Synthesis of optically active N6-alkyl derivatives of (R)-3-(adenin-9-yl)-2-hydroxypropanoic acid and related compounds

Article abstract of DOI:10.1135/cccc20030931

Reaction of ethyl (R)-oxiranecarboxylate (2a) with various nucleobases (adenine, 6-chloropurine, thymine, cytosine, N⁶-benzoyladenine, 4-methoxy-5-methylpyrimidin-2(1H)-one and 4-methoxypyrimidin-2(1H)-one) afforded ethyl 3-substituted-2-hydroxypropanoates 4-10. Enantioselectivity of this reaction is dependent on the type of the base: 6-chloropurine, N⁶-benzoyladenine, 4-methoxy-5-methylpyrimidin-2(1H)-one, thymine and cytosine gave optically pure R enantiomers. In other cases, partial or complete racemization occurred. Optically pure ethyl (R)-3-(6-chloropurin-9-yl)-2-hydroxypropanoate (5a) was hydrolyzed to give (R)-3-(6-chloropurin-9-yl)-2-hydroxypropanoic acid (11). Reactions of 11 with various primary or secondary amines led to N⁶-substituted (R)-3-(adenin-9-yl)-2-hydroxypropanoic acids 14-19. Enantiomeric purity was determined from ¹H NMR spectra measured in the presence of (-)-(R)-1-(9-anthryl)-2,2,2-trifluoroethan-1-ol.

Full text of DOI:10.1135/cccc20030931

Derivatives of (R)-3-(Adenin-9-yl)-2-hydroxypropanoic Acid
931
SYNTHESIS OF OPTICALLY ACTIVE N6-ALKYL DERIVATIVES
OF (R)-3-(ADENIN-9-YL)-2-HYDROXYPROPANOIC ACID AND
RELATED COMPOUNDS
1,
2
Marcela KREČMEROVÁ *, Miloš BUDĚŠÍNSKÝ , Milena MASOJÍDKOVÁ and
Antonín HOLÝ
3
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic,
1
Flemingovo nám. 2, 166 10 Prague 6, Czech Republic; e-mail: marcela@uochb.cas.cz,
2
3
budesinsky@uochb.cas.cz, holy@uochb.cas.cz
Received Novem ber 18, 2002
Accepted Jan uary 13, 2003
Dedicated to the memory of Professor Otakar Červinka.
Reaction of eth yl (R)-oxiran ecarboxylate (2a) with various n ucleobases (aden in e, 6-ch loro-
purin e, th ym in e, cytosin e, N6-ben zoyladen in e, 4-m eth oxy-5-m eth ylpyrim idin -2(1H)-on e an d
4-m eth oxypyrim idin -2(1H)-on e) afforded eth yl 3-substituted-2-h ydroxypropan oates 4–10.
En an tioselectivity of th is reaction is depen den t on th e type of th e base: 6-ch loropurin e,
N6-ben zoyladen in e, 4-m eth oxy-5-m eth ylpyrim idin -2(1H)-on e, th ym in e an d cytosin e gave
optically pure R en an tiom ers. In oth er cases, partial or com plete racem ization occurred. Op-
tically pure eth yl (R)-3-(6-ch loropurin -9-yl)-2-h ydroxypropan oate (5a) was h ydrolyzed to
give (R)-3-(6-ch loropurin -9-yl)-2-h ydroxypropan oic acid (11). Reaction s of 11 with various
prim ary or secon dary am in es led to N6-substituted (R)-3-(aden in -9-yl)-2-h ydroxypropan oic
acids 14–19. En an tiom eric purity was determ in ed from 1H NMR spectra m easured in th e
presen ce of (–)-(R)-1-(9-an th ryl)-2,2,2-trifluoroeth an -1-ol.
Keyw ord s: Oxiran e rin g open in g; En an tiom eric purity determ in ation ; Acyclic n ucleoside an -
alogues; Nucleosides; S-Aden osyl-L-h om ocystein e h ydrolase in h ibitors; SAH h ydrolase; Ade-
n in e; Purin es; Epoxides; An tivirals.
In our previous studies on acyclic aden osin e an alogues we h ave described
(RS)-3-(aden in -9-yl)-2-h ydroxypropan oic acid (AHPA) an d its alkyl esters1.
Th ese com poun ds possess in terestin g biological ch aracteristics: th ey in h ibit
various viruses, bein g n on -toxic to th e h ost cells at an tivirally active con -
cen tration s2. Due to th eir irreversible in h ibition of S-aden osyl-L-h om o-
cystein e h ydrolase (SAH h ydrolase, EC 3.3.1.1.) an d th e resultin g
disturban ce of m eth ylation reaction s in gen eral, AHPA an d its alkyl esters
exh ibit a n um ber of oth er biological activities3. However, availability of
Collect. Czech. Chem. Commun. (Vol. 68) (2003)
doi:10.1135/cccc20030931

932
Krečmerová, Buděšínský, Masojídková, Holý:
th ese com poun ds in larger quan tities was lim ited to th eir racem ic form 4.
Th e syn th esis of pure R an d S en an tiom ers of 3-(aden in -9-yl)-2-h ydroxy-
propan oic acid by oxidation of 5-(aden in -9-yl)-5-deoxyaldopen toses with
O2 in aqueous alkali5 or with periodate6 was com plicated by difficult purifi-
cation an d low yields of th e products. Th e aim of th is work is elaboration of
a sim ple an d effective syn th esis of pure R or S en an tiom ers of 3-(aden in -
9-yl)-2-h ydroxypropan oic acid an d its derivatives substituted in th e N6 po-
sition of th e aden in e m oiety, as well as th eir pyrim idin e con gen ers.
For th is purpose, we sough t a ch iral th ree-carbon atom syn th on wh ich
sh ould react with various n ucleobases givin g desired products in good
yields an d h igh optical purity. It sh ould be easily accessible from an in ex-
pen sive optically active m aterial. Th ese requirem en ts could be m et by
alkylation of th e n ucleobases with alkyl oxiran ecarboxylates 2. Th e syn th e-
sis of required eth yl (R)-oxiran ecarboxylate (2a) was perform ed startin g
from L-serin e (1a) usin g th e m eth od described for th e preparation of eth yl
(R,R)-2,3-epoxybutan oate from L-th reon in e via 2-brom o-3-h ydroxypropan -
oic acid7. Th e utilization of L-serin e for syn th eses of (R)-oxiran ecarboxylic
acid esters was also proposed8 (Sch em e 1). An alogously to 2a, we obtain ed
from D-serin e eth yl (S)-oxiran ecarboxylate (2b). However, th is preparation
of 2a an d 2b h as serious drawbacks: th e use of expen sive crown eth er an d
h arm ful dieth yl sulfate.
Th erefore we exam in ed an altern ative access to oxiran e 2a: tran sform a-
tion of L-serin e to eth yl (S)-2-ch loro-3-h ydroxypropan oate (3) followed by
th e oxiran e rin g closure on treatm en t with DBU (1,8-diazabicyclo[5.4.0]-
un dec-7-en e) (Sch em e 1). However, com plete racem ization occurred in th is
case so th at th e desired product, eth yl oxiran ecarboxylate, was obtain ed as
racem ate 2c. Th e racem ic n ature of th e so prepared oxiran e 2c was con -
firm ed n ot on ly by optical rotation m easurem en t but also from th e course
of its n ucleoph ilic open in g with 6-ch loropurin e. Th is reaction perform ed
(ii)
(i)
COOK
H
COOEt
H
(iii)
COOH
HO
HO
O
O
COOH
Br
Cl
HO
2a
NH2
1a
(iv)
COOH
COOEt
COOEt
H
(v)
HO
(vi)
O
Cl
2c
3
(i) HBr, NaNO2, KBr; (ii) KOH, EtOH; (iii) diethyl sulfate, 18-crown-6, CH2Cl2;
(iv) HCl, NaNO2; (v) EtOH, TsOH; (vi) DBU, acetonitrile
SCHEME 1
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Derivatives of (R)-3-(Adenin-9-yl)-2-hydroxypropanoic Acid
933
with racem ic oxiran e 2c afforded eth yl 3-(6-ch loropurin -9-yl)-2-h ydroxy-
propan oate as a racem ate. Reaction details an d optical purity determ in ation
of products is described below.
Nucleoph ilic open in g of th e oxiran e rin g in 2a or 2b by various n ucleo-
bases un der basic con dition s took place at C-3 with regiospecific form ation
of α-h ydroxy esters (4–10, Sch em e 2). Th is is in agreem en t with th e data on
th e n ucleoph ilic open in g of 2,3-epoxy esters or 2,3-epoxy am ides9.
COOEt
+
BH
B
B
O
O
H
COOEt
COOEt
+
2a
2b
HO
H
HO
H
COOEt
H
+
BH
4a - 10a
(R enantiomers)
4b - 10b
(S enantiomers)
4, B = adenin-9-yl
5, B = 6-chloropurin-9-yl
6, B = cytosin-9-yl
7, B = 4-methoxy-5-methyl-2-oxo-1,2-dihydropyrimidin-1-yl
8, B = 4-methoxy-2-oxo-1,2-dihydropyrimidin-1-yl
9, B = thymin-1-yl
10, B = N6-benzoyladenin-9-yl
SCHEME 2
For th e determ in ation of optical purity of esters 4–10, we h ave used th eir
1H NMR spectra m easured after th e addition of sligh t excess (≈2 m olar
equivalen ts) of optically pure (–)-(R)-1-(9-an th ryl)-2,2,2-trifluoroeth an -1-ol.
Th is ch iral solvatin g agen t is kn own to form weak diastereom eric com -
plexes with various com poun ds con tain in g h ydroxy, am in o, carbon yl, sul-
fon yl an d ph osph on yl groups (for details, see review10). Doublin g of som e
sign als was observed wh en both en an tiom ers of th e esters were presen t. Th e
ch em ical sh ift n on equivalen ce of proton s is very sm all (≤10 Hz at 500 HMz)
but observable (usually on resolution en h an ced sh arp triplets of ester
eth oxy proton s as it is illustrated in Fig. 1) an d relative in ten sities of sign als
allowed to determ in e th eir R:S ratio. Th e NMR spectra h ad to be m easured
in a n on polar solven t, wh ich itself does n ot associate with th e optically ac-
tive reagen t (CDCl3 was used). Th erefore, th e aden in e derivative 4 was ben -
zoylated with ben zoyl ch loride in pyridin e to ben zoate 20 an d cytosin e
derivatives 6 an d N6-ben zoyladen in e derivative 10a were con verted to ace-
tates 21 an d 22, wh ile oth er com poun ds were m easured directly sin ce th eir
solubility in CDCl3 was sufficien t.
