FR2712888A1 - Use of alpha-D-alkylglucopyranosides and esters thereof for the preparation of prodrugs capable of crossing the blood-brain barrier, prodrugs obtained and precursors thereof. - Google Patents

Abstract

The invention relates in particular to the use, as drug transporters to the central nervous system (CNS), of alpha-D-alkylglucopyranosides and esters thereof having the general formula (I): (CF DRAWING IN BOPI) in which R1 is an alkyl radical, linear or branched, C2 to C1 8; R2 is a group -CO-R where R is a hydrocarbon radical, linear or branched, saturated or ethylenically unsaturated, C5 to C1 7, or a group -CO- (CH2) n -COOH where n = 4 to 14; R3 and R4 are each, independently, H or the residue -CO-R 'of a fatty acid HOOC-R' where R 'is a hydrocarbon radical, linear or branched, saturated or ethylenically unsaturated C5 to C1 7, with the provided that only one of the groups R3 and R4 is a residue -CO-R '.

Description

The invention relates to the use of D-alkyl-

  glucopyranosides and esters thereof for the preparation of

  prodrugs capable of crossing the blood-brain barrier

  encephalic, the prodrugs obtained and precursors thereof. The central nervous system (CNS) is protected from variations in the concentrations of the different nutrients present in the blood compartment. This protection is conferred by a barrier that separates it from blood: the blood-brain barrier (BBB). Very selective, it ensures however a constant supply in the various substances which it needs for its operation. However, this barrier can become a major obstacle when dysfunction occurs within the CNS, as can cause certain viruses, bacteria, cancerous tumors, epileptic manifestations and other neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, chorea Huntington). Indeed, the transport of drugs within the CNS, through the BBB, at a concentration level where they would be effective, is difficult, if not impossible. This transfer is often the limiting step in the treatment of central conditions. The case of neurodegenerative diseases, and in particular Alzheimer-type senile dementias, represents a new challenge for the pharmaceutical industry as this type of dementia progresses with the increasing aging of the population. The latest estimates for the United States give the figures of 4 million patients today, and provide 23 million in the US

  world in the year 2000, including 5 to 8 million for the United States alone.

  United. The economic stakes are enormous: more than 2 billion dollars a year will be needed for the treatment of these

diseases.

  There is therefore a need for a means that would improve the passage through the BBB of active substances, which do not normally or very little pass through the BBB, so that they can act more

effectively on the CNS.

  The present invention aims to provide such a means.

  More particularly, the present invention relates to the use, as drug transporters to the central nervous system (CNS), of α-D-alkylglucopyranosides and esters thereof having the general formula (I):

CH2OR2

(I) OR

HO OR1

  OR3 wherein R1 is a linear or branched C2 to C12 alkyl radical, preferably n-butyl; R 2 is -CO-R o R is a linear or branched, saturated or ethylenically unsaturated, C 5 to C 17 hydrocarbon radical, or a group -CO- (CH 2), -COOH n = 4 to 14; R3 and R4 are each, independently, H or the residue -CO-R 'of a fatty acid HOOC-R' o R 'is a hydrocarbon radical, linear or branched, saturated or ethylenically unsaturated Cs to C17, with the proviso only one of groups R3 and R4 is a remainder

-HORN'.

  The invention is based on the discovery that one can improve the passage of drugs or neurotransmitters through the BBB by attaching them to suitable fat-soluble carrier compounds. The resulting products called "prodrugs" (carrier / active compound) are able to cross the BBB because they are

  more fat soluble than the individual active compound.

  To obtain an adequate liposolubility, it is of course necessary to choose a carrier adapted to the compound

active to carry.

  The compounds of formula (I) defined above are well suited for the attachment of active compounds containing a free carboxylic group which do not diffuse, or very little, through the BBB. Indeed, the OH groups available on the compounds of formula (I) are esterifiable by such compounds with production of esters, some of which are able to cross the BBB in increased proportion relative to

  to the active starting compound. In the case where R2 is a group -

  CO- (CH2) n-COOH, they are also suitable for binding active compounds containing a free primary amino or hydroxyl group. Indeed, the amino or hydroxyl group can

  react with the free carboxyl group of the group -CO- (CH2), -

  COOH with production of amides or esters.

