Anomalously coupled nucleosides, I tributylammonium phosphates in chloroform for direct coupling of...

J. Andersen and E . B. Pedrrsen 1837

Liebigs Ann. Chcm. 1986, 1837 - 1846

Anomalously Coupled Nucleosides, I

Tributylammonium Phosphates in Chloroform for Direct Coupling of 2-Deoxy-~-ribose with N6-Substituted Adenines

Jesper Andersen and Erik B. Pedersen * Department of Chemistry, Odense University, Campusvej 55, DK-5230 Odense M, Denmark

Received April 11, 1986

Phosphorus pentoxide reacts with water and tributylamine in chloroform to give a homo- geneous solution of tributylammonium phosphate, pyrophosphate, and trimetaphosphate. 3-(9-Adenyl)-2,3-dideoxy-~-threo-pentopyranoses 3 precipitate on treatment of 2-deoxy-~- ribose (2) with N6-substituted adenines 1 in this solution at 40°C after 7 days.

Ungewohnlich verknupfte Nucleoside, I. - Tributylammonium-phosphate in Chloroform zur direkten Verkniipfung von 2-Desoxy-~-ribose mit N6-substituierten Adeninen

Phosphorpentoxid reagiert mit Wasser und Tributylamin in Chloroform zu einer homo- genen Losung von Tributylammonium-phosphat, Pyrophosphat und Trimetaphosphat. 3-(9-Adcnyl)-2,3-didesoxy-~-threo-pentofuranosen 3 fallen kristallin an, wenn I-Desoxy-~- ribose (2) mit N‘-substituierten Adeninen 1 in dieser Losung 7 Tage bei 40°C umgesetzt wird.

In 1964 Carbon ’) reported an unsuccessful attempt of prebiotic synthesis of 2-deoxyadenosine by boiling 2-deoxy-~-ribose and adenine in water. Instead, coupling of adenine to C-3 of deoxyribose was observed and 2,3-dideoxy-3-(9- puriny1)-D-pentoses were isolated after laborious chromatographic work-up procedure. Later on, an amino acid-catalyzed condensation reaction of purines and pyrimidines with 2-deoxy-~-ribose in water was reported by Nelsestuen ’). The products in this case were mixtures of erythro and threo forms of 2,3-dideoxy-3- (I-pyrimidiny1)-D-pentose and 2,3-dideoxy-3-(9-purinyl)-~-pentose, respectively.

In this investigation we show that the condensation of 2-methyl-N6-aryladenines 3), N6-aryladenines4), and N6-furfuryladenine4’ 1 with 2-deoxy-~-ribose (2) can be completed in a reagent mixture from phosphorus pentoxide, water, and tributylamine in chloroform. After 7 days at 40°C an anomeric mixture of 2,3- dideoxy-3-(9-adenyl)-~-threo-pentopyranoses 3 precipitated in 14 - 73% yields (Scheme 1). The a: p ratio was approximately 2: 1. In most cases the crude 3 was too unstable for recrystallization and was therefore purified by precipitation from DMF with water.

From 31P NMR (6 values relative to 85% H,PO,) of a solution of the P4OlO/ H20/Bu3N reagent in chloroform, we found that the reagent was composed of

0 VCH Verlagsgesellschaft mbH, D-6940 Wcinheim, 1986 01 70- 2041/86/1111- 1837 $ 02.50/0

1838 J. Andersen and E. B. Pedersen

a

b c

d

1. 3 I R’ R2

C6H5 H 4-CH3C6H4 H

3 -CHjCgHq H

Furfuryl H

C6H5 CH3

1, 3 R’ R2

Scheme 2

CHO I y 2

> HCOH

HCOH I CH,OH

2c

path a

2 < I

P ~ O I I J / H ~ O / B U ~ N

P ~ O I O / H ~ O / B ~ ~ N

CHO I CH

F H HCOH

I CH20H

CHO I y 2 I 1

H?OPO,H-

HCOH I

path b

-H03P0

OH CH20H \

tributylammonium salts of trimetaphosphoric acid (6 = 22.6), pyrophosphoric acid (6 = 9.7), and phosphoric acid (6 = - 1.7) in a molar ratio of 0.5: 4: 10, along with some unidentified minor components. The chemical shift values found were

Liebigs Ann. Chem. 1986

Anomalously Coupled Nucleosides, I 1839

in fair agreement with those reported') considering the pH dependence of the shift values '1.

