11, 12, and 13 were obtained in 33% (2.5 g), 11%
(0.8 g), and 10% yield (0.7 g), respectively, in the form of
yellowish foams.
1
104.0674. H NMR and 13C NMR spectra were identical
to those of compound 8a.
4.1.15. (3R,4R)-1-N-Benzyl-3-dimethoxytrityloxy-4-hy-
droxypyrrolidine (9). Dimethoxytrityl chloride (21.5 g,
64.4 mmol) was added to a solution of 8a (8.4 g, 43 mmol)
in pyridine (500 mL) and the reaction mixture was stirred
at rt for 2 d. Anhydrous methanol (10 mL) was added and
the solution was concentrated in vacuo. Compound 9 was
obtained by chromatography on silica gel using a linear
gradient of toluene in petroleum ether followed by a linear
gradient of ethyl acetate in toluene in 56% yield (11.9 g)
in the form of a yellow foam.
HRMS for C32H33NO4 (M+H)+ calcd: 495.2420, found:
495.2414. H NMR (500 MHz, DMSO-d6): 1.55 (dd, 1H,
1
Compound 11. HRMS for C37H36N6O3 (M+H)+ calcd:
613.2927, found: 613.2872. RP-HPLC tR¼9.77 min (A to
Jgem¼10.5, J2b,3¼4.5, H-2b), 1.70 (dd, 1H, Jgem¼10.5,
J2a,3¼6.7, H-2a), 2.22 (dd, 1H, Jgem¼9.5, J5b,4¼4.8, H-
50b), 2.63 (dd, 1H, Jgem¼9.5, J5a,4¼6.3, H-5a), 3.31 and
3.34 (2ꢂd, 1H, Jgem¼13.1, CH2-Ph), 3.71 (s, 6H, CH3O-
DMTr), 3.78 (m, 1H, H-3), 4.13 (m, 1H, H-3), 4.89 (d, 1H,
JOH,4¼6.0, OH-4), 6.85 (m, 4H, H-m-C6H4-DMTr), 7.10
(m, 2H, H-o-Bn), 7.15–7.30 (m, 10H, H-o-C6H4-DMTr, H-
o,m,p-C6H5-DMTr, H-p-Bn), 7.45 (m, 2H, H-m-Bn). 13C
NMR (100.6 MHz, DMSO-d6): 55.185 (CH3O-DMTr),
58.99 (CH2-2), 59.81 (CH2-5), 60.28 (CH2-Ph), 76.77
(CH-3), 80.59 (CH-4), 86.00 (C-DMTr), 113.25 and
113.29 (CH-m-C6H4-DMTr), 126.71, 126.81, 127.88,
128.08 and 128.62 (CH-Bn, CH-C6H5-DMTr), 130.02 and
130.14 (CH-o-C6H4-DMTr), 136.48 and 136.93 (C-i-
C6H4-DMTr), 138.66 (C-i-C6H5-DMTr), 145.92 (C-i-Bn),
158.25 (C-p-C6H4-DMTr).
1
C/20 min). H NMR (500 MHz, DMSO-d6): 1.91 (dd, 1H,
0
0
00
Jgem¼9.3, J2 b,3 ¼4.6, H-2 b), 2.25 (dd, 1H, Jgem¼9.3,
0
0
0
00
J2 a,3 ¼6.9, H-2 a), 2.66 (dd, 1H, Jgem¼9.4, J5 b,4 ¼6.0, H-
50b), 2.92 (dd, 1H, Jgem¼9.4, J5 a,4 ¼7.3, H-5 a), 3.43 and
0
0
3.47 (2ꢂd, 2H, Jgem¼12.9, CH2-Ph), 3.66 and 3.63 (2ꢂs,
0
0
0
0 0
6H, CH3O-DMTr), 4.47 (m, 1H, J3 ,2 ¼6.9, 4.6, J3 ,4 ¼4.2,
H-30), 5.07 (m, 1H, J4 ,5 ¼7.3, 6.0, J4 ,3 ¼4.2, H-4 ), 6.57
(m, 2H, H-m-C6H4-DMTr), 6.68 (m, 2H, H-m-C6H4-
DMTr), 7.08 (m, 2H, H-o-C6H4-DMTr), w7.12 (br s, 2H,
NH2), 7.12 (m, 7H, H-o-C6H4-DMTr+H-Bn), 7.18 (m, 2H,
H-m-C6H5-DMTr), 7.21 (m, 1H, H-p-C6H5-DMTr), 7.26
(m, 2H, H-o-C6H5-DMTr), 8.09 (s, 1H, H-2), 8.13 (s, 1H,
H-8). 13C NMR (125.8 MHz, DMSO-d6): 55.04 and 55.12
(CH3O-DMTr), 57.32 (CH2-20), 58.99 (CH2-50), 59.56
(CH2-Ph), 60.56 (CH-30), 78.06 (CH-40), 86.50 (C-DMTr),
113.08 and 113.23 (CH-m-C6H4-DMTr), 118.95 (C-5),
126.78 (CH-p-Bn), 127.07 (CH-p-C6H5-DMTr), 127.62
(CH-o-Bn), 127.84 (CH-m-Bn), 128.26 and 128.67 (CH-
o,m-C6H5-DMTr), 129.65 and 129.86 (CH-m-C6H4-DMTr),
135.82 and 135.93 (C-i-C6H4-DMTr), 138.22 (C-i-Bn),
139.78 (CH-8), 145.43 (C-i-C6H5-DMTr), 149.48 (C-4),
0
0
0
0
4.1.16. (3R,4R)-1-N-Benzyl-4-dimethoxytrityloxy-3-
mesyloxypyrrolidine (10). Mesyl chloride (3.6 mL,
46.5 mmol) was added dropwise to the solution of 9
(11.5 g, 23 mmol) and DMAP (5.7 g, 46.5 mmol) in di-
chloromethane (120 mL) at 0 ꢁC. The reaction mixture

D. Rejman et al. / Tetrahedron 63 (2007) 1243–1253
1249
152.47 (CH-2), 156.22 (C-6), 158.16 and 158.30 (C-p-C6H4-
DMTr).