  The resulting compounds that are able to cross

  the BBB are those that have a fat-soluble character.

  Nonlimiting examples of water-soluble compounds containing a free carboxyl group, having a pharmacological interest as drugs or as neurotransmitters but whose use for treating disorders or diseases of the CNS has not given up to date the expected results due to their too low transfer through the BBB, are amino acids eg gamma-aminobutyric acid (GABA) and its derivatives, glycine, DOPA and others, short peptides (2-4 acids) amino acids, for example) and certain anti-inflammatory compounds which include a carboxyl group as

Diclofenac.

  Depending on the particular compound of formula (I) used, it is possible to react 2 or 3 molecules of carboxylic compound per molecule of compound of formula (I), depending on whether the latter

comprises 2 or 3 free -OH groups.

  Nonlimiting examples of water-soluble active compounds containing a free amino or hydroxyl reactive group are dopamine, serotonin, etc. A molecule of amine or hydroxyl compound can be reacted per molecule of compound of formula (I) comprising a group R2 to

free carboxyl group.

  The compounds of formula (I) useful for the purposes of the invention are those which have a lipophilic character. The lipophilicity of a given compound can be determined from its partition coefficient P in a toluene mixture (1: 1, by volume): p = Ctol / C.water o Cto1 is the concentration of the compound in the toluene phase ", and C.water is the concentration of the compound in the aqueous phase and is hereinafter expressed by the value Log P:

Log P = LogC - Log Cto - Log Cu.

  The concentration of the compound in each of the phases can be measured by anthrone colorimetric assay

(Λ max = 625 nm).

  Considering the sensitivity of the measurement methods, measured Log P values can range from -3 for highly water-soluble compounds, such as glucose, to +3 for highly fat-soluble molecules, such as benzene.

or octanol.

  In the case of a compound of formula (I), it must have a log P value of at least 0.50, preferably at least 1.4, so that its lipophilicity can counterbalance the hydrophilicity attached to the active compound with

which he will be reacted to.

  The invention also relates to the compounds, hereinafter referred to as prodrugs, obtained as a result of the reaction of the free -OH groups or the free -COOH group of the compounds

  of formula (I) with a compound reactive with said group -

COOH or said -OH groups.

  More particularly, the invention relates to prodrugs of general formula (II): CH20B

/ O-E

A (II)

1R1

A-0OR

  OD o R1 is a linear or branched C2-C18 alkyl radical, preferably n-butyl; A is H, -CO-R "o R" is a hydrocarbon radical, linear or branched, saturated or ethylenically unsaturated C1 to C17, or the -CO-X residue of an active compound HOOC-X having a reactive carboxyl group ; B is a residue -CO-R 'of a fatty acid HOOC-R' o R 'is a hydrocarbon radical, linear or branched, saturated or

  ethylenically unsaturated C5 to C17, or a group -CO-

  (CH 2) n-COO-W n = 4 to 14 and W is the residue of an active compound having a primary amino group or a primary hydroxyl group; D and E are each, independently, H or a residue -CO-X or -CO-R '; with the provisos that (i) when B is -CO-R ', at least two of the groups A, D and E are -CO-X, and (ii) when B is -CO- (CH2), - COO-W , A, D and E are H, -CO-R '

or -CO-R ".

  The invention also relates to prodrug precursors of formula II, which have the general formula III:

CH20C-R '

-C-Z \

(III)

X -C-O

"e 0 C - Z

0 "

0

  where R 1 is as defined above, the group -CO-X 'is the residue of an amino acid or a peptide whose amino group (s) are protected, -CO-Z is a group -CO-X 'or a group -CO-R' as defined above, at least

one of -CO-Z being -CO-X '.

