Bisubstrate inhibitors for the enzyme catechol O-methyltransferase (COMT): Dramatic effects of ribose modifications on binding affinity and binding mode

Article abstract of DOI:10.1002/hlca.200390093

Inhibition of the enzyme catechol O-methyltransferase (COMT) is of significant interest in the therapy of Parkinson's disease. Described herein are structural analogs of the potent bisubstrate inhibitor (-)-1 (IC₅₀ = 9 nM; Table 1) for COMT, wi

Full text of DOI:10.1002/hlca.200390093

Helvetica Chimica Acta Vol. 86 (2003)
1045
Bisubstrate Inhibitors for the Enzyme Catechol O-Methyltransferase
(COMT): Dramatic Effects of Ribose Modifications on BindingAffinity and
BindingMode
by Christian Lerner, Romain Siegrist, Eliane Schweizer, and FranÁois Diederich*
Laboratorium f¸r Organische Chemie der Eidgenˆssischen Technischen Hochschule, ETH-Hˆnggerberg, HCI,
CH-8093 Z¸rich
and
Volker Gramlich
Laboratorium f¸r Kristallographie der Eidgenˆssischen Technischen Hochschule, ETH-Zentrum,
Sonneggstrasse 5, CH-8092 Z¸rich
and
Roland Jakob-Roetne, Gerhard Z¸rcher, and Edilio Borroni
Pharma Division, Pr‰klinische Forschung, F. Hoffmann-La Roche AG, CH-4070 Basel
Dedicated, on the occasion of his 80th birthday, to Professor Jack D. Dunitz, a postdoctoral fellow in the
Diederich group since 1992
Inhibition of the enzyme catechol O-methyltransferase (COMT) is of significant interest in the therapy of
Parkinson×s disease. Described herein are structural analogs of the potent bisubstrate inhibitor (À)-1 (IC50
ˆ
9 nm; Table 1) for COMT, with target modifications of the central ribose moiety. Their synthesis involves, as key
intermediates, adenosine derivatives, which are transformed to the potential bisubstrate inhibitors by a similar
sequence of six steps (Schemes 1 4). The compounds were submitted to an enzymatic assay for determination
of their in vitro inhibitory activity against COMT, and the inhibition mechanism with respect to the binding side
of the cofactor S-adenosylmethionine (SAM) was analyzed by kinetics measurements (Fig. 3). Both binding
affinity and binding mode were exceedingly sensitive towards modifications of the ribose moiety (Table 1).
Removal of the 2'-OH group upon changing from (À)-1 to (À)-2 (IC50 ˆ 28 mm) led to a reduction in binding
affinity by more than three orders of magnitude. At the same time, competitive inhibition kinetics with respect
to the SAM binding site was maintained, thereby supporting a bisubstrate binding mode. Unlike (À)-2, the
dideoxyribose inhibitor (À)-3 (IC50 ˆ 3 mm) showed a mixed and the cyclopentane derivative (‡)-4 (IC50 ˆ 1 mm)
an uncompetitive inhibition mechanism with respect to the SAM binding site. In the complex of the latter, the
adenine-substituted cyclopentane ring orients most probably towards the surface of the enzyme into the
surrounding solution. The enantiomeric compounds (À)-5 (IC50 ˆ 43 mm) and (‡)-5 (IC50 ˆ 141 mm), wherein
the ribose had been replaced by a pyrrolidine ring, showed only low binding affinity.
1. Introduction. The enzyme catechol O-methyltransferase (COMT) catalyzes the
transfer of a Me group from the cofactor S-adenosylmethionine (SAM) to a OH group
of biologically active catechols in the presence of a Mg2‡ ion. The inhibition of COMT
reduces the peripheral degradation of l-dopa and increases its supply to the brain,
which is of significant interest for the l-dopa-based therapy of Parkinson×s disease [1].
NO2-Substituted catechols were found to be potent COMT inhibitors, and two of them
are currently in therapeutic use [2]. Based on the X-ray crystal structure of COMT [3],

1046
Helvetica Chimica Acta Vol. 86 (2003)
we developed the first effective bisubstrate inhibitor that binds to both cofactor and
catechol binding sites of the enzyme [4]. Further optimization of the linker between the
nucleoside and catechol moieties subsequently led to the highly active bisubstrate
inhibitor (À)-1 (IC50 ˆ 9 nm; IC50 ˆ concentration of inhibitor at which 50% Vmax is
observed) [5]. The bisubstrate binding mode of (À)-1 was confirmed by kinetic studies
and the X-ray crystal structure of the ternary complex formed between COMT, (À)-1,
and a Mg2‡ ion [5].
NH2
N
N
OH
O
N
N
HO
N
X
H
NO2
O
O
O
X =
HO
HO
OH
(–)-3
(+)-4
(–)-1
(–)-2
H
N
HN
(+)-5
(–)-5
In this paper, we present the synthesis and biological activity of a series of
derivatives of (À)-1, in which the ribose moiety has been modified. Compounds (À)-2,
(À)-3, and (‡)-4 were designed to probe the energetic contribution of the two H-bonds
formed between the two ribose OH-groups in (À)-1 with the side-chain carboxylate of
Glu90 in COMT, as seen in the X-ray crystal structure of the ternary complex [5].
Computer modeling, with the molecular-modeling program MOLOC with the MAB
force field [6], suggested that the 2'-deoxyribose derivative (À)-2 would adopt a
bisubstrate binding mode similar to the one observed for (À)-1, with the 3'-OH group
undergoing H-bonding to the side-chain carboxylate of Glu90 (Fig. 1). On the other
hand, the effect of removing both ribose OH-groups in (À)-3 and (‡)-4, thereby
eliminating any H-bonding to Glu90, was difficult to predict at the design stage. It is,
however, well-known that ribose pockets at the ATP binding sites of some kinases
tolerate the occupancy by highly lipophilic residues, even in the presence of side-chain
carboxylates [7]. A possible re-orientation of the side chain of Glu90 away from the
ribose pocket in the complexes of (À)-3 and (‡)-4, lacking H-bonding OH groups,
could not be excluded a priori. On the other hand, making the inhibitors more
lipophilic seemed attractive for further enhancing their binding affinity and bioavail-

Helvetica Chimica Acta Vol. 86 (2003)
1047
ability [8]. The modeling suggested that both enantiomers of 5 would be capable of
forming a salt bridge between their protonated pyrrolidine ring and the side-chain of
Glu90.
Fig. 1. a) Computer-modeled ternary complex between COMT, Mg2‡, and bisubstrate inhibitor (À)-2. The
Connolly surface of the inhibitor is shown. b) Schematic drawing of the H-bonding and metal-ion interactions
(dashed lines) in the ternary complex. Distances are given in ä.

1048
Helvetica Chimica Acta Vol. 86 (2003)
Here, we show that ribose substitutions in bisubstrate inhibitors of COMT are
extremely challenging, and that even small changes alter dramatically both binding
affinity and binding mode of the inhibitors.
2. Results and Discussion. 2.1. Synthesis. In analogy to the synthesis of (À)-1 [5],
the preparation of (À)-2 started with the selective one-pot 5'-oxidation of 2'-
deoxyadenosine with ortho-iodoxybenzoic acid (IBX) and olefination with
Ph3PCHCO2Et [9], followed by protection of the 3'-OH group, to give the ester (‡)-
6 (62%) (Scheme 1). Crystals of (‡)-6 suitable for X-ray analysis were obtained by slow
evaporation of a concentrated solution in MeOH. The compound crystallized in the
space group P212121. In the X-ray crystal structure (Fig. 2,a), the adenine moiety
adopts the syn conformation with respect to the deoxyribose ring. The crystal lattice
shows a layered structure of H-bonded pairs of nucleosides, with one adenine binding in
the Watson Crick and the other in the Hoogsteen mode (Fig. 2,b).
Reduction of (‡)-6 with DIBAL-H (diisobutylaluminum hydride) provided allylic
alcohol (‡)-7 (73%), which was transformed into phthalimide (‡)-8 by a Mitsunobu
reaction (84%). Phthalimide (‡)-8 was cleaved to the amine with MeNH2 [10], and the
silyl protective group was removed with Bu4NF. In the workup, addition of an aqueous
solution of NaClO4 led to precipitation of Bu4NClO4, which was removed conveniently
Scheme 1. Synthesis of the Inhibitor (À)-2
NH2
NH2
N
N
N
N
N
N
(+)-6 R = CO2Et
R
c)
N
N
HO
(+)-7 R = CH2OH
O
O
a), b)
O
d )
HO
(+)-8 R =
CH2N
Me2(t-Bu)SiO
O
O
OH
O
HO
N
O
NH2
O
N
N
N
N
10
NO2
H2N
e), f )
O
(−)-2
g)
HO
(+)-9
a) o-Iodoxybenzoic acid (IBX), Ph3PˆCHCO2Et, Me2SO, 208, 70 h. b) Me2(t-Bu)SiCl, 1H-imidazole, DMF,
208, 21 h; 62%. c) DIBAL-H, hexane, CH2Cl2, À788, 4 h; 73%. d) Phthalimide, diethyl azodicarboxylate
(DEAD), PPh3, THF, 208, 14 h; 84%. e) MeNH2, EtOH, 208, 35 h. f) Bu4NF, THF, 208, 16 h; 9 9 %g. ) 10,
NaHCO3, DME, H2O, 208, 20 h; 26%.

Helvetica Chimica Acta Vol. 86 (2003)
1049
Fig. 2. a) X-Ray crystal structure of (‡)-6. Arbitrary numbering. Atomic displacement parameters obtained at
295 K are drawn at the 50% probability level. b) H-Bonding between pairs of molecules in the crystal packing of
(‡)-6. N ¥¥¥ N Distances in ä.
by filtration [11]. The polar, fully deprotected amine (‡)-9 was isolated in quantitative
yield after purification by ion-exchange chromatography. The activated ester 10 [4]
reacted selectively with the primary amino group of (‡)-9 to give the inhibitor (À)-2
(26%). Similar yields of (À)-2 were obtained with either 1,2-dimethoxyethane (DME)/
H2O as solvent with NaHCO3 as a base [12], or DMF together with Et3N [4].
For the synthesis of (À)-3 (Scheme 2), 2',3'-dideoxyadenosine ((À)-11) was
prepared according to the procedure described in [13]. Following the protocol for
(‡)-9 (Scheme 1), amine (‡)-12 was obtained via the sequence (‡)-11 ! (‡)-13 ! (‡)-
14 ! (‡)-15 ! (‡)-12, and reaction with activated ester 10 afforded inhibitor (À)-3.
First attempts to purify (À)-3 by reversed-phase chromatography on SiO2 100 C18 with