HRMS for C9H17NO4 (M+H)+ calcd: 204.1236 found:
204.1245. H NMR (400 MHz, DMSO-d6): 1.39 (s, 9H,
1
CH3-tBu), 3.11 (dd, 2H, Jgem¼11.4, J¼3.5, CHbHa-N),
3.32+3.36 (dd, 2H, Jgem¼11.4, J¼3.9, CHaHb-N), 3.86
(br q, 2H, J¼3.9, 3.5, JCH,OH¼3.2, CHO), 5.06 (d, 2H,
JOH,CH¼3.2, OH). 13C NMR (100.6 MHz, DMSO-d6): 28.42
(CH3-tBu), 51.86+52.16 (CH2N), 73.85+74.67 (CHO),
78.28 (C-tBu), 154.13 (CO).
Compound 12. HRMS for C37H36N6O3 (M+H)+ calcd:
613.2927, found: 613.2909. RP-HPLC tR¼9.31 min (A to
1
C/20 min). H NMR (500 MHz, DMSO-d6): 1.98 (dd, 1H,
0
0
0
Jgem¼10.4, J2 b,3 ¼7.5, H-2 b), 2.16 (dd, 1H, Jgem¼10.4,
0
0
0
0
00
J2 a,3 ¼4.9, H-2 a), 2.78 (dd, 1H, Jgem¼10.2, J5 b,4 ¼5.9, H-
50b), 2.87 (dd, 1H, Jgem¼10.2, J5 a,4 ¼3.8, H-5 a), 3.46 and
0
0
3.50 (2ꢂd, 2H, Jgem¼12.8, CH2-Ph), 3.70 (s, 6H, CH3O-
4.1.19. (3S,4S)-1-N-tert-Butyloxycarbonyl-3,4-dihydroxy-
pyrrolidine (14b). Desired compound 14b was prepared
from 8b (5 g, 48.5 mmol) using the same procedure as for
14a in 85% yield (8.3 g) in the form of a white solid.
0
0
0
0
0 0
DMTr), 4.37 (dt, 1H, J3 ,2 ¼7.5, 4.9, J3 ,4 ¼7.5, H-3 ), 5.06
0
0
0
0
(ddd, 1H, J4 ,3 ¼7.5, J4 ,5 ¼5.9, 3.8, H-4 ), 6.70 (m, 4H, H-
m-C6H4-DMTr), 6.94 (m, 2H, H-o-C6H4-DMTr), 6.96 (m,
2H, H-o-C6H4-DMTr), 7.04 (m, 2H, H-Bn), 7.12 (br s, 2H,
NH2), 7.13 (m, 3H, H-Bn), 7.18 (m, 2H, H-m-C6H5-
DMTr), 7.21 (m, 1H, H-p-C6H5-DMTr), 7.27 (m, 2H, H-o-
C6H5-DMTr), 8.17 (s, 1H, H-2), 8.39 (s, 1H, H-8). 13C
NMR (125.8 MHz, DMSO-d6): 54.30 (CH-30), 55.16
(CH3O-DMTr), 57.56 (CH2-20), 58.54 (CH2-50), 58.98
(CH2-Ph), 71.79 (CH-40), 86.81 (C-DMTr), 113.27 (CH-m-
C6H4-DMTr), 118.26 (C-5), 126.80 (CH-p-Bn), 127.08
(CH-p-C6H5-DMTr), 127.61 (CH-o-Bn), 127.91 (CH-m-
Bn), 128.33 (CH-o,m-C6H5-DMTr), 128.59 (CH-o-C6H4-
DMTr), 129.76 (CH-C6H5-DMTr), 135.69 and 136.01
(C-i-C6H4-DMTr), 138.54 (C-i-Bn), 141.29 (CH-8), 145.26
(C-i-C6H5-DMTr), 150.38 (C-4), 152.37 (CH-2), 156.20 (C-
6), 158.32 (C-p-C6H4-DMTr).
1H NMR and 13C NMR spectra were identical to those of
compound 14a.
4.1.20. (3R,4R)-1-N-tert-Butyloxycarbonyl-3-dimethoxy-
trityloxy-4-hydroxypyrrolidine (15a). Dimethoxytrityl
chloride (35.4 g, 105 mmol) was added to the solution of
14a (19.3 g, 95 mmol) in pyridine (1 L). The reaction mix-
ture was stirred at rt for 5 d, quenched with methanol
(5 mL), and concentrated in vacuo. Pure compound 15a
was obtained by chromatography on silica gel using a linear
gradient of toluene in petroleum ether followed by a linear
gradient of ethyl acetate in toluene in 75% yield (36.2 g)
in the form of a yellowish foam (NMR: 3:2 ratio of amide
isomers; separated signals are arranged: major+minor).