Two reaction paths seem possible for the formation of 3 from adenine 1 and 2-deoxy-~- ribose 2 (Scheme 2). The reaction can proceed via the phosphorylated 2-desoxy-~-ribose 2a or 2b (path b) which is attacked by adenine in an SN2 substitution reaction to give the pure threo isomer 3. Or the reaction can proceed via the a$-unsaturated aldehyde 2d obtained by dehydration of the open-chain form 2c (path a) promoted by the reagent mixture. The final step in path a is a addition reaction of adenine to the a,P-unsaturated aldehyde 2d to give threu isomer 3 (inversion of configuration). The mechanism may be even more complex because elimination and addition reactions of phosphoric acid of 2 b and 2d, respectively, can be imagined. In spite of the fact that we only isolated the threo anomer 3 in agreement with path b the reaction proceeding via path a can explain that no reaction was observed when we used D-ribose instead of 2-deoxy-~-ribose. If phosphorylation reactions were es- sential, one should also expect phosphorylation somewhere in the ribose molecule followed by a substitution reaction with adenine. Therefore, path a seems likely, and the mixture of tributylammonium phosphates seems to function as a buffer in an aprotic solvent affording the optimum pH value for the reaction going on. Furthermore, in agreement with additional spots on tlc and the moderate yields obtained of 3 for some reactions, formation of the erythro anomer (retention of configuration) or N6-aryl-deoxyadenosine (prebiotic synthesis) cannot be excluded.

CL Scheme 3

5 OH I

H

An attempt was done to work up a reaction mixture from which no precipitate was collected. N6-(2-Chloropheny1)adenine (4) was treated according to the general procedure. The reaction mixture was worked up by ammonolysis of the phosphates with a saturated solution of ammonia in methanol (Scheme 3). After 2.5 h at room temperature the precipitated phosphates were filtered off. After removal of tri-


121


butylamine and evaporation the resulting semicrystalline material was again treated with a saturated solution of ammonia in methanol and 5 precipitated on standing. Structure 5 is in fair agreement with the “C-NMR spectrum and the FAB-mass spectrum including peak matching of the ions [M + 1]@ and [M - 244]@. The [M - 244]@ peak corresponds to loss of a protonated purine moiety.

The structures of the compounds 3 were confirmed by MS, ‘H NMR, and I3C NMR (coupled and decoupled) measurements. The data are shown in Tables 3-5. A 500-MHz ‘H-NMR and a 125-MHz l3C-NMR spectrum (coupled and decoupled spectra) were recorded7’ of 3e, and the carbohydrate moiety was shown to be in the C 1 conformation (Scheme 1). The assignments of chemical shift values and coupling constants were based on inspection of molecule models of the possible structures and conformations along with ‘H-NMR data of both erythro and threo forms of 2-deoxy-~-pentose’), 13C-NMR data of 2-deoxy-~-ribose’) and N6- aryladenines 3,10).

Experimental Preparation of the P,OIO/H20/Bu,N reagent: HzO (21.14 g, 1.173 mol) is added dropwise

with stirring to P40ro (100.0 g, 0.352 mol) in 400 ml of chloroform. 200 ml of chloroform is added and the inhomogeneous mixture is heated on an oil bath at 80°C for 0.5 h, and the suspension is allowed to cool to room temperature. Bu3N (136.0 g, 0.734 mol) is cautiously added under vigorous stirring until the reaction mixture is clear. The solution is allowed to cool to room temperature, and chloroform is added to a total volume of 1000 ml.