1050
Helvetica Chimica Acta Vol. 86 (2003)
MeCN/1% aqueous HCOOH or MeCN/0.1% aqueous CF3COOH (TFA) mixtures as
eluent failed due to decomposition of the acid-labile product. Purification was
eventually achieved with a volatile triethylammonium carbonate buffer, which was
readily obtained by bubbling CO2 through aqueous Et3N solution. Nevertheless,
1
subsequent buffer removal proved problematic as H-NMR product analysis showed
residual traces of buffer even after repeated lyophilization. It was, however, possible to
¾
‡
remove any residual buffer via ion exchange on Dowex 50WÂ 2 (NH4 ).
Scheme 2. Synthesis of Inhibitor (À)-3.
NH2
NH2
N
N
N
N
N
N
R
e)
a)
N
N
HO
(–)-3
O
O
(–)-11
(+)-13 R = CO2Et
b)
c)
d)
(+)-14 R = CH2OH
O
(+)-15 R = CH2N
O
(+)-12 R = CH2NH2
a) IBX, Ph3PˆCHCO2Et, Me2SO, 208, 37 h; 57% b) DIBAL-H, hexane, CH2Cl2, À788, 1 h; 67%. c)
Phthalimide, DEAD, PPh3, THF, 208, 18 h; 9 6%.d) MeNH2, EtOH, 208, 16 h; 83%. e) 10, Et3N, DMF, 208, 16 h;
63%.
The synthesis of the inhibitor (‡)-4 (Scheme 3) was achieved starting from the
enantiomerically pure building block (À)-16, which was prepared according to an
elegant procedure introduced by Crimmins et al. [14], involving an asymmetric aldol
addition [15] and a ring-closing metathesis reaction (for formation of the five-
membered ring) as key steps. Stereo- and regioselective introduction of the adenine
moiety by Pd-catalyzed substitution of the allylic acetate gave (À)-17 [16]. The best
results (55%) in this conversion were obtained with NaH as base and [Pd(PPh3)4] as
catalyst; in the absence of base or in the presence of weaker bases such as Et3N or
Cs2CO3, no conversion to the desired product was observed. Reduction of the CˆC
bond by catalytic hydrogenation, followed by the sequence of transformations as
described above for (À)-2 ((À)-17 ! (‡)-18 ! (‡)-19 ! (‡)-20 ! (‡)-21), afforded
amine (‡)-21, which reacted with 10 to give target compound (‡)-4.
For the synthesis of the pure enantiomers (À)-5 and (‡)-5, intermediates (À)-22
[17] and (‡)-22 [18], respectively, were prepared according to literature procedures.
Different leaving groups (methylsulfonyl (Ms), para-toluenesulfonyl (Ts), para-
bromobenzenesulfonyl (Bs), and para-nitrobenzenesulfonyl (Ns)) were tested for the
activation of the OH group in (À)-22, for the subsequent nucleophilic displacement
with adenine. The para-nitrobenzenesulfonyl (nosyl, Ns) group was found to be the

Helvetica Chimica Acta Vol. 86 (2003)
1051
Scheme 3. Synthesis of the Inhibitor (‡)-4.
NH2
NH2
N
N
N
N
N
R
N
N
N
HO
a), b)
c), d)
AcO
AcO
(–)-16
(–)-17
(+)-18 R = CO2Et
e)
(+)-19 R = CH2OH
O
f)
(+)-20 R = CH2N
g)
O
h)
(+)-4
(+)-21 R = CH2NH2
a) Adenine, NaH, [Pd(PPh3)4], THF, 458, 3 h. b) NaOH, H2O; 55%. c) H2, Pd/C, MeOH, 208, 3 h. d) IBX,
Ph3PˆCHCO2Et, Me2SO, 208, 15 h; 71% e) DIBAL-H, hexane, CH2Cl2, À788, 1 h; 38%. f) Phthalimide,
DEAD, PPh3, THF, 208, 15 h; 75%. g) MeNH2, EtOH, 208, 16 h; 9 9 %h. ) 10, Et3N, DMF, 208, 16 h; 25%.
best in this case. High yields for its introduction, leading to compound (À)-23 (87%),
and for the substitution step, providing (‡)-24 (72%), were obtained. According to
13C-NMR spectroscopy, adenine reacted regioselectively at the desired N(9) position
[19]. Ester (‡)-24 was reduced in 89% yield to the primary alcohol (À)-25 with NaBH4
in the presence of LiCl; in the absence of LiCl, no conversion was observed. Following
the sequence described above for the synthesis of (À)-2, amine (À)-26 was obtained via
(À)-25 ! (‡)-27 ! (‡)-28 ! (À)-29 ! (À)-26. Coupling the amine (À)-26 to 10 and
subsequent removal of the Boc protecting group provided (À)-5 (71%). Enantiomer
(‡)-5 was obtained analogously.
2.2. Biological Activity. All newly synthesized inhibitors were tested for in vitro
inhibitory activity against COMT obtained from rat liver. The IC50 values were
determined in a radiochemical assay as reported in [4][20] and are listed in the Table.
Table. IC50 Values (uncertainties Æ 5%) Determined by Radio-
chemical Assay with Preincubation for the Inhibitors of COMT
Compound
IC50 [mm]
(À)-1
(À)-2
(À)-3
(‡)-4
(À)-5
(‡)-5
0.009
28
3
1
43
141

1052
Helvetica Chimica Acta Vol. 86 (2003)
Scheme 4. Synthesis of the Inhibitor (À)-5 (the synthesis of (‡)-5 follows the same procedure, starting from
(‡)-22; yields are given in parentheses)
O
O
Boc
Boc
Boc
R
N
N
N
O
O
a)
b)
O
N
OH
O
S
NO2
N
N
O
N
(–)-22
(–)-23
NH2
(+)-24 R = CO2Me
c)
(–)-25 R = CH2OH
Boc
(+)-27 R = CO2Et
R
e)
f)
N
(+)-28 R = CH2OH
O
d)
h), i)
(–)-5
N
N
N
CH N
(–)-29 R =
2
N
g)
O
NH2
(–)-26 R = CH2NH2
a) NsCl, pyridine, 48, 14 h; 87% (85%). b) Adenine, K2CO3, 18-crown-6, DMF, 808, 6 h; 72% (60%). c) NaBH4,
LiCl, THF, EtOH, 08, 1 h then 558, 11 h; 89% (85%). d) IBX, Ph3PˆCHCO2Et, Me2SO, 208, 42 h; 54% (53%).
e) DIBAL-H, hexane, CH2Cl2, À788, 1 h; 50% (68%). f) Phthalimide, DEAD, PPh3, THF, 208, 16 h; 9 2%
(75%). g) MeNH2, EtOH, 208, 20 h; 74% (74%). h) 10, Et3N, DMF, 208, 20 h. i) TFA, H2O, 208, 2 h; 71%
(84%).
Removal of the 2'-OH group leads to a dramatic loss in binding affinity, with the
ternary complex formed by COMT, Mg2‡, and (À)-2 (IC50 ˆ 28 mm) being three orders
of magnitude less stable than the one formed by (À)-1 (IC50 ˆ 9 nm). Increasing the
hydrophobicity by removing the second OH group ((À)-3: IC50 ˆ 3 mm) and replacing
the ribose by a cyclopentane ring ((‡)-4: IC50 ˆ 1 mm) slightly increases the binding
affinity relative to (À)-2. Compounds (À)-5 (IC50 ˆ 43 mm) and (‡)-5 (IC50 ˆ 141 mm),
wherein the ribose had been replaced by a pyrrolidine ring, are the least active in this
series of inhibitors. Clearly, changes in the ribose substitution pattern have dramatic,
unfavorable effects on binding affinity. Also, replacement of the ribose moiety by a
pyrrolidium ring, which, in protonated form, could undergo ion pairing with the side-
chain carboxylate of Glu90, leads to a disappointingly low activity of the designed
bisubstrate inhibitors.
Kinetic studies were performed with (À)-2, (À)-3, and (‡)-4 [4] to determine the
inhibition mechanism with respect to the cofactor binding site. Similar measurements
were not conducted with respect to the catechol binding site, since the competitive
occupation of this site by nitrocatechols is amply documented [2][4][5]. In the
inhibition experiments, the concentration of SAM was varied at saturating benzene-1,2-

Helvetica Chimica Acta Vol. 86 (2003)
1053
diol concentration for different concentrations of inhibitor. Initial velocities were
determined without preincubation. Ki Values were calculated by globally fitting the
data to Eqns. 1, 2, or 3, corresponding to linear competitive, uncompetitive, or mixed
inhibition, respectively [21]. In these equations, Kic and Kiu are the competitive and
uncompetitive inhibition constants, respectively.
v ˆ V[S]/(Km(1 ‡ [I]/Kic) ‡ [S])
v ˆ V[S]/(Km ‡ [S](1 ‡ [I]/Kiu))
(1)
(2)
(3)
v ˆ V[S]/(Km(1 ‡ [I]/Kic) ‡ [S](1 ‡ [I]/Kiu))
Bisubstrate inhibitors in our previous studies had shown a competitive inhibition
mechanism with respect to the SAM binding site, and, in the case of (À)-1, this binding
mode had been confirmed by X-ray crystallography [5]. Similarly, (À)-2, although
lacking the 2'-OH group, shows a competitive mechanism with respect to the SAM
binding site (crossing of the lines on the y-axis in the Lineweaver Burk plot; Fig. 3,a).
The calculated inhibition constant is Ki ˆ Kic ˆ 14 Æ 1 mm. Although the elimination of
the 2'-OH group upon changing from (À)-1 to (À)-2 reduces the binding free energy by
as much as ca. 5 kcal molÀ1, the deoxyadenosine derivative is still competing for the
SAM cofactor binding site. On the other hand, compound (‡)-4, with a cyclopentyl ring
substituting for the ribose moiety, is no longer capable of occupying the SAM binding
site. This is clearly reflected by uncompetitive inhibition kinetics (parallel lines in the
Lineweaver Burk plot; Ki ˆ Kiu ˆ 0.56 Æ 0.03 mm). Only the catechol substrate binding
site is occupied by (‡)-4, whereas the adenine-substituted cyclopentane ring most
probably orients towards the periphery of the enzyme, into the surrounding solution.
Dideoxyadenosine derivative (À)-3 showed a mixed inhibition mechanism, Ki ˆ Kic ˆ
Kiu ˆ 2.7 Æ 0.1 mm (lines in the Lineweaver Burk plot cross on the x-axis); this case is
often referred to as a noncompetitive inhibition mechanism, although the use of this
terminology is disfavored [21]. These results demonstrate that a meaningful,
comparative discussion of the inhibition properties of bisubstrate inhibitors requires
detailed knowledge of the inhibition kinetics.
3. Conclusions. Biological assays and kinetic studies show that both binding
affinity and binding mode of potential bisubstrate inhibitors for COMT are extremely
sensitive towards changes of the ribose moiety. Thus, the dramatic decrease in affinity
by more than three orders of magnitude upon changing from ribose derivative (À)-1 to
2'-deoxyribose derivative (À)-2 both are bisubstrate inhibitors as revealed by the
enzyme kinetics strongly suggests that H-bonding of the two OH groups of the ribose
moiety to the side-chain carboxylate of Glu90 is necessary for efficient binding.
Apparently, a single OH group as in (À)-2 is not sufficient to −solvate× the carboxylate,
which obviously cannot adopt another orientation by turning away from the ribose
pocket. In future work, we intend to prepare the 3'-deoxyadenosine derivative to
further underline this statement. Most remarkably, a series of small changes in the
ribose ring while keeping the adenine and catechol moieties the same changes the
inhibition kinetics from competitive ((À)-2), to mixed ((À)-3), and to uncompetitive

1054
Helvetica Chimica Acta Vol. 86 (2003)
Fig. 3. Lineweaver Burk plots of reciprocal enzymatic activity vs. reciprocal SAM concentration for varying
concentrations of inhibitors (À)-2 (a), (À)-3 (b), and (‡)-4 (c) at saturating benzene-1,2-diol concentration.
DPM ˆ decays per min.

