Synthesis of 4-(4,6-di-O-benzyl-2,3-dideoxy-β-D-erythro-hex-2- enopyranosyl)pyrazoles from 3,4,6-tri-O-acetyl-D-glucal

Carbohydrate Research 308 (1998) 181±190

Note

Synthesis of 4-(4,6-di-O-benzyl-2,3-dideoxy-ꢀ-d-

erythro-hex-2-enopyranosyl)pyrazoles from

3,4,6-tri-O-acetyl-d-glucal

Pastora Borrachero-Moya, Francisca Cabrera-Escribano,

Manuel Gomez-Guillen*, Marõa del Rocõo Paredes-Leon

Â

Departamento de Quõmica Organica ``Profesor Garcõa Gonzalez'', Universidad de Sevilla, Apartado de

Â

Correos No. 553, E-41071 Seville, Spain

Â

Received 25 June 1997; accepted in revised form 26 February 1998

Abstract

3-(4,6-Di-O-benzyl-2,3-dideoxy-ꢀ-d-erythro-hex-2-enopyranosyl)-2,4-pentanedione and its ana-

logue 2-(4,6-di-O-benzyl-2,3-dideoxy-ꢀ-d-erythro-hex-2-enopyranosyl)-1-phenyl-1,3-butanedione,

prepared from 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-d-arabino-hex-1-enitol (3,4,6-tri-O-acetyl-d-

glucal), reacted with hydrazine and its methyl-, phenyl-, p-tolyl, and p-methoxyphenyl- derivatives

in ethanol, at room temperature, to aord, in 71±96% yields, a series of 4-(4,6-di-O-benzyl-2,3-

dideoxy-ꢀ-d-erythro-hex-2-enopyranosyl)-3-methylpyrazoles having the N-1 free or substituted by

the foregoing groups, and the C-5 substituted by a methyl or phenyl group. The reactions of the

1-phenyl-1,3-butanedione derivative were highly regioselective. Catalytic hydrogenation of some

of these novel compounds gave the respective 4⁰,6⁰-di-O-deprotected-2⁰,3⁰-saturated compounds in

51±67% yields. The acetolysis/methanolysis of one of the title compounds led to the formation of

the 4⁰,6⁰-di-O-debenzylated 2⁰,3⁰-unsaturated pyrazole C-nucleoside in poor yield. # 1998 Elsevier

Keywords: 4-(4,6-Di-O-benzyl-2,3-dideoxy-ꢀ-d-erythro-hex-2-enopyranosyl)-3-methylpyrazoles; 3,4,6-Tri-O-

acetyl-d-glucal; Hydrazines; Debenzylation with and without reduction of the 2⁰,3⁰double bond

The design of nucleoside analogues has in recent

years undergone renewed impetus due, among

other causes, to the activity shown by azidothymi-

dine (AZT) and other 2⁰,3⁰-dideoxynucleosides

against the human immunode®ciency virus (HIV)

as a consequence of their reverse transcriptase

inhibition eect. The lack of a 3⁰-OH group is cri-

tical for the anti-retroviral activity and, thus, other

2⁰,3⁰-dideoxynucleosides such as 2⁰,3⁰-dideoxy-

cytidine (ddC) and 2⁰,3⁰-dideoxyinosine (ddI) have

been also used as therapeutical agents [1]. Further

modi®cations may increase the eciency of drugs

of this type; thus, the presence of a 2⁰,3⁰double

bond is a structural feature that leads to a strong

and selective inhibition of the HIV replication, as is

the case [2] of 2⁰,3⁰-didehydro-2⁰,3⁰-dideoxy-

thymidine (d4T), a stereoselective synthesis of

which has been recently reported [3]. On the other

hand, the well known resistance of C-nucleosides

to hydrolysis has led us to design novel nucleoside

* Corresponding author.

PII S0008-6215(98)00059-7

182

P. Borrachero-Moya et al./Carbohydrate Research 308 (1998) 181±190

analogues having this additional feature, in order

to avoid a decrease of activity as a consequence of

the probable hydrolysis in the cell. As a ®rst

approach, we now describe the preparation of a

series of 4-(2-enoglycosyl)pyrazoles by reaction

of 2-(2,3-dideoxy-ꢀ-d-erythro-hex-2-enopyranosyl)-

1,3-diketones with hydrazines. To our knowledge,

the only 2⁰,3⁰-unsaturated-C-nucleoside of pyrazole

described [4] is a 3-(2-enoglycosyl)pyrazolo[4,3-d]-

pyrimidine, prepared from a formycin derivative.

anomer 3 for the preparation of the pure ꢀ C-gly-

cosides 4 and 5. Chaguir et al. have described [6]

that the ꢁ anomer of 3 reacts with 2,4-pentane-

dione in the presence of a large excess of triphenyl-

phosphine to aord exclusively the ꢀ anomer 4;

this fact allows one to increase the overall yield of 4

and 5 from 1.

Reaction of the 1,3-diketones 4 and 5 with

hydrazines resulted in a series of 4⁰,6⁰-di-O-benzyl-

2⁰,3⁰-unsaturated pyrazole C-nucleosides (6±15)

(Scheme 2). Besides hydrazine itself, its methyl-,

phenyl-, p-tolyl-, and p-methoxyphenyl- derivatives

have been used as the reagent. The new compounds

6±15 were isolated, after column chromatography,

as colourless syrups in good to high yields

(71±96%), and characterized on the basis of their

elemental analyses and/or spectral properties, in

1. Results and discussion

We have used as starting materials the unsatu-

rated sugar 1,3-diketones 4 and 5, derived from

2,4-pentanedione and 1-phenyl-1,3-butanedione,

respectively. Compound 4 was prepared following

the method described previously [5]. 3,4,6-Tri-O-

acetyl-1,5-anhydro-2-deoxy-d-arabino-hex-1-enitol

(3,4,6-tri-O-acetyl-d-glucal, 1) was ®rst transformed

into a mixture of phenyl 4,6-di-O-acetyl-2,3-

dideoxy-ꢁ- and ꢀ-d-erythro-hex-2-enopyranoside

(2ꢁ and 2ꢀ, respectively); after chromatographic

separation, the ꢀ-isomer (2ꢀ) was deacetylated and

benzylated to aord the 4,6-di-O-benzyl derivative

3, which was ®nally treated with 2,4-pentanedione

in THF in the presence of bis(dibenzylideneace-

tone) Pd(0) [Pd(dba)₂] associated with bis(diphenyl-

phosphino)ethane (DIPHOS) as the catalyst

(Scheme 1). The new compound 5, an analogue of

4, was prepared as a mixture of epimers at the new

stereogenic centre, by applying the same procedure

to 1-phenyl-1,3-butanedione.

1

particular the H and ¹³C NMR spectra (Tables 1

and 2, respectively). The mild conditions under

which the reaction was carried out (ethanol, room

temperature, 5 min) and the low basicity of the

hydrazines used as the reagent allowed us to expect

no anomerisation of the substrate (4 or 5) through

a reverse Michael reaction; in fact, the products

6±15 were obtained as pure ꢀ-anomers. In this

respect, it is known that related 2⁰,3⁰-unsaturated-

C-hexopyranosides had proved to be anomerically

stable to weak bases [7]. As their precursors (4 and

5) and other 2⁰,3⁰-unsaturated ꢀ-d-erythro-C-hexo-

pyranosides, compounds 6±15 should assume the

0

half-chair H₅conformation (Scheme 3), for which

0

the J_{4 ,5}is expected [8,9] to show values in the

range 8±10 Hz; that is so (Table 1) with the sole

exception of 9 (7.5 Hz). The ole®nic proton signals

had ꢂ values ranging from 5.70 to 5.84 ppm for

H-2⁰, and from 5.89 to 6.08 ppm for H-3⁰, the

assignments being con®rmed by COSY experi-

ments. Chemical shifts for the other protons at the

sugar moiety, and coupling constants between

Since the transformation of 3 into 4 occurs with

total retention of the ꢀ con®guration and, on the

other hand, the ꢁ anomer of 3 reacts with 2,4-pen-

tanedione under the same conditions to aord an

ꢁ/ꢀ mixture of C-glycosides [5], we chose the ꢀ

Scheme 1.

Scheme 2.