Surprisin gly, both eth yl oxiran ecarboxylates 2a an d 2b reacted with som e
n ucleobases en an tioselectively, wh ile with oth ers a partial racem isation
took place. Th e latter fin din g con trasts with our previous results of an alo-
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

934
Krečmerová, Buděšínský, Masojídková, Holý:
gous reaction s of n ucleobases with optically pure glycidols: th us, base-
catalyzed reaction s of (R)-2,3-epoxypropyl butyrate with various h etero-
cyclic bases (aden in e, cytosin e, 2,6-diam in opurin e, 2-am in o-6-ch loropu-
rin e) gave optically pure (R)-2,3-dih ydroxypropyl derivatives11. Also th e
oxiran e rin g open in g in (S)-[(trityloxy)m eth yl]oxiran e with various 8-sub-
stituted purin e bases afforded (after deprotection of trityl group) optically
pure S en an tiom ers of th e correspon din g 2,3-dih ydroxypropyl derivatives12.
Th e exten t of racem ization in th e course of oxiran e rin g open in g in th e
reaction s of 2a or 2b with aden in e, 6-ch loropurin e, 4-m eth oxy-5-m eth yl-
pyrim idin -2-(1H)-on e, 4-m eth oxypyrim idin -2-(1H)-on e, cytosin e, N6-ben z-
oyladen in e an d th ym in e in th e presen ce of diverse bases (NaH, Cs2CO3,
DBU) depen ds on th e ch aracter of th e h eterocyclic base (Sch em e 2, Table I).
Th us, with aden in e th e reaction affords partially racem ic eth yl 3-(aden in -
9-yl)-2-h ydroxypropan oate (4): with 2a an d sodium salt of aden in e (by
treatm en t with NaH) in dim eth ylform am ide we obtain ed th e R en an tiom er
of 4 in 75% optical purity on ly. With Cs2CO3, th e R/S ratio of en an tiom ers
in 4 was 65:35. Th e racem ization was com plete in th e reaction of 2b with
th e DBU salt of aden in e in DMF 13. Con trary to aden in e, 6-ch loropurin e re-
acted with both oxiran es, 2a or 2b, in DMF in th e presen ce of Cs2CO3 with -
out racem isation an d gave optically pure eth yl (R)-3-(6-ch loropurin -9-yl)-
b
ppm
1.23
9
8
7
6
5
4
2
ppm
a
8
7
6
5
4
3
2
1
ppm
FIG. 1
1H NMR spectrum of m eth yl proton s of eth oxy group in com poun d 20: a in CDCl3; b after ad-
dition of (–)-(R)-1-(9-an th ryl)-2,2,2-trifluoroeth an -1-ol
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Derivatives of (R)-3-(Adenin-9-yl)-2-hydroxypropanoic Acid
935
2-h ydroxypropan oate (5a) or eth yl (S)-3-(6-ch loropurin -9-yl)-2-h ydroxypro-
pan oate (5b), respectively, in satisfactory yields. Un der th e sam e con di-
tion s, cytosin e afforded with both en an tiom ers of 2 optically pure com -
poun ds 6. Reaction of eth yl (R)-oxiran ecarboxylate (2a) with 4-m eth oxy-
5-m eth ylpyrim idin -2(1H)-on e an d NaH in DMF afforded 95% of optically
pure R en an tiom er 7a , wh ile th e (S)-oxiran e 2b gave S en an tiom er 7b in
85% en an tiom eric purity. However, th e reaction with 4-m eth oxypyrim idin -
2(1H)-on e gave un expectedly n early com pletely racem ized com poun d 8 un -
der essen tially th e sam e con dition s. Direct reaction of oxiran es 2 with th y-
m in e gave a m ixture of N-1 an d N-3 isom ers. To circum ven t th is problem ,
th ym in e was first con verted by reaction with h exam eth yldisilazan e to
5-m eth yl-2,3-bis[(trim eth ylsilyl)oxy]pyrim idin e an d subsequen tly treated
with oxiran e 2a in aceton itrile with Sn Cl4 as a catalyst. Th is m eth od af-
forded (after desilylation ) eth yl (2R)-2-h ydroxy-3-(5-m eth yl-2,4-dioxo-3,4-
dih ydropyrim idin -1(2H)-yl)propan oate (9a) with excellen t optical purity.
Fin ally, th e reaction of oxiran e 2a with N6-ben zoyladen in e perform ed in
DMF in th e presen ce of Cs2CO3 gave com poun d 10a with out racem ization ,
in con trast to free aden in e, wh ere all attem pts to prepare an optically pure
product failed (see Table I). In all cases, th e exact NMR determ in ation of
th e ratio of en an tiom ers was n ecessary.
TABLE I
Reaction of eth yl (R)-oxiran ecarboxylate 2a with various purin e an d pyrim idin e bases
Yield
%
R:S
ratio
Base
Con dition s
Product
Aden in e
NaH, DMF, 65 °C, 2 h
Cs2CO3, DMF, 105 °C, 2 h
DBU, DMF, 110 °C, 30 m in
4
4
4
40
31
49
77:23
65:35
44:56
6-Ch loropurin e
Cytosin e
Cs2CO3, DMF, 105 °C, 2 h
Cs2CO3, DMF, 105 °C, 2 h
NaH, DMF, 80 °C, 1.5 h
5
6
7
55
100:0
20–40 100:0
4-Meth oxy-5-m eth ylpyrim idin -
40
95:5
2(1H)-on e
4-Meth oxypyrim idin -2(1H)-on e
NaH, DMF, 80 °C, 1.5 h
8
9
55
55
47:53
100:0
5-Meth yl-2,4-bis[(trim eth ylsilyl)-
oxy]pyrim idin e
Sn Cl4, aceton itrile, r.t.
N6-Ben zoyladen in e
Cs2CO3 DMF, 105 °C, 2 h
10
30
100:0
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936
Krečmerová, Buděšínský, Masojídková, Holý:
Optical rotation m easurem en t was n ot always very exact an d useful due
to extrem ely low values of [α]D of som e products, specifically 6-ch loro-
purin e an d aden in e derivatives.
Neverth eless, con sisten cy of sign s of [α]D of partially racem ic aden in e de-
rivative 4 an d optically pure eth yl (R)-3-(aden in -9-yl)-2-h ydroxypropan oate
described in literature5 in dicates th at R en an tiom er in com poun d 4 is dom i-
n an t. Aden in e derivative 4 obtain ed by m eth ods A, B (see Experim en tal)
was also subm itted to CD spectra m easurem en t. Th e course of CD curves
was foun d iden tical with CD curve of auth en tic sam ple of m eth yl (R)-3-
(aden in -9-yl)-2-h ydroxypropan oate (obtain ed by oxidative degradation of
5-(aden in e-9-yl)-5-deoxy-D-ribofuran ose an d subsequen t esterification 1,6).
Th is is an oth er con firm ation th at product 4 obtain ed by m eth ods A an d B
is predom in an tly R en an tiom er.
With respect to th e kn own facts con cern in g th e m ech an ism of th e
oxiran e rin g open in g, supported by a n um ber of our previous results, we
suppose th at ch iral oxiran ecarboxylates react with n ucleobases with an alog-
ical stereoch em ical course as optically pure ch iral glycidols11,12. It m ean s
th at eth yl (R)-oxiran ecarboxylate (2a) sh ould react with n ucleobases to R
con figurated eth yl 3-substituted-2-h ydroxypropan oates, respectively R en -
an tiom er sh ould be dom in an t in cases with partial product racem ization
(see Table I). In order to verify th is assum ption we selected eth yl (R)-3-
(6-ch loropurin -9-yl)-2-h ydroxypropan oate (5a), th e key in term ediate for
furth er syn th eses, an d con firm ed experim en tally its absolute con figuration .
For th is purpose com poun d 5a was con den sed with (+)-(R)-3,3,3-trifluoro-
2-m eth oxy-2-ph en ylpropan oic acid ((R)-MTPA) as well as with its (–)-(S) en -
an tiom er ((S)-MTPA) an d 1H NMR spectra of both so obtain ed diastereo-
isom eric esters 34 an d 35 were com pared. Th e differen ces of th e observed
ch em ical sh ifts of proton s in th e vicin ity of ch iral carbon atom are in agree-
m en t with a sh ieldin g effect of ph en yl rin g in th e preferred con form ation
of correspon din g MTPA-esters 34 an d 35 an d prove th e (R)-con figuration in
startin g alcoh ol 5a (see Fig. 2).
Easy availability of th e optically pure 6-ch loropurin e derivative 5a was
exploited for th e preparation of a series of N6-substituted 3-(aden in -9-yl)-
2-h ydroxypropan oic acids. In order to avoid N-substituted carboxam ide for-
m ation in am in olysis of th e ester group, th e eth yl esters h ad to be tran s-
form ed first to th e carboxylic acids. Attem pts to rem ove ester groups by
treatm en t of 5a with brom otrim eth ylsilan e or iodotrim eth ylsilan e repeat-
edly failed. Th e esters were com pletely resistan t to both reagen ts: h eatin g of
5a for several h ours with a m ixture of brom otrim eth ylsilan e an d potassium
iodide afforded th e h ypoxan th in e derivative 12, wh ile a direct reaction
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Derivatives of (R)-3-(Adenin-9-yl)-2-hydroxypropanoic Acid
937
NHCOCH3
N
R
N
R
N
O
N
N
N
N
N
N
N
N
N
NH
N
O
COOH
COOC2H5
COOC2H5
COOC2H5
HO
H
OR'
OH
OCOCH3
21a, b
13, R = R' = H
11, R = Cl
12
20, R = NHCOC6H5; R' = COC6H5
22a, R = NHCOC6H5; R' = COCH3
14, R = (CH3)2N-
15, R =
16, R =
NH
N
( In formulae 21, 22: a = R enantiomer; b = S enantiomer )
17, R =
O
N
18, R = CH3OCH2CH2NH-
19, R = CH2=CHCH2NH-
with iodotrim eth ylsilan e resulted in th e reductive rem oval of h alogen an d
form ation of purin e derivative 13; in both cases, th e ester groups were pre-
served. En an tiom eric purity of com poun ds 12 an d 13 was n ot studied. Both
com poun ds were form ed in relatively h igh yields. We did n ot fin d an y litera-
ture preceden t of such type of reaction .