Table 1. Preparation of 3

Yielda) M.p. Yielda) M . P

No. (%) [°C](solvent) No. (%) [ O C ] (solvent)

b) 3a 23 223-4 (H20) 3f 49 231(dec.) (DMF/H20)

3g 14 212-3 (CH OH/H20) 3b 35 229-32 (DMF/H20)b) 3

3c 24 217-9 (DMF/H20)b) 3h 35 217-20 (DMF/H20)b)

b) 3d 42 220-1 (CH30H) 3i 41 223-5 (DMF/H20)

3e 55 230-1 (DMF/H20) b) 3j 73 255(dec . ) (DMF/H20) b )

a) Yield of analytical pure compound. - b, The compound is dissolved in DMF by heating gently, the solution is filtered, and the product is precipitated by water.



Table 2. Elemental analysis of 3

No.

Molecular formula

(molecular mass)

Analysis

C H N

3a

3b

3c

3d

3e

3f

3 g

3h

3 i

3.i

-

C16H17N503 0.25 H20

( 331.9)

C17H19N503

(341.4)

C17H19N503

(341.4)

C15H17N504

(331.3)

C17H19N503

(341.4)

C18H21N503 * 0 .5 H20

(364.4)

Cl9HZ3N5O3 * 0.5 H20

(378.4)

C20H25N503 * 0.5 H20

(388.0)

C21H27N503

(397.5)

C17H18N503C1 * 0 . 5 H20

(384.8)

Calc.

Found

Calc.

Found

Calc.

Found

Calc.

Found

Calc.

Found

Calc.

Found

Calc.

Found

Calc.

Found

Calc.

Found

Calc.

Found

57.91

58.09

59.81

59.79

59.81

59.42

54.38

54.02

59.81

59.45

59.33

59.02

60.30

60.19

61.92

62 .10

63.46

63.09

53.06

53.19

5.32

5.18

5.61

5.62

5.61

5.63

5.17

5.16

I 5.61

5.67

6.08

5.83

6.39

6.15

6.63

6.57

6.85

6.99

4.98

4.77

21.10

21.05

20.52

20.15

20.52

20.08

21.14

20.97

20.52

20.29

19.22

19.10

18.51

18.20

18.05

18.32

17.62

17.78

18.20

18.26

2,3-Dideoxy-3- (Ppurinyl)-~-threo-pentopyranoses (3). - General procedure: P4OI0/H20/ Bu3N reagent (1 15 ml), Bu3N (I 3.60 g, 0.073 mol), and N6-aryladenine 1 (0.025 mol) are mixed at room temperature with stirring. The mixture is refluxed on an oil bath at 80°C until a clear solution .i.s obtained. The mixture is cooled to 40T, 2-deoxy-~-ribose (6.71 g, 0.050 mol) is added, and the mixture is stirred at 40°C for 7 days. The product precipitated is collected by filtration and washed carefully with chloroform.

Bis(3-[N6-(2-chlorophenyl)-9-adenyl]-2,3-dideoxy-~-~-threo-pentopyranosyl)amine (5): N6-(2-chloropheny1)adenine (4) (1.34 g, 0.0055 mol), P4Oio/H20/Bu3N reagent (25 ml), Bu3N


121'

1842 J. Anderseii and E. B. Pedersen

Table 3. Mass spectroscopic data of 3

MS S e l e c t e d Ions m / z ( % )

Other peaks a ) [RHCH=CH~ I + a ) [RH J + a ) R + No. M+

3a 327 (15) 238 (38) 211 (69) 210 (100)

3b 341 (18) 252 (30) 225 (82) 224 (100)

3c 341 (1.2) 252 (2.6) 225 (66) 224 (100)

3d 331 (100) 242 (30) 215 ( 4 0 ) 214 (28) 81 (95)

3e 341 (31) 252 225 (97) 224 (99)

3f 355 (37) 266

3g 369 (14) 280

3h 383 (13) 2 94

3i 397 (10) 308

339 (100) 338 (93) 58 )

19 1 253 (100) 252 (43) 238 (89)

15) 267 (63) 266 (10) 252 (100)

281. (59) 280 (8.3) 238 (100) 11 1

3j 375 (22) 286 (44) 259 (100) 258 (81)

a) R = N6-substituted 9-adenyl. - b, The composition is determined by measurement of the exact mass.