P. Borrachero-Moya et al./Carbohydrate Research 308 (1998) 181±190

183

Table 1

Selected 500 MHz H NMR data for compounds 6±15 in CDCl₃

1

0

Coupling constant, J_{4 ,5}(Hz)

0

Compound

Chemical shift, ꢂ (ppm)

H-3⁰

H-2⁰

H-1⁰

H-4⁰

6

7

8

9

10

11

12

13

14

15

6.00 ddd

5.94 ddd

6.08 ddd

5.89 ddd

6.05 ddd

5.97 ddd

6.07 ddd

5.96 ddd

6.06 ddd

5.96 ddd

5.74 ddd

5.76 ddd

5.73 ddd

5.70 ddd

5.81 ddd

5.80 ddd

5.84 ddd

5.79 ddd

5.83 ddd

5.80 ddd

5.16 m

5.24 m

5.13 m

4.99 m

5.23 m

5.11 m

5.25 m

5.10 m

5.24 m

5.10 m

4.15 dddd

4.16 dddd

4.17 dddd

4.07 dddd

4.19 dddd

4.15 dddd

4.23 dddd

4.13 dddd

4.21 dddd

4.13 dddd

8.6

7.5

8.6

8.4

8.3

8.6

8.4

them, have values within narrow ranges. The ¹³C

NMR resonances were assigned on the basis of the

data reported for related compounds, and were

con®rmed by heteronuclear 2D correlated experi-

ments. In agreement with the ꢀ anomeric con®g-

uration, C-5⁰gives rise to a signal at 77.43±

77.84 ppm (Table 2), in the range (77.3±78.4)

observed [5,6,9] for 4 and related compounds; for ꢁ

anomers, the range expected [5,6,9] for C-5⁰is

71.9±74.5 ppm. The ꢀ con®guration was con®rmed

for compound 11 by 1D NOESY experiments, as

unambiguous proof [6,9]; thus, irradiation at the

H-1⁰proton produced the inversion of the H-5⁰

signal, as expected [6,9] for ꢀ anomers of this kind.

Apart from the reaction with unsubstituted hydra-

zine, which aords a mixture of tautomers, the

regioselectivity observed for the reactions of the 1-

phenyl-1,3-butanedione derivative 5, leading to 3-

methyl-5-phenylpyrazoles (9, 11, 13, 15), is evi-

denced by the down®eld shift observed for the C-4

signal on substituting the Me-5 of 8, 10, 12, 14 by

Ph. For simpler, structurally related pyrazole deriva-

tives, such a change of substituents at C-5 causes

[10] a down®eld shift of 1.0 ppm, whereas the same

change, performed at C-3, gives rise to an up®eld

shift of 2.2 ppm on the signal of C-4. Actually, for

each of the pairs 8±9, 10±11, 12±13, and 14±15, the

shift observed is a down®eld shift (0.89, 1.19, 1.37,

and 1.00 ppm, respectively). Another structural

feature that can be deduced from the NMR spectra

refers to the coplanarity of a phenyl ring and the

pyrazole ring when they are directly bonded one to

the other. It is well known [11] that, in 1,5-diphenyl-

pyrazoles, both phenyl rings are twisted out of the

plane of the pyrazole ring. This seems to be the

case also for the 1-methyl-5-phenylpyrazole 9,

which has the Ph-5, as its analogues 11, 13, and 15,

¯anked by two bulky groups, since on going from

the ®rst to the second component of each pair of

the N-methyl or N-aryl compounds 8±9, 10±11,

and so on, the C-1⁰signal undergoes an up®eld

shift of 0.14±0.33 ppm. This fact may be attributed

to the anisotropy eect of the non-coplanar phenyl

R⁵in the corresponding compounds. In agreement

with that, a similar up®eld shift of 0.12±0.15 ppm is

Table 2

Selected 125.8 MHz ¹³C NMR data for compounds 6±15 in

CDCl₃

Compound

Chemical shift, ꢂ (ppm)

C-2⁰

C-4

C-5⁰

C-1⁰

6

7

8

9

10

11

12

13

14

15

130.88

130.87

131.13

130.78

130.39

130.14

130.75

130.64

130.89

130.71

114.18

114.09

114.98

115.87

116.50

117.69

116.08

117.45

116.12

117.12

77.59 69.38

77.66 69.41

77.84 69.86

77.43 69.53

77.68 69.68

77.46 69.54

77.70 69.84

77.54 69.61

77.78 69.96

77.52 69.66

a

Overlapped with one of the aromatic C signals (double

intensity).

observed for the H-1⁰signal in the H NMR spec-

1

tra of the 5-phenylpyrazoles 9, 11, 13, and 15, in

relation to the respective 5-methylpyrazoles. The

in¯uence of the anisotropic eect of the twisted

phenyl group at C-5 seems to aect also C-2⁰, C-5⁰,

Scheme 3.

184

P. Borrachero-Moya et al./Carbohydrate Research 308 (1998) 181±190

and H-2⁰, since all these nuclei become slightly

shielded in the 5-phenyl derivatives in comparison

with the corresponding 5-methyl substituted ana-

logues, as shown in Tables 1 and 2.

Hydrogenation of compounds 9, 13, and 15 at

atmospheric pressure in the presence of Pd(OH)₂/C

as the catalyst aorded 51±67% of the 4⁰,6⁰-di-O-

debenzylated-2⁰,3⁰-saturated pyranosyl-C-nucleo-

sides 16±18 (Scheme 4), respectively. From the

2⁰,3⁰-unsaturated product in poor, but appreciable

yield, was observed only when the acetolysis/

methanolysis procedure [14] was applied to 13. The

main product of the acetolysis was, after chroma-

tography, a 2.5:1 mixture of two epimers tenta-

tively formulated, from the NMR data and fast-

atom bombardment high-resolution mass spectrum

(FABHRMS), as 19 (29%), the formation of

which may be explained if the participation of the

4⁰-O-benzyl group of an intermediate 5⁰,6⁰-di-O-

acetyl-4⁰-O-benzyl open-chain allylic cation is

0

observed values of J_{1 ,2 ax}(11.6, 11.7, and 11.7 Hz)

was evidenced the ꢀ con®guration, which was

unambiguously [6,9] con®rmed for 18 by 1D

NOESY experiments: irradiation at the H-1⁰pro-

ton inverted the signals of the H-2⁰eq, H-3⁰ax,

H-5⁰ax, and Me-3 protons; irradiation at the H-4⁰

proton aected similarly the H-2⁰ax and H-3⁰eq

signals. This fact indirectly demonstrates that the

parent 2⁰,3⁰-unsaturated compounds should have

also the ꢀ con®guration. The novel compounds 16±

18 possess a 2⁰,3⁰-dideoxy saturated sugar moiety

and, in this respect, are similar to ddC and ddI; this

fact allows one to expect for them some biological

activity.

0

assumed; the high value of J_{1 ,2}(16.1 Hz) again

indicates that the ethylenic protons must have the

trans relationship. Another fraction (18%) of the

acetolysis mixture contained as the main compo-

nent a product, tentatively formulated as the

expected 4⁰,6⁰-di-O-acetyl-2⁰,3⁰-unsaturated C-nucle-

1

oside 20 (10% yield from 13, by H NMR), the

FABHRMS and NMR data of which being con-

sistent with this structure; particularly, the value of

0

J_{2 ,3}(10.3 Hz) evidenced the Z con®guration of the

0

double bond, and the high values of J_{4 ,5}(8.9 Hz)

and ꢂ for C-5⁰(74.71 ppm) agreed with those

expected from the ꢀ con®guration (a related com-

pound, as the 4⁰,6⁰-di-O-acetyl-2⁰,3⁰-dideoxy-ꢀ-d-

erythro-hex-2⁰-enopyranosyl derivative of aceto-

A preliminary study on the di-O-debenzylation

of any of the 2⁰,3⁰-unsaturated compounds 6±15

without reducing the 2⁰,3⁰double bond was carried

out. Besides sodium in liquid ammonia, we used

some other reagents for which certain examples of

selective debenzylation in the presence of carbon±

carbon double bonds have been reported, such as

boron tri¯uoride/ethanethiol [12], and cyclohexene

as hydrogen donor in the presence of palladium on

charcoal [13]. These methods, as applied to 8 (Na/

liq. NH₃) and 13, proved to be ineective, since

NMR of the complex reaction mixtures obtained in

all cases indicated the lack of ethylenic protons or

the presence of open-chain unsaturated sugar deri-

vatives as main products (J&16 Hz for trans

arranged ethylenic protons, incompatible with the

inclusion of the double bond in a six-membered

ring), as well as partially debenzylated products.

The formation of the desired di-O-debenzylated-

0

phenone shows [7] values of 8.7 Hz for J_{4 ,5}and

74.531 ppm for ꢂ of C-5⁰, while for its ꢁ isomer the

respective values are 3.5 Hz and 68.295 ppm).

Treatment of the crude product 20 with sodium

methoxide in methanol led, after preparative TLC,

to a mixture, of which a main component was ten-

0

tatively identi®ed by NMR (J_{2 ,3}10.5 Hz, J_{4 ,5}

8.7 Hz, ꢂ for C-5⁰76.01 ppm) and DCIHRMS data

as the desired 4⁰,6⁰-di-O-deacetylated-2⁰-enoglycosyl

compound 21.

In conclusion, the 4⁰,6⁰-di-O-benzyl-2⁰,3⁰-unsatu-

rated C-nucleosides of pyrazole 6±15, easily

obtained in a short sequence starting from triace-

tylglucal, are immediate precursors of interesting

saturated, deprotected sugar derivatives such as

16±18. However, an improved method for the

transformation of 6±15 into deprotected 2⁰-enogly-

cosyl derivatives such as 21 should be developed.

2. Experimental

General methods.ÐTLC was performed on Silica

Gel 60 plates (DC-Alufolien F₂₅₄, E. Merck, or

ALUGRAM SIL G/UV₂₅₄, Macherey-Nagel), and

detection with UV light (254 nm) or by charring

Scheme 4.