8.73
H
8.70
H
1.25 3.39
4.81 4.84
1.28 3.59
N
CH3-CH2-O-OC
O
4.67 4.83
N
CH3-CH2-O-OC
CH2
N
CH2
N
N
N
O
H
H3CO
Cl
H
8.00
N
OCH3
Cl
H
N
7.82
F3C
F3C
O
O
(R)-MTPA ester (34)
(S)-MTPA ester (35)
FIG. 2
Th e preferred con form ation of (R)- an d (S)-MTPA esters 34 an d 35 of com poun d 5a. Sh ieldin g
effect of ph en yl rin g is in dicated with arrows an d th e observed ch em ical sh ifts of in volved pro-
ton s con firm (R)-con figuration of 5a
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

938
Krečmerová, Buděšínský, Masojídková, Holý:
Ester 5a was ultim ately h ydrolyzed with aqueous sodium h ydroxide an d
th en acidified to give quan titatively th e free acid 11. Un der th e reaction
con dition s, th ere was n o detectable form ation of h ypoxan th in e derivatives.
(R)-3-(6-Ch loropurin -9-yl)-2-h ydroxypropan oic acid 11 gave on treat-
m en t with various prim ary an d secon dary am in es (cyclopropylam in e,
pyrrolidin e, m orph olin e, 2-m eth oxyeth ylam in e, allylam in e) an d/or di-
m eth ylam m on ium dim eth ylcarbam ate th e correspon din g 6-alkylam in o-
purin e derivatives 14–19 as fin al products. For th e optical purity
determ in ation of th ese com poun ds by NMR, th eir esterification was n eces-
sary in order to obtain com poun ds soluble in CDCl3. Th is esterification h ad
to be perform ed un der very m ild con dition s to avoid product racem ization .
Th e acids 14–19 were tran sform ed to th eir lith ium salts by n eutralization
with LiOH an d th e salts were treated with excess m eth yl iodide or dieth yl
sulfate in DMF at room tem perature. Un der th ese con dition s 2-m eth oxy or
2-eth oxy derivatives of correspon din g m eth yl or eth yl esters 23, 25, 27, 29,
31 an d 32 were obtain ed. Th e structure of th ese un expected easily form ed
1
com poun ds was proved by th eir H NMR spectra. In m ost cases th ese com -
poun ds were obtain ed togeth er with esters bearin g a free h ydroxy group,
i.e. com poun ds 24, 26, 28, 30 an d 33. Both types of esters can be separated
by colum n ch rom atograph y. Th e fully protected com poun ds 23, 25, 27, 29,
31 an d 32 cam e out to be m ore suitable for 1H NMR m easurem en t with
R
N
N
N
N
COOR'
R''O
H
O
N
23, R = (CH3)2N-; R' = R'' = CH3
29, R =
30, R =
; R' = R'' = CH2CH3
24, R = (CH3)2N-; R' = CH3; R'' = H
O
N
; R' = CH2CH3; R'' = H
25, R =
26, R =
; R' = R'' = CH3
NH
NH
31, R = CH3OCH2CH2NH-; R' = R'' = CH3
32, R = CH2=CHCH2NH-; R' = R'' = CH3
33, R = CH2=CHCH2NH-; R' = CH3; R'' = H
; R' = CH3; R'' = H
27, R =
28, R =
; R' = R'' = CH2CH3
N
; R' = CH2CH3; R'' = H
N
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Derivatives of (R)-3-(Adenin-9-yl)-2-hydroxypropanoic Acid
939
(R)-(–)-1-(9-an th ryl)-2,2,2-trifluoroeth an -1-ol th an esters bearin g free h y-
droxyl group. Optical purity of th e products is given in Table II. It is evi-
den t th at un der th e con dition s of am in olysis of com poun d 11, n o
substan tial racem ization occurred.
In con clusion , N6-alkyl derivatives of a biologically active com poun d,
(R)-3-(aden in -9-yl)-2-h ydroxypropan oic acid were prepared usin g of eth yl
(R)-oxiran ecarboxylate as an easily accessible th ree-carbon atom ch iral
syn th on . A sim ilar m eth od is applicable to th e syn th esis of S-en an tiom ers.
Biological activity tests of th ese com poun ds are un der way.
EXPERIMENTAL
Un less stated oth erwise, solven ts were evaporated at 40 °C/2 kPa an d com poun ds were dried
at 13 Pa. Meltin g poin ts were determ in ed on a Kofler block an d are un corrected. An alytical
TLC was perform ed on Silufol UV254 plates (Kavalier Votice, Czech Republic). Colum n ch ro-
m atograph y was perform ed on silica gel 60 µm (Fluka). 1H NMR spectra were recorded on a
Varian UNITY 500 in strum en t (at 500 MHz) in DMSO-d6 (referen ced to th e solven t sign al at
δ 2.50) or in CDCl3 (with TMS as in tern al referen ce). 13C NMR spectra were recorded on th e
sam e in strum en t (at 125.7 MHz) usin g APT pulse sequen ce in DMSO-d6 (referen ced to th e
solven t sign al δ 39.70). Ch em ical sh ifts are given in ppm (δ-scale) an d couplin g con stan ts
(J) in Hz. (–)-(R)-1-(9-An th ryl)-2,2,2-trifluoroeth an -1-ol (Aldrich Ch em . Co.) was used as a
ch iral solvatin g agen t for NMR determ in ation of optical purity. Mass spectra were m ea-
sured on ZAB-EQ (VG An alytical) spectrom eter usin g FAB (ion ization with xen on , accelerat-
in g voltage 8 kV, glycerol m atrix). NMR an d m ass spectra of S-en an tiom ers 5b–7b were
iden tical with spectra of correspon din g R-en an tiom ers. Optical rotation s were m easured on
AUTOPOL IV polarim eter (Rudolph Research An alytical, U.S.A.) at 20 °C, [α]D values are
given in 10–1 deg cm 2 g–1. CD spectra were m easured on a Jobin –Yvon –Spex CD6 usin g soft-
ware CDMAX.
TABLE II
Optical purity of N6-alkyl derivatives of (R)-3-(aden in -9-yl)-2-h ydroxypropan oic acid 14–19
determ in ed by 1H NMRa
Com poun d
Ratio R:S
14
15
16
17
18
19
97:3
95:5
94:6
91:9
94:6
95:5
a
Correspon din g esters 23, 25, 27, 29, 31 an d 33 were used for th e determ in ation .
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

940
Krečmerová, Buděšínský, Masojídková, Holý:
Startin g Materials an d Solven ts
All ch em icals were purch ased from Sigm a–Aldrich (Czech Republic). N6-Ben zoyladen in e was
prepared accordin g to a publish ed procedure14, 4-m eth oxypyrim idin -2(1H)on e an d 4-m eth -
oxy-5-m eth yl-2-pyrim idin o-2(1H)on e accordin g to ref.15 Dim eth ylform am ide an d aceton i-
trile were dried by distillation from CaH2 (DMF in vacuo) an d stored over m olecular sieves.
Silica gel was a product of Sigm a (U.S.A.).
Eth yl (S)-2-Ch loro-3-h ydroxypropan oate (3)
A solution of sodium n itrite (19.7 g, 285.0 m m ol) in water (42 m l) was added dropwise un -
der stirrin g at –5 °C durin g 4 h to solution of L-serin e (1a) (20.0 g, 190.0 m m ol) in a m ixture
of water (75 m l) an d 37% h ydroch loric acid (40 m l). Th e reaction m ixture was th en kept at
room tem perature overn igh t an d taken down in vacuo at 40 °C. Th e residue was codistilled
with water (4 × 150 m l) an d th en absolute eth an ol (150 m l) was added to precipitate NaCl.
Th e solid m aterial was filtered off an d wash ed with absolute eth an ol. Com bin ed filtrates
were taken down an d codistilled with a m ixture of ben zen e an d absolute eth an ol (5:2, 2 ×
150 m l). A m ixture of ben zen e (94 m l), absolute eth an ol (40 m l) an d TsOH (0.62 g, 3.2 m m ol)
was added to a syrupy residue. Th e reaction m ixture was refluxed for 5 h an d th e volatiles
distilled off un der atm osph eric pressure. Th e sam e volum e of ben zen e an d eth an ol was
added to th e residue, th e m ixture was refluxed for addition al 4 h an d distilled off again . Th e
–
residue was diluted with absolute eth an ol (50 m l) an d n eutralized with Dowex 1 (HCO3
form ). Solven ts were evaporated un der atm osph eric pressure an d th e residue was th en dis-
tilled in vacuum to give com poun d 3. Yield 13.88 g (48%), colourless liquid, b.p. 80–85 °C
(1 kPa), [α ]2D0 +8.9 (c 1.25, eth an ol). For C5H9ClO3 (152.6) calculated: 39.36% C, 5.95% H,
23.24% Cl; foun d: 39.51% C, 6.10% H, 23.06% Cl. MS (EI), m/z (rel.%): 153 (12) [M+]. 1H
NMR (DMSO-d6): 5.45 t, 1 H, J(OH,3) = 6.0 (OH); 4.50 t, 1 H, J(2,3) = 6.0 (H-2); 4.17 q, 2 H,
J(vic) = 7.0 (CH2); 3.75 t, 2 H, J(3,2) = J(3,OH) = 6.0 (H-3); 1.22 t, 3 H, J(vic) = 7.0 (CH3).
Eth yl (R)-Oxiran ecarboxylate (2a)
Th e com poun d was prepared by a publish ed procedure7 from L-serin e (10.5 g, 100 m m ol).
Yield 4.6 g (40%) of 2a as colourless liquid. 1H NMR spectrum is in agreem en t with ref.16
[α ]D20 +11.9 (c 0.90, m eth an ol), ref.7 [α ]2D0 +12.8.
Eth yl (S)-Oxiran ecarboxylate (2b)
Th e com poun d was prepared from D-serin e (5.0 g, 47.6 m m ol) by th e sam e m an n er as 2a.