Compound 13. HRMS for C37H36N6O3 (M+H)+ calcd:
613.2927, found: 613.2876. RP-HPLC tR¼8.21 min (A to
HRMS for C30H35NO6 (M+H)+ calcd: 506.2543, found:
1
1
C/20 min). H NMR (500 MHz, DMSO-d6): 2.01 (dd, 1H,
Jgem¼10.0, J2 b,3 ¼3.8, H-2 b), 2.31 (dd, 1H, Jgem¼10.0,
506.2506. H NMR (500 MHz, DMSO-d6): 1.29+1.37 (s,
9H, CH3-tBu), 2.31+2.52 (dd, 1H, Jgem¼11.8, J2b,3¼2.0,
H-2b), 2.66+2.82 (dd, 1H, Jgem¼11.8, J2a,3¼4.6, H-2a), 3.42
(m, 2H, H-5), 3.74+3.735 (s, 6H, CH3O-DMTr), 3.79+3.81
(m, 1H, J3,2¼4.6, 2.0, J3,4¼2.4, H-3), 3.88+3.77 (m, 1H,
J4,OH¼3.8, J4,3¼2.4, H-4), 5.14+5.06 (d, 1H, JOH,4¼3.8,
OH-4), 6.90 (m, 4H, H-m-C6H4-DMTr), 7.14–7.41 (m, 9H,
H-o-C6H4-DMTr+H-C6H5-DMTr). 13C NMR (125.8 MHz,
DMSO-d6): 28.17+28.30 (CH3-tBu), 49.84+50.07 (CH2-5),
51.51+52.13 (CH2-2), 55.19 (CH3O-DMTr), 72.98+73.58
(CH-4), 77.31+76.75 (CH-3), 78.11+78.36 (C-tBu), 86.27+
86.37 (C-DMTr), 113.44+113.47 (CH-m-C6H4-DMTr),
126.89+126.94 (CH-p-C6H5-DMTr), 127.86+127.94 (CH-
m-C6H5-DMTr), 128.02 (CH-o-C6H5-DMTr), 129.94+
129.98 (CH-o-C6H4-DMTr), 136.07+136.21 (C-i-C6H4-
DMTr), 136.37+136.26 (C-i-C6H4-DMTr), 145.50 (C-i-
C6H5-DMTr), 153.91+153.88 (CO), 158.44+158.37 (C-p-
C6H4-DMTr).
0
0
0
0
0
0
0
00
J2 a,3 ¼6.9, H-2 a), 2.81 (dd, 1H, Jgem¼9.8, J5 b,4 ¼7.8, H-
50b), 2.96 (dd, 1H, Jgem¼9.8, J5 a,4 ¼7.4, H-5 a), 3.43 and
0
0
3.46 (2ꢂd, 2H, Jgem¼12.8, CH2-Ph), 3.63 and 3.66 (2ꢂs,
0
0
0
0
6H, CH3O-DMTr), 4.74 (ddd, 1H, J3 ,2 a¼6.9, J3 ,2 b¼3.8,
0
0
0
0
0
0
0
J3 ,4 ¼4.2, H-3 ), 5.24 (ddd, 1H, J4 ,3 ¼4.2, J4 ,5 a¼7.4,
J4 ,5 b¼7.2, H-40), 6.54 and 6.66 (2ꢂm, 4H, H-m-C6H4-
DMTr), 7.06 and 7.10 (2ꢂm, 4H, H-o-C6H4-DMTr), 7.10
(m, 2H, H-o-Bn), 7.18–7.28 (m, 8H, H-m-Bn, H-p-Bn,
C6H5-DMTr), 7.71 (s, 1H, H-2), 7.85 and 7.96 (2ꢂbr s,
2H, NH2), 8.34 (s, 1H, H-8). 13C NMR (125.8 MHz,
DMSO-d6): 55.06 and 55.13 (CH3O-DMTr), 56.41 (CH2-
20), 59.03 (CH2-Ph), 59.69 (CH2-50), 66.89 (CH-30), 76.88
(CH-40), 86.52 (C-DMTr), 113.04 and 113.19 (CH-m-
C6H4-DMTr), 120.76 (C-5), 126.78 (CH-p-Bn), 127.09
(CH-p-C6H5-DMTr), 127.63 (CH-o-Bn), 127.81 (CH-m-
Bn), 128.28 and 128.70 (CH-o-C6H4-DMTr), 129.67 (CH-
o-C6H5-DMTr), 129.88 (CH-m-C6H5-DMTr), 135.86 and
135.89 (C-i-C6H4-DMTr), 138.27 (C-i-Bn), 142.60 (CH-8),
145.47 (C-i-C6H5-DMTr), 149.44 (C-4), 152.54 (CH-2),
154.86 (C-6), 158.15 and 158.29 (C-p-C6H4-DMTr).
0
0
4.1.21. (3S,4S)-1-N-tert-Butyloxycarbonyl-3-dimethoxy-
trityloxy-4-hydroxypyrrolidine (15b). Desired compound
15b was prepared from 14b (39.2 g, 193 mmol) using the
same procedure as for 15a in 80% yield (77.8 g) in the
form of a yellowish foam.
4.1.18. (3R,4R)-1-N-tert-Butyloxycarbonyl-3,4-dihydroxy-
pyrrolidine (14a). tert-Butyloxycarbonyl anhydride (15 g,
70 mmol) was added dropwise to the vigorously stirred mix-
ture of 8a (4.8 g, 46.6 mmol) and sodium hydrogen carbon-
ate (34 g, 400 mmol) in 50% aqueous dioxane (400 mL).
The reaction mixture was stirred at rt for 2 h. The suspension
was filtered and the filtrate was concentrated in vacuo. Pure
compound 14a was obtained by chromatography on silica gel
using a linear gradient of ethanol in chloroform in 89% yield
(8.4 g) as a white solid (NMR: 1:1 ratio of amide isomers).