P. Borrachero-Moya et al./Carbohydrate Research 308 (1998) 181±190

185

0

with H₂SO₄. Silica Gel 60 (E. Merck) was used for

column chromatography and hexane±EtOAc mix-

tures as eluants. Solutions were concentrated under

diminished pressure at <40^ꢀ. Optical rotations

were measured with a Perkin-Elmer 241 MC

polarimeter. IR spectra (®lms on KBr discs) were

recorded with a FTIR Bomem Michelson MB-120

spectrometer. UV spectra were obtained on a Phi-

1.9 Hz, H-3⁰), 5.73 (ddd, 1 H, J_{1 ,2}&J_{2 ,4}1.6 Hz,

H-2⁰), 4.85 (dddd, 1 H, J_{1 ,3}8.4 Hz, J_{1 ,4}1.3 Hz, H-

1⁰), 4.61 and 4.47 (each d, each 1 H, J 11.5 Hz,

CH₂Ph), 4.55 and 4.51 (each d, each 1 H, J

0

12.3 Hz, CH₂Ph), 4.02 (dddd, 1 H, J_{4 ,5}8.4 Hz, H-

4⁰), 3.81 (d, 1 H, H-3), 3.70 (dd, 1 H, J_{5 ,6 a}3.9,

J_{6 a,6 b}9.2 Hz, H-6⁰a), 3.65±3.60 (m, 2 H, H-5⁰and

H-6⁰b), 2.24 (s, 3 H, Me), and 2.21 (s, 3 H, Me);

¹³C NMR (125.8 MHz): d 202.37 and 202.22 (2

C O), 138.26 and 137.86 (C-2⁰and C-3⁰), 128.37,

128.30, 128.18, 127.85, 127.79, 127.64, and 127.49

(2 Ph), 77.30 (C-5⁰), 73.55 (C-1⁰), 72.29 (C-4⁰),

73.21 and 71.20 (2 OCH₂Ph), 69.92 (C-3), 69.43

(C-6⁰), 30.74 (Me), and 29.67 (Me).

2(R,S)-2-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-ery-

thro-hex-2-enopyranosyl)-1-phenyl-1,3-butanedione

(5): 0.409 g, 87%; 67:33 epimeric mixture, by H

NMR [from 1-phenyl-1,3-butanedione (0.324 g)];

0

1

lips PU 8710 spectrophotometer. H NMR spectra

(500 MHz) and ¹³C NMR spectra (125.8 MHz)

were recorded for solutions in CDCl₃with a Bru-

ker AMX-500 spectrometer. Assignments were

con®rmed by decoupling and/or homonuclear 2D

COSY, 1D NOESY, and heteronuclear 2D corre-

lated (HETCOR) experiments. HR-EI mass spec-

tra (70 eV) were measured with a Kratos MS-

80RFA instrument, with an ionising current of

100 mA, an accelerating voltage of 4 kV, and a

resolution of 10,000 (10% valley de®nition). Fast-

atom bombardment mass spectrometry (FABMS)

was performed on the same instrument; ions were

produced by a beam of xenon atoms (6±7 keV)

using a matrix consisting of nitrobenzene or thio-

glycerol and NaI as salt. FABHRMS was obtained

on a VG Autospec spectrometer (Fisons Instru-

ments) (30 keV). DCIHRMS (methane) were

recorded with an AutospecQ instrument (Micro-

mass).

1

l_max(CH₂Cl₂) 251 nm (e_mM10.29); ꢃ_max1719,

1

1672 cm ; FABMS: m/z 493 (100, [M+Na]⁺).

Anal. Calcd for C₃₀H₃₀O₅: C, 76.57; H, 6.43.

1

Found: C, 76.72; H, 6.32. Major isomer H NMR:

0

ꢂ 8.02±7.14 (m, 15 H, 3 Ph), 5.91 (ddd, 1H, J_{2 ,3}

10.5, J_{1 ,3}&J_{3 ,4}1.9 Hz, H-3⁰), 5.72 (ddd, 1 H,

0

J_{1 ,2}&J_{2 ,4}1.7 Hz, H-2⁰), 5.13 (m, 1 H, J_{1 ,4}3.1 Hz,

0

H-1⁰), 4.64 (d, 1 H, J_{1 ,2}9.6 Hz, H-2), 4.60, 4.47

0

(each d, each 1 H, J_H,H11.8 Hz, CH₂Ph), 4.55, 4.52

(each d, each 1 H, J_H,H12.2 Hz, CH₂Ph), 3.99

0

General procedure for the preparation of 2-(4,6-

di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-2-enopy-

ranosyl) derivatives of 1,3-dicarbonyl compounds

(4, 5).ÐA solution of phenyl 4,6-di-O-benzyl-2,3-

dideoxy-ꢀ-d-erythro-hex-2-enopyranoside (3) [5]

(0.40 g, 1 mmol) in THF (3 mL), was transferred

at room temperature, under nitrogen, into a

stirred solution of bis(dibenzylideneacetone)Pd(0)

[Pd(dba)₂, 29 mg, 0.05 mmol] [15], and 1,2-bis(di-

(dddd, 1 H, J_{1 ,4}3.1, J_{2 ,4}&J_{3 ,4}1.9, J_{4 ,5}8.7 Hz,

H-4⁰), 3.71 (dd, 1 H, J_{5 ,6 a}1.8, J_{6 a,6 b}10.6 Hz, H-

6⁰a), 3.67 (ddd, 1 H, J_{5 ,6 a}1.7, J_{5 ,6 b}5.3, J_{4 ,5}

0

8.7 Hz, H-5⁰), 3.61 (dd, 1 H, J_{5 ,6 b}5.2, J_{6 a,6 b}

10.5 Hz, H-6⁰b), and 2.27 (s, 3 H, Me); ¹³C NMR: ꢂ

201.73 (Me±C O), 193.60 (PhC=O), 138.25±

127.31 (C-2⁰, C-3⁰, and 3 Ph), 77.30 (C-5⁰), 74.63

(C-1⁰), 73.16 and 71.11 (2 CH₂Ph), 69.91 (C-4⁰),

69.33 (C-6⁰), 67.86 (C-2), and 28.33 (Me). Minor

isomer ¹H NMR: ꢂ 8.02±7.14 (m, 15 H, 3 Ph), 6.01

0

phenylphosphino)ethane

(DIPHOS,

24 mg,

(ddd, 1H, J_{2 ,3}10.5, J_{1 ,3}&J_{3 ,4}1.9 Hz, H-3⁰), 5.95

0

0.056 mmol) in THF (2 mL). To this mixture was

then added the 1,3-dicarbonyl compound (2_ꢀmmol)

and the reaction mixture was heated at 70 C and

stirred until complete transformation of 3 had

taken place (TLC, 4:1 hexane±EtOAc, several

hours). After evaporation of the solvent at reduced

pressure, the residue was puri®ed by column chro-

matography on silica gel (10:1 to 6:1 gradient of

hexane±EtOAc) to aord pure C-glycosides (4, 5).

3-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-2,4-pentanedione (4): mp 76±77 ^ꢀC,

(ddd, 1 H, J_{1 ,2}&J_{2 ,4}1.6 Hz, H-2⁰), 5.03 (m, 1 H,

0

H-1⁰), 4.75 (d, 1 H, J_{1 ,2}7.8 Hz, H-2), 4.60, 4.47

0

(each d, each 1 H, J_H,H11.8 Hz, CH₂Ph), 4.55, 4.52

(each d, each 1 H, J_H,H12.2 Hz, CH₂Ph), 4.09 (m,

1 H, H-4⁰), 3.73±3.60 (m, 3 H, H-5⁰, H-6⁰a, and H-

6⁰b), and 2.21 (s, 3 H, Me); ¹³C NMR: ꢂ 201.73

(Me±C O), 194.68 (PhC O), 138.25±127.31 (C-

2⁰, C-3⁰, and 3 Ph), 77.49 (C-5⁰), 74.33 (C-1⁰), 73.03

and 71.11 (2 CH₂Ph), 69.78 (C-4⁰), 69.15 (C-6⁰),

66.03 (C-2), and 30.55 (Me).

29

D

20

D

lit. oil [5]; ꢁ +38^ꢀ(c 1, CH₂Cl₂), lit. ꢁ

General procedure for the preparation of 4-(4,6-

di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-2-enopy-

ranosyl)pyrazoles (6±15).ÐTo a soln of the 2-(4,6-

ꢀ

1

+33.1 [5]; H NMR (500 MHz): ꢂ 7.40±7.20 (m,

0

10 H, 2 Ph), 5.97 (ddd, 1 H, J_{2 ,3}10.4, J_{1 ,3}&J_{3 ,4}

186

P. Borrachero-Moya et al./Carbohydrate Research 308 (1998) 181±190

4⁰), 3.87 (bs, 1 H, H-1), 3.74 (dd, 1 H, J_{5 ,6 a}5.4,

0

di-O-benzyl-2,3-dideoxy-ꢀ-d-erythro-hex-2-enopy-

ranosyl)-1,3-dicarbonyl compound (4, 5) (1 mmol)

in EtOH (10 mL), the corresponding hydrazine

(8.2 mmol) (the p-tolyl and p-anisyl derivatives

were released by treatment of the respective

hydrochloride with aq NaHCO₃) was gradually

added. The resulting solution was stirred at room

temperature until complete transformation of the

starting sugar derivative (5 min, monitored by

TLC, 4:1 hexane±EtOAc). The solvent was then

evaporated under reduced pressure and the residue

was puri®ed by column chromatography on silica

gel (1:3 hexane±EtOAc) to give the pure pyrazole

derivative (6±15).