Yield 2.5 g (45%), [α ]D20 –11.6 (c 0.87, m eth an ol).
Eth yl (RS)-Oxiran ecarboxylate (2c)
A solution of com poun d 3 (12 g, 78.6 m m ol) in aceton itrile (45 m l) was h eated with DBU
(15.6 m l, 101.7 m m ol) at 65 °C for 25 m in . After coolin g to room tem perature, th e reaction
m ixture was brough t to pH 8 with acetic acid an d taken down at 20 °C to h alf of its vol-
um e. Th is solution was applied on to a colum n of silica gel (300 m l) an d eluted with a m ix-
ture pen tan e–aceton e (4:1). Product-con tain in g fraction s were distilled at atm osph eric
pressure, th e residue th en distilled in vacuum (13 Pa) at 60 °C to give 3 g (33%) of 2c as
colourless liquid. 1H NMR spectrum is in agreem en t with ref.16 [α ]2D0 +0.37 (c 1.32, eth an ol).
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Derivatives of (R)-3-(Adenin-9-yl)-2-hydroxypropanoic Acid
Eth yl Esters 4–8 an d 10. Gen eral Procedure
941
Method A. A suspen sion of an appropriate n ucleobase (5 m m ol) an d NaH dispersion in
60% paraffin oil (200 m g, 5 m m ol) in DMF (15 m l) was stirred at room tem perature (7 an d
8) or at 60 °C (4). Oxiran e 2a or 2b (580 m g, 5 m m ol) was added an d th e reaction m ixture
was h eated for 1.5–2 h (see Table I). After coolin g to room tem perature, th e m ixture was
n eutralized with acetic acid, taken down in vacuo, th e residue codistilled with xylen e (20 m l)
an d partition ed between water (50 m l) an d eth yl acetate (10 × 30 m l). Com bin ed organ ic ex-
tracts were dried over an h ydrous sodium sulfate. Th e solven t was evaporated an d th e crude
product was purified on a colum n of silica gel (200 m l).
Method B. A suspen sion of an appropriate n ucleobase (5.6 m m ol), oxiran e 2a or 2b
(697 m g, 6 m m ol) an d Cs2CO3 (390 m g, 1.2 m m ol) in DMF (35 m l) was stirred at 105 °C for
2 h . Th e reaction m ixture was filtered wh ile h ot th rough a pad of Celite, th e filtrate n eutral-
ized with several drops of acetic acid an d taken down in vacuo. Th e residue was codistilled
with xylen e (50 m l) an d th en partition ed between water (70 m l) an d eth yl acetate (8 ×
60 m l). Com bin ed organ ic extracts were dried over an h ydrous sodium sulfate an d taken
down . Th e crude product was purified on a colum n of silica gel (300 m l).
Eth yl 3-(6-Am in o-9H-purin -9-yl)-2-h ydroxypropan oate (4)
Methods A, B. Ch rom atograph y in th e system eth yl acetate–aceton e–eth an ol–water
(15:3:4:3) an d subsequen t crystallization from eth an ol gave ch rom atograph ically pure par-
tially racem ic product 4, m .p. 176–178 °C. For yields an d optical purity, see Table I. Product
of m eth od A: [α]D +7.3 (c 0.626, CH3OH), ref.5: [α]D +8.3 (c 0.60, CH3OH) for pure R en an -
tiom er 4. CD spectrum : [Θ]220 –4000, [Θ]250 –200, [Θ]285 –1800 (c 4.98 × 10–4 m ol/l,
CH3OH). CD spectrum of m eth yl (R)-3-(aden in -9-yl)-2-h ydroxypropan oate1,6: [Θ]215 –2000,
[Θ]250 +100, [Θ]285 –200 (c 1.06 × 10–3 m ol/l, CH3OH). Product of m eth od B: [α]D +1.22
(c 0.572, CH3OH). CD spectrum : [Θ]220 –2600, [Θ]250 –50, [Θ]285 –1200 (c 4.98 × 10–4 m ol/l,
CH3OH). 1H NMR data (DMSO-d6) are in agreem en t with ref.5 FAB MS, m/z (rel.%): 252
(100) [M + H].
Method C. A suspen sion of aden in e (1.5 m m ol) an d DBU (0.25 m l, 1.65 m m ol) in DMF
(4 m l) was h eated at 110 °C un till a clear solution was obtain ed. Oxiran e 2a (232 m g,
2 m m ol) was added an d th e m ixture was stirred at 110 °C for 30 m in . After coolin g to room
tem perature an d n eutralization with acetic acid, water (1 m l) was added to th e residue an d
th e m ixture taken down . Th e crude product was ch rom atograph ed on a colum n of silica gel
(100 m l). For yields an d optical purity, see Table I. [α]D –0.5 (c 0.55, CH3OH). 1H NMR data
(DMSO-d6) are in agreem en t with ref.5
Eth yl (R)-3-(6-Ch loro-9H-purin -9-yl)-2-h ydroxypropan oate (5a)
From 6-ch loropurin e an d oxiran e 2a by th e m eth od B. Th e pure product was obtain ed by
ch rom atograph y in eth yl acetate. Yield 591 m g (39%) as an am orph ous m aterial, [α]D –1.42
(c 0.112, CH3OH). For C10H11ClN4O3 (270.7) calculated: 44.37% C, 4.10% H, 13.10% Cl,
20.70% N; foun d: 43.97% C, 4.18% H, 13.18% Cl, 20.42% N. FAB MS, m/z (rel.%): 271 (100)
[M + H]. 1H NMR (CDCl3): 8.71 s, 1 H an d 8.26 s, 1 H (H-2, H-8); 4.67 m , 2 H (H-3′a, H-3′b);
4.62 m , 1 H (H-2′); 4.23 dq, 1 H, J(gem ) = 10.6, J(vic) = 7.0 an d 4.18 dq, 1 H, J(gem ) = 10.6,
J(vic) = 7.0 (O-CH2); 3.90 br, 1 H (OH); 1.27 t, 3 H, J(vic) = 7.0 (CH3).
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

942
Krečmerová, Buděšínský, Masojídková, Holý:
Eth yl (S)-3-(6-Ch loro-9H-purin -9-yl)-2-h ydroxypropan oate (5b)
From oxiran e 2b usin g essen tially th e sam e procedure as described for 5a. Yield 508 m g
(33%), [α]D +1.1 (c 0.281, CH3OH).
Eth yl (RS)-3-(6-Ch loro-9H-purin -9-yl)-2-h ydroxypropan oate (5)
From racem ic oxiran e 2c in th e sam e way as described for 5a (m eth od B). Yield 560 m g
(37%). 1H NMR data (CDCl3) iden tical with 5a. R:S 54:46 was determ in ed by NMR.
Eth yl (R)-3-(4-Am in o-2-oxopyrim idin -1(2H)-yl)-2-h ydroxypropan oate (6a)
From cytosin e an d oxiran e 2a by m eth od B. Th e crude product was ch rom atograph ed in th e
system eth yl acetate–aceton e–eth an ol–water (15:3:4:3), th e product-con tain in g fraction s
were com bin ed, decolourised with active ch arcoal an d taken down . Th e pure product was
crystallized from m eth an ol. Yield 255 m g (20%), m .p. 207 °C. For C9H13N3O4 (227.2) calcu-
lated: 47.57% C, 5.77% H, 18.49% N; foun d: 47.54% C, 5.70% H, 18.45% N. FAB MS, m/z
(rel.%): 228 (100) [M + H]. 1H NMR (DMSO-d6): 7.44 d, 1 H, J(6,5) = 7.2 (H-6); 7.09 br s, 1 H
an d 7.02 br s, 1 H (NH2); 5.61 d, 1 H, J(5,6) = 7.2 (H-5); 4.28 dd, 1 H, J(2′,3′a) = 4.5, J(2′,3′b) =
8.3 (H-2′); 4.08 q, 2 H, J(CH2,CH3) = 7.1 (O-CH2); 4.06 dd, 1 H, J(3′a,2′) = 4.5, J(gem ) = 13.4
(H-3′a); 3.57 dd, 1 H, J(3′b,2′) = 8.3, J(gem ) = 13.4 (H-3′b); 1.18 t, 3 H (CH3). 13C NMR data
(DMSO-d6), see Table III.
Eth yl (S)-3-(4-Am in o-2-oxopyrim idin -1(2H)-yl)-2-h ydroxypropan oate (6b)
From oxiran e 2b by th e sam e procedure as described for 6a. Yield 410 m g (42%).1H NMR
data (DMSO-d6) iden tical with 6a.
Eth yl (R)-2-Hydroxy-3-(4-m eth oxy-5-m eth yl-2-oxopyrim idin -1(2H)-yl)propan oate (7a)
From oxiran e 2a an d 4-m eth oxy-5-m eth ylpyrim idin -2(1H)-on e by m eth od A. Ch rom atogra-
ph y in th e system eth yl acetate–aceton e–eth an ol–water (18:3:1:1) afforded 500 m g (39%) of
7a as colourless syrup, [α]D +22.0 (c 0.109, CH3OH). For C11H16N2O5 (256.3) calculated:
51.56% C, 6.29% H, 10.93% N; foun d: 51.26% C, 6.33% H, 10.99% N. FAB MS, m/z (rel.%):
257 (100) [M + H]. 1H NMR (CDCl3): 7.28 q, 1 H, J(6,CH3) = 1.0 (H-6); 4.58 dd, 1 H, J(2′,3′a) =
3.5, J(2′,3′b) = 6.8 (H-2′); 4.34 dd, 1 H, J(3′a,3′b) = 13.8, J(3′a,2′) = 3.5 (H-3′a); 4.27 m , 2 H
(O-CH2); 3.97 s, 3 H (OCH3); 3.95 dd, 1 H, J(3′b,3′a) = 13.8, J(3′b,2′) = 6.8 (H-3′b); 1.93 d, 3 H,
J(CH3,6) = 1.0 (5-CH3); 1.32 t, 3 H, J(vic) = 7.0 (CH3).
Eth yl (S)-2-Hydroxy-3-(4-m eth oxy-5-m eth yl-2-oxopyrim idin -1(2H)-yl)propan oate (7b)
From oxiran e 2b by th e sam e procedure as described for 7a. Yield 553 m g (43%), [α]D –18.8
(c 0.107, CH3OH). 1H NMR data (CDCl3) iden tical with 7a.