Table 4. 'H-NMR data of 3a)

'H NMR [ D6 ]DMSO/TMS

No. 6 values

3a 1.86-2.43 (m, 2'-H), 3.26-5.27 (m, l ' , 3', 4', 5'-H), 6.98-8.00

( m , Ar-H), 8.36-8.38 (ZH, 8-H1, 9.74 ( s , N6-H).

1.89-2.43 (m, 2'-H, C H 3 ) , 3.28-5.32 ( r n , l ' , 3', 4', 5'-H, 4'-0H),

6.36-6.57 (m, l'-OH), 7.10-7.92 ( m , Ar-H), 8.33-8.46 (Z-H, 8-H).

9.64 ( s , N6-H).

3b

3c 1.88-2.45 (m, 2'-H, CH ) , 3.25-5.35 ( m , l', 3'. 4 ' , 5'-H, 4'-0H),

6.28-6.45 (m, 1q-0~1, 8.40-8.47 (2-H, HI, 9.58 (s. N~-H).

3d 1.86-2.46 (m, 2'-H), 3.23-5.28 (m, CH2. l', 3', 4', 5'-H, 4'-OHI,

6.22-7.52 ( m , l'-OH, Ar-H), 8.00 ( s , N6-H), 8.19-8.24 (Z-H, 8-H).



Table 4 (Continued)

'H NMR ( [D6]DMSO/TMS)

No. 6 values

3e 1.99 [ d d d , 2'-H,(a)]. 2.11 [ d d d , 2'-He(B)], 2.32 [ t d , 2'-H,(6)1,

2.47 [ t d , 2'-Ha(aI], 2.54 [ s , 2-CH3(a11, 2.55 [ s , 2-CH3(6)1, 3.27

[dd, 5'-H (811, 3.64 [ d d , 5'-He(a1], 3.74 [t, 5'-Ha(n)], 3.90

[ d d , 5'-H (B)], 4.17 [ t d , 4'-H(nI, 4'-H(Bl], 4.43 [ d d d , 3'-H(6)],

4.71 [ d d d , 3'-H(a)], 4.83 [ d d , l'-H(Bl], 5.26 [ d , l'-H(a)],

6.99-7.99 ( m , Ar-HI, 8.25 [ s , 8-H(6)], 8.30 [ s . 8-H(all, 9.56

[ s , N6-H(0)], 9.57 [ s , N6-H(B)].

3f 1.85-2.57 (m, 2'-H, CH 2-CH 1 , 3.30-5.23 (m, 1', 3', 4', 5'-H), 3 3

7.10-7.97 (m, Ar-HI, 8.25 [ s , 8-H(6)], 8.33 I s . 8-H(al], 9.55

( 5 , N ~ - H ) .

3g 1.18 ( t , 7.5 Hz, CH 1 , 1.98-2.78 (m, 2'-H, CH2 2-CH ) , 3.35-5.27

(m, l', 3', 4', 5'-H), 7.07-7.93 (m, Ar-H), 8.25 [ s , 8-H(6)], 8.30

[ s , 8-H(a)], 9.55 ( s . N6-H).

3h 1.23 ( d , 7 Hz, CH3), 1.82-5.28 (m, 2'-H. 2-CH3, CH, 1' 3', 4',

5'-H), 7.10-7.93 (m, Ar-H), 8.24 [8-H(6)1, 8 . 2 8 [8-H(a)l, 9.52

( s , N6-H).

0.77-2.77 (m, CH2CH2CH2CH3, 2'-H, 2-CH31. 3.27-5.28

(m, 1', 3', 4', 5'-HI, 7.05-7.95 (m, Ar-HI, 8.25 [8-H(6)], 8.30

[ s , 8-H(a)], 9.50 ( S , N6-H).