J_{6 a,6 b}10.2 Hz, H-6⁰a), 3.84±3.78 (m, 2 H, H-5⁰

and H-6⁰b), and 2.14 (s, 3 H, Me); ¹³C NMR:

ꢂ 148.09 (C-3), 143.29 (C-5), 130.87 (C-2⁰), 138.36,

138.04, 131.79, 128.60, 128.29, 128.23, 128.16,

127.98, 127.73, 127.64, 127.59, and 127.35 (3 Ph),

126.00 (C-3⁰), 114.09 (C-4), 77.66 (C-5⁰), 73.37 and

71.04 (2 OCH₂Ph), 70.53 (C-4⁰), 69.90 (C-6⁰), 69.41

(C-1⁰), and 11.30 (Me); FABMS: m/z 489 (60,

[M+Na]⁺), 467 (100, [M+H]⁺); HRMS: m/z

466.2265 (Calcd for C₃₀H₃₀N₂O₃: 466.2256). Anal.

Calcd for C₃₀H₃₀N₂O₃: C, 77.23; H, 6.48; N, 6.00.

Found: C, 77.36; H, 6.60; N, 5.94.

0

4-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-1,3,5-trimethylpyrazole (8): 0.376 g

(90%) [from 4 (0.41 g) and methylhydrazine

4-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-3,5-dimethyl-1H-pyrazole

0.388 g (96%) [from 4 (0.408 g) and hydrazine

(6):

24

(0.377 g, 0.43 mL)]; ꢁ +150^ꢀ(c 1, CHCl₃); ꢄ_max

D

22

D

hydrate (0.410 g, 0.50 mL)]; ꢁ

+92^ꢀ(c 1,

(CH₂Cl₂) 259 nm (e_mM3.79); ꢃ_max1724, 1661

1

CHCl₃); ꢄ_max(CH₂Cl₂) 230, 252 nm (e_mM7.90,

9.25); ꢃ_max3202 (NH), 1721, 1657 (C C), 1497

(C C), 1597, 1495 (Ph), 1572 cm

(pyrazole

C N); ¹H NMR: ꢂ 7.34±7.24 (m, 10 H, 2 Ph), 6.08

(ddd, 1 H, J_{2 ,3}10.3, J_{1 ,3}&J_{3 ,4}1.8 Hz, H-3⁰), 5.73

1

0

(phenyl), 1587 cm (pyrazole C N); H NMR: ꢂ

(ddd, 1 H, J_{1 ,2}&J_{2 ,4}1.7 Hz, H-2⁰), 5.13 (m, 1 H,

H-1⁰), 4.65 and 4.50 (each d, each 1 H, J 11.5 Hz,

CH₂Ph), 4.59 and 4.52 (each d, each 1 H, J

0

7.34±7.26 (m, 10 H, 2 Ph), 6.00 (ddd, 1 H, J_{2 ,3}

0

10.3, J_{1 ,3}&J_{3 ,4}2.1 Hz, H-3⁰), 5.74 (ddd, 1 H,

0

J_{1 ,2}&J_{2 ,4}1.7 Hz, H-2⁰), 5.55 (bs, 1 H, H-1), 5.16

(m, 1 H, H-1⁰), 4.66 and 4.51 (each d, each 1 H, J

11.4 Hz, CH₂Ph), 4.60 and 4.53 (each d, each 1 H,

0

12.2 Hz, CH₂Ph), 4.17 (dddd, 1 H, J_{1 ,4}3.1, J_{4 ,5}

8.6 Hz, H-4⁰), 3.73 (dd, 1 H, J_{5 ,6 a}5.4, J_{6 a,6 b}

10.8 Hz, H-6⁰a), 3.80±3.76 (m, 2 H, H-5⁰and H-

6⁰b), 3.65 (s, 3 H, Me-1), and 2.19 (s, 6 H, Me-3

and Me-5); ¹³C NMR: ꢂ 145.81 (C-3), 138.43 (C-5),

131.13 (C-2⁰), 138.11, 137.46, 128.32, 128.19,

127.77, 127.66, 127.59, and 127.36 (2 Ph), 125.71

(C-3⁰), 114.98 (C-4), 77.84 (C-5⁰), 73.26 and 71.20

(2 OCH₂Ph), 70.60 (C-4⁰), 69.92 (C-6⁰), 69.86 (C-

1⁰), 35.55 (Me-1), 12.18 (Me-3), and 9.84 (Me-5);

HRMS: m/z 418.2241 (Calcd for C₂₆H₃₀N₂O₃:

0

J 12.3 Hz, CH₂Ph), 4.15 (dddd, 1 H, J_{1 ,4}3.1, J_{4 ,5}

8.6 Hz, H-4⁰), 3.73 (dd, 1 H, J_{5 ,6 a}5.4, J_{6 a,6 b}

10.7 Hz, H-6⁰a), 3.81±3.70 (m, 2 H, H-5⁰and H-

6⁰b), and 2.21 (s, 6 H, 2 Me); ¹³C NMR: ꢂ 142.80

(C-3 and C-5), 130.88 (C-2⁰), 138.21, 137.97,

128.21, 128.08, 127.66, 127.56, and 127.28 (2 Ph),

125.60 (C-3⁰), 114.18 (C-4), 77.59 (C-5⁰), 73.15 and

71.07 (2 OCH₂Ph), 70.50 (C-4⁰), 69.73 (C-6⁰), 69.38

(C-1⁰), and 10.99 (2 Me); FABMS: m/z 427 (100,

[M+Na]⁺), 405 (50, [M+H]⁺); HRMS: m/z

404.2089 (Calcd for C₂₅H₂₈N₂O₃: 404.2099). Anal.

Calcd for C₂₅H₂₈N₂O₃: C, 74.23; H, 6.98; N, 6.92.

Found: C, 74.28; H, 6.61; N, 6.77.

0

.

418.2256). Anal. Calcd for C₂₆H₃₀N₂O₃0.75 H₂O:

C, 72.28; H, 7.35; N, 6.48. Found: C, 72.49; H,

7.08; N, 6.50.

4-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-1,3-dimethyl-5-phenylpyrazole (9):

0.370 g (77%) [from 5 (0.470 g) and methylhy-

4-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-3(5)-methyl-5(3)-phenyl-1H-pyr-

azole (7): 0.441 g (95%) [from 5 (0.470 g) and

drazine (0.377 g, 0.43 mL)]; ꢁ²²+87^ꢀ(c 1, CHCl₃);

D

hydrazine hydrate (0.410 g, 0.50 mL)]; ꢁ²²+67^ꢀ(c

ꢄ_max(CH₂Cl₂) 243 nm (e_mM9.33); ꢃ_max1605

D

1

1, CHCl₃); ꢄ_max(CH₂Cl₂) 243 nm (e_mM9.32); ꢃ_max

(C C), 1578 (Ph), 1554 cm (pyrazole C N);

3194 (NH), 1721, 1655 (C C), 1605 and 1495

¹H NMR: ꢂ 7.40±7.23 (m, 15 H, 3 Ph), 5.89 (ddd, 1

H, J_{2 ,3}10.3, J_{1 ,3}2.5, J_{3 ,4}1.7 Hz, H-3⁰), 5.70

0 0 0 0 0 0

1

(Ph), 1585 cm

7.55±7.24 (m, 15 H, 3 Ph), 5.94 (ddd, 1 H, J_{2 ,3}

(pyrazole C N); ¹H NMR: ꢂ

(ddd, 1 H, J_{1 ,2}&J_{2 ,4}1.7 Hz, H-2⁰), 4.99 (m, 1 H,

H-1⁰), 4.61 and 4.47 (each d, each 1 H, J 11.5 Hz,

CH₂Ph), 4.60 and 4.52 (each d, each 1 H, J

0

10.3, J_{1 ,3}&J_{3 ,4}1.7 Hz, H-3⁰), 5.76 (ddd, 1 H,

0

J_{1 ,2}&J_{2 ,4}1.6 Hz, H-2⁰), 5.24 (m, 1 H, H-1⁰), 4.63

and 4.49 (each d, each 1 H, J 11.6 Hz, CH₂Ph),

4.61 and 4.53 (each d, each 1 H, J 12.3 Hz,

0

12.1 Hz, CH₂Ph), 4.07 (dddd, 1 H, J_{1 ,4}2.8, J_{4 ,5}

7.5 Hz, H-4⁰), 3.82±3.69 (m, 3 H, H-5⁰, H-6⁰a, and

H-6⁰b), 3.67 (s, 3 H, Me-1), and 2.29 (s, 3 H, Me-3);

0

CH₂Ph), 4.16 (dddd, 1 H, J_{1 ,4}3.0, J_{4 ,5}8.6 Hz, H-

0

P. Borrachero-Moya et al./Carbohydrate Research 308 (1998) 181±190

187

¹³C NMR: ꢂ 146.63 (C-3), 142.73 (C-5), 130.78 (C-

2⁰), 138.35, 137.96, 129.93, 128.55, 128.48, 128.18,

128.07, 127.63, 127.52, 127.48, and 127.25 (3 Ph),

125.72 (C-3⁰), 115.87 (C-4), 77.43 (C-5⁰), 73.14 and

70.91 (2 OCH₂Ph), 70.41 (C-4⁰), 69.89 (C-6⁰), 69.53

(C-1⁰), 36.49 (Me-1), and 12.53 (Me-3); FABMS:

m/z 503 (60, [M+Na]⁺), 481 (100, [M+H]⁺);

HRMS: m/z 480.2409 (Calcd for C₃₁H₃₂N₂O₃:

480.2413). Anal. Calcd for C₃₁H₃₂N₂O₃: C, 77.47;

H, 6.71; N, 5.83. Found: C, 77.40; H, 6.93; N, 5.82.