HRMS for C30H35NO6 (M+H)+ calcd: 506.2543, found:
1
506.2506. H NMR, 13C NMR spectra were identical to
those of compound 15a.
4.1.22. (3R,4R)-1-N-tert-Butyloxycarbonyl-4-dimethoxy-
trityloxy-3-mesyloxypyrrolidine (16a). Mesyl chloride
(1.6 mL, 20 mL) was added dropwise to the solution of
15a (2 g, 4 mmol) and DMAP (2.4 g, 20 mmol) in DCM

1250
D. Rejman et al. / Tetrahedron 63 (2007) 1243–1253
(30 mL) at 0 ꢁC. The reaction mixture was stirred at rt for
1 h, cooled to 0 ꢁC, and quenched with water (3 mL). The
solution was washed with a saturated solution of sodium
hydrogen carbonate, and the organic layer was dried over
sodium sulfate. Solvents were evaporated and pure com-
pound 16a was obtained by chromatography on silica gel
using a linear gradient of toluene in petroleum ether fol-
lowed by a linear gradient of ethyl acetate in toluene in
83% yield (1.93 g) in the form of a yellowish foam (NMR:
3:2 ratio of amide isomers; separated signals are arranged:
major+minor).
55.22+55.24 (CH3O-DMTr), 71.40+70.78 (CH-30), 78.69+
79.03 (C-tBu), 87.01 (C-DMTr), 108.85+108.71 (C-5),
113.43+113.48 (CH-m-C6H4-DMTr), 126.96, 127.70, and
128.04 (CH-C6H5-DMTr), 130.03 (CH-o-C6H4-DMTr),
135.44 and 136.01+135.64 and 135.89 (C-i-C6H4-DMTr),
139.16+139.44 (CH-6), 145.26 (C-i-C6H5-DMTr), 151.69+
151.55 (C-2), 153.46+153.14 (CO), 158.55 (C-p-C6H4-
DMTr), 163.86 (C-4).
4.1.25. (3R,4S)-4-(Adenin-9-yl)-1-N-tert-butyloxycar-
bonyl-3-dimethoxytrityloxypyrrolidine (17b). Compound
17b was prepared from 16a (5.2 g, 9 mmol) using the same
procedure as for the compound 11 (DMSO was used as a sol-
vent instead of DMF) in 55% yield (3.1 g) in the form of
a yellow foam (NMR: 3:2 ratio of amide isomers; separated
signals are arranged: major+minor).
HRMS for C31H37NO8S (M+H)+ calcd: 584.2318, found:
1
584.2379. H NMR (400 MHz, DMSO-d6): 1.29+1.38 (s,
9H, CH3-tBu), 2.29+2.57 (br dd, 1H, Jgem¼12.3, J5b,4¼2.2,
H-5b), 2.63+2.83 (dd, 1H, Jgem¼12.3, J5a,4¼4.5, H-5a),
3.23+3.18 (s, 3H, CH3S), 3.39+3.46 (br dd, 1H, Jgem¼12.7,
J2b,3¼1.8, H-2b), 3.70 (br d, 1H, Jgem¼12.7, H-2a), 3.74 (s,
6H, CH3O-DMTr), 4.15 (m, 1H, H-4), 5.11+4.93 (br dt,
1H, J3,4¼4.5, J3,2¼1.8, H-3), 6.90 (m, 4H, H-m-C6H4-
DMTr), 7.16 (m, 1H, H-p-C6H5-DMTr), 7.22–7.36 (m, 6H,
H-m-C6H5-DMTr and H-o-C6H4-DMTr), 7.44+7.41 (m,
2H, H-o-C6H5-DMTr). 13C NMR (100.6 MHz, DMSO-d6):
28.06+28.20 (CH3-tBu), 37.77 (CH3-S), 49.38+49.76 (CH2-5),
49.51+49.90 (CH2-2), 55.24 (CH3O-DMTr), 75.16+74.53
(CH-4), 78.84+79.19 (C-tBu), 81.57+82.12 (CH-3),
87.08+7.15 (C-DMTr), 113.62+113.66 (CH-m-C6H4-DMTr),
127.13 (CH-p-C6H5-DMTr), 127.79+127.89 (CH-m-C6H5-
DMTr), 128.20 (CH-o-C6H5-DMTr), 129.96+130.07 (CH-o-
C6H4-DMTr), 135.37+135.54 (C-i-C6H4-DMTr), 135.81+
135.66(C-i-C6H4-DMTr), 144.96(C-i-C6H5-DMTr),153.62+
153.48 (CO), 158.64+158.58 (C-p-C6H4-DMTr).