Helvetica Chimica Acta Vol. 86 (2003)
1055
((‡)-4). The different inhibition mechanisms of (À)-3 and (‡)-4 suggest that the O-
atom in the furan ring is also relevant for recognition in the ribose pocket. The
pyrrolidine rings of (À)-5 and (‡)-5 are poor replacements for the ribose moiety and
most probably are pointing towards the surface of the enzyme into the surrounding
solution rather than into the SAM binding site. These investigations clearly show that
modifications of the ribose moiety in bisubstrate inhibitors of COMT are delicate and
remain a true challenge for future investigations.
Experimental Part
General. Solvents and reagents were purchased reagent-grade and used without further purification. All
reactions were carried out under an Ar atmosphere. The following compounds were prepared according to
literature procedures: 10 [4] [22], (À)-11 [13], (À)-16 [14], (À)-22 [17], (‡)-22 [18], and IBX [23]. THF was
freshly distilled from sodium benzophenone ketyl, CH2Cl2 from CaH2. Anh. Me2SO and DMF, stored over
molecular sieves, were purchased from Fluka. Evaporation in vacuo was performed at ca. 20 Torr. All products
were dried under high vacuum (0.05 Torr) before anal. characterization. Thin-layer chromatography (TLC) was
performed on glass plates coated with Merck SiO2 60 F254. Column chromatography (CC) was performed with
Fluka SiO2 60 (230 400 mesh, 0.040 0.063 mm). Reversed-phase CC was performed with Fluka SiO2 100 C18
(230 400 mesh, 0.040 0.063 mm). M.p. were determined with a B¸chi B-540 melting-point apparatus and are
uncorrected. Optical rotations were measured on a Perkin-Elmer 241 polarimeter at l ˆ 365, l ˆ 589, or l ˆ
578 nm and are given in 10À1 deg cm2 gÀ1. IR Spectra: Perkin-Elmer 1600-FT-IR spectrometer. 1H- and 13C-NMR
Spectra (d [ppm]; J [Hz]): Varian Gemini 300, Varian Mercury 300, or Varian Gemini 200 spectrometers.
MALDI Mass spectra: IonSpec Ultima instrument with 2,5-dihydroxybenzoic acid (DHB) or 2,4,5-
trihydroxyacetophenone/diammonium citrate 2 :1 (THA) as a matrix. Elemental analyses were performed
by the Mikrolabor at the Laboratorium f¸r Organische Chemie, ETH Z¸rich. The nomenclature was generated
with the computer program ACD-Name (ACD/Labs).
General Procedure A (GP A) for the Oxidation of Primary Alcohols and Subsequent Horner-Wittig
Olefination. To a soln. of primary alcohol (40 mmol) in dry Me2SO (100 ml), Ph3PˆCHCO2Et (42.8 g,
100 mmol) and IBX (27.8 g, 100 mmol) were added. The mixture was stirred at 208 for 15 70 h. H2O (500 ml)
was added, and the mixture was extracted with AcOEt (2 Â 500 ml). The combined org. phases were dried
(Na2SO4) and concentrated to a residue, which was purified by CC.
General Procedure B (GP B) for the Reduction of a,b-Unsaturated Esters to Allylic Alcohols. To a soln. of
unsaturated ester (1 mmol) in CH2Cl2 (3 ml), a 1m soln. of DIBAL-H in hexane (4 ml, 4 mmol) was added
dropwise. The mixture was stirred at À788 for 1 4 h and then quenched with MeOH (5 ml). A sat. aq. soln. of
potassium sodium tartrate monohydrate (Rochelle salt, 50 ml) was added and the resulting suspension was
stirred vigorously for 16 h at 208, then extracted with AcOEt (3 Â 50 ml). The combined org. phases were dried
(Na2SO4) and evaporated to dryness.
General Procedure C (GP C) for the Mitsunobu Reaction of Allylic Alcohols with Phthalimide. DEAD
(0.234 ml, 97%, 1.46 mmol) was added dropwise to a stirred suspension of allylic alcohol (1.46 mmol),
phthalimide (215 mg, 1.46 mmol), and Ph3P (383 mg, 1.46 mmol) in THF (7 ml). After stirring for 14 18 h at
208, the mixture was evaporated to dryness and the residue purified by CC.
General Procedure D (GP D) for the Cleavage of N-Alkylated Phthalimides with MeNH2. To N-alkylated
phthalimide (1.91 mmol), a soln. of MeNH2 in EtOH (33%, 30 ml) was added, and the mixture was stirred at 208
for 16 35 h. Method A: After evaporation, the residue was dissolved in MeOH (10 ml) and loaded onto a
¾
‡
column of Dowex 50W 4 (NH4 , 1 cm  25 cm). Washing with MeOH/H2O 1:1 (400 ml) and elution with
MeOH/13% aq. NH3 soln. 1:1, followed by evaporation of MeOH, left an aq. product-containing soln. that was
lyophilized. Method B: After evaporation, the residue was dissolved in CHCl3 (20 ml) and extracted with 10%
aq. AcOH (30 ml). The aq. phase was washed with CHCl3 (3 Â 25 ml), adjusted to pH > 12 with 2n NaOH, and
then extracted again with CHCl3 (4 Â 25 ml). The combined org. phases were dried (Na2SO4) and evaporated to
dryness.
General Procedure E for the Amide Synthesis with N-Hydroxysuccinimide Ester 10. Method A: To a soln. of
amine (0.3 mmol) in dry DMF (5 ml), Et3N (1 mmol) and 10 (0.3 mmol) were added, and the resulting red
mixture was stirred at 208 for 16 20 h. H2O (100 ml) was added, and the mixture was adsorbed on a column with
reversed-phase SiO2 (1 cm  25 cm). After washing with 1% aq. HCOOH (200 ml), the amide was eluted with

