The chemical resolution of racemic CIS-2-hydroxymethyl-5-(Cytosine-1′-YL)-1,3-oxathiolane (BCH-189) - One direct method to obtain lamivudine as anti-HIV and anti-HBV agent

Article abstract of DOI:10.1081/SCC-120006006

Racemic cis-BCH-189 can be resolved to (-)-enantiomer (lamivudine) and (+)-enantiomer by esterification of cis-2-hydroxymethyl-5-(N′₄-acetylcyto sine-1′-yl)-1,3-oxathiolane and (+)-menthyl chloroformate in CH₃CN with pyridine as base. The two diastereomers of ester were seperated by recrystallization in methanol at 0°C. Lamivudine was obtained by deprotection of (-)-diastereomer with high yield.

Full text of DOI:10.1081/SCC-120006006

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SYNTHETIC COMMUNICATIONS
Vol. 32, No. 15, pp. 2355–2359, 2002
THE CHEMICAL RESOLUTION OF
RACEMIC CIS-2-HYDROXYMETHYL-5-
0
(
CYTOSINE-1 -YL)-1,3-OXATHIOLANE
(BCH-189)—ONE DIRECT METHOD
TO OBTAIN LAMIVUDINE AS ANTI-HIV
AND ANTI-HBV AGENT
Ji-zhen Li,* Lian-xun Gao, and Meng-xian Ding
State Key Laboratory of
Polymer Physics and Chemistry, Changchun Institute of
Applied Chemistry, Chinese Academy of Sciences,
ChangChun 130022, China
ABSTRACT
Racemic cis-BCH-189 can be resolved to (À)-enantiomer
(
hydroxymethyl-5-(N -acetylcytosine-1 -yl)-1,3-oxathiolane and
lamivudine) and (þ)-enantiomer by esterification of cis-2-
0 0
4
(
base. The two diastereomers of ester were seperated by recrys-
þ)-menthyl chloroformate in CH CN with pyridine as
3
ꢀ
tallization in methanol at 0 C. Lamivudine was obtained by
deprotection of (À)-diastereomer with high yield.
*
Corresponding author. E-mail: lijizhen11@yahoo.com
2
355
DOI: 10.1081/SCC-120006006
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356
LI, GAO, AND DING
-Hydroxymethyl-5-(cytosine-1 -yl)-1,3-oxathiolane (BCH-189) has
potential biological activity as anti-HIV and anti-HBV agent, among the
0
2
four enantiomers, the b-L-(À)-enantiomer (lamivudine) is considerably less
[
1,2]
toxic than other three corresponding ones.
of optical resolution of cis-BCH-189 by biological enzyme using such as
Numerous efficient methods
[
3,4]
specially Mucor miehei lipase etc. have been reported.
However, these
multistep procedures are time consuming and proceed in low yields or low
enantiomer purity.
In this article, we report a new, inexpensive, practical, and efficient
method for the resolution of racemic cis-BCH-189, (À)-camphanic acid
chloride and (þ)-menthyl chloroformate were chosen as resolving agents.
We found that the former almost has no effect for the resolution but the
latter is an excellent resolving agent for resolution of racemic cis-BCH-189
in the solvent of methanol.
The NH group of racemic cis-BCH-189 was firstly protected by acety-
2
lation using the equivalent molar Ac O in DMF at room temperature to
2
afford the corresponding N -acetyl-BCH-189 (2) in 95% chemical yield as
4
shown in Scheme 1. Racemic compound 2 reacts with (þ)-menthyl chloro-
formate in presence of 3 equivalent molar pyridine to give a mixture of two
diastereomers of (À)-3a and (þ)-3b. Complete seperation of the two diaste-
ꢀ
reomers was achieved in a single recrystallization from methanol at 0 C. The
(
lized by concentration of the mother liquor followed by cooling to 0 C for one
À)-3a crystallized firstly in needle form, the diastereoisomer (þ)-3b crystal-
ꢀ
day. After deprotection of (À)-3a and (þ)-3b, the enantiomers of (À)-1a
(
ively, from 1 as shown in Scheme 2. The specific rotation of lamivudine thus
lamivudine) and (þ)-1b were obtained with yield 45.7 and 73.6%, respect-
2
D
0
ꢀ
obtained was ½aꢁ À 137 (c 0.21, MeOH), comparing with that reported in
2
D
2
ꢀ
[5]
21
D
ꢀ
literatures showing ½aꢁ À 135 (c 1.01, MeOH) and ½aꢁ À 135 (c 0.38,
[6]
MeOH) in 96% ee, the lamivudine obtained in this word should have the
2
D
0
ꢀ
optical purity>97% and (þ)-enantiomer ½aꢁ +34:1 (c 0.20, MeOH) should
have the optical purity only 29% relative to lamivudine.
Scheme 1.