  Preferably the amino group of the amino acid is

  protected by a t-butyloxy-carbamate group (abbreviated as

  Boc). The compounds of formula (I) can be prepared by enzymatic esterification of the appropriate α-D-alkylglucopyranoside with a C 6 -C 18 fatty acid or a C 6 -C 16 dicarboxylic diacid in a non-polar solvent, such as hexane at reflux and in the presence of a lipase. Nonlimiting examples of lipases that can be used are Mucor miehei lipase adsorbed on an anionic resin, such as the Lipozyme product or Candida antartica lipase, such as the Novozym product, both sold by the company NOVO INDUSTRI (Denmark). This esterification mainly produces the monoester in

  position 6 with a little diester in position 2, 6. On the 6th

  monoester can then be esterified under

  similar to give the 2,6-diester. The a-D-

  starting alkylglucopyranosides are commercially available compounds or obtainable by

  enzymatic resolution of a commercial mixture of a- and B-

  D-alkylglucopyranosides using a β-glucosidase.

  Useful fatty acids are, for example, lauric acid, palmitic acid, stearic acid,

  linoleic, oleic acid, etc.

  Useful dicarboxylic diacids have the formula HOOC- (CH2), -COOH n = 4-14. Adipic acid and acid

  hexadecanedioic acid are preferred diacids.

  Some of the compounds of formula (II) may be prepared by coupling (esterifying) a compound having a free carboxylic group with the free -OH groups of a compound of formula (I). If the compound with free carboxylic group has another functional group capable of reaction during synthesis, as is the case, for example, with amino acids which comprise a -NH 2 reactive group, this other functional group must be protected before carrying out the reaction. In the case of an -NH 2 group of an amino acid, it may, for example, be protected by means of 2- (tert-butyloxycarbonyloxyimino) -2-phenylacetonitrile abbreviated to BOC-ON. described for example by Itoh, M .;

  Hagiwara, D and Kamiya, J. (1975), Tetrahedron Letters, 4393-

  4394. Protected amino acids are, however,

commercially available.

  The coupling of the optionally protected carboxylated compound with the compound of formula (I) can be carried out, for example, as described by Hassner, A. and Alexanian, V.

  (1978) Tetrahedron Letters, 4475-4478, using N, N-

  dicyclohexylcarbodiimide in the presence of N, N-

dimethylaminopyridine in CH2Cl2.

  Depending on the compound of formula (I) used (diester or monoester), one can couple 2 or 3 molecules of compound

  carboxylated per molecule of compound of formula (I).

  After coupling, deprotection of the protected groups is carried out, if appropriate, for example by hydrolysis using 50% by volume trifluoroacetic acid in CH 2 Cl 2 at 0 ° C. for 30 minutes, as taught. Lundt, BF; Johansen, N.L .; Volund, A. and Markussen, J. (1978), International Journal of Peptide and Protein Research 12, 258-268. In this case the compounds of formula (II) are

  obtained in salified form (trifluoroacetate).

  In the case where compounds of formula II are prepared by reacting a compound of formula (I), R2 is a group -CO- (CH2), -COOH with an amino or hydroxyl-containing compound.

  reagent, a protection operation is not necessary.

  The ability of the compounds of formula (II) and their salts to cross the BBB has been demonstrated by means of in vitro tests.

in vitro and in vivo in mice.

  The following non-limiting examples are given in

the purpose of illustrating the invention.

  Example 1 Preparation of α-Butylglucopyranoside (compound 1) 277 ml of an aqueous solution containing 50 g of a mixture of the anomers a and B of D-butylglucopyranoside (available from the company CERESTAR HOLDING) comprising 60% of the anomere a and 10 mM sodium acetate buffer (pH 5) were incubated with 27 g of almond powder [containing BD-glucosidase enzyme (EC: 3.2.1.2.1)] for 18 hours at 50 minutes. C. At the end of this time the anomer B had completely disappeared as shown by high performance liquid chromatography (HPLC). The resulting mixture was filtered and concentrated to dryness. Α-D-Butylglucopyranoside (Compound 1) (25 g, 83% yield) was extracted from the residue with hot CH 2 Cl 2 and used without further purification for further synthesis. Compound 1 has a value of Log P equal to 0.56. Example 2 Preparation of acylated derivatives of compound 1 (a) 1.7 g (8.5 mmol) of lauric acid and 1 g (4.23 mmol) of compound 1 prepared in Example 1 were added to Hexane boiling in a Dean-Stark apparatus. 0.15 g of Lipozyme (marketed by the company NOVO INDUSTRI) was added and the resulting suspension was stirred at 70 ° C. for 3 days, after which time the formation of diester was detected. The reaction mixture was filtered