1056
Helvetica Chimica Acta Vol. 86 (2003)
MeCN/1% aq. HCOOH 2 :8 ! 3 :8. Product-containing fractions were evaporated to dryness by lyophilization.
Method B: To a soln. of amine (0.1 mmol) and NaHCO3 (17 mg, 0.2 mmol) in H2O (0.8 ml), a soln. of 10 (30 mg,
0.1 mmol) in DME (1 ml) was added dropwise. The mixture was stirred at 208 for 20 h. After evaporation of
DME, the remaining aq. soln. was purified as described in Method A.
Ethyl (E)-3-((2R,3S,5R)-5-(6-Amino-9H-purin-9-yl)-3-{[1-(tert-butyl)-1,1-dimethylsilyl]oxy}-2,3,4,5-tetra-
hydrofuran-2-yl)prop-2-enoate ((‡)-6). According to GP A, a soln. of 2'-deoxyadenosine (5.0 g, 19mmol), IBX
(15.5 g, 56 mmol), and Ph3PˆCHCO2Et (14.3 g, 41 mmol) in Me2SO (55 ml) was stirred for 70 h. H2O (900 ml)
was added. The resulting precipitate was removed by filtration and washed with CH2Cl2/MeOH/Et3N 9 0 :9 :1
(3 Â 100 ml). The aq. phase was extracted with AcOEt (8 Â 500 ml). The combined org. phases were dried
(Na2SO4) and evaporated to dryness. The resulting brown oil, (t-Bu)Me2SiCl (6.72 g, 44 mmol), and 1H-
imidazole (1.52 g, 22 mmol) were dissolved in DMF (40 ml). The mixture was stirred for 21 h at 208. H2O
(600 ml) was added, and the aq. layer was extracted with AcOEt (4 Â 200 ml). The combined org. phases were
evaporated and purified by CC (SiO2; CH2Cl2/MeOH/Et3N 95 :4 :1) to afford (‡)-6 (5.04 g, 62%). White solid.
M.p. 125 1268 (Et2O). [a]2D0 ˆ ‡27.0 (c ˆ 1, CHCl3). IR (KBr): 3334s, 3162s, 2930m, 2856w, 1718s, 1667s, 1601s,
1573m, 1480m, 1442m, 1365s, 1328m, 1306m, 1252s, 1206m, 1191m, 1098s, 1052s, 9 84m, 9 51m, 9 26w, 864w, 834m,
776m, 724w, 654w. 1H-NMR (300 MHz, CDCl3): 0.11 (s, 6 H); 0.92 (s, 9 H); 1.28 (t, J ˆ 7.1, 3 H); 2.40 2.48 (m,
1 H); 2.85 2.95 (m, 1 H); 4.20 (q, J ˆ 7.1, 2 H); 4.50 4.58 (m, 2 H); 5.85 (br. s, 2 H); 6.07 (dd, J ˆ 15.6, 1.6,
1 H); 6.43 (t, J ˆ 6.5, 1 H); 7.04 (dd, J ˆ 15.6, 5.3, 1 H); 7.93 (s, 1 H); 8.36 (s, 1 H). 13C-NMR (75 MHz, CDCl3):
À4.8; 14.2; 18.0; 25.8; 39.7; 60.8; 75.6; 84.8; 86.3; 120.6; 122.8; 139.4; 144.1; 150.0; 153.4; 155.8; 166.3. HR-
‡
‡
MALDI-MS: 434.2228 ([M ‡ H] , C20H32N5O4Si ; calc. 434.2224). Anal. calc. for C20H31N5O4Si (433.58):
C 55.40, H 7.21, N 16.15; found: C 55.58, H 7.20, N 16.16. X-Ray: see Fig. 2.
(E)-3-((2R,3S,5R)-5-(6-Amino-9H-purin-9-yl)-3-{[1-(tert-butyl)-1,1-dimethylsilyl]oxy}-2,3,4,5-tetrahydro-
furan-2-yl)prop-2-en-1-ol ((‡)-7). According to GP B, a soln. of (‡)-6 (4.39g, 10 mmol) in CH 2Cl2 (50 ml) was
treated with a 1m soln. of DIBAL-H in hexane (40 ml, 40 mmol). The mixture was stirred at À788 for 4 h.
Workup followed by CC (SiO2; CH2Cl2/MeOH 9:1), provided ( ‡)-7 (2.90 g, 73%). Pale-yellow solid. M.p. 74
768. [a]2D0 ˆ ‡30.6 (c ˆ 1, CHCl3). IR (KBr): 3443s, 3322s, 3178s, 2929s, 2856s, 2356w, 1664s, 1602m, 1473m,
1422m, 1372m, 1337m, 1306m, 1253m, 1156m, 1102m, 1036m, 836s, 778m. 1H-NMR (300 MHz, CDCl3): 0.09( s,
6 H); 0.91 (s, 9H); 1.95 (br. s, 1 H); 2.43 (ddd, J ˆ 13.2, 6.3, 4.2, 1 H); 2.84 (dt, J ˆ 13.2, 6.3, 1 H); 4.19( d, J ˆ 3.7,
2 H); 4.39 4.48 ( m, 2 H); 5.83 (br. s, 2 H); 5.89 6.00 ( m, 2 H); 6.38 (t, J ˆ 6.3, 1 H); 7.94 (s, 1 H); 8.34 (s, 1 H).
13C-NMR (75 MHz, CDCl3): À4.7; 18.1; 25.8; 40.0; 62.3; 75.9; 84.5; 87.6; 120.1; 127.9; 133.4; 139.1; 149.5; 153.0;
‡
‡
155.6. HR-MALDI-MS: 414.1936 ([M ‡ Na] , C18H29N5NaO3Si ; calc. 414.1937). Anal. calc. for C18H29N5O3Si
(391.54): C 55.22, H 7.47, N 17.89; found: C 55.27, H 7.37, N 17.71.
2-[(E)-3-((2R,3S,5R)-5-(6-Amino-9H-purin-9-yl)-3-{[1-(tert-butyl)-1,1-dimethylsilyl]oxy}tetrahydrofuran-
2-yl)prop-2-enyl]-2,3-dihydro-1H-isoindole-1,3-dione ((‡)-8). According to GP C, a soln. of (‡)-7 (1.451 g,
3.7 mmol), phthalimide (655 mg, 4.5 mmol), and PPh3 (1.167 g, 4.5 mmol) in THF (10 ml) was treated with
DEAD (0.7 ml, 4.5 mmol) and stirred for 14 h. A white solid precipitated. The suspension was filtered, and the
product (‡)-8 (839mg, 43%) was washed with Et 2O (3  15 ml). The filtrate was evaporated and purified by CC
(SiO2; CH2Cl2/MeOH 19:1) to afford additional ( ‡)-8 (789mg, 41%). White solid. M.p. 219 8 (dec.). [a]D20
ˆ
‡21.9( c ˆ 1, CHCl3). IR (KBr): 3313m, 3200m, 2928m, 2856m, 1764m, 1711s, 1676m, 1601m, 1467w, 1398m,
1257m, 1107m, 1055m, 9 36w, 836m, 777w, 722w. 1H-NMR (300 MHz, CDCl3): 0.05 (s, 6 H); 0.85 (s, 9H); 2.40
(ddd, J ˆ 13.0, 6.5, 4.7, 1 H); 2.74 2.83 (dt, J ˆ 13.0, 6.5, 1 H); 4.30 (d, J ˆ 3.7, 2 H); 4.33 4.45 (m, 2 H); 5.85
5.87 (m, 2 H); 6.00 (br. s, 2 H); 6.36 (t, J ˆ 6.5, 1 H); 7.71, 7.85 (AA'BB', J ˆ 5.4, 3.0, 4 H); 7.92 (s, 1 H); 8.25 (s,
1 H). 13C-NMR (75 MHz, CDCl3): À4.8; 18.0; 25.7; 38.8; 39.9; 75.7; 84.4; 87.0; 120.3; 123.4; 127.0; 131.3; 132.0;
‡
‡
134.1; 139.1; 149.6; 153.0; 155.6; 167.8. HR-MALDI-MS: 543.2140 ([M ‡ Na] , C26H32N6NaO4Si ; calc.
543.2152). Anal. calc. for C26H32N6O4Si (520.66): C 59.98, H 6.19, N 16.14; found: C 60.01, H 6.02, N 16.14.
(2R,3S,5R)-2-[(E)-3-Aminoprop-1-enyl]-5-(6-amino-9 H-purin-9-yl)-2,3,4,5-tetrahydrofuran-3-ol ((‡)-9).
According to GP D, (‡)-8 (579mg, 1.1 mmol) was dissolved in MeNH 2 in EtOH (33%, 25 ml). The mixture was
stirred for 35 h and then evaporated. To the residue, a 1m soln. of Bu4NF in THF (11 ml, 11 mmol) was added.
The soln. was stirred for 16 h at 208 and then evaporated. The residue was dissolved at 08 in an aq. phosphate
buffer (pH 7.2) containing NaClO4. The resulting precipitate was removed by filtration. Purification by ion-
exchange chromatography according to GP D (Method A) afforded (‡)-9 (300 mg, 99%). Brown oil. [a]D20
ˆ
‡15.0 (c ˆ 1, MeOH). IR (KBr): 3354s, 1652s, 1600s, 1578s, 1477s, 1333m, 1300m, 1250m, 1091m, 1033m, 9 67w,
928w, 649m. 1H-NMR (300 MHz, CD3OD): 2.44 (ddd, J ˆ 13.7, 6.5, 4.6, 1 H); 2.82 (dt, J ˆ 13.7, 6.5, 1 H); 3.24 (d,
J ˆ 4.4, 2 H); 4.35 (t, J ˆ 4.3, 1 H); 4.43 (m, 1 H); 5.81 5.85 (m, 2 H); 6.40 (t, J ˆ 6.5, 1 H); 8.18 (s, 1 H); 8.24 (s,
1 H). 13C-NMR (75 MHz, CD3OD): 40.2; 43.6; 75.9; 85.3; 88.7; 120.6; 130.0; 134.3; 141.0; 150.5; 153.9; 157.4.
‡
‡
HR-ESI-MS: 299.1233 ([M ‡ Na] , C12H16N6NaO2 ; calc. 299.1227).

Helvetica Chimica Acta Vol. 86 (2003)
1057
N-{(E)-3-[(2R,3S,5R)-5-(6-Amino-9H-purin-9-yl)-2,3,4,5-tetrahydro-3-hydroxyfuran-2-yl]prop-2-enyl}-
2,3-dihydroxy-5-nitrobenzamide ((À)-2). According to GP E (Method B), a soln. of (‡)-9 (28 mg, 0.1 mmol)
and NaHCO3 (17 mg, 0.2 mmol) in H2O (0.8 ml) was treated with a soln. of 10 (30 mg, 0.1 mmol) in DME
(1 ml). The mixture was stirred for 20 h. Workup according to GP E afforded (À)-2 (12 mg, 26%). Yellow solid.
M.p. 1728 (dec.). [a]D20 ˆ À29.0 (c ˆ 0.5, MeOH). IR (KBr): 3370s, 1689w, 1638s, 1594m, 1561m, 1477m, 1417w,
1
1294s, 1264s, 1081w, 1039w, 9 72w. H-NMR (300 MHz, (CD3)2SO): 2.25 2.30 (m, 1 H); 2.80 2.88 (m, 1 H);
3.94 (t, J ˆ 5.3, 2 H); 4.25 4.36 (m, 2 H); 5.52 (br. s, 1 H); 5.72 5.90 (m, 2 H); 6.32 (t, J ˆ 6.7, 1 H); 7.29(br. s,
2 H); 7.38 7.41 (m, 1 H); 8.10 (s, 1 H); 8.31 (s, 1 H); 8.36 (d, J ˆ 2.8, 1 H); 9.43 (t, J ˆ 5.3, 1 H). 13C-NMR
(75 MHz, (CD3)2SO): 73.8; 74.1 83.3; 86.8; 111.9; 114.2; 114.4; 128.6; 129.8; 138.3; 141.2; 146.9; 147.8; 148.4;
‡
‡
152.4; 156.1; 167.8. HR-MALDI-MS: 480.1230 ([M ‡ Na] , C19H19N7NaO7 ; calc. 480.1244).
Ethyl (E)-3-[(2S,5R)-5-(6-Amino-9H-purin-9-yl)-2,3,4,5-tetrahydofuran-2-yl]prop-2-enoate ((‡)-13). Ac-
cording to GP A, a soln. of (À)-11 (1.856 g, 7.9mmol), IBX (6.590 g, 23.7 mmol), and Ph 3PˆCHCO2Et (4.120 g,
11.8 mmol) in Me2SO (24 ml) was stirred for 37 h. Workup and purification by CC (SiO2; CH2Cl2/MeOH/Et3N
94 :5 :1) gave (‡)-13 (1.36 g, 57%). White solid. M.p. 103 1058 (CHCl3/hexane 1:2). [a]2D0 ˆ ‡16.8 (c ˆ 1,
CHCl3). IR (KBr): 3310m, 3116s, 2978m, 1718s, 1648s, 1600s, 1479m, 1415m, 1371m, 1302s, 1257m, 1180m,
1089m, 1045m, 9 77m, 79 9w, 644w. 1H-NMR (300 MHz, CDCl3): 1.29( t, J ˆ 7.2, 3 H); 2.03 2.10 (m, 1 H); 2.32
2.42 (m, 1 H); 2.56 2.63 (m, 2 H); 4.21 (q, J ˆ 7.2, 2 H); 4.76 4.79( m, 1 H); 5.86 (br. s, 2 H); 6.07 (dd, J ˆ 15.6,
1.6, 1 H); 6.37 (t, J ˆ 4.8, 1 H); 7.04 (dd, J ˆ 15.6, 5.1, 1 H); 7.97 (s, 1 H); 8.36 (s, 1 H). 13C-NMR (75 MHz,
CDCl3): 14.2; 30.1; 32.6; 60.7; 80.0; 85.6; 120.1; 122.1; 138.7; 145.2; 149.3; 152.4; 155.1; 166.0. HR-MALDI-MS:
‡
‡
326.1206 ([M ‡ Na] , C14H17N5NaO3 ; calc. 326.1229). Anal. calc. for C14H17N5O3 (303.32): C 55.44, H 5.65,
N 23.09; found: C 55.51, H 5.74, N 23.03.
(E)-3-[(2S,5R)-5-(6-Amino-9H-purin-9-yl)-2,3,4,5-tetrahydrofuran-2-yl]prop-2-en-1-ol ((‡)-14). Accord-
ing to GP B, a soln. of (‡)-13 (702 mg, 2.0 mmol) in CH2Cl2 (11 ml) was treated with a 1m soln. of DIBAL-H in
hexane (9.3 ml, 9.3mmol). The mixture was stirred at À788 for 1 h. Workup, followed by CC (SiO2; CHCl3/
MeOH 92 :8) provided (‡)-14 (407 mg, 67%). White solid. M.p. 141 1438. [a]2D0 ˆ ‡18.0 (c ˆ 1, MeOH). IR
(KBr): 3306s, 3131s, 1671s, 1605s, 1574m, 1474m, 1421m, 1375m, 1338m, 1301m, 1215m, 1048m, 9 58m, 862w,
797m. 1H-NMR (300 MHz, CDCl3): 1.87 1.94 (m, 1 H); 2.19 2.27 ( m, 1 H); 2.49 2.56 ( m, 2 H); 3.4 (br. s,
1 H); 4.21 (d, J ˆ 4.1, 2 H); 4.60 4.67 (m, 1 H); 5.85 6.00 (m, 2 H); 6.17 (br. s, 2 H); 6.30 (t, J ˆ 4.5, 1 H); 7.97
(s, 1 H); 8.31 (s, 1 H). 13C-NMR (75 MHz, CDCl3): 30.2; 33.1; 62.2; 81.9; 85.6; 120.0; 129.3; 133.2; 138.5; 149.1;
‡
‡
153.0; 155.6. HR-MALDI-MS: 262.1300 ([M ‡ H] , C12H16N5O2 ; calc. 262.1304).
2-{(E)-3-[(2S,5R)-5-(6-Amino-9H-purin-9-yl)-2,3,4,5-tetrahydrofuran-2-yl]prop-2-enyl}-2,3-dihydro-1H-
isoindole-1,3-dione ((‡)-15). According to GP C, a soln. of (‡)-14 (134 mg, 0.5 mmol), PPh3 (160 mg,
0.6 mmol), and phthalimide (90 mg, 0.6 mmol) in THF (2 ml) was treated with DEAD (92 ml, 0.6 mmol). The
mixture was stirred for 18 h. Workup followed by CC (SiO2; CHCl3/MeOH 95 :5) afforded (‡)-15 (192 mg,
96%). Colorless solid. M.p. 169 1708. [a]2D0 ˆ ‡26.3 (c ˆ 1, CHCl3). IR (KBr): 3385s, 3156s, 1765m, 1709s,
1654s, 1598s, 1468m, 1397s, 1338m, 1295m, 1212m, 1062m, 9 35m, 800w, 723m, 654m, 529m. 1H-NMR (300 MHz,
CDCl3): 1.89 1.97 ( m, 1 H); 2.20 2.26 (m, 1 H); 2.48 2.55 (m, 2 H); 4.32 (d, J ˆ 4.4, 2 H); 4.57 4.64 (m,
1 H); 5.82 5.96 (m, 2 H); 6.10 (br. s, 2 H); 6.29( t, J ˆ 4.7, 1 H); 7.71, 7.87 (AA'BB', J ˆ 5.4, 3.0, 4 H); 7.96 (s,
1 H); 8.31 (s, 1 H). 13C-NMR (75 MHz, CDCl3): 30.1; 33.0; 38.9; 81.2; 85.5; 120.2; 123.5; 126.7; 132.0; 132.8;
‡
‡
134.1; 138.6; 149.2; 153.0; 155.6; 167.9. HR-MALDI-MS: 391.1507 ([M ‡ H] , C20H19N6O3 ; calc. 391.1519).
Anal. calc. for C20H18N6O3 (390.40): C 61.53, H 4.65, N 21.53; found: C 61.27, H 4.77, N 21.52.
9-{(2R,5S)-5-[(E)-3-Aminoprop-1-enyl]-2,3,4,5-tetrahydrofuran-2-yl}-9H-purin-6-amine ((‡)-12). Ac-
cording to GP D, (‡)-15 (561 mg, 1.7 mmol) was dissolved in MeNH2 in EtOH (33%, 26 ml). The mixture
was stirred for 16 h. Workup and ion-exchange chromatography according to GP D (Method A) gave (‡)-12
(363 mg, 83%). White solid. M.p. 110 1158. [a]2D0 ˆ ‡21.0 (c ˆ 1, CHCl3). IR (KBr): 3355s, 3167s, 1652s, 1596s,
1
1474s, 1330m, 1303m, 1246m, 1210m, 1055m, 79 6w, 69 6m, 649m. H-NMR (300 MHz, CDCl3): 1.86 1.99 (m,
1 H); 2.17 2.27 (m, 1 H); 2.45 2.60 (m, 2 H); 3.39( d, J ˆ 5.1, 2 H); 4.61 (q, J ˆ 6.9, 1 H); 5.75 (dd, J ˆ 15.4,
6.9, 1 H); 5.92 (dt, J ˆ 15.4, 5.1, 1 H); 6.30 (dd, J ˆ 5.5, 3.6, 1 H); 7.98 (s, 1 H); 8.33 (s, 1 H). 13C-NMR (75 MHz,
CDCl3): 30.3; 33.1; 43.2; 82.2; 85.5; 120.2; 128.3; 135.6; 138.6; 149.2; 153.0; 155.5. HR-MALDI-MS: 283.1282
‡
‡
([M ‡ Na] , C12H16N6NaO ; calc. 283.1283).
N-{(E)-3-[(2S,5R)-5-(6-Amino-9H-purin-9-yl)-2,3,4,5-tetrahydrofuran-2-yl]prop-2-enyl}-2,3-dihydroxy-5-
nitrobenzamide ((À)-3). According to GP E (Method A), a mixture of (‡)-12 (219mg, 0.84 mmol), 10 (235 mg,
0.79mmol), and Et 3N (320 ml, 2.4 mmol) in DMF (15 ml) was stirred for 16 h. The product was purified
according to GP E, with the acid component of the aqueous mobile phase replaced with volatile
triethylammonium carbonate buffer (pH 8, adjusted by bubbling CO2 through a 0.3m soln. of Et3N in H2O).
After lyophilization, the residue was dissolved in H2O (50 ml), evaporated, taken up in MeOH/H2O 1:1