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LAMIVUDINE AS ANTI-HIV AND ANTI-HBV AGENT
2357
Scheme 2.
In conclusion, the present work offers a simpler resolution method of
racemic cis-BCH-189 to enantiomerically pure lamivudine. So, it is
conveniently to prepare multi-gram quantities of this important nucleoside
analogue.
EXPERIMENTAL SECTION
Measurements and Materials
1
H-NMR spectra were recorded on a VARIAN UNITY 400. The
chemical values ꢀ were expressed in ppm relative to tetramethylsilane.
Elemental analysis were performed using Vario EL apparatus. The melting
points were determined on a RY-1 apparatus and were uncorrected. The
optical rotation readings were obtained on a 341LC polarimeter. All sol-
vents used in reactions dried and distilled before use according to standard
procedures. (þ)-Menthyl chloroformate was bought from ACROS. Cis-
[
7]
BCH-189 was synthesized in our laboratory according to the literature.
0
0
Preparation of cis-2-Hydroxymethyl-5-(N -acetylcytosine-1 -yl)-
1
4
,3-oxathiolane (2)
Ac O (0.1 mL) was added drop by drop to 1 (0.229 g, 1.0 mmol) in
2
anhydrous DMF (10 mL) with stiring at room temperature under N2

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2
358
LI, GAO, AND DING
protection, the mixture was kept over night. Then, solvent evaporated under
vacuo and toluene (5 mL) was added to the mixture and evaporated under
the same conditions. The product was obtained by silica gel column chro-
matography using EtOAc and MeOH (5 : 1) as eluent yielding white powder
ꢀ
1
0
3
5
.26 g, yield 95%. M.p. 164 C (dec). H-NMR (DMSO) ꢀ: 2.21 (s, 3H),
.30–3.33 (dd, 1H), 3.65–3.69 (dd, 1H), 3.92–3.95 (m, 2H), 5.37 (t, 1H),
.56 (t, 1H), 6.32(t, 1H), 7.31 (d, 1H), 8.51 (d, 1H), 11.01 (s, 1H). Anal.
calcd for C H O N S: C, 44.28; H, 4.80; N, 15.50; S, 11.81; Found: C,
4
1
0
13
3
44.35; H, 4.91; N, 15.40; S, 11.75.
Preparation of Diasteromerically Pure Menthyl Esters (3)
(
solution of 2 (3.70 g, 13.6 mmol) in CH CN (100 mL) and pyridine
þ)-Menthyl chloroformate (3 mL, 13.6 mmol) was dripped to the
3
ꢀ
(3.5 mL, 40 mmol) with stirring at 0 C under N , then kept for 48 h.
Removal of the solvent under vacuo condition gave the light yellow residue,
2
purified through silica gel column with ethyl acetate as eluent to afford white
1
solid (ꢂ)-3 4.50 g in a 73% chemical yield. H-NMR (CDCl ) ꢀ: 0.78 (d,
3
3H), 0.81 (d, 3H), 0.91 (d, 3H), 0.86–2.06 (m, 10H), 2.28 (s, 3H), 3.19–3.23
(
dd, 1H), 3.61–3.65 (dd, 1H), 4.51–4.65 (m, 2H), 5.41 (s, 1H), 6.34 (s, 1H),
7.46 (dd,1H), 8.22 (dd, 1H), 9.47 (s, 1H). Anal. calcd for C H O N S: C,
21 31 6 3
55.60; H, 6.84; N, 9.27; S, 7.06; Found: C, 55.41; H, 6.50; N 9.18; S, 7.32.
Preparation of Diasteromers of (R)-3a and (Q)-3b
Menthyl esters (ꢂ)-3 (4.50 g) in methanol (100 mL) refluxed for 0.5 h
under N and then kept in refrigerator for one day, filtered, and the solid
2
was recrystallized from methanol (50 mL) two times, the (À)-3a was
obtained as white needle crystals 1.56 g, theory yield 50.6%. M.p.
ꢀ
20
D
ꢀ
1
86–188 C. ½aꢁ À 12:5 (c 0.01, CHCl ).
3
All the filtrate were collected and concentrated to a quarter volume,
and cooled at 0 C, white solid (þ)-3b was obtained 2.51 g, theory yield
ꢀ
ꢀ
20
ꢀ
8
1.5%. M.p. 136–138 C. ½aꢁ +56:3 (c 0.01, CHCl ).
D
3
Preparation of the Enantiomers of (R)-1a (Lamivudine) and (Q)-1b
A mixture of (À)-3a (0.6 g, 1.32mmol) and K CO (0.54 g, 3.97 mmol)
2
3
ꢀ
in MeOH (50 mL) was stirred at 0 C for about 10 h. The resulting clear
solution was filtered and after solvent evaporation, the product was purified