4-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-3,5-dimethyl-1-phenylpyrazole (10):

128.25, 128.20, 127.64, 127.55, 127.49, 127.27,

126.02, and 124.68 (4 Ph), 126.60 (C-3⁰), 117.69

(C-4), 77.46 (C-5⁰), 73.15 and 70.97 (2 OCH₂Ph),

70.38 (C-4⁰), 69.83 (C-6⁰), 69.54 (C-1⁰), and 12.82

(Me); FABMS: m/z 565 (45, [M+Na]⁺), 543

(100, [M+H]⁺); HRMS: m/z 542.2547 (Calcd

for C₃₆H₃₄N₂O₃: 542.2569). Anal. Calcd for

.

C₃₆H₃₄N₂O₃0.6 H₂O: C, 78.12; H, 6.41; N, 5.06.

Found: C, 78.39; H, 6.58; N, 4.74.

4-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-3,5-dimethyl-1-(p-tolyl)pyrazole

(12): 0.385 g (78%) [from 4 (0.408 g) and p-tolyl-

0.451 g (94%) [from 4 (0.408 g) and phenylhy-

+88^ꢀ(c 1,

CHCl₃); ꢄ_max(CH₂Cl₂) 252 nm (e_mM16.11); ꢃ_max

hydrazine (released from its hydrochloride: 1.30 g)];

23

D

21

D

drazine (0.886 g, 0.81 mL)]; ꢁ

ꢁ +153^ꢀ(c 0.8, CHCl₃); ꢄ_max(CH₂Cl₂) 252 nm

(e_mM11.0); ꢃ_max1723, 1661 (C C), 1586, 1497

1

1719, 1653 (C C), 1597, 1505 (Ph), 1570 cm

(Ph), 1568 cm

7.41±7.30 (m, 14 H, 2 Ph and p-C₆H₄±Me), 6.07

(pyrazole C N); ¹H NMR: ꢂ

1

(pyrazole C N); H NMR: ꢂ 7.60±6.57 (m, 15 H,

3 Ph), 6.05 (ddd, 1 H, J_{2 ,3}10.3, J_{1 ,3}2.4, J_{3 ,4}

(ddd, 1 H, J_{2 ,3}10.3, J_{1 ,3}1.6, J_{3 ,4}1.5 Hz, H-3⁰),

0 0 0 0 0 0

0

1.9 Hz, H-3⁰), 5.81 (ddd, 1 H, J_{1 ,2}&J_{2 ,4}1.7 Hz,

H-2⁰), 5.23 (m, 1 H, H-1⁰), 4.67 and 4.51 (each d,

each 1 H, J 11.4 Hz, CH₂Ph), 4.61 and 4.54 (each

d, each 1 H, J 12.3 Hz, CH₂Ph), 4.19 (dddd, 1 H,

5.84 (ddd, 1 H, J_{1 ,2}1.6, J_{2 ,4}1.5 Hz, H-2⁰), 5.25

(m, 1 H, H-1⁰), 4.70 and 4.54 (each d, each 1 H, J

11.5 Hz, CH₂Ph), 4.64 and 4.57 (each d, each 1 H,

0

J 12.3 Hz, CH₂Ph), 4.23 (dddd, 1 H, J_{1 ,4}2.8, J_{4 ,5}

8.3 Hz, H-4⁰), 3.86±3.84 (m, 2 H, H-5⁰and H-6⁰b),

J_{1 ,4}3.3, J_{4 ,5}8.6 Hz, H-4⁰), 3.83±3.81 (m, 1 H, H-

5⁰), 3.82 (dd, 1 H, J_{5 ,6 b}2.0, J_{6 a,6 b}11.0 Hz, H-6⁰b),

0

3.79 (dd, 1 H, J_{5 ,6 a}5.6, J_{6 a,6 b}11.1 Hz, H-6⁰a),

2.41 (s, 3 H, p-Me±C₆H₄), 2.31 (s, 3 H, Me-3), and

2.26 (s, 3 H, Me-5); ¹³C NMR: ꢂ 147.49 (C-3),

138.27 (C-5), 130.75 (C-2⁰), 137.96, 137.65, 137.18,

137.04, 129.36, 128.23, 128.09, 127.67, 127.58,

127.51, 127.28, and 124.92 (2 Ph and p-C₆H₄±Me),

125.81 (C-3⁰), 116.08 (C-4), 77.70 (C-5⁰), 73.16 and

71.12 (2 OCH₂Ph), 70.45 (C-4⁰), 69.84 (C-1⁰), 69.74

(C-6⁰), 20.89 (p-C₆H₄±Me), 12.27 (Me-3), and 10.78

(Me-5); FABMS: m/z 517 (60, [M+Na]⁺), 495 (20,

[M+H]⁺), 413 (100, [M 81]); HRMS: m/z

494.2566 (Calcd for C₃₂H₃₄N₂O₃: 494.2569). Anal.

Calcd for C₃₂H₃₄N₂O₃: C, 77.70; H, 6.93; N, 5.66.

Found: C, 77.62; H, 6.96; N, 5.43.

0

3.75 (dd, 1 H, J_{5 ,6 a}5.6 Hz, H-6⁰a), 2.32 (s, 3 H,

Me-3), and 2.26 (s, 3 H, Me-5); ¹³C NMR: ꢂ 147.63

(C-3), 138.78 (C-5), 130.39 (C-2⁰), 138.23, 138.16,

137.89, 129.19, 128.90, 128.23, 128.10, 127.68,

127.61, 127.52, 127.32, and 125.17 (3 Ph), 126.09

(C-3⁰), 116.50 (C-4), 77.68 (C-5⁰), 73.18 and 71.15

(2 OCH₂Ph), 70.37 (C-4⁰), 69.68 (C-1⁰), 69.65

(C-6⁰), 12.02 (Me-3), and 10.83 (Me-5); FABMS:

m/z 503 (90, [M+Na]⁺), 481 (100, [M+H]⁺);

HRMS: m/z 480.2384 (Calcd for C₃₁H₃₂N₂O₃:

480.2413).

0

4-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-3-methyl-1,5-diphenylpyrazole (11):

0.412 g (76%) [from 5 (0.470 g) and phenylhy-

4-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-3-methyl-5-phenyl-1-(p-tolyl)pyr-

azole (13): 0.417 g (75%) [from 5 (0.470 g) and

21

D

drazine (0.886 g, 0.81 mL)]; ꢁ

+84^ꢀ(c 1,

CHCl₃); ꢄ_max(CH₂Cl₂) 256 nm (e_mM14.42); ꢃ_max

1724 (C C), 1599, 1505 (Ph), 1562 cm ¹(pyrazole

C N); ¹H NMR: ꢂ 7.39±7.14 (m, 20 H, 4 Ph), 5.97

p-tolylhydrazine (released from its hydrochloride:

21

D

1.30 g)]; ꢁ +89^ꢀ(c 1, CHCl₃); ꢄ_max(CH₂Cl₂)