HRMS for C35H38N6O5 (M+H)+ calcd: 623.2982, found:
623.3004. H NMR (400 MHz, DMSO-d6): 1.29+1.36 (s,
1
9H, CH3-tBu), 2.31+2.58 (dd, 1H, Jgem¼11.8, J2 b,3 ¼4.7,
0
0
0
H-20b), 2.53+2.73 (dd, 1H, Jgem¼11.8, J2 a,3 ¼6.5, H-2 a),
0
0
3.70 (s, 6H, CH3O-DMTr), 3.77 (m, 1H, H-50b), 3.97+3.91
0
0
0
0
(dd, 1H, Jgem¼11.3, J5 a,4 ¼6.0, H-5 a), 4.22 (q, 1H,
0
0
0
0
0
0
0
0
J3 ,2 ¼6.5, 4.7, J3 ,2 ¼6.0, H-3 ), 5.21 (q, 1H, J4 ,3 ¼J4 ,5 ¼6.0,
H-40), 6.67–6.78 (m, 4H, H-m-C6H4-DMTr), 6.93–7.00 (m,
4H, H-o-C6H4-DMTr), 7.03–7.18 (m, 5H, C6H5-DMTr),
7.33 (br s, 2H, NH2), 8.16+8.14 (s, 1H, H-2), 8.35+8.24 (s,
1H, H-8). 13C NMR (100.6 MHz, DMSO-d6): 28.10+28.24
(CH3-tBu), 47.06+48.15 (CH2-50), 49.68 (CH2-20),
54.50+55.04 (CH-40), 55.17 (CH3O-DMTr), 71.65+71.13
(CH-30), 78.70+79.05 (C-tBu), 86.59 (C-DMTr), 113.32
(CH-m-C6H4-DMTr), 118.81 (C-5), 126.84, 127.58,
127.73, and 127.91 (CH-C6H5-DMTr), 129.93 (CH-o-
C6H4-DMTr), 135.37, 135.82+135.64, and 135.71 (C-i-
C6H4-DMTr), 139.91 (CH-8), 145.09 (C-i-C6H5-DMTr),
150.61+150.50 (C-4), 152.68 (CH-2), 153.55+153.31
(CO), 156.34 (C-6), 158.43+158.49 (C-p-C6H4-DMTr).
4.1.23. (3S,4S)-1-N-tert-Butyloxycarbonyl-4-dimethoxy-
trityloxy-3-mesyloxypyrrolidine (16b). Desired com-
pound 16b was prepared from 15b (7.2 g, 14.2 mmol)
using the same procedure as for 16b in 90% yield (7.5 g)
in the form of a yellowish foam.
4.1.26. (3S,4R)-1-N-tert-Butyloxycarbonyl-3-dimethoxy-
trityloxy-4-(thymin-1-yl)-pyrrolidine (17c). Compound
17c was prepared from 16b (4.5 g, 7.8 mmol) using the
same procedure as for the compound 11 (DMSO was used
as a solvent instead of DMF) in 35% yield (1.7 g) in the
form of a yellow foam.
1H NMR, 13C NMR and HRMS spectra were identical to
those of compound 16a.
4.1.24. (3R,4S)-1-N-tert-Butyloxycarbonyl-3-dimethoxy-
trityloxy-4-(thymin-1-yl)-pyrrolidine (17a). Compound
17a was prepared from 16a (1.8 g, 3.1 mmol) and thymine
(0.8 g, 6 mmol) using the same procedure as for the com-
pound 11 (DMSO was used as a solvent instead of DMF)
in 33% yield (0.6 g) in the form of a yellow foam (NMR:
3:2 ratio of amide isomers; separated signals are arranged:
major+minor).
HRMS for C35H39N3O7 (M+H)+ calcd: 614.2866, found:
1
614.2868. H NMR and 13C NMR spectra were identical
to those of compound 17a.
4.1.27. (3S,4R)-4-(Adenin-9-yl)-1-N-tert-butyloxycar-
bonyl-3-dimethoxytrityloxypyrrolidine (17d). Compound
17d was prepared from 16b (6.9 g, 12 mmol) using the same
procedure as for the compound 11 (DMSO was used as a
solvent instead of DMF) in 54% yield (4 g) in the form of
a yellow foam.
HRMS for C35H39N3O7 (M+H)+ calcd: 614.2866, found:
614.2884. H NMR (500 MHz, DMSO-d6): 1.27+1.36 (br
1
s, 9H, CH3-tBu), 1.83 (br s, 3H,0CH3-5), 2.11+2.43 (br dd,
0
0
1H, Jgem¼11.4, J2 b,3 ¼4.1, 0H-2 b), 2.43+2.69 (br dd, 1H,
0
0
Jgem¼11.4, J2 a,3 ¼5.9, H-2 a), 3.58+3.66 (br m, 1H, H-
50b), 3.68+3.66 (br m, 1H, H-50a), 3.74 (s, 6H, CH3O-
DMTr), 4.13+4.25 (br m, 1H, H-30), 5.16+5.03 (br m, 1H,
H-40), 6.86 (m, 4H, H-m-C6H4-DMTr), 7.11–7.36 (m, 4H,
H-o-C6H4-DMTr+C6H5-DMTr), 7.63+7.57 (br s, 1H, H-6),
11.49+11.44 (br s, 1H, NH). 13C NMR (100.6 MHz,
DMSO-d6): 12.22 (CH3-5), 28.05+28.22 (CH3-tBu), 46.06+
46.93 (CH2-50), 50.03+50.24 (CH2-20), 54.68 (CH-40),
HRMS for C35H38N6O5 (M+H)+ calcd: 623.2982, found:
1
623.2983. H NMR and 13C NMR spectra were identical
to those of compound 17b.
4.1.28. (3S,4R)-1-N-tert-Butyloxycarbonyl-3-dimethoxy-
trityloxy-4-(4-nitro-benzoyloxy)-pyrrolidine (18a).
mixture of 15a (39 g, 77 mmol), 2,6-lutidine (26.8 mL,
A

D. Rejman et al. / Tetrahedron 63 (2007) 1243–1253
1251
231 mmol), p-nitrobenzoic acid (19.4 g, 115.5 mmol), and
triphenylphosphine (60.6 g, 231 mmol) was co-evaporated
with THF (2ꢂ200 mL), dissolved in the same solvent
(770 mL), and DIAD (44.8 mL, 231 mmol) was added at
0 ꢁC under argon atmosphere. The reaction mixture was
stirred at rt for 3 h, concentrated in vacuo, and compound
18a was obtained by chromatography on silica gel using a
linear gradient of toluene in petroleum ether followed by a
linear gradient of ethyl acetate in toluene in 88% yield
(44.3 g) in the form of a yellow foam (NMR: 3:2 ratio of
amide isomers; separated signals are arranged: major+minor).