1058
Helvetica Chimica Acta Vol. 86 (2003)
‡
(20 ml), filtered over an ion-exchange column (DOWEX 50W 2, NH4 , 2 cm  45 cm), and eluted with
MeOH. MeOH was evaporated, and H2O was added (10 ml). Lyophilization gave (À)-3 (219mg, 63%). Yellow
solid. M.p. 1258 (i-PrOH/Et2O). [a]2D0 ˆ À20.0 (c ˆ 0.5, MeOH). IR (KBr): 3367s, 3211s, 1639s, 1544m, 1478m,
1439m, 1333m, 1249s, 1077m, 9 77w, 79 4w, 69 9w, 644w, 560w. 1H-NMR (300 MHz, CD3OD): 1.97 2.10 (m, 1 H);
2.22 2.31 (m, 1 H); 2.45 2.55 (m, 2 H); 4.08 (d, J ˆ 2.8, 2 H); 4.62 4.67 (m, 1 H); 5.93 5.95 (m, 2 H); 6.30
(dd, J ˆ 6.5, 2.8, 1 H); 7.49( d, J ˆ 2.8, 1 H); 8.18 (s, 1 H); 8.26 (s, 1 H); 8.50 (d, J ˆ 2.8, 1 H). 13C-NMR
(75 MHz, CD3OD): 31.5; 33.8; 41.4; 83.4; 86.7; 108.5; 116.7; 120.8; 121.7; 131.1; 132.1; 133.8; 140.8; 150.3; 150.8;
‡
‡
154.1; 157.6; 168.8; 170.0. HR-MALDI-MS: 464.1293 ([M ‡ Na] , C19H19N7NaO6 ; calc. 464.1294).
[(1S,4R)-4-(6-Amino-9H-purin-9-yl)cyclopent-2-enyl]methanol ((À)-17). A suspension of NaH (66% in
mineral oil, 96 mg, 2.4 mmol) and adenine (364 mg, 2.6 mmol) in degassed dry Me2SO (6 ml) was stirred at 458
for 15 min. A soln. of [Pd(PPh3)4] (112 mg, 0.1 mmol) and (À)-16 (396 mg, 2 mmol) in degassed THF (6 ml) was
added. The mixture was stirred at 458 for 3 h. H2O (25 ml) was added, and the mixture was extracted with
AcOEt (9 Â 30 ml). The combined org. phases were dried (Na2SO4) and evaporated. 1m NaOH (5 ml) was
added to the residue. The mixture was stirred at 208 for 45 min. H2O (200 ml) was added, and the mixture was
extracted with AcOEt (8 Â 250 ml). The combined org. phases were dried (Na2SO4) and evaporated. The
residue was purified by CC (SiO2; MeOH/CHCl3 1 :9) to give (À)-17 (265 mg, 55%). Colorless solid. M.p. 183
1858 (MeOH/CHCl3) ([24]: 183 1868). 1H-NMR (200 MHz, CD3OD): 1.71 (dt, J ˆ 13.7, 5.6, 1 H); 2.78 (dt, J ˆ
13.7, 8.7, 1 H); 2.99 3.05 (m, 1 H); 3.49 3.70 ( m, 2 H); 5.65 5.73 (m, 1 H); 5.92 5.97 (m, 1 H); 6.20 6.24 (m,
1 H); 8.13 (s, 1 H); 8.20 (s, 1 H).
Ethyl (E)-3-[(1R,3S)-3-(6-Amino-9 H-purin-9-yl)cyclopentyl]prop-2-enoate ((‡)-18). A soln. of (À)-17
(503 mg, 2.18 mmol) in MeOH (45 ml) was hydrogenated (6 bar H2) in the presence of 10% Pd/C (145 mg) for
3 h. The catalyst was removed by filtration and the solvent evaporated. According to GP A, the residue was
reacted with IBX (1.831 g, 6.54 mmol) and Ph3PˆCHCO2Et (1.519g, 4.36 mmol) in dry Me 2SO (22 ml). The
mixture was stirred for 15 h. Workup and CC (SiO2; CH2Cl2/MeOH/Et3N 94 :5 :1) provided (‡)-18 (467 mg,
71%). Brown oil. [a]2D0 ˆ ‡6.6 (c ˆ 1.0, CHCl3). IR (CHCl3): 3412w, 2995m, 1710m, 1630s, 1472w, 1437w, 1265m,
1048m, 69 3w. 1H-NMR (300 MHz, CDCl3): 1.26 (t, J ˆ 7.2, 3 H); 1.85 2.18 (m, 4 H); 2.29 2.46 ( m, 2 H); 2.81
2.89( m, 1 H); 4.17 (q, J ˆ 7.2, 2 H); 4.91 4.97 (m, 1 H); 5.85 (d, J ˆ 15.6, 1 H); 5.94 (br. s, 2 H); 7.00 (dd, J ˆ
15.6, 7.8, 1 H); 7.84 (s, 1 H); 8.31 (s, 1 H). 13C-NMR (75 MHz, CDCl3): 14.3; 30.0; 31.7; 38.9; 40.9; 55.5; 60.5;
‡
‡
121.1; 129.6; 133.8; 138.8; 150.8; 153.1; 155.9; 166.8. HR-MALDI-MS: 302.1613 ([M ‡ H] , C15H20N5O2
:
302.1617).
(E)-3-[(1R,3S)-3-(6-Amino-9H-purin-9-yl)cyclopentyl]prop-2-en-1-ol ((‡)-19). According to GP B, (‡)-
18 (381 mg, 1.47 mmol) in CH2Cl2 (10 ml) was treated with a 1m soln. of DIBAL-H in hexane (5.92 ml,
5.92 mmol). The mixture was stirred at À788 for 1 h. Workup followed by CC (SiO2; MeOH/CHCl3 1:9) gave
(‡)-19 (143 mg, 38%). Colorless solid. M.p. 118 1218. [a]2D0 ˆ ‡23.8 (c ˆ 0.48, MeOH). IR (KBr): 3197m,
1667m, 1606w, 1566w, 1479w, 1414w, 1340w, 1310w, 1256w, 9 85w, 668w. 1H-NMR (300 MHz, CDCl3): 1.73 2.13
(m, 4 H); 2.29 2.52 ( m, 2 H); 2.70 2.76 (m, 1 H); 4.14 (d, J ˆ 5.0, 2 H); 4.92 4.98 (m, 1 H); 5.68 5.83 (m,
4 H); 7.87 (s, 1 H); 8.35 (s, 1 H). 13C-NMR (75 MHz, CD3OD): 31.8; 32.5; 40.6; 42.6; 57.1; 63.6; 120.5; 130.0;
‡
‡
135.9; 141.0; 150.7; 153.5; 157.3. HR-MALDI-MS: 260.1505 ([ M ‡ H] , C13H18N5O ; calc. 260.1511).
2-{(E)-3-[(1R,3S)-3-(6-Amino-9H-purin-9-yl)cyclopentyl}prop-2-enyl}-2,3-dihydro-1H-isoindole-1,3-di-
one ((‡)-20). According to GP C, a mixture of (‡)-19 (26 mg, 0.1 mmol), phthalimide (18 mg, 0.12 mmol), PPh3
(31 mg, 0.12 mmol), and DEAD (19 ml, 0.12 mmol) in THF (1 ml) was stirred for 15 h. Workup and CC (SiO2;
CHCl3/MeOH 9:1) gave ( ‡)-20 (29mg, 75%). Colorless crystals. M.p. 207 209 8. [a]2D0 ˆ ‡21.1 (c ˆ 0.37,
MeOH). IR (KBr): 3111 (br.), 1716m, 1672w, 1603w, 1396w, 725w. 1H-NMR (200 MHz, CDCl3): 1.65 2.06 (m,
4 H); 2.21 2.45 (m, 2 H); 2.61 2.67 (m, 1 H); 4.22 (d, J ˆ 5.9, 2 H); 2.82 4.93 (m, 1 H); 5.50 5.82 (m, 2 H);
6.39(br. s, 2 H); 7.65 7.69( m, 2 H); 7.76 7.81 (m, 2 H); 7.82 (s, 1 H); 8.27 (s, 1 H). 13C-NMR (75 MHz, CDCl3):
168.3; 156.0; 153.0; 150.3; 138.7; 137.4; 134.2; 132.4;123.5; 123.2;120.1; 55.3; 40.9; 39.5; 39.4; 31.9; 30.4. HR-
‡
‡
MALDI-MS: 389.1718 ([M ‡ H] , C21H21N6O2 ; calc. 389.1726).
9-{(1S,3R)-3-[(E)-3-Aminoprop-1-enyl]cyclopentyl}-9H-purin-6-amine ((‡)-21). According to GP D
(Method B), (‡)-20 (200 mg, 0.51 mmol) was dissolved in MeNH2 in EtOH (33%, 20 ml). The mixture was
stirred for 12 h. Workup afforded (‡)-21 (144 mg, 99%). Colorless oil. [a]2D0 ˆ ‡20.1 (c ˆ 1, MeOH). IR (KBr):
3329(br.), 1647 m, 1594m, 1475m, 1414w, 1303w, 1250w, 9 72w, 79 8w, 650w. 1H-NMR (300 MHz, CD3OD):
1.76 2.15 (m, 4 H); 2.25 2.44 (m, 2 H); 2.69 2.73 ( m, 1 H); 3.18 3.31 (m, 2 H); 4.84 4.98 (m, 1 H); 5.58
5.74 (m, 2 H); 8.19( s, 1 H); 8.21 (s, 1 H). 13C-NMR (75 MHz, CD3OD): 31.9; 32.5; 40.6; 42.7; 44.2; 57.1; 120.5;
‡
‡
130.4; 135.6; 141.0; 150.7; 153.5; 157.3. HR-MALDI-MS: 259.1669 ([M ‡ H] , C13H19N6 ; calc. 259.1671).
N-{(E)-3-[(1R,3S)-3-(6-Amino-9H-purin-9-yl)cyclopentyl]prop-2-enyl}-2,3-dihydroxy-5-nitrobenzamide
((‡)-4). According to GP E (Method A), a mixture of (‡)-21 (26 mg, 0.1 mmol), Et3N (42 ml, 0.3 mmol), and 10