Eth yl 2-Hydroxy-3-(4-m eth oxy-2-oxopyrim idin -1(2H)-yl)propan oate (8)
From 4-m eth oxypyrim idin -2(1H)-on e an d oxiran e 2a by m eth od A. Ch rom atograph y in th e
system eth yl acetate–aceton e–eth an ol–water (18:3:1:1) gave 670 m g (55%) of syrupy com -
poun d 8 wh ich crystallized on stan din g overn igh t at am bien t tem perature, m .p. 135–136 °C.
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Derivatives of (R)-3-(Adenin-9-yl)-2-hydroxypropanoic Acid
943
For C10H14N2O5 (242.2) calculated: 49.58% C, 5.83% H, 11.56% N; foun d: 49.29% C, 5.77% H,
11.78% N. FAB MS, m/z (rel.%): 243 (100) [M + H]. 1H NMR (CDCl3): 7.47 d, 1 H, J(6,5) =
7.2 (H-6); 5.87 d, 1 H, J(5,6) = 7.2 (H-5); 4.55 ddd, 1 H, J(2′,3′a) = 3.7, J(2′,3′b) = 6.6, J(2′,OH) =
5.3 (H-2′); 4.35 dd, 1 H, J(3′a,3′b) = 13.6, J(3′a,2′) = 3.7 (H-3′a); 4.30 dq, 1 H, J(gem ) = 10.6,
J(vic) = 7.2 an d 4.28 dq, 1 H, J(gem ) = 10.6, J(vic) = 7.2 (O-CH2); 3.99 dd, 1 H, J(3′b,3′a) =
13.6, J(3′b,2′) = 6.6 (H-3′b); 3.96 s, 3 H (OCH3); 3.51 d, 1 H, J(OH,2′) = 5.3 (OH); 1.33 t, 3 H,
J(vic) = 7.0 (CH3).
TABLE III
13C NMR ch em ical sh ifts of com poun ds 6a an d 11–19 in DMSO-d6
Com -
poun d
C-2
C-4
C-5
C-6
C-8
–
C-3′
C-2′
C-1′ Oth er carbon s
6a
156.07 166.34
93.05 147.41
52.21
68.23 172.21 OCH2: 60.64
CH3: 14.21
11
12
151.71 152.29 130.85 149.09 148.33 47.01
145.68 148.62 123.86 156.79 141.15 46.46
68.37 173.01
–
68.84 171.58 OCH2: 60.68
CH3: 14.08
13
14
15
16
152.13 151.43 133.64 147.85 147.79 46.18
151.78 150.66 119.24 154.44 140.49 47.78
152.35 149.60 119.07 155.68 141.45 47.45
152.15 150.30 119.35 152.69 140.88 47.61
68.48 171.58 OCH2: 60.92
CH3: 14.03
70.30 174.32 NCH3: 39.70
an d 38.11
69.96 173.95 NCH: 24.13
CH2: 6.64(2)
70.15 174.00 2×NCH2: 48.50
an d 47.11
2×CH2: 25.88
an d 23.95
17
18
19
151.73 151.04 119.08 153.37 140.94 47.63
152.28 149.30 119.01 154.63 141.41 47.74
152.32 149.00 119.05 154.44 141.43 47.52
70.09 174.53 2×OCH2: 66.40
an d 64.37
2×NCH2: 45.00
an d 43.33
70.60 173.92 2×OCH2: 70.62
an d 68.65
2×NCH2: 58.23
an d 58.08
69.98 173.78 =CH: 136.09
=CH2: 115.09
NCH2: 43.00
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

944
Krečmerová, Buděšínský, Masojídková, Holý:
Eth yl (R)-3-(6-Ben zam ido-9H-purin -9-yl)-2-h ydroxypropan oate (10a)
From N6-ben zoyladen in e an d 2a by m eth od B. After ch rom atograph y in eth yl acetate an d
crystallization from m eth an ol, 10a (597 m g, 30%) was isolated as wh ite crystals, m .p. 72–
77 °C, [α]D +21.8 (c 0.313, C2H5OH). For C17H17N5O4 (355.4) calculated: 57.46% C, 4.82% H,
19.71% N; foun d: 57.01% C, 4.88% H, 19.21% N. FAB MS, m/z (rel.%): 356 (100) [M + H].
1H NMR (CDCl3): 9.38 br, 1 H (NH); 8.72 s, 1 H an d 8.11 s, 1 H (H-2, H-8); 8.00 m , 2 H,
7.46 m , 2 H an d 7.56 m , 1 H (C6H5); 4.68 dd, 1 H, J(2′,3′a) = 3.4, J(2′,3′b) = 6.8 (H-2′); 4.67 dd,
1 H, J(3′a,3′b) = 14.4, J(3′a,2′) = 3.4 (H-3′a); 4.59 dd, 1 H, J(3′b,3′a) = 14.4, J(3′b,2′) = 6.8
(H-3′b); 4.13 m , 2 H (-OCH2); 1.26 t, 3 H, J(vic) = 7.0 (CH3).
Eth yl (R)-2-Hydroxy-3-(5-m eth yl-2,4-dioxo-3,4-dih ydropyrim idin -1(2H)-yl)propan oate (9a)
5-Meth yl-2,4-bis[(trim eth ylsilyl)oxy]pyrim idin e17 (1.87 g, 6.9 m m ol) an d stan n ic ch loride
(0.5 m l, 2.7 m m ol) were added to a stirred solution of 2a (800 m g, 6.9 m m ol) in aceton itrile
(35 m l) at 0 °C un der argon . Th e m ixture was stirred at room tem perature for 3 h an d th en
set aside at 4 °C overn igh t. After dilution with ch loroform (100 m l), th e m ixture was poured
in to a saturated solution of sodium h ydrogen carbon ate (100 m l) an d filtered th rough a pad
of Celite. Th e organ ic layer was separated, th e aqueous ph ase was extracted with ch loroform
(8 × 40 m l). Th e com bin ed extracts were dried over an h ydrous m agn esium sulfate an d taken
down . Th e residue gave by ch rom atograph y on a silica gel colum n (360 m l) in th e system
eth yl acetate–aceton e–eth an ol–water (36:6:1:1) 919 m g (55%) of 9a as a syrup th at crystal-
lized after stan din g overn igh t, [α]D +26.2 (c 0.137, CH3OH). For C10H14N2O5 (242.2) calcu-
lated: 49.58% C, 5.83% H, 11.56% N; foun d: 49.57% C, 5.83% H, 11.44% N. FAB MS, m/z
(rel.%): 243 (100) [M + H]. 1H NMR (CDCl3): 8.51 br, 1 H (NH); 7.11 q, 1 H, J(6,CH3) = 1.1
(H-6); 4.46 dt, 1 H, J(2′,3′a) = 4.0, J(2′,3′b) = 6.4, J(2′,OH) = 4.0 (H-2′); 4.31 dq, 1 H, J(gem ) =
10.7, J(vic) = 7.2 an d 4.27 dq, 1 H, J(gem ) = 10.7, J(vic) = 7.2 (O-CH2); 4.14 dd, 1 H,
J(3′a,3′b) = 14.2, J(3′a,2′) = 4.0 (H-3′a); 3.91 dd, 1 H, J(3′b,3′a) = 14.2, J(3′b,2′) = 6.4 (H-3′b);
3.39 br, 1 H (OH); 1.33 t, 3 H, J(vic) = 7.0 (CH3).
(R)-3-(6-Ch loro-9H-purin -9-yl)-2-h ydroxypropan oic Acid (11)
A solution of ester 5a (1.0 g, 3.69 m m ol) in 0.5 M aqueous sodium h ydroxide solution (15 m l)
was stirred at room tem perature for 10 m in an d th en m ade weakly acidic with Dowex 50X4
(H form ). Th e resin was filtered off, th e filtrate taken down an d codistilled with absolute
eth an ol (2 × 30 m l) to give 900 m g (100%) of free acid 11 as a solid foam , [α]D +12.4
(c 0.611, C2H5OH). For C8H7ClN4O3 (242.6) calculated: 39.60% C, 2.91% H, 14.61% Cl,
23.09% N; foun d: 39.54% C, 3.16% H, 13.92% Cl, 22.44% N. FAB MS, m/z (rel.%): 243
(65) [M + H]. 1H NMR (DMSO-d6): 8.78 s, 1 H an d 8.61 s, 1 H (H-2 an d H-8); 7.00 br, 2 H
(OH + COOH); 4.60 m , 1 H an d 4.45 m , 2 H (H-3′ an d H-2′). 13C NMR data (DMSO-d6), see
Table III.
Eth yl 2-Hydroxy-3-(6-oxo-1,6-dih ydro-9H-purin -9-yl)propan oate (12)
Brom otrim eth ylsilan e (382 m g, 2.5 m m ol) was added to a solution of ester 5a (76 m g,
0.28 m m ol) in DMF un der argon . After stirrin g at room tem perature overn igh t (n o reaction
took place accordin g to TLC), potassium iodide (20 m g, 0.12 m m ol) was added an d th e stir-
rin g was con tin ued at room tem perature for 2 days followed by h eatin g at 75 °C for 8 h .
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Th e reaction m ixture was n eutralized with 2 M trieth ylam m on ium h ydrogen carbon ate an d
taken down in vacuo an d th e residue was codistilled with water (3 × 5 m l). Th e crude prod-
uct was purified by C18 reverse ph ase ch rom atograph y. After elution of salts with water, th e
product was eluted with a m eth an ol–water gradien t (0–30% m eth an ol). Product-con tain in g
fraction s were taken down an d codistilled with eth an ol to give 60 m g (85%) of 12 as wh ite
solid m aterial. 1H NMR (DMSO-d6): 12.30 br s, 1 H (=NH); 8.04 s, 1 H an d 7.99 s, 1 H (H-2,
H-8); 6.03 d, 1 H, J(OH,2′) = 5.4 (2′-OH); 4.45 m , 1 H (H-2′); 4.41 dd, 1 H, J(3′a,2′) = 4.4,
J(gem ) = 13.8 (H-3′a); 4.30 dd, 1 H, J(3′b,2′) = 7.4, J(gem ) = 13.8 (H-3′b); 4.07 m , 2 H
(O-CH2); 1.13 t, 3 H, J(vic) = 7.1 (CH3). 13C NMR data (DMSO-d6), see Table III.