  and evaporated the solvent under reduced pressure. A flash-

  silica column chromatography (94: 6 CH 2 Cl 2 -MeOH) of the obtained residue (2.60 g) gave the 6-lauroyl derivative (compound 2) (1.4 g, 80% yield). Compound (Z) had a melting point of 25 ° C; a rotatory power [a] n: + 29 (c 1.3, CHCl 3), a Log P equal to 0.87, and the IR analysis

  showed lines at 3490 (OH), 2980 (CH) and 1730 (C = O) cm-1.

  Calcd for C22H4207: C, 63.10, H, 10.04. Find:

C, 62.72; H, 10.04.

  (b) Using the procedure of (a) above except that lauric acid was replaced with the appropriate acid, 6-0-palmitoyl derivatives (compound 3) were prepared. ), 6-O-stearoyl (compound 4) and 6-O-oleoyl (compound 5). Compound 4 has a log P of 0.93. Table 1 below summarizes certain data concerning compounds 3,

4 and 5 obtained.

TABLE 1

: .. ANALYSIS

  Compound N Pf, C Yield% [a] 20 * Calculated Gross Formula Found

  3 30 78 +43 C28H5007 C, 64.56 64.38

H, 10.62, 10.65

  4 37 78 +36 C30H5407 C, 66.89 66.60

H, 10.82 11.08

  oil 80.5 +32 C30H5207 C, 65.98 65, 85

H, 10.48 10.39

o

* C 1.3, CHC13

  o, o, o, (c) To a molten mixture of 1 g (4.23 mmol) of compound 1 and 2.41 g of stearic acid (8.46 mmol) at 75 ° C, was added 0, 15 g of Lipozyme. After 72 hours of reaction, analysis by C13 NMR spectroscopy showed that the product obtained was a mixture of compound 4, 2,6-distearoyl derivative (compound 6) and 3-O-stearoyl derivative (compound 7).

  (d) Preparation of 2,6-di-O-stearoyl-a-D-

  Butylglucopyranoside (Compound 5) The synthesis of compound F from compound 4 and 1 equivalent of stearic acid was carried out according to the method.

  general procedure of part (a) of example 2 hereinafter

  above. The resulting crude product was flashed

  silica column chromatography (98: 2 CH 2 Cl 2 -MeOH) and compound 6 was obtained with an overall yield of 96%. This compound 6 had the following properties: mp 42 ° C; Log P KB 3480 (OH) 2970 1.76; [?] 20: + 34 (c 1.3, CHCl 3); 3480 (OH), 2970 (CH) and 1730 (C = O) cm- '. Analysis calculated for C46H8808: C,

  71.82; H, 11.53. Found: C, 71.74; H, 11.52.

  It should be noted that in the absence of an enzyme, it does not form

no esters.

  (e) Preparation of 2-O-lauroyl-6-O-stearoyl-a-D-

  Butylglucopyranoside (Compound 8) Compound 4 (1. g, 1.99 mmol) and lauric acid (0.4 g, 1.99 mmol) were reacted as described in (a) above for the preparation of Compound 6. After purification by flash chromatography as described in (d), 1.30 g of compound 8 (96% overall yield) were obtained. The compound had the following properties: Pf 39 C; [a] 0: + 58D (c 1, 16, CHCl 3). Elemental analysis calculated for C34H6408:

  C, 67.96; H, 10.73. Found C, 67.92; H, 11.10.

  (f) Preparation of 2,6-di-O-lauroyl-a-D-

  Butylglucopyranoside (Compound 9) Compound 9 was prepared following the procedure used in (d) above except that it replaced

  stearic acid with lauric acid.

  The melting point of this compound is below room temperature and has not been measured. Mass spectrometry: M '+ 17: 618; M + 601. Compound 9 has an equal Log P

at 1.41.

  The compounds 2 to 6, to and 9 are compounds corresponding to the general formula (I).