Helvetica Chimica Acta Vol. 86 (2003)
1059
(30 mg, 0.1 mmol) in DMF (1.5 ml) was stirred for 15 h. Workup according to GP E gave (‡)-4 (11 mg, 25%).
Yellow solid. 208 2098 (dec.). [a]2D0 ˆ ‡11.8 (c ˆ 1, Me2SO). IR (KBr): 3398s, 3100s, 1700s, 1617m, 1513m,
1422w, 1339s, 1278m, 1200s, 1133m, 9 67w, 889w, 833w, 79 4w, 723m. 1H-NMR (300 MHz, CD3OD): 1.75 2.08 (m,
4 H); 2.18 2.36 (m, 2 H); 2.67 2.73 (m, 1 H); 3.90 3.95 (m, 2 H); 4.91 4.96 (m, 1 H); 5.59( dt, J ˆ 15.3, 5.3,
1 H); 5.76 (dd, J ˆ 15.3, 7.2, 1 H); 7.71 (d, J ˆ 2.5, 1 H); 8.34 (s, 1 H); 8.46 (d, J ˆ 2.5, 1 H); 8.49( s, 1 H).
13C-NMR (125 MHz, (CD3)2SO): 30.3; 31.1; 40.7; 40.8; 48.6; 55.3; 112.0; 114.3; 114.5; 118.7; 124.8; 135.2; 138.4;
‡
‡
146.9; 148.6; 151.7; 156.2; 158.1; 158.3; 167.8. HR-MALDI-MS: 440.1681 ([ M ‡ H] , C20H22N7O5 ; calc.
440.1682).
1-(1,1-Dimethylethyl) 2-Methyl (2S,4R)-4-{[(4-Nitrophenyl)sulfonyl]oxy}-2,3,4,5-tetrahydro-1H-pyrrole-
1,2-dicarboxylate ((À)-23). To (À)-22 (12.264 g, 50 mmol) in pyridine (90 ml), 4-nitrobenzenesulfonyl chloride
(18.395 g, 83 mmol) was added at 08. The mixture was stored at 48 for 14 h. The reaction was quenched with H2O
(90 ml), AcOEt (250 ml) was added, and the org. phase was washed with 0.5n HCl (250 ml), H2O (250 ml), and
sat. aq. NaCl soln. (250 ml), dried (Na2SO4), and evaporated. The residue was recrystallized from Et2O/pentane
to yield (À)-23 (18.8 g, 87%). Reddish crystals. M.p. 968 (Et2O/pentane). [a]2D0 ˆ À31.9( c ˆ 1, CHCl3). IR
(KBr): 2975w, 1741s, 1700s, 1533s, 1405s, 1288m, 1184s, 1044m, 9 12m, 747m, 687w, 620m, 577m, 464w. 1H-NMR
(300 MHz, CDCl3): 1.36, 1.40 (2s, 9H, rotamers); 2.16 2.25 ( m, 1 H); 2.40 2.61 (m, 1 H); 3.58 3.66 (m, 2 H);
3.71 (s, 3 H); 4.31 4.41 (m, 1 H); 5.15 (s, 1 H); 8.08, 8.39( AA'BB', J ˆ 8.7, 4 H). 13C-NMR (75 MHz, CDCl3):
28.2, 28.3 (rotamers); 36.1, 37.3 (rotamers); 51.8, 52.2 (rotamers); 52.4, 52.6 (rotamers); 57.0, 57.3 (rotamers);
‡
79.9, 80.4 (rotamers); 81.0; 124.6; 129.0; 142.0; 150.7; 153.0, 153.6 (rotamers); 172.3. ESI-MS: 453 ([M ‡ Na] ).
Anal. calc. for C17H22N2O9S (430.43): C 47.44, H 5.15, N 6.51; found: C 47.58, H 5.26, N 6.45.
1-(1,1-Dimethylethyl) 2-Methyl (2R,4S)-4-{[(4-Nitrophenyl)sulfonyl]oxy}-2,3,4,5-tetrahydro-1H-pyrrole-
1,2-dicarboxylate ((‡)-23). The procedure as for ((À)-23), starting from (‡)-22, gave ((‡)-23) in 85% yield.
M.p. 93 958 (Et2O/pentane). [a]2D0 ˆ ‡30.8 (c ˆ 1, CHCl3).
1-(1,1-Dimethyethyl) 2-Methyl (2S,4S)-4-(6-Amino-9H-purin-9-yl)-2,3,4,5-tetrahydro-1H-pyrrole-1,2-dicar-
boxylate ((‡)-24). A suspension of adenine (337 mg, 2.5 mmol), K2CO3 (346 mg, 2.5 mmol), 18-crown-6
(105 mg, 0.4 mmol), and (À)-23 (430 mg, 1 mmol) in DMF (5 ml) was stirred at 808 for 6 h. CHCl3 (25 ml) and
H2O (25 ml) were added. The layers were separated, and the aq. phase was extracted with CHCl3 (25 ml). The
combined org. phases were dried (Na2SO4) and evaporated. The residue was purified by CC (SiO2; MeOH/
CH2Cl2 8 :100), then recrystallized from AcOEt/hexane to afford (‡)-24 (261 mg, 72%). Colorless crystals. M.p.
1878 (AcOEt/hexane). [a]2D0 ˆ ‡17.3 (c ˆ 1, CHCl3). IR (KBr): 3325m, 3176m, 2976w, 1749s, 1699s, 1598s,
1475m, 1401s, 1300m, 1257m, 1158s, 89 6w, 79 8w, 727w, 648w. 1H-NMR (300 MHz, CDCl3): 1.39( s, 9H); 2.34
2.54 (m, 1 H); 2.75 2.90 (m, 1 H); 3.59( s, 3 H); 3.75 3.99 (m, 1 H); 4.03 4.17 (m, 1 H); 4.31 4.49( m, 1 H);
5.05 5.18 (m, 1 H); 6.33 (s, 2 H); 7.9 3 (s, 1 H); 8.27 (s, 1 H). 13C-NMR (125 MHz, CDCl3): 28.1, 28.2 (rotamers);
35.1, 36.3 (rotamers); 50.2, 50.9(rotamers); 51.6; 52.3, 52.5 (rotamers); 57.3, 57.8 (rotamers); 81.0; 119.6, 120.0
(rotamers); 138.3; 149.8, 150.0 (rotamers); 152.9; 153.2, 153.8 (rotamers); 155.8; 172.3. ESI-MS: 363 ([M ‡
‡
H] ). Anal. calc. for C16H22N6O4 (362.39): C 53.03, H 6.12, N 23.19; found: C 53.15, H 6.31, N 23.13.
1-(1,1-Dimethylethyl) 2-Methyl (2R,4R)-4-(6-Amino-9H-purin-9-yl)-2,3,4,5-tetrahydro-1H-pyrrole-1,2-di-
carboxylate ((À)-24). The procedure as for ((‡)-24), starting from (‡)-23, gave (À)-24 in 60% yield. M.p. 183
1878 (AcOEt/hexane). [a]2D0 ˆ À13.0 (c ˆ 1, CHCl3).
1,1-Dimethylethyl (2S,4S)-4-(6-amino-9H-purin-9-yl)-2-(hydroxymethyl)-2,3,4,5-tetrahydro-1H-pyrrole-1-
carboxylate ((À)-25). A soln. of (‡)-24 (257 mg, 0.7 mmol) in THF (2 ml) was cooled to 08, then LiCl
(89mg, 2.1 mmol) and NaBH 4 (79mg, 2.1 mmol) were added. After addition of EtOH (4 ml), the mixture was
stirred at 08 for 1 h, followed by 11 h at 558. The mixture was cooled to 208. Aq. AcOH (10%, 15 ml) was added,
and the soln. was concentrated and purified by CC (SiO2; MeOH/CH2Cl2 7:93! 10 :90). Recrystallization from
Et2O/hexane afforded (À)-25 (208 mg, 89%). Colorless crystals. M.p. 1108 (Et2O/hexane). [a]2D0 ˆ À8.5 (c ˆ 1,
MeOH). IR (KBr): 3329m, 3176m, 2975w, 1651m, 1598w, 1475w, 1418m, 1163m. 1H-NMR (300 MHz, CD3OD):
1.48 (s, 9H); 2.48 2.63 ( m, 1 H); 2.64 2.77 (m, 1 H); 3.59 3.69( m, 1 H); 3.70 3.89( m, 2 H); 3.98 4.09 (m,
1 H); 4.19 4.28 ( m, 1 H); 4.97 5.10 (m, 1 H); 8.19( s, 1 H); 8.23 (s, 1 H). 13C-NMR (75 MHz, CD3OD): 28.5;
33.8, 34.6 (rotamers); 51.7, 52.0 (rotamers); 53.3; 59.0; 63.7; 81.4; 120.0; 140.4; 150.4; 153.3; 155.8; 156.9.
‡
ESI-MS: 335 ([M ‡ H] ). Anal. calc. for C15H22N6O3 (334.38): C 53.88, H 6.63, N 25.13; found: C 53.88,
H 6.69, N 25.27.
1,1-Dimethylethyl (2R,4R)-4-(6-Amino-9H-purin-9-yl)-2-(hydroxymethyl)-2,3,4,5-tetrahydro-1H-pyrrole-
1-carboxylate ((‡)-25). The procedure as for ((À)-25), starting from (À)-24, gave (‡)-25 in 85% yield. M.p.
107 1098 (Et2O/hexane). [a]2D0 ˆ ‡8.1 (c ˆ 1, MeOH).
1,1-Dimethylethyl (2S,4S)-4-(6-Amino-9H-purin-9-yl)-2-[(E)-3-ethoxy)-3-oxoprop-1-enyl]-2,3,4,5-tetrahy-
dro-1H-pyrrole-1-carboxylate ((‡)-27). According to GP A, a soln. of (À)-25 (321 mg, 0.96 mmol) in Me2SO