9H, CH3-tBu), 2.20+2.46 (dd, 1H, Jgem¼10.6, J2b,3¼6.7,
H-2b), 2.49+2.68 (dd, 1H, Jgem¼10.6, J2a,3¼7.3, H-2a),
w3.10 (m, 2H, H-5), 3.735+3.73 (s, 6H, CH3O-DMTr),
3.78+3.85 (m, 1H, J3,2¼7.3, 6.7, J3,4¼3.8, H-3), 3.88+3.69
(m, 1H, J4,OH¼4.0, J4,3¼3.8, H-4), 5.03+4.93 (d, 1H,
JOH,4¼4.0, OH-4), 6.89+6.90 (m, 4H, H-m-C6H4-DMTr),
7.24 (m, 1H, H-p-C6H5-DMTr), 7.305 (m, 2H, H-m-C6H5-
DMTr), 7.37–7.41 (m, 4H, H-o-C6H4-DMTr), 7.545+7.51
(m, 2H, H-o-C6H5-DMTr). 13C NMR (125.8 MHz,
DMSO-d6): 28.11+28.22 (CH3-tBu), 47.50+47.27 (CH2-5),
50.86+51.61 (CH2-2), 55.16 (CH3O-DMTr), 69.41+69.83
(CH-4), 73.44+72.98 (CH-3), 78.05+78.28 (C-tBu), 86.23
(C-DMTr)), 113.32+113.39 (CH-m-C6H4-DMTr), 126.74+
126.82 (CH-p-C6H5-DMTr), 127.86+127.97 (CH-m-C6H5-
DMTr), 127.92 (CH-o-C6H5-DMTr), 129.99+130.05 (CH-
o-C6H4-DMTr), 136.23+136.43 (C-i-C6H4-DMTr), 136.72+
136.59 (C-i-C6H4-DMTr), 145.79 +145.73 (C-i-C6H5-
DMTr), 153.67+153.50 (CO), 158.42+158.32 (C-p-C6H4-
DMTr).
HRMS for C37H39N2O9 (M+H)+ calcd: 677.2475, found:
1
677.2452. H NMR (500 MHz, DMSO-d6): 1.30+1.32 (s,
9H, CH3-tBu), 2.27+2.73 (dd, 1H, Jgem¼10.5, J2b,3¼7.3, H-
2b), 2.72+2.93 (t, 1H, Jgem¼10.5, J2a,3¼9.0, H-2a),
3.38+3.39 (br d, 1H, Jgem¼13.0, J5b,4ꢃ2, H-5b), 3.47+3.45
(dd, 1H, Jgem¼13.0, J5a,4¼4.0, H-5a), 3.71 (s, 3H, CH3O-
DMTr), 3.72 (s, 3H, CH3O-DMTr), 4.18+4.28 (dt, 1H,
J3,2¼9.0, 7.3, J3,4¼4.0, H-3), 5.49+5.13 (br t, 1H, J4,5¼4.0,
ꢃ2, J4,3¼4.0, H-4), 6.82–6.87 (m, 4H, H-m-C6H4-DMTr),
7.12–7.25 (m, 5H, H-C6H5-DMTr), 7.30–7.40 (m, 4H, H-o-
C6H4-DMTr), 8.32+8.30 (m, 2H, C6H4-NO2), 8.41 (m, 2H,
C6H4-NO2). 13C NMR (125.8 MHz, DMSO-d6): 28.05+
28.13 (CH3-tBu), 47.90+47.68 (CH2-2), 48.52+49.31 (CH2-
5), 55.14+55.17 (CH3O-DMTr), 71.90+71.36 (CH-3),
74.06+74.56 (CH-4), 78.86+78.83 (C-tBu), 86.74+86.61
(C-DMTr), 113.50+113.40 (CH-m-C6H4-DMTr), 124.10
(CH-C6H4NO2), 126.89+127.00 (CH-p-C6H5-DMTr),
127.47+127.65 (CH-m-C6H5-DMTr), 128.01 (CH-o-C6H5-
DMTr), 129.84+129.97 (CH-o-C6H5-DMTr), 130.98
(CH-C6H4NO2), 135.37 (C-i-C6H4NO2), 135.37+135.57
(C-i-C6H4-DMTr), 136.01+135.90 (C-i-C6H4-DMTr),
145.27+145.19 (C-i-C6H5-DMTr), 150.57 (C-i-C6H4NO2),
153.50+153.27 (CO-carbamate), 158.61+158.50 (C-p-
C6H4-DMTr), 164.12+164.00 (CO-ester).
4.1.31. (3S,4R)-1-N-tert-Butyloxycarbonyl-3-dimethoxy-
trityloxy-4-hydroxypyrrolidine (19b). Compound 19b
was prepared from 18b (9.5 g, 14.6 mmol) using the same
procedure as for the compound 19a in 97% yield (7.2 g) in
the form of a yellow foam.
1H NMR, 13C NMR and HRMS spectra were identical to
those of compound 19a.
4.1.32. (3S,4R)-1-N-tert-Butyloxycarbonyl-4-dimethoxy-
trityloxy-3-mesyloxypyrrolidine (20a). Compound 20a
was prepared from 19a (30.8 g, 61 mmol) using the same
procedure as for the compound 16a in 85% yield (30.2 g)
in the form of a yellow foam (NMR: 3:2 ratio of amide
isomers; separated signals are arranged: major+minor).