3i

3j 1.83-2.58 (m, 2'-H, 2-CH ) , 3.28-5.33 (a, l', 3', U ' , 5'41,

7.28-8.31 (m, A r - H ) , 8.30 I s , 8-H(6)], 8.35 [ s , 8-H(a)l, 9.82

(8 , N~-H).

The spectra of 3 were recorded at 60 MHz except for 3e which was recorded at 500 MMz. - b, J [Hz]-a(P): J(l'-H, 2'-H,) = 1.3 (2.0), (1'-H, 2'-Ha) = 2.8 (9.5), 2'-H,, 2'- Ha) = 12.8 (12.5), (2'-He, 3'-H) = 4.3 (4.4), (2'-H,, 3'-H) = 12.8 (12.7), (3'-H, 4'-H) = 11.0 (10.9), (4'-H, 5'-H,) = 5.5 (5.0), 4'-H, 5'-Ha) = 11.0 (10.7), (5'-Hc, 5'-Ha) = 11.0 (11.5').

(2.96 g, 0.016 mol) and 2-deoxy-~-ribose (1.48 g, 0.011 mol) is treated according to the general procedure. No precipitate is formed, and the chloroform is evaporated. 200 ml of a saturated solution of ammonia in methanol is added to the residue and the solution is stirred at room temperature for 2.5 h. The precipitated phosphates are removed by filtration and the methanol is evaporated to give a sirup, which is washed with ether and water. The resulting semicrystalline material is dissolved in 50 ml of a saturated solution of ammonia



in methanol and i s stirred for 2 days. 5 is isolated by filtration. Yield 0.49 g (25%), m. p. 160-165°C. - FAB-MS: m/z = 704 (1.6%, Me), 459 (5.1), 246 (100).

C31H31C12N1104 Calc. 704.2016 Found 704.2000

Table 5. l3C-NMR data ([D,]DMSO/TMS; 6 values) of 3 and 5

Pentose C Purine ca)

No. Anomer C-1' C-2' C-3' C-4' C-5' C-2 c-4 c-5

a E

a B

a E

a E

a E

a B

a 6

a E

a B

a B

90.0 94.7

89 .9 94.6

89.8 94.5

89.9 94 .5

90.07 94.68

90.0 94.6

90.0 94.6

89 .9 94.6

89.9 94.6

89.8 94.4

83.6

36.0 54.8 67.2 38.0 57.7 66.6

35.9 54.6 67 .1 38 .0 57.6 66 .5

35.9 54.6 67.0 38.0 57.6 66 .5

54.4 67.0 "" 57.4 66.4

36.29 54.37 67.34 37.96 57.39 66.69

36.2 54.1 67.3 38.0 57.2 66.6

36.2 54.1 67 .2 38.0 57.2 66.6

36.2 54.1 67.2 38.0 57.1 66.6

36.2 54.1 67.2 38 .0 57.2 66.6

36.0 54.2 67.1 38.0 57.2 66 .5

38.0 58.8 66.5

62.6 67.2

62.5 67 .1

62.5 67 .0

62.5 67.0

62.71 67.34

62.6 67.3

62.6 67.2

62.5 67.2

62 .5 67 .2

62.4 67.1

68.3

151.4

151.3

151.3

151.7

160.43 160.48

160.2

160.2

160.1

160.1

159.9

151.4

149.9

149.7

149.7

f) 153 .O

h ) 150.87 15O.7lh)

150.6

150.6

150.6

150.6

150.7

149.8

120.3

120.2

120.2

119.5

118.3 118.40

118.2

118.2

118.1

118.1

118.2

120.2

3a 152.0 141.4 139.7 120.7 128.3 122.5

3b 152.0 141.2 137.1 120.8 128.7 131.3

3c 151.9 141.2 137.3 121.1 139.6 123.1 128.1 117.9



Table 5 (Continued)