Example -a:

  Compounds (prodrugs) of formula II were prepared

  from compounds Z, 4, 6, and 9 and 4-amino acid.

  butyric acid or 4-amino-butanoic acid (abbreviated GABA) after protection of the reactive amino group of the latter. Protected forms of GABA are commercially available, particularly under the name t-bocGABA. GABA is an amino acid that has been chosen as a drug because, apart from the fact that GABA can not cross the BBB under normal conditions, it is known that its metabolism is impaired in diseases such as Alzheimer's, Parkinson's, Huntington's and epilepsy. The obtained compounds of formula II (GABA prodrugs) were evaluated for their ability to cross the BBB on an in vitro model of BBB. Their in vivo biological properties in the mouse were also evaluated by a mouse test.

  selection of anticonvulsant drugs.

  A) Preparation of 6-O-lauroyl 2.3.4-tri-O (N-tBoc 4-

  aminobutanoyl) α-D-butylglucopyranoside (compound 12) 1.31 g (5.5 mmol) of compound 2, 3.75 g (18.14 mmol) of N, N'-dicyclohexylcarbodiimide (DCC), 0.22 g (1 8 mmol) of N, N-dimethyl-amino-4-pyridine (DMAP) and 3.7 g (18.15 mmol) of tBoc-GABA of formula (CH3) 3COCONH (CH2) 3COOH (sold, for example, by the company ALDRICH CHEMICALS) are dissolved, with magnetic stirring, in 30 ml of dichloromethane at room temperature under a nitrogen atmosphere. A precipitate appears a few minutes after the addition of the reagents (corresponding to N, N'-dicyclohexylurea (DCU)), and the reaction medium is stirred for a further 2 hours. The precipitate is then removed by filtration, and the filtrate washed successively with aqueous solutions of 0.1 N HCl, 5% NaHCO 3 and saturated NaCl. The organic phase, dried over sodium sulphate is evaporated to dryness. The residual yellow oil is purified by flash chromatography on silica gel to give 2.95 g (3 mmol) of final product, with an overall yield of 70% after purification. Compound 12 has the following properties: Rotatory power [a] 20 + 58 (C 0.4, CH 3 OH) - Melting point: 89 C - Infrared analysis (NaCl): vNH amide: 3454 cm -1 CH 2 CH 2 CH 3: 2979.2960 cm -1 (CH 3) 3 C (strain CH): 1393/1363 (ratio 1/2) cm -1 = ester: 1745 cm -1; vC = O carbamate: 1654 cm- 'v- (CH 3) 3 C (tBoc backbone): 1250 cm -1 Elemental analysis for C 53 H 95 N 3 O 6: Calc .: C 60.43 H 9.03 N 4.31 Found: C: 60.35 H: 8.53 N: 4.20

  B) Preparation of 6-O-lauroyl 2,3,4-tri-O- (4-ammonium)

  butanoyl) α-D-butylglucooyranoside-tris-trifluoroacetate (compound 22) 0.2 g (2.06 × 10 -4 mol) of compound 12 is dissolved with stirring, at 0 ° C., in 1.5 ml of CH 2 Cl 2, and under an atmosphere of nitrogen, 1.5 ml of trifluoroacetic acid are then added and 30 minutes later, the reaction medium is brought to dryness by distillation under reduced pressure. The residual oil is purified by preparative thin layer chromatography (TLC) on RP-18 grafted silica. The strip corresponding to the product is scraped, washed with methanol and concentrated. This methanol phase, diluted 30 times in water, is freeze-dried to yield 0.205 g of product

  final with a quantitative yield.

  Compound 22 has the following properties - Rotatory power: [α] 20 + 52 (C 0.434, CH 3 OH)

- Melting point: hygroscopic.