HRMS for C31H37NO8S (M+H)+ calcd: 584.2318, found:
1
4.1.29. (3R,4S)-1-N-tert-Butyloxycarbonyl-3-dimethoxy-
trityloxy-4-(4-nitro-benzoyloxy)-pyrrolidine (18b). Com-
pound 18b was prepared from 15a (7.6 g, 15 mmol) using
the same procedure as for the compound 18a in 97% yield
(9.5 g) in the form of a yellow foam.
584.2379. H NMR (500 MHz, DMSO-d6): 1.26+1.32 (s,
9H, CH3-tBu), 1.95+2.32 (dd, 1H, Jgem¼10.7, J5b,4¼7.4,
H-5b), 2.37+2.52 (dd, 1H, Jgem¼10.7, J5a,4¼9.2, H-5a),
3.31 (s, 3H, CH3S), w3.38 (m, 2H, H-2), 3.75 (s, 6H,
CH3O-DMTr), 4.06+4.18 (ddd, 1H, J4,5¼9.2, 7.4, J4,3a
¼
3.9, H-4), 5.17+4.96 (m, 1H, J3,4¼3.9, H-3), 6.905+6.92
(m, 4H, H-m-C6H4-DMTr), 7.25+7.23 (m, 1H, H-p-C6H5-
DMTr), 7.32 (m, 2H, H-m-C6H5-DMTr), 7.34+7.37 (m,
4H, H-o-C6H4-DMTr), 7.50+7.46 (m, 2H, H-o-C6H5-
DMTr). 13C NMR (125.8 MHz, DMSO-d6): 27.99+28.13
(CH3-tBu), 38.47 (CH3-S), 47.34+47.12 (CH2-5), 48.96+
49.66 (CH2-2), 55.17 (CH3O-DMTr), 71.32+70.90 (CH-4),
78.65+78.96 (C-tBu), 80.23+80.76 (CH-3), 86.90+86.88
(C-DMTr), 113.57+113.38 (CH-m-C6H4-DMTr), 126.92+
127.04 (CH-p-C6H5-DMTr), 127.70+127.91 (CH-m-C6H5-
DMTr), 128.09 (CH-o-C6H5-DMTr), 129.91+130.01 (CH-
o-C6H4-DMTr), 135.53+135.78 (C-i-C6H4-DMTr), 136.20+
136.04 (C-i-C6H4-DMTr), 145.20+145.08 (C-i-C6H5-
DMTr), 153.33+153.11 (CO), 158.56+158.45 (C-p-C6H4-
DMTr).
1H NMR, 13C NMR and HRMS spectra were identical to
those of compound 18a.
4.1.30. (3R,4S)-1-N-tert-Butyloxycarbonyl-3-dimethoxy-
trityloxy-4-hydroxypyrrolidine (19a). Gaseous ammonia
was introduced into the solution of 18a (44.3 g,
67.7 mmol) in methanol (200 mL) at 0 ꢁC over a period of
20 min. The solution was set aside at rt for 1 h, methanol
was evaporated, and the residue was treated with a mixture
of petroleum ether/toluene (1:1, 500 mL). 4-Nitrobenzoic
amide was filtered off and the filtrate was concentrated in
vacuo. Desired product 19a was obtained by chromato-
graphy on silica gel using a linear gradient of toluene in
petroleum ether followed by a linear gradient of ethyl acetate
in toluene in 90% yield (30.8 g) in the form of yellow foam
(NMR: 3:2 ratio of amide isomers; separated signals are
arranged: major+minor).
4.1.33. (3R,4S)-1-N-tert-Butyloxycarbonyl-4-dimethoxy-
trityloxy-3-mesyloxypyrrolidine (20b). Compound 20b
was prepared from 19b (7.2 g, 14.2 mmol) using the same
procedure as for the compound 16a in 90% yield (7.5 g) in
the form of a yellow foam.
HRMS for C30H35NO6 (M+H)+ calcd: 505.2464, found:
505.2456. H NMR (500 MHz, DMSO-d6): 1.27+1.32 (s,
1

1252
D. Rejman et al. / Tetrahedron 63 (2007) 1243–1253
1H NMR, 13C NMR and HRMS spectra were identical to
those of compound 20a.
4.1.36. (3S,4S)-4-(Thymin-1-yl)-1-N-tert-butyloxycar-
bonyl-3-dimethoxytrityloxypyrrolidine (21c). Compound
21c was prepared from 20b (7.5 g, 13 mmol) using the
same procedure as for the compound 11 (DMSO was used
as a solvent instead of DMF) in 25% yield (2 g) in the
form of a yellow foam.
4.1.34. (3R,4R)-N-tert-Butyloxycarbonyl-3-dimethoxy-
trityloxy-4-(thymin-1-yl)-1-pyrrolidine (21a). Compound
21a was prepared from 20a (8.7 g, 15 mmol) and thymine
(3.8 g, 30 mmol) using the same procedure as for the com-
pound 11 (DMSO was used as a solvent instead of DMF)
in 33% yield (0.6 g) in the form of a yellow foam.
HRMS for C35H39N3O7 (M+H)+ calcd: 614.2866, found:
1
614.2874. H NMR and 13C NMR spectra were identical
to those of compound 21a.