NO. C-6

f' 3d 154.1

3e 151.64 151.66

3f 151.6

3g 151.6

3h 151.6

3i 151.6

3j 151.1

5 152.2

~~ ~~ ~

140.5

140.83: 26.09 140.83'' 26.09

140.5 26.0

140.5 26.0

140.4 26.0

140.5 26.0

140.6 25.8

141.9

149.4

140.06 140.06

137.4

137.6

137.6

137.6

138.9

135.7

106.5

120.44 120.44

120.6

120.6

120.6

120.5

1.21.6

n )

110.3

128.52 128.52

128.7

127.5

126.0

128.0

127.9

129.4

141.7

122.38 122.38

131.1

137.6

142.2

136.1

125.6

126.5') 127.5 125.9O)

a) No differences were observed between the shift values of the a and p anomer in the spectra of 3a-d and 3f-j recorded at 15 MHz. - b, 6 = 20.4 (CH,). - 6 = 21.2 (CH,). - dl 6 = 36.6 (CH,). - e, Not observed. - The assignments may be interchanged. -

Recorded at 125 MHz. - h, J(C-4, 3'-H) = 4 Hz. - ') J(C-8, 3'-H) = 4 Hz. - J J 6 = 20.4

N i t observed. - The assignments may be inter- (CH3). - k, 6 = 27.6 (CH,), 15.7 (CH ) ') F = 32.8 (C?), 24.0 (CH3). - m, 6 = 34.2, 33.2, 21.6 (CH2CH2CH2), 13.7 (CH,). - changed.

CAS Registry Numbers

l a : 1210-66-8 / l b : 5446-36-6 / l c : 82760-82-5 / Id: 525-79-1 / l e : 96960-71-3 / If: 97314- 43-7 / l g : 97314-45-9 / I h : 97314-46-0 / l i : 97314-47-1 / l j : 97314-41-5 / 3a (a-anomer): 104091-17-0 / 3a (p-anomer): 104091-27-2 / 3b (a-anomer): 104091-18-1 / 3b (0-anomer): 104091-28-3 / 3c (a-anomer): 104091-19-2 / 3c (p-anomer): 104091-29-4 / 3d (a-anomer): 104091-20-5 / 3d (p-anomer): 104091-30-7 / 3e (a-anomer): 104091-21-6 / 3e (p-anomer): 104091-31-8 / 3f (a-anomer): 104091-22-7 / 3f (p-anomer): 104091-32-9 / 3g (a-anomer): 104091-23-8 / 3g (p-anomer): 104091-33-0 / 3h (a-anomer): 104091-24-9 / 3h (p-anomer): 104091-34-1 / 3i (a-anomer): 104091-25-0 / 3i (p-anomer): 104091-35-2 / 3j (a-anomer): 104091-26-1 / 3j (0-anomer): 104091-36-3 / 4: 6296-90-8 / 5 : 104091-37-4 2-deoxy- D-ribose: 533-67-5

') J. A . Carbon, J . Am. Chem. SOC. 86, 720 (1964). 2, G. L. Nelsestuen, Biochemistry 18, 2843 (1979). 3, K. E. Andersen and E. B. Pedersen, Liebigs Ann, Chem. 1985, 921. 4, N. S . Girgis and E. B. Pedersen, Synthesis 1982, 480.


1846 J. Andersen and E. 8. Pedersen

5 , D. G . Knorre, A. V. Lebedev, ,A. S . Levina, A . I. Rezvukhin, and V. F. Zarytova, Tetrahedron

6, E. B. Pedersen and J. P. Jacobsen, J. Chem. Soc., Perkin Trans. 2, 1979, 1477. ’) K. Bock, The Technical University of Denmark, is greatly acknowledged for recording

*) M . Y. H. Wong and G. R. Gray, J. Am. Chem. SOC. 100, 3548 (1978). 9, E. Breitmaier, G. Jung, and W. Voelter, Chimia 26, 136 (1972).

lo) K . E. Nielsen and E. B. Pedersen, Chem. Scr. 24, 224 (1984).

30, 3073 (1974).

NMR spectra.

C W 6 1

Liebigs Ann. Chern. 1986

Anomalously coupled nucleosides, I tributylammonium phosphates in chloroform for direct coupling of...

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