  Infrared Analysis (KBr): ν-NH 3 +: 3250 cm -1 CH 2 CH 2: 2924 cm -1 vC = O ester: 1739 cm -1 ν-COO-: 1677 cm -1 ν-CF: 1197.1135 cm -1 Elemental Analysis for C40H66FgN3O16: Calc .: C: 47.29 H: 6.50 N: 4.13 Found: C: 46.93 H: 6.83 N: 4.09 Following the general procedures described in parts A) and B) above, except that a different compound of formula I was started, a series of prodrug precursors and a series of corresponding prodrugs were prepared as summarized in following table II:

TABLE II

  Prodrug Formula Precursor formula I compound prodrogue

2 12 22

4 14 24

6 16 26

9 19 29

  The prodrug precursors had the general formula III wherein R1, Z, X 'and Y had the following meanings: ## STR1 ## The prodrugs corresponded to the formula II o R1, Z, X and Y had the following meanings: RI compound DA and EB No 22 C4H9 CF3COO- + H3N CF3COO-H3N-CO-ClH23

(CH2) 3-CO- (CH2) 3-CO-

  24 C4H CF3COO- + H3N CF3COO- + H3N-CO-C17H35

(CH2) 3-CO- (CH2) 3-CO-

  C4H9 C17H35-CO-CF3COO- + H3N -CO-C17H35

(CH2) 3-CO-

  29 C4H9CllH23-CO-CF3COO-) H3N -CO-CllH23

  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (CH 2) 3-C O -

  The prodrug precursors had the following properties: Power Point Elemental Analysis Compound Rotational Fusion Spectrum of C [a] 20 C H N mass

(C, CHC13) M ++ 17M +

  Cs55H99N3016 14 +89 +58 Calc.62,42 9,42 4,00 1075 1058 (0,67) Exp.62,59 9,56 3, 97

C64H118N2014

  16 +40 +47 Calc.67.45 10.43 2, 46 1156 1130 (0.70) Exp.67.33 10.51 2.50

C52H94N2014

  19 +35 +46 Calc.64.30 10.43 2, 46 988 971 ________________ (0.52) Exp. 64.53 9.89 3.00 - Infrared analysis (KBr): see the data of compound 12 The prodrug 24 had the following properties: - Rotatory power [a] 20 + 38 C (c 0.47, CH30H) Elemental analysis for C46H78F6N3O16, H20: Calcd .: C: 49.42 H: 7.16 N: 3.76 Found: C: 49.33 H: 7.48 N: 3.70. The prodrug 2f had the following properties: - Rotatory power [a] 20 + 32 (c 3.33, CH30H) Elemental analysis for C58H104F6N2O14.2H2O Calc .: C: 58.09 H: 9.01 N: 2.33

Found: C, 58.11, H, 8.66, N, 2.17.

  The prodrug 29 had the following properties: - Rotatory power [a] 20 + 55 (c 0.67, CH 3 OH) Elemental analysis for C 46 H 80 F 6 N 2 O 4, H 2 O Calc .: C: 54.33 H: 8.07 N: 2.76 Found : C: 54.27 H: 8.03 N: 2.89 All prodrugs were obtained as a white powder or oil with an overall yield of

synthesis of the order of 60%.

  The ability of the prodrugs of the invention to cross the BBB more easily than GABA itself was first demonstrated by in vitro testing, and then by in vivo testing.

the mouse.

  In vitro tests: In these tests, an in vitro model of BBB was used

  developed at the Institut Pasteur in Lille and described by Marie

  Pierre Dehouck et al. in Journal of Neurochemistry, 58, 1790-1797 (1992) to which reference may be made for more details. Briefly, the test consists of placing a Ringer-HEPES solution (NaCl, 150 mM, KCl, 5.2 mM, CaCl2, 2.2 mM;

  MgCl₂H₂O, 0.2 mM; NaHCO3, 6 mM; HEPES [N- (2-hydroxyethyl) -

  piperazine-N '- (2-ethanesulfonic acid)], 5 mM; 2.8mM glucose) in the lower compartment of a 6-well dish (2ml per well). A filter impregnated with collagen and coated with a monolayer of endothelial cells of brain cerebral capillaries produced as described by Dehouck et al., Supra, is transferred to the first well. 2 ml of the Ringer-HEPES solution containing the test molecule are deposited in the upper compartment of the filter at a concentration of 150 μM. At the time, 20, 40, 60, 90 and 120 min after addition of the molecule, the filters are transferred to another well in order to minimize the return of the compartment molecule.

  lower to the upper compartment.