HRMS for C35H39N3O7 (M+H)+ calcd: 614.2866, found:
614.2876. H NMR (400 MHz, DMSO-d6): 1.26+1.32 (br
1
4.1.37. (3S,4S)-4-(Adenin-9-yl)-1-N-tert-butyloxycar-
bonyl-3-dimethoxytrityloxypyrrolidine (21d). Compound
21a was prepared from 20b (7 g, 27.5 mmol) using the same
procedure as for the compound 11 (DMSO was used as a
solvent instead of DMF) in 51% yield (3.8 g) in the form
of a yellow foam.
s, 9H, CH3-tBu), 1.73+1.69 (br s, 3H, CH3-5), 2.15+2.46
0
0
0
(dd, 1H, Jgem¼11.4, J2 b,3 ¼7.1, H-2 b), 2.33+2.51 (dd, 1H,
0
0
0
0
0
Jgem¼11.4, J2 a,3 ¼7.7, H-2 a), 3.15 (br t, 1H, Jgem¼J5 b,4
¼
10.2, H-50b), 3.50+3.56 (br t, 1H, Jgem¼J5 a,4 ¼10.2, H-
0
0
50a), 3.73+3.72 (s, 6H, CH3O-DMTr), 4.27+4.39 (br q, 1H,
0
0
0
0
0
0
0
J3 ,2 ¼7.7, 7.1, J3 ,4 ¼8.0, H-3 ), 5.14 (br q, 1H, J4 ,5 ¼10.2,
J4 ,3 ¼8.0, H-4 ), 6.79 and 6.85 (2ꢂm, 4H, H-m-C6H4-
DMTr), 7.13–7.27 (m, 7H, H-o-C6H4-DMTr, H-m,p-C6H5-
DMTr), 7.30–7.38 (m, 2H, H-o-C6H5-DMTr), 7.59+7.49
(br s, 1H, H-6), 11.43+11.37 (br s, 1H, NH). 13C NMR
(100.6 MHz, DMSO-d6): 12.18 (CH3-5), 28.05+28.17
(CH3-tBu), 44.53+45.39 (CH2-50), 49.64+49.46 (CH2-20),
55.17 (CH3O-DMTr), 59.43+59.94 (CH-40), 73.49+73.84
(CH-30), 78.62+78.95 (C-tBu), 85.95 (C-DMTr), 110.03+
109.93 (C-5), 113.37 (CH-m-C6H4-DMTr), 126.96,
127.57, and 127.99 (CH-C6H5-DMTr), 130.06 (CH-o-
C6H4-DMTr), 135.45, 136.04+135.79, and 135.88 (C-i-
C6H4-DMTr), 138.99+138.76 (CH-6), 145.34 (C-i-C6H5-
DMTr), 151.35 (C-2), 153.19+153.10 (CO), 158.57+
158.46(C-p-C6H4-DMTr), 163.99 (C-4).
1H NMR, 13C NMR, and HRMS spectra were identical to
those of compound 21b.
0
0
0
Acknowledgements
Support by grants # 203/02/D150 and 203/05/0827 (Czech
Science Foundation), and Centre for Biomolecules and
Complex Molecular Systems (LC512) under research pro-
ject Z40550506 is gratefully acknowledged. Authors are in-
debted to the staff of the Department of Organic Analysis,
Dr. Kvetoslava Kertisova, Dr. Blanka Kralova and Dr. Karel
Ubik, for measurements of HRMS. Excellent technical
assistance of Dr. Petr Simek and Mr. Jiri Strnad, both of
Service laboratories of this Institute is also gratefully
acknowledged. Authors are indebted to Dr. Ivan Votruba
from this Institute and Professor Dr. Erik De Clercq (Rega
Institute, Leuven) for examination of cytostatic and antiviral
activities, respectively.
4.1.35. (3R,4R)-4-(Adenin-9-yl)-1-N-tert-butyloxycar-
bonyl-3-dimethoxytrityloxypyrrolidine (21b). Compound
21b was prepared from 20a (16 g, 27.5 mmol) using the
same procedure as for the compound 11 (DMSO was used
as a solvent instead of DMF) in 46% yield (8.4 g) in the
form of a yellow foam (NMR: 3:2 ratio of amide isomers;
separated signals are arranged: major+minor).
References and notes
HRMS for C35H38N6O5 (M+H)+ calcd: 623.2982, found:
623.2995. H NMR (400 MHz, DMSO-d6): 1.28+1.32 (s,
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9H, CH3-tBu), 2.15+2.46 (dd, 1H, Jgem¼11.8, J2 b,3 ¼7.1,
0
0
0
H-20b), 2.35+2.55 (dd, 1H, Jgem¼11.8, J2 a,3 ¼7.6, H-2 a),
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(br s, 2H, NH2), 8.07+8.05 (s, 1H, H-2), 8.36+8.28 (s, 1H,
H-8). 13C NMR (100.6 MHz, DMSO-d6): 28.04+28.16
(CH3-tBu), 44.94+45.89 (CH2-50), 49.53+49.33 (CH2-20),
55.17+55.08 (CH3O-DMTr), 58.50+59.05 (CH-40), 73.89+
73.43 (CH-30), 78.72+79.05 (C-tBu), 86.03 (C-DMTr),
113.18 and 113.32 (CH-m-C6H4-DMTr), 119.86 (C-5),
126.79, 127.27, and 127.86 (CH-C6H5-DMTr), 129.54,
129.97+129.44, and 129.87 (CH-o-C6H4-DMTr), 135.24,
135.84+135.57, and 135.67 (C-i-C6H4-DMTr), 140.87+
140.68 (CH-8), 145.27+145.18 (C-i-C6H5-DMTr), 149.93+
149.81 (C-4), 152.54 (CH-2), 153.22+153.07 (CO), 156.46
(C-6), 158.36, 158.61+158.22, and 158.41(C-p-C6H4-
DMTr).

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