Eth yl 2-Hydroxy-3-(9H-purin -9-yl)propan oate (13)
Iodotrim eth ylsilan e (0.57 m l, 4.0 m m ol) was added un der argon to a stirred suspen sion of
ester 5a (120 m g, 0.44 m m ol) in aceton itrile (4 m l). Th e resultin g solution was stirred in th e
dark at room tem perature for 12 h , th en n eutralized with 2 M solution of trieth ylam m on ium
h ydrogen carbon ate an d subsequen tly worked up as described for com poun d 12. Yield 70 m g
(67%) of 13 as a wh ite solid. 1H NMR (DMSO-d6): 9.15 s, 1 H (H-6); 8.93 s, 1 H (H-2); 8.53 s,
1 H (H-8); 6.08 d, 1 H, J(OH,2′) = 5.6 (OH); 4.56 m , 2 H an d 4.48 m , 1 H (H-3′, H-2′);
4.06 m , 2 H (O-CH2); 1.10 t, 3 H, J(vic) = 7.1 (CH3). 13C NMR data (DMSO-d6), see Table III.
3-[6-(Alkylam in o)-9H-purin -9-yl]-2-h ydroxypropan oic Acids 14–19. Gen eral Procedure
A suspen sion of ch loro com poun d 11 (400 m g, 1.65 m m ol) in aceton itrile (30 m l) was
refluxed with excess of dim eth ylam m on ium dim eth ylcarbam ate (6.0 m m ol) or appropriate
am in e (cyclopropylam in e, pyrrolidin e, m orph olin e, 2-m eth oxyeth ylam in e an d allylam in e)
(8.0 m m ol) for 30 m in . After coolin g to room tem perature, th e m ixture was taken down , th e
residue was th en codistilled with toluen e (2 × 10 m l), eth an ol (15 m l) an d applied on to a
Dowex 50 (H form , 100 m l). Th e colum n was eluted with water (1000 m l) an d th en with
2.5% aqueous am m on ia. Product-con tain in g fraction s of th e am m on ia eluate were evapo-
rated, th e residue codistilled with eth an ol (3 × 15 m l) an d dried at 50 °C in vacuo.
(R)-3-[6-(Dimethylamino)-9H-purin-9-yl]-2-hydroxypropanoic acid (14). Yield 315 m g (76%) as
a solid foam , [α]D +41.7 (c 0.532, CH3OH). HR MS (FAB): for C10H14N5O3 [M + H] calculated
252.1097, foun d 252.1076. FAB MS, m/z (rel.%): 252 (45) [M + H]. 1H NMR (DMSO-d6):
8.19 s, 1 H an d 8.05 s, 1 H (H-2, H-8); 7.40 br, 2 H (OH + COOH); 4.50 dd, 1 H, J(3′a,2′) =
3.0, J(gem ) = 13.7 (H-3′a); 4.04 dd, 1 H, J(3′b,2′) = 8.4, J(gem ) = 13.7 (H-3′b); 3.97 dd, 1 H,
J(2′,3′a) = 3.0, J(2′,3′b) = 8.4 (H-2′); 3.42 br s, 6 H (N(CH3)2). 13C NMR data (DMSO-d6), see
Table III.
(R)-3-[6-(Cyclopropylamino)-9H-purin-9-yl]-2-hydroxypropanoic acid (15). Yield 139 m g (32%)
as a solid foam , [α]D +29.8 (c 0.532, CH3OH). HR MS (FAB): for C11H14N5O3 [M + H] calcu-
lated 264.1097, foun d 264.1066. FAB MS, m/z (rel.%): 264 (40) [M + H]. 1H NMR (DMSO-d6):
8.23 s, 1 H an d 8.04 s, 1 H (H-2, H-8); 7.83 br s, 1 H (NH); 7.30 br, 2 H (OH + COOH);
4.49 m , 1 H an d 4.08 m , 2 H (H-3′, H-2′); 3.05 m , 1 H (NCH); 0.71 m , 2 H an d 0.60 m , 2 H
(2 × CH2-cyclopropyl). 13C NMR data (DMSO-d6), see Table III.
(R)-2-Hydroxy-3-(6-pyrrolidin-1-yl-9H-purin-9-yl)propanoic acid (16). Yield 407 m g (89%) as a
solid foam , [α]D +29.3 (c 1.320, CH3OH). HR MS (FAB): for C12H16N5O3 [M + H] calculated
278.1253, foun d 278.1183. FAB MS, m/z (rel.%): 278 (100) [M + H]. 1H NMR (DMSO-d6):
8.18 s, 1 H an d 8.02 s, 1 H (H-2, H-8); 7.40 br, 2 H (OH + COOH); 4.49 dd, 1 H, J(3′a,2′) =
3.0, J(gem ) = 13.6 (H-3′a); 4.03 dd, 1 H, J(3′b,2′) = 8.4, J(gem ) = 13.6 (H-3′b); 4.02 m , 2 H
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Krečmerová, Buděšínský, Masojídková, Holý:
an d 3.60 m , 2 H (2 × N-CH2); 3.97 dd, 1 H, J(2′,3′a) = 3.0, J(3′b,2′) = 8.4 (H-2′); 1.92 m , 4 H
(CH2CH2). 13C NMR data (DMSO-d6), see Table III.
(R)-2-Hydroxy-3-(6-morpholino-9H-purin-9-yl)propanoic acid (17). Th e product was isolated
as m orph olin ium salt. Yield 400 m g (64%) as a solid foam . Recrystallization from eth an ol
gave com poun d 17, m .p. 144–147 °C, [α]D +38.5 (c 0.259, C2H5OH). HR MS (FAB): for
C
12H16N5O4 [M + H] calculated 294.1202, foun d 294.1185. FAB MS, m/z (rel.%): 294 (16)
[M + H of th e free acid], 88 (100), [M + H of m orph olin e]. 1H NMR (DMSO-d6): 8.24 s, 1 H
an d 8.10 s, 1 H (H-2, H-8); 6.80 br, 2 H (OH + COOH); 4.50 dd, 1 H, J(3′a,2′) = 3.3, J(gem ) =
13.7 (H-3′a); 4.10 dd, 1 H, J(3′b,2′) = 8.3, J(gem ) = 13.7 (H-3′b); 4.00 dd, 1 H, J(2′,3′a) = 3.3,
J(2′,3′b) = 8.3 (H-2′); 4.19 m , 2 H, 3.70 t, 2 H, 3.69 t, 2 H an d 2.98 t, 2 H (2 × OCH2 an d 2 ×
NCH2, m orph olin e). 13C NMR data (DMSO-d6), see Table III.
(R)-2-Hydroxy-3-{6-[(2-methoxyethyl)amino]-9H-purin-9-yl}propanoic acid (18). Th e product
was isolated as 2-m eth oxyeth ylam m on ium salt. Yield 418 m g (59%), am orph ous m aterial,
[α]D +31.5 (c 0.545, CH3OH). HR MS (FAB): for C11H16N5O4 [M + H] calculated 282.1202,
foun d 282.1235. FAB MS, m/z (rel.%): 282 (70) [M + H of th e free acid], 76 (100) [M + H of
2-m eth oxyeth ylam in e). 1H NMR (DMSO-d6): 8.20 s, 1 H an d 8.04 s, 1 H (H-2, H-8); 7.56 br s,
1 H (NH); 7.00 br, 2 H (OH + COOH); 4.48 dd, 1 H, J(3′a,2′) = 2.9, J(gem ) = 13.7 (H-3′a);
4.03 dd, 1 H, J(3′b,2′) = 8.4, J(gem ) = 13.7 (H-3′b); 3.93 dd, 1 H, J(2′,3′a) = 2.9, J(2′,3′b) = 8.4
(H-2′); 3.64 m , 2 H, 3.51 t, 2 H, 3.50 t, 2 H an d 2.95 t, 2 H (2 × NCH2-CH2O); 3.51 s, 3 H
an d 3.50 s, 3 H (2 × OCH3). 13C NMR data (DMSO-d6), see Table III.
(R)-3-[6-(Allylamino)-9H-purin-9-yl]-2-hydroxypropanoic acid (19). Yield 308 m g (71%) as a
solid foam , [α]D +36.0 (c 0.434, CH3OH). HR MS (FAB): for C11H14N5O3 [M + H] calculated
264.1097, foun d 264.1115. FAB MS, m/z (rel.%): 264 (100) [M + H]. 1H NMR (DMSO-d6):
8.19 s, 1 H an d 8.05 s, 1 H (H-2, H-8); 7.85 br s, 1 H (NH); 7.20 br, 1 H (OH); 5.95 ddt, 1 H,
J(2′′,1′′) = 5.1, J(2′′,3′′a) = 10.3, J(2′′,3′′b) = 17.2 (H-2′′); 5.15 dq, 1 H, J(3′′b,1′′) = J(gem ) = 1.8,
J(3′′b,2′′) = 17.2 (H-3′′b); 5.04 dq, 1 H, J(3′′a,1′′) = 1.6, J(3′′a,2′′) = 10.3, J(gem ) = 1.8 (H-3′′a);
4.48 dd, 1 H, J(3′a,2′) = 2.7, J(gem ) = 13.2 (H-3′a); 4.15 m , 2 H (H-1′′); 4.07 dd, 1 H, J(3′b,2′) =
8.6, J(gem ) = 13.2 (H-3′b); 4.02 dd, 1 H, J(2′,3′a) = 2.7, J(2′,3′b) = 8.6 (H-2′). 13C NMR data
(DMSO-d6), see Table III.
Eth yl 3-(6-Ben zam ido-9H-purin -9-yl)-2-(ben zoyloxy)propan oate (20)
Ben zoyl ch loride (0.03 m l, 0.25 m m ol) was added to a solution of com poun d 4 (28 m g,
0.11 m m ol) in pyridin e (1 m l). Th e m ixture was set aside overn igh t at room tem perature,
eth an ol (1 m l) was added an d th e m ixture taken down . Th e residue was partition ed between
water (10 m l) an d eth yl acetate (2 × 10 m l), th e organ ic extracts were dried over an h ydrous
sodium sulfate an d taken down . Th e residue was ch rom atograph ed on a colum n of silica gel
(20 m l) in th e system toluen e–eth yl acetate 3:2. Yield 35 m g (69%) as colourless oil.