  The experiments are performed on three sets of wells, with filters covered with endothelial cells

  of cerebral capillaries or collagen alone as a control.

  The amount of substance is determined in the different lower compartments by counting the radioactivity or

  dosing the cold molecule by HPLC.

  In each experiment, 3 filters, taken at random from the series, are used to determine permeability to sucrose and inulin (these substances do not diffuse under physiological conditions), in order to verify the integrity of the monolayer of endothelial cells. In order to determine the endothelial permeability coefficient (PE) of the prodrugs, the clearance, expressed in pI, of each substance is determined according to the following structural formula: Clearance (pl) = Q / S where Q is the amount of substance in the compartment lower o S is the concentration of substance in the

upper compartment.

  For 60 min, the clearance increases linearly with time. On the clearance graph = f (t), the measurement of the slope corresponds to the value of "PSt" where PS corresponds to the product of the permeability by the surface of the monolayer of endothelial cells, expressed in pl / min. For the control filters, "PSf" is calculated in the same way. The permeability of the endothelial cell monolayer alone (PSe) is given by the following relation: 1 / PSe = 1 / PSt-1 / PSf The endothelial permeability coefficient "Pe" is calculated by dividing PSe by the surface of the monolayer of endothelial cells (4.2 cm2). The coefficient "Pe"

is expressed in cm / min.

  GABA served in this study. He is known for

  not disseminate significantly through the BBB.

  The evaluation of the transfer of GABA on this in vitro model of

  BBB was the first step.

  The GABA assay method uses a radioactive count, which involves the use of 14C-labeled GABA. In the table below, permeability values

  GABA obtained in a series of trials are presented.

  Count of radioactivity (14C) PSf (pl / min) 12.83 (r = 0.99) PSt (pl / min) 2.05 (r = 0.99) Pe (10-3 cm / min) 0, 58 * The values in parentheses correspond to the linear regression coefficients of straight lines whose

  coefficients PSt and PSf are the slopes.

  The value of the GABA Pe obtained confirms that GABA does not

  passes only very weakly through this model of BBB.

  In order to be able to compare the different values of Pe obtained during all the experiments, the value of Pe of a prodrug was divided by that of GABA obtained in the same series of experiments. This resulted in the expression of a coefficient "C", defined as follows: C = prodrug pe / Pe GABA Study of the transfer of prodrugs 22, 24. 26 and 29 on the

in vitro model of BBB.

  In order to be able to measure the PE of each of the above-mentioned prodrugs by radioactive counting, prodrugs 22, 24, 26 and 29 labeled with 14C have been prepared by carrying out their synthesis as described above, except that we have left radioactive GABA. marked at 14C. Pe has been determined by radioactive counting as GABA.5 The Table below presents the set of values of the different permeability coefficients as well as the

  C-value values for prodrugs of the liposoluble ester family by radioactive counting.

Prodrogue PSt PSf C *

22- [U-14C] 8.33 13.68 3.01

24- [U-14C] 6.83 14.68 1.81

26- [U-14C] 4.51 13.44 2.80

1 29- [U-14C] 4.88 13.22 3.17

* C = Pe / Pe ..

  These results show that the 4 prodrugs tested diffuse better than GABA through this in vitro model of BBB, in particular the prodrugs 22, 26 and 29. It is interesting to note that the compound 22 has a

  coefficient C identical to that of glucose, a molecule

  even known to be well transferred through this model and through the BBB by an active transport mechanism. In Vivo Tests The inhibitory activity of GABA and prodrugs of the invention on the CNS was evaluated by an anticonvulsant drug selection test. This test consists of looking for a given substance, the protection it gives to mice vis-à-vis a crisis

  epileptiform induced by picrotoxin.

  The induced crisis is characterized by the chronological appearance of the following phenomena: * tremor, * catatonus: stiffening of the tail, * clonic crisis: muscle twitches associated with myoclonic movements, * tonic crisis: flexion / extension of the hind legs,

* deaths.

  The protection of the epileptiform crisis, conferred by

  a prodrug, will be evaluated by the percentage of survival.