(ddd, 1 H, J_{2 ,3}10.3, J_{1 ,3}2.5, J_{3 ,4}1.7 Hz, H-3⁰),

239, 254 nm (e_mM18.67, 18.05); ꢃ_max1723 (C C),

0

5.80 (ddd, 1 H, J_{1 ,2}&J_{2 ,4}1.6 Hz, H-2⁰), 5.11 (m, 1

H, H-1⁰), 4.64 and 4.49 (each d, each 1 H, J

11.5 Hz, CH₂Ph), 4.63 and 4.55 (each d, each 1 H,

1609, 1497 (Ph), 1587 cm (pyrazole C N); H

NMR: ꢂ 7.35±7.03 (m, 19 H, 3 Ph and p-C₆H₄±

1

0

Me), 5.96 (ddd, 1 H, J_{2 ,3}10.3, J_{1 ,3}2.6, J_{3 ,4}

0

J 12.1 Hz, CH₂Ph), 4.15 (dddd, 1 H, J_{1 ,4}3.0, J_{4 ,5}

1.7 Hz, H-3⁰), 5.79 (ddd, 1 H, J_{1 ,2}1.6, J_{2 ,4}1.7 Hz,

H-2⁰), 5.10 (m, 1 H, H-1⁰), 4.63 and 4.49 (each d,

each 1 H, J 11.5 Hz, CH₂Ph), 4.62 and 4.55 (each

d, each 1 H, J 12.1 Hz, CH₂Ph), 4.13 (dddd, 1 H,

8.4 Hz, H-4⁰), 3.86±3.72 (m, 3 H, H-5⁰, H-6⁰a, and

H-6⁰b), and 2.38 (s, 3 H, Me); NOE contacts (1D

NOESY): H-1⁰, H-2⁰, H-5⁰and Me-3; ¹³C NMR: ꢂ

148.60 (C-3), 141.88 (C-5), 130.14 (C-2⁰), 139.68,

138.32, 137.94, 130.56, 130.14, 129.64, 128.48,

J_{1 ,4}3.0, J_{4 ,5}8.6 Hz, H-4⁰), 3.83±3.71 (m, 3 H, H-

5⁰, H-6⁰a, and H-6⁰b), 2.37 (s, 3 H, p-Me±C₆H₄),

0

188

P. Borrachero-Moya et al./Carbohydrate Research 308 (1998) 181±190

and 2.29 (s, 3 H, Me-3); ¹³C NMR: ꢂ 148.36 (C-3),

141.98 (C-5), 130.64 (C-2⁰), 138.41, 138.03, 137.16,

136.61, 130.23, 129.70, 129.16, 128.28, 128.16,

128.13, 127.72, 127.63, 127.57, 127.35, and 124.64

(3 Ph and p-C₆H₄±Me), 126.10 (C-3⁰), 117.45 (C-4),

77.54 (C-5⁰), 73.23 and 71.05 (2 OCH₂Ph), 70.47

(C-4⁰), 69.92 (C-6⁰), 69.61 (C-1⁰), 20.87 (p-C₆H₄±

Me), and 12.83 (Me-3); FABMS: m/z 579 (70,

[M+Na]⁺), 557 (100, [M+H]⁺); HRMS: m/z

556.2724 (Calcd for C₃₇H₃₆N₂O₃: 556.2726). Anal.

Calcd for C₃₇H₃₆N₂O₃: C, 79.83; H, 6.52; N, 5.03.

Found: C, 79.62; H, 6.57; N, 4.83.

each 1 H, J 11.5 Hz, CH₂Ph), 4.62 and 4.55 (each

d, each 1 H, J 12.0 Hz, CH₂Ph), 4.13 (dddd, 1 H,

J_{1 ,4}2.9, J_{4 ,5}8.4 Hz, H-4⁰), 3.84±3.73 (m, 3 H, H-

5⁰, H-6⁰a, and H-6⁰b), 3.76 (s, 3 H, OMe), and 2.36

(s, 3 H, Me-3); ¹³C NMR: ꢂ 148.23 (C-3), 141.97

(C-5), 130.71 (C-2⁰), 138.40, 158.20, 138.01, 133.04,

130.23, 129.72, 128.28, 128.20, 128.16, 128.10,

127.72, 127.62, 127.57, 127.34, 126.19, and 113.74

(3 Ph and p-C₆H₄±OMe), 126.02 (C-3⁰), 117.12 (C-

4), 77.52 (C-5⁰), 73.21 and 71.03 (2 OCH₂Ph), 70.47

(C-4⁰), 69.91 (C-6⁰), 69.66 (C-1⁰), 55.27 (OMe), and

12.87 (Me-3); FABMS: m/z 595 (100, [M+Na]⁺),

573 (80, [M+H]⁺); HRMS: m/z 572.2676 (Calcd

for C₃₇H₃₆N₂O₄: 572.2675). Anal. Calcd for

C₃₇H₃₆N₂O₄: C, 77.60; H, 6.34; N, 4.89. Found: C,

77.59; H, 6.56; N, 4.76.

0

4-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-1-(p-methoxyphenyl)-3,5-dimethy-

lpyrazole (14): 0.367 g (72%) [from 4 (0.408 g) and

p-methoxyphenylhydrazine (released from its

22

D

hydrochloride: 1.43 g)]; ꢁ +111^ꢀ(c 1, CHCl₃);

Catalytic hydrogenation of 4-(4,6-di-O-benzyl-

2,3-dideoxy-b-d-erythro-hex-2-enopyranosyl)pyra-

zoles.ÐDry 20% Pd(OH)₂/C catalyst (91 mg)

was added to a solution of the corresponding,

thoroughly dried, substrate (0.12 mmol) in dry

MeOH (6 mL). Hydrogen (atmospheric pressure)

was bubbled through this suspension for 5 min,

and the mixture was then kept under stirring in a

hydrogen atmosphere at room temperature for 24 h

(monitoring by TLC, 2:1 hexane±EtOAc). If

necessary, a similar additional amount of the cata-

lyst was used and the hydrogen atmosphere reset

for 1 h. The catalyst was ®ltered o and washed

with MeOH. Evaporation of the solvent aorded

the product as an oil.

ꢄ_max(CH₂Cl₂) 251 nm (e_mM18.19); ꢃ_max1721

1

(C C), 1607, 1589, and 1518 (Ph), 1570 cm

1

(pyrazole C N); H NMR: ꢂ 7.37±6.95 (m, 14 H,

0

2 Ph and p-C₆H₄±OMe), 6.06 (ddd, 1 H, J_{2 ,3}10.3,

0

J_{1 ,3}1.9, J_{3 ,4}1.5 Hz, H-3⁰), 5.83 (ddd, 1 H,

0

J_{1 ,2}&J_{2 ,4}1.7 Hz, H-2⁰), 5.24 (m, 1 H, H-1⁰), 4.69

and 4.53 (each d, each 1 H, J 11.5 Hz, CH₂Ph),

4.64 and 4.56 (each d, each 1 H, J 12.3 Hz,

0

CH₂Ph), 4.21 (dddd, 1 H, J_{1 ,4}3.0, J_{4 ,5}8.4 Hz, H-

4⁰), 3.86±3.81 (m, 2 H, H-5⁰and H-6⁰b), 3.78 (dd, 1

H, J_{5 ,6 a}5.7, J_{6 a,6 b}11.1 Hz, H-6⁰a), 3.85 (s, 3 H, p-

MeO±C₆H₄), 2.30 (s, 3 H, Me-3), and 2.23 (s, 3 H,

Me-5); ¹³C NMR: ꢂ 147.42 (C-3), 138.37 (C-5),

130.89 (C-2⁰), 158.83, 138.05, 137.89, 132.77,

128.35, 128.21, 127.79, 127.70, 127.62, 127.41,

126.64, and 113.38 (2 Ph and p-C₆H₄±OMe),

125.87 (C-3⁰), 116.12 (C-4), 77.78 (C-5⁰), 73.26 and

71.24 (2 OCH₂Ph), 70.55 (C-4⁰), 69.96 (C-1⁰), 69.83

(C-6⁰), 55.44 (OMe), 12.38 (Me-3), and 10.89 (Me-

5); FABMS: m/z 533 (80, [M+Na]⁺), 511 (85,

[M+H]⁺); HRMS: m/z 510.2524 (Calcd for

C₃₂H₃₄N₂O₄: 510.2518). Anal. Calcd for

C₃₂H₃₄N₂O₄: C, 75.27; H, 6.71; N, 5.45. Found: C,

75.43; H, 6.79; N, 5.45.

0

4-(2,3-Dideoxy-b-d-erythro-hexopyranosyl)-1,3-

dimethyl-5-phenylpyrazole (16): 21 mg (58%) [from

9 (58 mg)]; ꢄ_max(CH₂Cl₂) 246 nm (e_mM4.55); ꢃ_max

1

3336 br (OH), 1503 (Ph), 1553 cm

1

(pyrazole

C N); H NMR: ꢂ 7.48±7.25 (m, 5 H, Ph), 4.23

(dd, 1 H, J_{1 ,2 ax}11.6, J_{1 ,2 eq}2.3 Hz, H-1⁰), 3.77 (dd,

0

1 H, J_{6 a,6 b}11.5, J_{5 ,6 a}4.5 Hz, H-6⁰a), 3.73 (dd, 1

0

H, J_{5 ,6 b}4.7 Hz, H-6⁰b), 3.61 (s, 3 H, Me-1), 3.52

0

(ddd, 1 H, J_{4 ,5}&J_{3 ax,4}9.2, J_{3 eq,4}4.7 Hz, H-4⁰),

0

3.19 (ddd, 1 H, H-5⁰), 2.34 (s, 3 H, Me-3), 2.06

0 0 0 0

(dddd, 1 H, J_gem12.7, J_{2 ax,3 eq}3.8, J_{2 eq,3 eq}6.5 Hz,

4-(4,6-Di-O-benzyl-2,3-dideoxy-b-d-erythro-hex-

2-enopyranosyl)-1-(p-methoxyphenyl)-3-methyl-5-

phenylpyrazole (15): 0.406 g (71%) [from 5 (0.470 g)

H-3⁰eq), 1.83 (dddd, 1 H, J_gem13.7, J_{2 ax,3 ax}

0

11.7 Hz, H-2⁰ax), 1.68 (dddd, 1 H, J_{2 eq,3 ax}4.0 Hz,

H-2⁰eq), and 1.47 (dddd, 1 H, H-3⁰ax); ¹³C NMR: ꢂ

145.60 (C-3), 141.90 (C-5), 130.32, 129.91, 128.78,

128.72, 128.47, and 128.21 (Ph), 117.45 (C-4), 81.43

(C-5⁰), 72.69 (C-1⁰), 67.25 (C-4⁰), 63.41 (C-6⁰), 36.45

(Me-1), 32.84 (C-3⁰), 30.97 (C-2⁰), and 13.02 (Me-

3); FABMS: m/z 325 (100, [M+Na]⁺), 303 (19,

[M+H]⁺); HRMS: m/z 302.1633 (Calcd for

C₁₇H₂₂N₂O₃: 302.1630).