1H NMR (CDCl3): 8.63 s, 1 H an d 8.22 s, 1 H (H-2, H-8); 7.20–8.10 m , 10 H (2 × C6H5);
5.70 dd, 1 H, J(2′,3′a) = 4.5, J(2′,3′b) = 5.6 (H-2′); 4.91 dd, 1 H, J(3′a,3′b) = 14.7, J(3′a,2′) =
4.5 (H-3′a); 4.88 dd, 1 H, J(3′b,3′a) = 14.7, J(3′b,2′) = 5.6 (H-3′b); 4.22 dq, 1 H, J(gem ) =
10.7, J(vic) = 7.2 an d 4.20 dq, 1 H, J(gem ) = 10.7, J(vic) = 7.2 (OCH2); 1.22 t, 3 H, J(vic) =
7.2 (CH3).
Acetylation of Com poun ds 6 an d 10
Acetic an h ydride (51 m g, 0.5 m m ol) an d 4-(dim eth ylam in o)pyridin e (5 m g, 0.04 m m ol)
were added to a suspen sion of 6a, 6b or 10a (0.22 m m ol) in aceton itrile (3 m l). Th e reaction
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Derivatives of (R)-3-(Adenin-9-yl)-2-hydroxypropanoic Acid
947
m ixture was stirred at room tem perature for 2 h , th en diluted with eth an ol (1 m l) an d taken
down . Th e residue was ch rom atograph ed on a colum n of silica gel (20 m l) in system eth yl
acetate–aceton e–eth an ol–water (18:3:1:1).
Ethyl (R)-3-(4-acetamido-2-oxopyrimidin-1(2H)-yl)-2-acetoxypropanoate (21a). From 6a, yield
35 m g (51%) as a solid foam . FAB MS, m/z (rel.%): 312 (100) [M + H]. 1H NMR (CDCl3):
9.54 bs, 1 H (NH); 7.59 d, 1 H, J(6,5) = 7.4 (H-6); 7.42 d, 1 H, J(5,6) = 7.4 (H-5); 5.39 dd,
1 H, J(2′,3′a) = 4.1, J(2′,3′b) = 7.9 (H-2′); 4.52 dd, 1 H, J(3′a,3′b) = 13.9, J(3′a,2′) = 4.1 (H-3′a);
4.26 dq, 1 H, J(gem ) = 10.7, J(vic) = 7.2 an d 4.23 dq, 1 H, J(gem ) = 10.7, J(vic) = 7.2 (O-CH2);
4.08 dd, 1 H, J(3′b,3′a) = 13.9, J(3′b,2′) = 7.9 (H-3′b); 2.28 s, 3 H (N-CO-CH3); 2.12 s, 3 H
(O-CO-CH3); 1.30 t, 3 H, J(vic) = 7.2 (CH3).
Ethyl (S)-3-(4-acetamido-2-oxopyrimidin-1(2H)-yl)-2-acetoxypropanoate (21b). From 6b, yield
41 m g (60%) as a solid foam . FAB MS, m/z (rel.%): 312 (100) [M + H]. 1H NMR (CDCl3):
9.54 bs, 1 H (NH); 7.61 d, 1 H, J(6,5) = 7.4 (H-6); 7.45 d, 1 H, J(5,6) = 7.4 (H-5); 5.39 dd,
1 H, J(2′,3′a) = 4.1, J(2′,3′b) = 8.0 (H-2′); 4.52 dd, 1 H, J(3′a,3′b) = 13.8, J(3′a,2′) = 4.1 (H-3′a);
4.25 dq, 1 H, J(gem ) = 10.7, J(vic) = 7.2 an d 4.22 dq, 1 H, J(gem ) = 10.7, J(vic) = 7.2 (O-CH2);
4.09 dd, 1 H, J(3′b,3′a) = 13.8, J(3′b,2′) = 8.0 (H-3′b); 2.30 s, 3 H (N-CO-CH3); 2.12 s, 3 H
(O-CO-CH3); 1.29 t, 3 H, J(vic) = 7.2 (CH3).
Ethyl (R)-2-acetoxy-3-(6-benzamido-9H-purin-9-yl)propanoate (22a). From 10a, yield 63 m g
(72%) as a solid foam . FAB MS, m/z (rel.%): 398 (47) [M + H], 105 (100) [M+ ben zoyl].
1H NMR (CDCl3): 9.06 bs, 1 H (NH); 8.80 s, 1 H an d 8.08 s, 1 H (H-2, H-8); 8.03 m , 2 H,
7.61 m , 1 H an d 7.53 m , 2 H (C6H5); 5.47 dd, 1 H, J(2′,3′a) = 4.2, J(2′,3′b) = 6.3 (H-2′);
4.80 dd, 1 H, J(3′a,3′b) = 15.7, J(3′a,2′) = 4.2 (H-3′a); 4.74 dd, 1 H, J(3′b,3′a) = 15.7, J(3′b,2′) =
6.3 (H-3′b); 4.21 m , 2 H (OCH2); 2.12 s, 3 H (O-CO-CH3); 1.26 t, 3 H, J(vic) = 7.2 (CH3).
Esterification of Com poun ds 14–19. Gen eral Procedure
Lith ium h ydroxide m on oh ydrate (8.4 m g, 0.2 m m ol) was added to a solution of carboxylic
acid 14–19 (0.2 m m ol) in absolute m eth an ol (5 m l), th e solution taken down an d th e resi-
due codistilled with DMF (2 × 5 m l). DMF (5 m l) an d m eth yl iodide (0.03 m l, 0.5 m m ol) or
dieth yl sulfate (0.06 m l, 0.5 m m ol) were added an d th e reaction m ixture stirred at room
tem perature for 2–12 h . Th e reaction course was m on itored by TLC in system eth yl acetate–
aceton e–eth an ol–water (15:3:4:3). Acetic acid (on e drop) was added, th e reaction m ixture
taken down an d th e residue codistilled with xylen e (4 m l). Th e crude m ixtures of dim eth yl
an d m on om eth yl derivatives (23 an d 24, 25 an d 26, 31 an d 32, 33 an d 34) an d m ixtures of
dieth yl an d m on oeth yl derivatives (27 an d 28, 29 an d 30) were separated on a colum n of
silica gel (20 m l) in system eth yl acetate–aceton e–eth an ol–water (18:3:1:1). In all cases
2-alkoxy esters (23, 25, 27, 29, 31 an d 33) were eluted first.
Methyl (R)-3-[6-(dimethylamino)-9H-purin-9-yl]-2-methoxypropanoate (23). Yield 15 m g (27%)
as a colourless oil. FAB MS, m/z (rel.%): 280 (100) [M + H]. 1H NMR (CDCl3): 8.35 s, 1 H an d
7.80 s, 1 H (H-2, H-8); 4.63 dd, 1 H, J(3′a,3′b) = 14.4, J(3′a,2′) = 3.7 (H-3′a); 4.34 dd, 1 H,
J(3′b,3′a) = 14.4, J(3′b,2′) = 7.9 (H-3′b); 4.17 dd, 1 H, J(2′,3′a) = 3.7, J(2′,3′b) = 7.9 (H-2′);
3.77 s, 3 H (COOCH3); 3.54 vb, 6 H (N(CH3)2); 3.39 s, 3 H (OCH3).
Methyl (R)-3-[6-(dimethylamino)-9H-purin-9-yl]-2-hydroxypropanoate (24). Yield 26 m g (49%)
as a wh ite solid. FAB MS, m/z (rel.%): 266 (55) [M + H]. 1H NMR (CDCl3): 8.31 s, 1 H an d
7.74 s, 1 H (H-2, H-8); 5.20 vb, 1 H (OH); 4.64 dd, 1 H, J(2′,3′a) = 3.8, J(2′,3′b) = 4.7 (H-2′);
4.56 m , 2 H (H-3′a, H-3′b); 3.73 s, 3 H (COOCH3); 3.52 vb, 6 H (N(CH3)2).
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Krečmerová, Buděšínský, Masojídková, Holý:
Methyl (R)-3-[6-(cyclopropylamino)-9H-purin-9-yl]-2-methoxypropanoate (25). Yield 13 m g
(22%) as a colourless oil. FAB MS, m/z (rel.%): 292 (100) [M + H]. 1H NMR (CDCl3): 8.49 s,
1 H an d 7.73 s, 1 H (H-2, H-8); 4.62 dd, 1 H, J(3′a,3′b) = 14.4, J(3′a,2′) = 3.6 (H-3′a); 4.37 dd,
1 H, J(3′b,3′a) = 14.4, J(3′b,2′) = 7.7 (H-3′b); 4.17 dd, 1 H, J(2′,3′a) = 3.6, J(2′,3′b) = 7.7 (H-2′);
3.77 s, 3 H (COOCH3); 3.40 s, 3 H (OCH3); 3.05 b, 1 H, 0.93 m , 2 H an d 0.67 m , 2 H
(cyclopropyl); 2.10 vb, 1 H (NH).
Methyl (R)-3-[6-(cyclopropylamino)-9H-purin-9-yl]-2-hydroxypropanoate (26). Yield 26 m g
(47%) as a wh ite solid. FAB MS, m/z (rel.%): 278 (62) [M + H]. 1H NMR (CDCl3): 8.41 s, 1 H
an d 7.72 s, 1 H (H-2, H-8); 6.16 bs, 1 H an d 5.39 b, 1 H (NH an d OH); 4.64 dd, 1 H,
J(3′a,3′b) = 15.8, J(3′a,2′) = 4.3 (H-3′a); 4.63 m , 1 H (H-2′); 4.50 dd, 1 H, J(3′b,3′a) = 15.8,
J(3′b,2′) = 5.4 (H-3′b); 3.84 s, 3 H (COOCH3); 2.96 b, 1 H, 0.89 m , 2 H, 0.70 m , 1 H an d
0.67 m , 1 H (cyclopropyl).