1060
Helvetica Chimica Acta Vol. 86 (2003)
(3.9ml), IBX (806 mg, 2.88 mmol), and Ph 3PˆCHCO2Et (669mg, 1.92 mmol) was stirred for 42 h. Workup and
CC (SiO2; MeOH/AcOEt 10 :90) yielded (‡)-27 (208 mg, 54%). Colorless crystals. M.p. 978 (CH2Cl2/pentane).
[a]2D0 ˆ ‡11.3 (c ˆ 1, CHCl3). IR (KBr): 3328m, 3179m, 2978w, 1699s, 1645s, 1597m, 1475m, 1394s, 1368m,
1301m, 1265m, 1162m, 1125w, 1040w, 9 80w, 865w, 79 8w, 648w. 1H-NMR (300 MHz, CDCl3): 1.20 (t, J ˆ 7.2, 3 H);
1.38 (s, 9H); 2.36 2.46 ( m, 1 H); 2.68 2.77 (m, 1 H); 3.79 3.69( m, 1 H); 4.08 4.20 (m, 3 H); 4.50 (br. s, 1 H);
4.95 5.05 (m, 1 H); 5.86 (d, J ˆ 15.5, 1 H); 6.48 (s, 2 H); 6.83 (dd, J ˆ 15.5, 6.7, 1 H); 7.82 (s, 1 H); 8.26 (s, 1 H).
13C-NMR (75 MHz, CDCl3): 14.4; 28.5; 37.6; 50.3; 52.3; 57.0; 60.7; 81.0; 120.1; 121.7; 138.3; 147.6; 150.2; 153.1;
‡
‡
154.2; 156.0; 166.2. HR-MALDI-MS: 425.1906 ([M ‡ Na] ), C19H26N6NaO4 ; calc. 425.1913). Anal. calc. for
C19H26N6O4 (402.45): C 56.70, H 6.51, N 20.88; found C 56.85, H 6.42, N 20.79.
1,1-Dimethylethyl (2R,4R)-4-(6-Amino-9H-purin-9-yl)-2-[(E)-3-ethoxy-3-oxoprop-1-enyl]-2,3,4,5-tetrahy-
dro-1H-pyrrole-1-carboxylate ((À)-27). The procedure as for (‡)-27, starting from alcohol (‡)-25 gave (À)-27 in
53% yield. M.p. 988 (CH2Cl2/pentane). [a]2D0 ˆ À12.6 (c ˆ 1, CHCl3).
1,1-Dimethylethyl (2S,4S)-4-(6-Amino-9H-purin-9-yl)-2-[(E)-3-hydroxyprop-1-enyl]-2,3,4,5-tetrahydro-
1H-pyrrole-1-carboxylate ((‡)-28). According to GP B, (‡)-27 (5.6 g, 13.9mmol) in THF (60 ml) was treated
with a 1m DIBAL-H soln. in hexane (73.9ml, 73.9mmol). The mixture was stirred at À788 for 1 h. Workup and
CC (SiO2; MeOH/AcOEt 15 :85 ! 18 :82) gave (‡)-28 (2.51 g, 50%). Colorless foam. [a]2D0 ˆ ‡20.9( c ˆ 1,
CHCl3). IR (KBr): 3326m, 3181m, 2976m, 1690s, 1645s, 1598m, 1576m, 1476m, 1411s, 1366m, 1331m, 1301m,
1256m, 1162m, 1117w, 1013w, 9 76w, 874w, 798w, 649w. 1H-NMR (300 MHz, CDCl3): 1.42 (s, 9H); 2.28 2.39( m,
1 H); 2.61 2.73 (m, 1 H); 3.73 3.83 (m, 1 H); 4.08 4.18 (m, 3 H); 4.44 (br. s, 1 H); 5.01 (t, J ˆ 7.5, 1 H); 5.66
(br. s, 2 H); 6.15 (br s, 2 H); 7.85 (s, 1 H); 8.28 (s, 1 H). 13C-NMR (75 MHz, CDCl3): 28.6; 38.0; 50.8; 52.7; 57.5;
‡
62.6; 80.6; 120.0; 130.7; 131.5; 138.7; 150.2; 153.2; 154.6; 155.8. HR-MALDI-MS: 383.1815 ([M ‡ Na] ,
‡
C17H24N6NaO3 ; calc. 383.1813).
1,1-Dimethylethyl (2R,4R)-4-(6-Amino-9H-purin-9-yl)-2-[(E)-3-hydroxyprop-1-enyl]-2,3,4,5-tetrahydro-
1H-pyrrole-1-carboxylate ((À)-28). The procedure as for (‡)-28, starting from (À)-27 gave (À)-28 in 68%
yield. M.p. 99 1018. [a]2D0 ˆ À19.6 (c ˆ 1, CHCl3).
1,1-Dimethylethyl (2S,4S)-4-(6-Amino-9H-purin-9-yl)-2-[(E)-3-(1,3-dioxo-2,3-dihydro-1H-isoindole-2-yl)-
prop-1-enyl]-2,3,4,5-tetrahydro-1H-pyrrole-1-carboxylate ((À)-29). According to GP C, a soln. of (‡)-28
(360 mg, 1 mmol), phthalimide (177 mg, 1.2 mmol), and PPh3 (315 mg, 1.2 mmol) in THF (4 ml) was treated
with DEAD (187 ml, 1.2 mmol). The mixture was stirred for 16 h. Workup and CC (SiO2; MeOH/AcOEt 10 :90)
afforded (À)-29 (452 mg, 92%). Yellowish foam. [a]2D0 ˆ À3.9( c ˆ 1, CHCl3). IR (KBr): 3324m, 3175m, 2976m,
2930w, 1772m, 1717s, 1638s, 1595m, 1574m, 1469m, 1394s, 1366m, 1330m, 1299m, 1252m, 1162s, 1112m, 1046w,
956w, 874w, 79 8w, 722m, 648w. 1H-NMR (300 MHz, CDCl3): 1.38 (s, 9H); 2.28 2.40 ( m, 1 H); 2.65 2.77 (m,
1 H); 3.68 3.77 (m, 1 H); 4.12 4.32 (m, 3 H); 4.41 (br. s, 1 H); 5.00 (t, J ˆ 7.5, 1 H); 5.57 5.76 (m, 2 H); 6.17
(br. s, 2 H); 7.70, 7.84 (AA'BB', J ˆ 5.6, 3.1, 4 H); 7.84 (s, 1 H); 8.29( s, 1 H). 13C-NMR (75 MHz, CDCl3): 28.3;
37.8; 38.8; 50.5; 52.1; 57.2; 80.4; 119.8; 123.2; 124.5; 131.9; 133.9; 134.2; 138.2; 149.9; 152.8; 154.0; 155.5; 167.6.
‡
‡
HR-MALDI-MS: 390.1675 ([M ‡ Na] , C25H27N7NaO4 ; calc. 390.1673).
1,1-Dimethylethyl (2R,4R)-4-(6-Amino-9H-purin-9-yl)-2-[(E)-3-(1,3-dioxo-2,3-dihydro-1H-isoindole-2-
yl)prop-1-enyl]-2,3,4,5-tetrahydro-1H-pyrrole-1-carboxylate ((‡)-29). The procedure as for (À)-29, starting
from (À)-28, gave (‡)-29 in 75% yield. M.p. 101 1108. [a]2D0 ˆ ‡3.2 (c ˆ 1, CHCl3).
1,1-Dimethylethyl (2S,4S)-2-[(E)-3-aminoprop-1-enyl]-4-(6-amino-9H-purin-9-yl)-2,3,4,5-tetrahydro-1H-
pyrrole-1-carboxylate ((À)-26). According to GP D, (À)-29 (1.000 g, 2.04 mmol) was dissolved in MeNH2 in
EtOH (33%, 47 ml). The mixture was stirred for 20 h. Workup and ion-exchange chromatography according to
20
GP D (Method A) afforded (À)-26 (542 mg, 74%). Colorless solid. M.p. 127 1348 (Et2O). [a]
ˆ À1.7 (c ˆ
Hg365
1, MeOH). IR (KBr): 3322m, 3171m, 2975w, 2919w, 2359m, 2336m, 1681s, 1650s, 1597m, 1572m, 1471m, 1399s,
1365m, 1329m, 1298m, 1253m, 1158m, 1110w, 9 65w, 870w, 772w, 724w, 646w. 1H-NMR (300 MHz, CD3OD): 1.46
(s, 9H); 2.43 2.53 ( m, 1 H); 2.66 2.77 (m, 1 H); 3.20 (d, J ˆ 6.0, 2 H)); 3.82 (dd, J ˆ 11.0, 9.0, 1 H); 4.16 (dd,
J ˆ 11.0, 7.0, 1 H); 4.42 (dd, J ˆ 13.0, 7.5, 1 H); 4.97 5.08 (m, 1 H); 5.54 5.73 (m, 2 H); 8.19( s, 1 H); 8.19( s,
1 H). 13C-NMR (75 MHz, CD3OD): 28.6; 38.2; 43.5; 51.0; 53.8; 58.9; 81.3; 120.1; 131.9; 140.6; 150.4; 153.3;
‡
‡
155.8; 156.9; one peak is missing due to signal overlap. HR-MALDI-MS: 260.1620 ([ M ‡ H] , C17H26N7O2
;
calc. 260.1618).
1,1-Dimethylethyl (2R,4R)-2-[(E)-3-Aminoprop-1-enyl]-4-(6-amino-9H-purin-9-yl)-2,3,4,5-tetrahydro-
1H-pyrrole-1-carboxylate ((‡)-26). The procedure as for (À)-26, starting from (‡)-29, gave (‡)-26 in 74%
20
yield. M.p. 1268 (MeOH/Et2O). [a]
ˆ ‡1.6 (c ˆ 1, MeOH).
Hg365
N-{(E)-3-[(2S,4S)-4-(6-Amino-9H-purin-9-yl)-2,3,4,5-tetrahydro-1H-pyrrol-2-yl]prop-2-enyl}-2,3-dihy-
droxy-5-nitrobenzene-1-carboxamide ((À)-5). According to GP E (Method A), a soln. of (À)-26 (50 mg,
0.14 mmol), Et3N (58 ml, 0.42 mmol), and 10 (41 mg, 0.14 mmol) in DMF (3 ml) was stirred for 20 h. The