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LAMIVUDINE AS ANTI-HIV AND ANTI-HBV AGENT
2359
by silica gel column chromatography with EtOAc and MeOH (6 : 1) as
ꢀ
eluent yielding white solid 0.29 g, yield 95%. M.p. 156 C (dec).
ꢀ
2
D
0
1
½
aꢁ À 137 (c 0.21, MeOH). H-NMR (DMSO) ꢀ: 3.01–3.05 (dd, 1H),
3
1
.32–3.42 (dd, 1H), 3.70–3.74 (m, 2H), 5.16 (t, 1H), 5.29 (t, 1H), 5.73 (dd,
H), 6.20 (t, 1H), 7.17–7.22 (dd, 2H), 7.81 (dd, 1H). Anal. calcd for
C H O N S: C, 41.91; H, 4.84; N, 18.33; S, 13.99. Found: C, 41.81; H,
8
11
3
3
4
.98; N, 18.25; S, 13.72.
(
þ)-3b was deprotected according to the above method to afford white
ꢀ
20
D
ꢀ
solid (þ)-1b also in 95% yield. M.p. 153 C (dec). [a]
þ 34.1 (c 0.20,
1
MeOH), optical purity 29%. H-NMR (DMSO) ꢀ: 3.01–3.05 (dd, 1H),
3
1
.32–3.42 (dd, 1H), 3.70–3.74 (m, 2H), 5.16 (t, 1H), 5.29 (t, 1H), 5.73 (dd,
H), 6.20 (t, 1H), 7.17–7.22 (dd, 2H), 7.81 (dd, 1H). Anal. calcd for
C H O N S: C, 41.91; H, 4.84; N, 18.33; S, 13.99. Found: C, 41.85; H,
8
11
3
3
4.78; N, 18.25; S, 14.11.
REFERENCES
1
2
. Coates, J.A.V.; Cammack, N.; Jenkinson, H.J.; Mutton, I.M.;
Pearson, B.A.; Storer, R.; Cameron, J.M.; Penn, C.R. Antimicrob.
Agent Chemother 1992, 36, 733.
. Chung K. Chu; Warren Beach, J.; Lak S. Jeong; Bo G. Choi; Frank i.
Comer; Antonio J. Alves; Raymond F. Schinazi. J. Org. Chem. 1991,
56, 6503–6505.
3
4
5
6
7
. Rick, P.C. Cousins; Mahmoud Mahmoudian; Peter M. Youds.
Tetrahedron: Asymmetry 1995, 6(2), 393–396.
. John Milton; Stephen Brand; Martin F. Jones; Christopher M. Rayner.
Tetrahedron: Asymmetry 1995, 6(8), 1903–1906.
. Haolun Jin; Arshad Siddiqui, M.; Colleen, A. Evans; Allan Tse, H.L.;
Tarek S. Mansour. J. Org. Chem. 1995, 60, 2621–2623.
. David C. Humber; Martin F. Jones; Jeremy, J. payne; Michael V.J.
Ramsay. Tetrahedron Letters 1992, 33(32), 4625–4628.
. Ji-zhen Li; Xue-peng Qiu; Lian-xun Gao; Meng-xian Ding. Chinese
Chemical Letters 2001, 12(6), 487–488.
Received in Japan March 20, 2001

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