Ethyl (R)-2-ethoxy-3-(6-pyrrolidin-1-yl-9H-purin-9-yl)propanoate (27). Yield 15 m g (23%) as a
colourless oil. 1H NMR (CDCl3): 8.36 s, 1 H an d 7.84 s, 1 H (H-2, H-8); 4.64 dd, 1 H,
J(3′a,3′b) = 14.2, J(3′a,2′) = 3.6 (H-3′a); 4.32 dd, 1 H, J(3′b,3′a) = 14.2, J(3′b,2′) = 8.4 (H-3′b);
4.23 dd, 1 H, J(2′,3′a) = 3.6, J(2′,3′b) = 8.4 (H-2′); 4.23 q, 2 H, J(vic) = 7.0 (COOCH2CH3);
4.20 um , 2 H, 3.75 um , 2 H an d 2.04 um , 4 H (pyrrolidin e); 3.71 dq, 1 H, J(gem ) = 9.0,
J(vic) = 7.0 an d 3.34 dq, 1 H, J(gem ) = 9.0, J(vic) = 7.0 (OCH2CH3); 1.28 t, 3 H, J(vic) = 7.0
(COOCH2CH3); 1.13 t, 3 H, J(vic) = 7.0 (OCH2CH3).
Ethyl (R)-2-hydroxy-3-(6-pyrrolidin-1-yl-9H-purin-9-yl)propanoate (28). Yield 29 m g (47%) as a
wh ite solid m aterial. FAB MS, m/z (rel.%): 306 (100) [M + H]. 1H NMR (CDCl3): 8.31 s, 1 H
an d 7.84 s, 1 H (H-2, H-8); 4.63 dd, 1 H, J(2′,3′a) = 3.8, J(2′,3′b) = 4.8 (H-2′); 4.55 m , 2 H
(H-3′a, H-3′b); 4.17 m , 2 H (O-CH2); 4.15 um , 2 H, 3.75 um , 2 H an d 2.05 um , 4 H
(pyrrolidin e); 1.22 t, 3 H, J(vic) = 7.0 (CH3).
Ethyl (R)-2-ethoxy-3-(6-morpholino-9H-purin-9-yl)propanoate (29). Yield 15 m g (21%) as a
colourless oil. FAB MS, m/z (rel.%): 350 (100) [M + H]. 1H NMR (CDCl3): 8.36 s, 1 H an d
7.86 s, 1 H (H-2, H-8); 4.65 dd, 1 H, J(3′a,3′b) = 14.2, J(3′a,2′) = 3.6 (H-3′a); 4.33 dd, 1 H,
J(3′b,3′a) = 14.2, J(3′b,2′) = 8.2 (H-3′b); 4.30 m , 4 H an d 3.84 m , 4 H (m orph olin e); 4.22 dd,
1 H, J(2′,3′a) = 3.6, J(2′,3′b) = 8.2 (H-2′); 4.22 q, 2 H, J(vic) = 7.2 (COOCH2CH3); 3.71 dq,
1 H, J(gem ) = 9.0, J(vic) = 7.0 an d 3.35 dq, 1 H, J(gem ) = 9.0, J(vic) = 7.0 (OCH2CH3); 1.28 t,
3 H, J(vic) = 7.2 (COOCH2CH3); 1.14 t, 3 H, J(vic) = 7.0 (OCH2CH3).
Ethyl (R)-2-hydroxy-3-(6-morpholino-9H-purin-9-yl)propanoate (30). Yield 31 m g (48%) as a
wh ite solid. FAB MS, m/z (rel.%): 322 (100) [M + H]. 1H NMR (CDCl3): 8.32 s, 1 H an d
7.78 s, 1 H (H-2, H-8); 4.61 dd, 1 H, J(2′,3′a) = 3.7, J(2′,3′b) = 5.0 (H-2′); 4.56 m , 2 H (H-3′a,
H-3′b); 4.30 m , 4 H an d 3.83 m , 4 H (m orph olin e); 4.20 dq, 1 H, J(gem ) = 10.8, J(vic) = 7.1
an d 4.16 dq, 1 H, J(gem ) = 10.8, J(vic) = 7.1 (OCH2); 1.24 t, 3 H, J(vic) = 7.1 (CH3).
Methyl (R)-2-methoxy-3-{6-[(2-methoxyethyl)amino]-9H-purin-9-yl}propanoate (31). Yield 5 m g
(8%) as a colourless oil. 1H NMR (CDCl3): 8.36 s, 1 H an d 7.80 s, 1 H (H-2, H-8); 4.62 dd,
1 H, J(3′a,3′b) = 14.3, J(3′a,2′) = 3.6 (H-3′a); 4.33 dd, 1 H, J(3′b,3′a) = 14.3, J(3′b,2′) = 7.9
(H-3′b); 4.25 bs, 1 H (NH); 4.17 dd, 1 H, J(2′,3′a) = 3.6, J(2′,3′b) = 7.9 (H-2′); 3.78 s, 3 H
(COOCH3); 3.71 t, 2 H, J(vic) = 5.5 (OCH2); 3.55 um , 2 H (N-CH2); 3.39 s, 3 H (O-CH3);
3.37 s, 3 H (OCH3).
Methyl (R)-3-[6-(allylamino)-9H-purin-9-yl]-2-methoxypropanoate (32). Yield 17 m g (29%) as a
wh ite solid m aterial. FAB MS, m/z (rel.%): 291 (52) [M+], 276 (100) [M – CH3]. 1H NMR
(CDCl3): 8.41 s, 1 H an d 7.84 s, 1 H (H-2, H-8); 6.10 bt, 1 H, J(NH,CH2) = 5.5 (NH); 6.02 m ,
1 H, 5.31 dq, 1 H an d 5.19 dq, 1 H (CH=CH2); 4.63 dd, 1 H, J(3′a,3′b) = 14.4, J(3′a,2′) = 3.6
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(H-3′a); 4.37 dd, 1 H, J(3′b,3′a) = 14.4, J(3′b,2′) = 7.8 (H-3′b); 4.33 m , 1 H (NCH2); 4.18 dd,
1 H, J(2′,3′a) = 3.6, J(2′,3′b) = 7.8 (H-2′); 3.77 s, 3 H (COOCH3); 3.40 s, 3 H (OCH3).
Methyl (R)-3-[6-(allylamino)-9H-purin-9-yl]-2-hydroxypropanoate (33). Yield 16 m g (29%) as a
wh ite solid m aterial. FAB MS, m/z (rel.%): 277 (30) [M+], 262 (55) [M – CH3]. 1H NMR
(CDCl3): 8.33 s, 1 H an d 7.53 s, 1 H (H-2, H-8); 6.18 b, 1 H (NH); 5.99 m , 1 H, 5.28 dq, 1 H
an d 5.18 dq, 1 H (CH=CH2); 5.45 b, 1 H (OH); 4.64 dd, 1 H, J(2′,3′a) = 4.7, J(2′,3′b) = 3.5
(H-2′); 4.61 dd, 1 H, J(3′a,3′b) = 14.1, J(3′a,2′) = 4.7 (H-3′a); 4.52 dd, 1 H, J(3′b,3′a) = 14.1,
J(3′b,2′) = 3.5 (H-3′b); 4.26 b, 1 H an d 4.18 b, 1 H (NCH2); 3.80 s, 3 H (COOCH3).
(R)-1-[(6-Ch loro-9H-purin -9-yl)m eth yl]-2-eth oxy-2-oxoeth yl
(R)-3,3,3-Trifluoro-2-m eth oxy-2-ph en ylpropan oate (34)
(+)-(R)-2-Meth oxy-3,3,3-trifluoro-2-ph en ylpropan oic acid (8 m g, 0.034 m m ol), dicycloh exyl-
carbodiim ide (7 m g, 0.034 m m ol) an d 4-(dim eth ylam in o)pyridin e (0.5 m g, 0.004 m m ol)
were added to a solution of 5a (9 m g, 0.034 m m ol) in dich lorom eth an e (0.1 m l). Th e reac-
tion m ixture was stirred at room tem petature for 2 h an d th en taken down . Th e residue was
applied on to a colum n of silica gel (5 m l) an d ch rom atograph ed in system petroleth er–eth yl
acetate 1:1. Yield 11 m g (66%) as a colourless oil. 1H NMR (CDCl3): 8.70 s, 1 H (H-2); 7.82 s,
1 H (H-8); 7.31–7.44 m , 5 H (C6H5); 5.66 dd, 1 H, J(2′,3′a) = 6.8, J(2′,3′b) = 3.6 (H-2′);
4.83 dd, 1 H, J(3′a,3′b) = 15.0, J(3′a,2′) = 6.8 (H-3′a); 4.67 dd, 1 H, J(3′b,3′a) = 15.0, J(3′b,2′) =
3.6 (H-3′b); 4.24 m , 2 H (OCH2CH3); 3.59 q, 3 H, J(OCH3,F) = 1.3 (OCH3); 1.28 t, 3 H, J(vic) =
7.0 (OCH2CH3).
(R)-1-[(6-Ch loro-9H-purin -9-yl)m eth yl]-2-eth oxy-2-oxoeth yl
(S)-3,3,3-Trifluoro-2-m eth oxy-2-ph en ylpropan oate (35)
Th is com poun d was prepared from 5a (9 m g, 0.034 m m ol) an d (–)-(S)-2-m eth oxy-3,3,3-tri-
fluoro-2-ph en ylpropan oic acid by th e sam e m an n er as described for 34. Yield 12 m g (73%)
as a colourless oil. 1H NMR (CDCl3): 8.73 s, 1 H (H-2); 8.00 s, 1 H (H-8); 7.34–7.45 m , 5 H
(C6H5); 5.65 dd, 1 H, J(2′,3′a) = 6.0, J(2′,3′b) = 4.7 (H-2′); 4.84 dd, 1 H, J(3′a,3′b) = 15.0,
J(3′a,2′) = 6.0 (H-3′a); 4.81 dd, 1 H, J(3′b,3′a) = 15.0, J(3′b,2′) = 4.7 (H-3′b); 4.22 m , 2 H
(OCH2CH3); 3.39 q, 3 H, J(OCH3,F) = 1.2 (OCH3); 1.25 t, 3 H, J(vic) = 7.0 (OCH2CH3).
This study is a part of research project Z4 055 905 of the Institute of Organic Chemistry and Bio-
chemistry. It was supported by the programme of targeted projects of the Academy of Sciences of the
Czech Republic (No. S4055109) and by the COST programme of the Ministry of Education, Youth and
Sports of the Czech Republic (D.13.20).
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