0

and p-methoxyphenylhydrazine (released from its

23

D

hydrochloride: 1.43 g); ꢁ +80^ꢀ(c 1, CHCl₃);

ꢄ_max(CH₂Cl₂) 240 nm (e_mM26.28); ꢃ_max1719

1

(C C), 1516 (Ph), 1578 cm (pyrazole C N);

¹H NMR: ꢂ 7.36±6.75 (m, 19 H, 3 Ph and p-C₆H₄±

0

OMe), 5.96 (ddd, 1 H, J_{2 ,3}10.3, J_{1 ,3}&J_{3 ,4}

1.7 Hz, H-3⁰), 5.80 (ddd, 1 H, J_{1 ,2}&J_{2 ,4}1.7 Hz,

0

H-2⁰), 5.10 (m, 1 H, H-1⁰), 4.63 and 4.49 (each d,

P. Borrachero-Moya et al./Carbohydrate Research 308 (1998) 181±190

189

4-(2,3-Dideoxy-b-d-erythro-hexopyranosyl)-3-

methyl-5-phenyl-1-(p-tolyl)pyrazole (17): 23 mg

(51%) [from 13 (67 mg)]; ꢄ_max(CH₂Cl₂) 242sh and

254 nm (e_mM10.79 and 11.10); ꢃ_max3420 and 3178

(4.75 mL) was added under stirring to a cold (ice

bath) soln of 13 (0.200 g, 0.36 mmol) in a mixture

of glacial HOAc (2.0 mL) and Ac₂O (4.75 mL). The

mixture was kept in the ice bath under stirring for

2 h, then in the refrigerator until 13 was completely

consumed (16 h; TLC, 4:1 and 3:1 hexane±EtOAc).

The reaction mixture was poured into ice, stirred

for 3.5 h, and extracted with EtOAc (4Â50 mL).

The combined organic extracts were washed with

satd aq NaHCO₃until pH&7 and then with water

(2Â50 mL). After drying (MgSO₄), evaporation of

the organic solvent gave a syrup, which was sub-

jected to preparative TLC (3:1 hexane±EtOAc).

Two main fractions were studied (in order of

decreasing mobility): A (58.3 mg) and B (30.0 mg).

Fraction A consists of a 2.5:1 mixture of two epimers

tentatively formulated as 4R- and 4S-{E-2-[5-phenyl-

1-(p-tolyl)pyrazol-4-yl]vinyl}-3S-(d-glycero-1,2-

diacetoxyethyl)-3,4-dihydro-1H-benzo[c]pyran (19);

FABMS: m/z 573 (100, [M+Na]⁺), 551

(84, [M+H]⁺); FABHRMS: m/z 573.2326

(54, [M+Na]⁺; calcd for C₃₄H₃₄N₂O₅+Na:

573.2365), 551.2587 (100, [M+H]⁺; calcd for

C₃₄H₃₄N₂O₅+H: 551.2546); major isomer: ¹H

NMR (for convenience, the numbering of the

sugar moiety is maintained): ꢂ 7.40±6.98 (m, Ph, p-

1

br (OH), 1611, 1518, 1493 (Ph), 1588 cm (pyr-

1

azole C N); H NMR: ꢂ 7.37±6.97 (m, 9 H, Ph

0

and p-C₆H₄±Me), 4.33 (dd, 1 H, J_{1 ,2 ax}11.7, J_{1 ,2 eq}

0

2.3 Hz, H-1⁰), 3.81 (dd, 1 H, J_{6 a,6 b}11.5, J_{5 ,6 a}

0

4.3 Hz, H-6⁰a), 3.77 (dd, 1 H, J_{5 ,6 b}4.8 Hz, H-6⁰b),

0

3.60 (ddd, 1 H, J_{4 ,5}9.2 J_{3 ax,4}11.1, J_{3 eq,4}4.4 Hz,

H-4⁰), 3.23 (ddd, 1 H, H-5⁰), 2.44 (s, 3 H, Me-3),

2.28 (s, 3 H, p-Me±C₆H₄), 2.11 (dddd, 1 H, J_gem

12.5, J_{2 ax,3 eq}4.1, J_{2 eq,3 eq}3.7 Hz, H-3⁰eq), 1.96

(dddd, 1 H, J_gem13.7, J_{2 ax,3 ax}11.5 Hz, H-2⁰ax),

0

1.77 (dddd, 1 H, J_{2 eq,3 ax}4.1 Hz, H-2⁰eq), and 1.51

(dddd, 1 H, H-3⁰ax); ¹³C NMR: ꢂ 147.28 (C-3),

141.09 (C-5), 137.27, 136.66, 130.46, 130.21,

129.21, 128.42, 128.29, and 124.67 (Ph and p-

C₆H₄±Me), 118.88 (C-4), 81.52 (C-5⁰), 72.70 (C-1⁰),

67.42 (C-4⁰), 63.55 (C-6⁰), 32.93 (C-3⁰), 30.96 (C-2⁰),

20.93 (p-C₆H₄±Me), and 13.39 (Me-3); FABMS:

m/z 401 (100, [M+Na]⁺), 379 (25, [M+H]⁺);

HRMS: m/z 378.1948 (Calcd for C₂₃H₂₆N₂O₃:

378.1943).

0

4-(2,3-Dideoxy-b-d-erythro-hexopyranosyl)-1-(p-

methoxyphenyl)-3-methyl-5-phenylpyrazole

32 mg (67%) after column chromatography [from

(18):

C₆H₄±Me, and ±C₆H₄± of benzo[c]pyran), 6.17 (d,

0

15 (69 mg)]; ꢄ_max(CH₂Cl₂) 242 and 254sh nm (e_mM

13.52 and 12.87); ꢃ_max3404 br (OH), 1609, 1516

1 H, J_{1 ,2}16.1 Hz, H-1 ), 5.91 (dd, 1 H, J_{2 ,3}9.5 Hz,

0

H-2⁰), 5.04 (ddd, 1 H, J_{4 ,5}9.7, J_{5 ,6 a}2.3, J_{5 ,6 b}

4.3 Hz, H-5⁰), 4.90 and 4.81 (each d, each 1 H, J

0

1

(Ph), 1588 cm

7.36±6.70 (m, 9 H, Ph and p-C₆H₄±OMe), 4.33 (dd,

(pyrazole C N); ¹H NMR: ꢂ

0 0

15.0 Hz, CH₂Ph), 4.59 (dd, 1 H, J_{6 a,6 b}12.3 Hz, H-

6⁰a), 4.30 (dd, 1 H, H-6⁰b), 3.94 (dd, 1 H, J_{3 ,4}2.7,

0 0

1 H, J_{1 ,2 ax}11.7, J_{1 ,2 eq}2.3 Hz, H-1⁰), 3.80 (dd, 1 H,

0

J_{6 a,6 b}11.4, J_{5 ,6 a}4.4 Hz, H-6⁰a), &3.75 (dd, 1 H,

J_{4 ,5}9.7 Hz, H-4⁰), 3.42 (dd, 1 H, H-3⁰), 2.38 (s, 3

H, Me-3), 2.28 (s, 3 H, p-Me±C₆H₄), 2.05 (s, 3 H,

AcO-5⁰), and 1.92 (s, 3 H, AcO-6⁰); ¹³C NMR: ꢂ

170.7 and 169.4 (2 C O), 147.2 (C-3), 140.6 (C-5),

128.3 (C-2⁰), 138±124 (Ph and 2 C₆H₄), 122.3 (C-

1⁰), 116.8 (C-4), 74.7 (C-4⁰), 71.1 (C-5⁰), 68.7

(OCH₂Ph), 62.5 (C-6⁰), 44.2 (C-3⁰), 20.9 (p-Me±

C₆H₄), 20.7 (2 MeCOO), and 14.1 (Me-3); minor

isomer: ¹H NMR: ꢂ 7.40±6.98 (m, Ph, p-C₆H₄±Me,

0

J_{5 ,6 b}4.8 Hz, H-6⁰b), 3.74 (s, 3 H, OMe), 3.56 (ddd,

0

1 H, J_{4 ,5}9.2, J_{3 ax,4}11.0, J_{3 eq,4}4.6 Hz, H-4⁰), 3.22

0

(ddd, 1 H, H-5⁰), 2.43 (s, 3 H, Me-3), 2.10 (dddd, 1

H, J_gem12.5, J_{2 ax,3 eq}3.7, J_{2 eq,3 eq}4.0 Hz, H-3⁰eq),

0

1.95 (dddd, 1 H, J_gem13.5, J_{2 ax,3 ax}11.5 Hz, H-

2⁰ax), 1.76 (dddd, 1 H, J_{2 eq,3 ax}2.7 Hz, H-2⁰eq),

and 1.50 (dddd, 1 H, H-3⁰ax); NOE contacts (1D

NOESY): H-1⁰, H-2⁰eq, H-3⁰ax, H-5⁰ax, and Me-3;

H-4⁰, H-2⁰ax, and H-3⁰eq; ¹³C NMR: ꢂ 147.12 (C-

3), 141.24 (C-5), 158.38, 132.96, 130.39, 130.22,

128.40, 128.27, 126.30, and 113.83 (Ph and p-

C₆H₄±OMe), 118.65 (C-4), 81.56 (C-5⁰), 72.73 (C-

1⁰), 67.38 (C-4⁰), 63.53 (C-6⁰), 55.34 (OMe), 32.91

(C-3⁰), 30.95 (C-2⁰), and 13.27 (Me-3); FABMS: m/

z 417 (100, [M+Na]⁺), 395 (57, [M+H]⁺);

HRMS: m/z 394.1897 (Calcd for C₂₃H₂₆N₂O₄:

394.1893).