Helvetica Chimica Acta Vol. 86 (2003)
1061
mixture was evaporated to dryness. H2O (0.8 ml) and TFA (2.0 ml) were added, and the soln. was stirred at 208
for 2 h. The solvent was evaporated, and the residue was purified by prep. reversed-phase HPLC (2.5 cm Â
28 cm; 200 ml 0.5% HCOOH in H2O, then 1% HCOOH in H2O/MeCN 100 :0 ! 0 :100 in 100 min) to give (À)-
20
5 (44 mg, 71%). Yellow solid. M.p. 217 2228 (dec., MeOH/Et2O). [a]
ˆ À9.7 (c ˆ 0.3, TFA/Me2SO 1:20).
Hg578
IR (KBr): 3419m, 3188m, 1635s, 1600m, 1473m, 1418w, 1331m, 1261s, 1076w, 9 82w, 9 01w, 825w, 79 4w, 648w.
1H-NMR (300 MHz, (CD3)2SO ‡ 1 drop CF3COOD): 2.28 2.50 (m, 1 H); 2.68 2.84 (m, 1 H); 3.56 3.67 (m,
1 H); 3.74 3.87 (m, 1 H); 3.94 4.04 (m, 2 H); 4.24 4.38 (m, 1 H); 5.37 5.50 (m, 1 H); 5.88 (dd, J ˆ 16.0, 8.0,
1 H); 6.00 6.12 (m, 1 H); 7.75 (d, J ˆ 2.5, 1 H); 8.45 (d, J ˆ 2.5, 1 H); 8.53 (s, 1 H); 8.64 (s, 1 H). 13C-NMR
(75 MHz, (CD3)2SO ‡ 1 drop CF3COOD): 36.1; 47.9; 52.1; 59.6; 64.9; 112.0; 114.4; 118.4; 124.0; 133.7; 138.5;
‡
‡
142.3; 145.0; 146.8; 148.3; 150.2; 155.5; 167.7. HR-MALDI-MS: 441.1632 ([M ‡ H] , C19H21N8O5 ; calc.
441.1629).
N-{(E)-3-[(2R,4R)-4-(6-amino-9H-purin-9-yl)-2,3,4,5-tetrahydro-1H-pyrrol-2-yl]prop-2-enyl}-2,3-dihy-
droxy-5-nitrobenzene-1-carboxamide ((‡)-5). The procedure as for (À)-5, starting from (‡)-26, gave (‡)-5 in
20
84% yield. M.p. 217 2258 (dec., MeOH/Et2O). [a]
ˆ ‡9.7 (c ˆ 0.3, TFA/Me2SO 1:20).
Hg578
X-Ray Crystal Structure of (‡)-6. Crystals were grown by slow evaporation of a soln. of (‡)-6 in MeOH.
X-Ray crystal data for C20 H31N5O4Si (Mr 433.6): orthorhombic space group P212121, Dc ˆ 1.171 g cmÀ3, Z ˆ 4,
a ˆ 8.473(5), b ˆ 16.350(12), c ˆ 17.753(12) ä, Vˆ 2459(3) ä3, CuKa radiation, l ˆ 1.54178 ä, 3.688 ꢀ q ꢀ
50.038, 1460 unique reflections, Tˆ 293 K. The structure was solved by direct methods (SHELXS 86) and
refined by full-matrix least-squares analysis (SHELXTL PLUS (VMS)). All heavy atoms were refined
anisotropically, H-atoms isotropically; H-positions are based on stereochemical considerations. Final R(F) ˆ
0.0401, wR(F 2) ˆ 0.1039for 272 parameters and 1384 reflections with I > 2s(I). Crystallographic data
(excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre, deposition No. CCDC-198755. Copies of the data can be obtained, free of charge,
on application to the CCDC, 12 Union Road, Cambridge CB21EZUK (fax: ‡ 44(1223)336033; e-mail:
deposit@ccdc.cam.ac.uk).
Enzymatic Studies. Full experimental details of the radiochemical assay to determine IC50 values and the
kinetic measurements for determining the enzyme inhibition mechanisms are given in [4][20].
We thank F. Hoffmann-La Roche AG, Basel, for generous support of this work. We are grateful to P.
Malherbe for the cloning of COMT, P. Caspers for the expression of COMT, A. Cesura for enzyme purification,
B. Wipf for fermentation, and H. W. Lahm for sequencing.
REFERENCES
[1] P. T. M‰nnistˆ, I. Ulmanen, K. Lundstrˆm, J. Taskinen, J. Tenhunen, C. Tilgmann, S. Kaakkola, Prog. Drug
Res. 1992, 39, 291; P. T. M‰nnistˆ, S. Kaakkola, Pharmacol. Rev. 1999, 51, 593; V. V. Myllyla, M. Jackson,
J. P. Larsen, H. Baas, Eur. J. Neurol. 1997, 4, 333; H. Baas, A. G. Beiske, J. Ghika, M. Jackson, W. H. Oertel,
W. Poewe, G. Ransmayr, J. Neurol. Neurosurg. Psychiatry 1997, 63, 421; M. C. Kurth, C. H. Adler, M. St.
Hilaire, C. Singer, C. Waters, P. LeWitt, D. A. Chernik, E. E. Dorflinger, K. Yoo, Neurology 1997, 48, 81.
[2] J. Borgulya, H. Bruderer, K. Bernauer, G. Z¸rcher, M. Da Prada, Helv. Chim. Acta 1989, 72, 952; J.
Borgulya, M. Da Prada, J. Dingemanse, R. Scherschlicht, B. Schl‰ppi, G. Z¸rcher, Drugs Future 1991, 16,
719; E. Nissinen, I. B. Linden, E. Schultz, P. Pohto, Naunyn-Schmiedebergs Arch. Pharmacol. 1992, 346,
262; J. Vidgren, M. Ovaska, in −Structure-based Drug Design×, Ed. P. Veerapandian, Marcel Dekker, New
York, 1997, pp. 343 363; M. J. Bonifacio, M. Archer, M. L. Rodrigues, P. M. Matias, D. A. Learmonth,
M. A. Carrondo, P. Soares-da-Silva, Mol. Pharmacol. 2002, 62, 795.
[3] J. Vidgren, L. A. Svensson, A. Liljas, Nature (London) 1994, 368, 354.
[4] B. Masjost, P. Ballmer, E. Borroni, G. Z¸rcher, F. K. Winkler, R. Jakob-Roetne, F. Diederich, Chem. Eur.
J. 2000, 6, 971.
[5] C. Lerner, A. Ruf, V. Gramlich, B. Masjost, G. Z¸rcher, R. Jakob-Roetne, E. Borroni, F. Diederich, Angew.
Chem. 2001, 113, 4164; Angew. Chem., Int. Ed. 2001, 40, 4040; C. Lerner, B. Masjost, A. Ruf, V. Gramlich,
R. Jakob-Roetne, G. Z¸rcher, E. Borroni, F. Diederich, Org. Biomol. Chem. 2003, 1, 42.
[6] P. R. Gerber, K. M¸ller, J. Comput.-Aided Mol. Des. 1995, 9, 251.
[7] T. Schindler, F. Sicheri, A. Pico, A. Gazit, A. Levitzki, J. Kuriyan, Mol. Cell. 1999, 3, 639; T. G. Davies, J.
Bentley, C. E. Arris, F. T. Boyle, N. J. Curtin, J. A. Endicott, A. E. Gibson, B. T. Golding, R. J. Griffin, I. R.
Hardcastle, P. Jewsbury, L. N. Johnson, V. Mesguiche, D. R. Newell, M. E. M. Noble, J. A. Tucker, L. Wang,
H. J. Whitfield, Nat. Struct. Biol. 2002, 9, 745.

1062
Helvetica Chimica Acta Vol. 86 (2003)
[8] H.-J. Bˆhm, G. Klebe, H. Kubinyi, −Wirkstoffdesign×, Spektrum, Heidelberg, 1996.
[9] D. Crich, X.-S. Mo, Synlett 1999, 67.
[10] S. Wolfe, S. K. Hasan, Can. J. Chem. 1970, 48, 3572.
[11] J. C. Craig, E. T. Everhart, Synth. Commun. 1990, 20, 2147.
[12] G. W. Anderson, J. E. Zimmerman, F. M. Callahan, J. Am. Chem. Soc. 1963, 85, 3039.
[13] H. Shiragami, Y. Amino, Y. Honda, M. Arai, Y. Tanaka, H. Iwagami, T. Yukawa, K. Izawa, Nucleosides
Nucleotides 1996, 15, 31.
[14] M. T. Crimmins, B. W. King, W. J. Zuercher, A. L. Choy, J. Org. Chem. 2000, 65, 8499.
[15] M. T. Crimmins, B. W. King, E. A. Tabet, K. Chaudhary, J. Org. Chem. 2001, 66, 894.
[16] B. M. Trost, L. Li, S. D. Guile, J. Am. Chem. Soc. 1992, 114, 8745.
¬
[17] K. K. Schumacher, J. Jiang, M. M. Joullie, Tetrahedron: Asymmetry 1998, 9, 47.
[18] G. Lowe, T. Vilaivan, J. Chem. Soc., Perkin Trans. 1 1997, 539.
[19] M.-T. Chenon, R. J. Pugmire, D. M. Grant, R. P. Panzica, L. B. Townsend, J. Am. Chem. Soc. 1975, 97, 4627.
[20] G. Z¸rcher, M. Da Prada, J. Neurochem. 1982, 38, 19 1.
[21] A. Cornish-Bowden, C. W. Warthon, −Enzyme Kinetics×, IRL Press Limited, Oxford, 1988.
[22] B. Masjost, doctoral dissertation No. 13719, ETH-Z¸rich, 2000.
[23] R. E. Ireland, L. Liu, J. Org. Chem. 1993, 58, 2899.
[24] B. Brown, L. S. Hegedus, J. Org. Chem. 2000, 65, 1865.
Received January 9, 2003