0

and ±C₆H₄± of benzo[c]pyran), 6.47 (d, 1 H, J_{1 ,2}

0

16.1 Hz, H-1⁰), 5.68 (dd, 1 H, J_{2 ,3}8.6 Hz, H-2⁰),

0

5.45 (ddd, 1 H, J_{4 ,5}&J_{5 ,6 a}3.0, J_{5 ,6 b}12.6 Hz, H-

5⁰), 4.55 (dd, 1 H, J_{6 a,6 b}12.3 Hz, H-6⁰a), 4.31±4.26

0

(m, 1 H, H-6⁰b), 3.94 (dd, 1 H, J_{3 ,4}&10 Hz, H-4 ),

3.65 (dd, 1 H, H-3⁰), 2.41 (s, 3 H, Me-3), 2.30 (s, 3

H, p-Me±C₆H₄), 2.09 (s, 3 H, AcO-5⁰), and 1.98 (s,

3 H, AcO-6⁰); ¹³C NMR: ꢂ 170.6 and 170.2 (2

C=O), 147.3 (C-3), 140.8 (C-5), 127.9 (tentative

for C-2⁰), 138±124 (Ph and 2 C₆H₄), 122.5 (tenta-

tive for C-1⁰), 116.7 (C-4), 78.8 (C-4⁰), 72.2 (C-5⁰),

0

Acetolysis of 13.ÐA cold soln of concd H₂SO₄

(0.27 mL), glacial HOAc (2.0 mL) and Ac₂O

190

P. Borrachero-Moya et al./Carbohydrate Research 308 (1998) 181±190

68.4 (OCH₂Ph), 62.2 (C-6⁰), 44.9 (C-3⁰), and 21.0

(p-Me±C₆H₄). Fraction B: FABMS: m/z 461 (100,

[M+H]⁺), 483 (62, [M+Na]⁺); FABHRMS: m/z

483.1889 (13, [M+Na]⁺; calcd for C₂₇H₂₈N₂O₅

+Na: 483.1895), 461.2071 (100, [M+H]⁺; calcd for

C₂₇H₂₈N₂O₅+H: 461.2076; the major component

is tentatively formulated as 4-(4,6-di-O-acetyl-2,3-

dideoxy-ꢀ-d-erythro-hex-2-enopyranosyl)-3-methyl-

5-phenyl-1-(p-tolyl)pyrazole (20, 10% yield from

130.5±124.5 (Ph and p-C₆H₄±Me), 127.91 (C-2⁰),

117.23 (C-4), 76.01 (C-5⁰), 72.93 (C-6⁰), 69.61 (C-

1⁰), 66.63 (C-4⁰), 20.97 (p-C₆H₄±Me), and 12.82

(Me-3).

Acknowledgements

The authors thank Professor A. Gomez-Sanchez

for helpful discussions, the Direccion General de

Investigacion Cientõ®ca y Tecnica (DGICYT)

(Project PB91-0615) and the Consejerõa de Educa-

cion y Ciencia de la Junta de Andalucõa for ®nan-

cial support. One of us (M.R.P.-L.) thanks the

same Consejerõa for a predoctoral fellowship.

1

13, by H NMR): H NMR: ꢂ 7.38±6.99 (m, 9 H,

0

Ph and p-C₆H₄±Me), 5.88 (ddd, 1 H, J_{2 ,3}10.3,

0

J_{1 ,3}&J_{3 ,4}1.7 Hz, H-3⁰), 5.80 (ddd, 1 H, J_{1 ,2}

0

2.7, J_{2 ,4}1.9 Hz, H-2⁰), 5.40 (dddd, 1₀H, J_{1 ,4}3.3,

0

J_{4 ,5}8.9 Hz, H-4 ), 5.13 (ddd, 1 H, H-1 ), 4.27 (dd, 1

0

H, J_{6 a,6 b}12.1 Hz, H-6⁰a), 4.20 (dd, 1 H, H-6⁰b),

0

3.86 (ddd, 1 H, J_{5 ,6 a}2.4, J_{5 ,6 b}5.6 Hz, H-5⁰), 2.38

(s, 3 H, Me-3), 2.29 (s, 3 H, p-Me±C₆H₄), 2.12 (s, 3

H, AcO-4⁰), and 2.09 (s, 3 H, AcO-6⁰); ¹³C NMR: ꢂ

170.86 and 170.29 (2 C O), 148.41 (C-3), 142.09

(C-5), 131.94 (C-3⁰), 137.33, 136.77, 130.26, 129.27,

128.54, 128.45, 128.32, 128.25, and 124.70 (Ph and

p-C₆H₄±Me), 125.11 (C-2⁰), 116.72 (C-4), 74.71 (C-

5⁰), 69.92 (C-1⁰), 65.32 (C-4⁰), 63.63 (C-6⁰), 21.00

(MeCOO), 20.95 (p-C₆H₄±Me), 20.81 (MeCOO),

and 12.93 (Me-3).

0

References

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Methanolysis of crude 20.ÐTo a soln of Fraction

B without more puri®cation (26 mg) in dry MeOH

(2.1 mL) was added M NaOMe (0.1 mL), and the

mixture was kept under stirring at room tempera-

ture for 1.5 h. TLC (3:1 hexane±EtOAc) showed

the consumption of the starting material. After

neutralisation with Amberlite IRA-120 (H⁺) resin,

the solvent was evaporated to give an oily product

(17 mg): DCIHRMS: m/z 377.1845 (100, [M+1]⁺;

calcd for C₂₃H₂₄N₂O₃+H: 377.1865) 376.1805

(53.9, [M]⁺); calcd for C₂₃H₂₄N₂O₃: 376.1787; one

main component of the mixture obtained is tenta-

tively formulated as 4-(2,3-dideoxy-ꢀ-d-erythro-

hex-2-enopyranosyl)-3-methyl-5-phenyl-1-(p-tolyl)-

pyrazole (21, &25% in the mixture, ¹H NMR): ¹H

NMR (CDCl₃+D₂O): ꢂ 7.41±7.01 (m, 9 H, Ph and

0

p-C₆H₄±Me), 5.96 (ddd, 1 H, J_{2 ,3}10.5, J_{1 ,3}2.2,

0

J_{3 ,4}2.0 Hz, H-3⁰), 5.71 (ddd, 1 H, J_{1 ,2}1.8, J_{2 ,4}

0

1.9 Hz, H-2⁰), 5.11 (ddd, 1 H,J_{1 ,4}3.0 Hz, H-1⁰),

0

[13] C. Choquet-Farnier, I. Stasik, and D. Beaupere,

Carbohydr. Res., 303 (1997) 185±191.

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Soc., 76 (1954) 1757±1760.

[15] R.J. Angeligi (Ed.), Inorganic Synthesis, Vol. 28,

Wiley, 1990, p 111.

4.46 (dddd, 1 H, J_{4 ,5}8.7 Hz, H-4⁰), 4.30±4.26 (m, 1

0

H, H-5⁰), 4.17 (dd, 1 H, J_{6 a,6 b}10.1, J_{5 ,6 a}5.3 Hz,

0

H-6⁰a), 3.78 (dd, 1 H, J_{5 ,6 b}3.2 Hz, H-6⁰b), 2.46 (s,

3 H, p-Me±C₆H₄), and 2.27 (s, 3 H, Me-3); ¹³C

NMR: ꢂ 149.84 (C-3), 142.51 (C-5), 131.27 (C-3⁰),

0

Article Doi

Synthesis of 4-(4,6-di-O-benzyl-2,3-dideoxy-β-D-erythro-hex-2- enopyranosyl)pyrazoles from 3,4,6-tri-O-acetyl-D-glucal

DOI: 10.1016/S0008-6215(98)00059-7

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Article abstract of DOI:10.1016/S0008-6215(98)00059-7

Full text of DOI:10.1016/S0008-6215(98)00059-7

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