  Picrotoxin The convulsive agent (picrotoxin) was injected i. p. in the mouse, at 7.5 mg / kg,

  corresponding to the LD50 (Merck Index, XIth Edition, 1989).

  Under the experimental conditions used in this study, 17% and not 50% of the mice survived the picrotoxin injection. A higher dose of picrotoxin would not have shown any protection by the prodrugs, while at a lower dose (5mg / kg) 80% of the animals survived. Therefore, the use of this dose of convulsant would not have allowed to observe a difference between the GABA and the prodrugs. Under these conditions, the death appears 24.2 1.9 min (n = 42) after picrotoxin injection (reference time). Prodrugs and GABA are injected

  ip 15 min before injection of picrotoxin.

  GABA The results obtained after injection of doses

  increasing amounts of GABA are shown in the table below.

  after: co coo n Cq S000'0> d: e auuaXow and saeD9 sap auwwos: .S seznuTw ue ewTadxa seoep np uoT: Taeddep uaow sdwal: aywT xnewTue, p eaqwoN: u (6'0) |% 0 t 1 '6'6T 8E61 00' SS (t''T) | % 0 The 1 TT 61 696 00T L 8z 6 (9'0) |% 0 O'T Z'LT t8t OS S 'zS (o'T)% LT 6'T z'tz 0 0 6'8Z Z | TAUans ap WaS UTW l / IOwd 5: / 6m 6 aBe6uaoanod Y.wT. esoa SPTOd u GABA does not provide any protection against death for doses between 50 and 200 mg / kg. The survival percentage is 0% and, although lower than the result obtained in the absence of GABA, it is not significantly different. Prodrugs 26 and 29: These prodrugs include within their structure 2 molecules of GABA. In order to have an element of comparison between the different prodrugs, the dose administered was reduced to a dose in pmol / kg of injected GABA. The values of the survival percentages and the TMADs obtained for the prodrugs of the liposoluble ester family, as a function of the dose injected, are

  presented in the Table below.

  Prodrug n Weight g Dose TMAD Percent mg / kg pmol / kg min SEM survival

- 42 28.9 0 0 24.2 1.9 17%

(O)

29 9 24.8 50 100 25.2 4.6 22%

(0.3)

2129 9 30.4 100 200 27.7 3.0 11%

(1.8)

2 9 10 25.2 200 400 27.9 4.6 33%

(0.5)

4 24.2 400 800 30.9 5.3 25%

(0.8)

26 E 4 23.7 50 86 16.9 2.3 0%

(0.5)

26 9 32.4 100 172 34.0 3.6 33%

(1,4)

23.6 200 344 30.5 6.7 25%

(0,5) n: Number of animals

  TMAD: Average time of onset of death expressed in minutes.

  SEM: Sum of the deviations from the average It is seen from the results above that prodrugs 26 and 29 make it possible to double the percentage of survival with respect to picrotoxin (33%) at doses of 200 and 100 mg / kg respectively. The fact of doubling these doses does not however make it possible to note an improvement: a

  plateau of activity seems to be reached.

  It is interesting to note that at no dose has there been any reported acute toxicity causing death before

the injection of picrotoxin.

  These results show that the prodrugs of the invention are potentially useful therapeutic agents for treating CNS dysfunctions and diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's chorea, epilepsy, etc. .,

  as well as the phenomena of anxiety and stress.

  The prodrugs of the invention may be administered intraperitoneally as an aqueous suspension, for example at doses of 10 to 100 pmol / kg body weight. For the prodrug 29 this corresponds to about 5 to 50

mg / kg of body weight.

* It goes without saying that the described embodiments are only examples and that one could modify them, in particular by substitution of equivalent techniques, without

  to get out of the scope of the invention.

Claims (8)

  1. Use, as carriers of drugs   to the central nervous system (CNS), from a-D-   alkylglucopyranosides and esters thereof having the general formula (I): CH2OR2 (I) OR4O HO OR1   OR3 wherein R1 is a linear or branched C2 to C18 alkyl radical; R2 is a group -CO-R o R is a hydrocarbon radical, linear or branched, saturated or ethylenically unsaturated, Cs to C17, or a group -CO- (CH2) n-COOH o n = 4   at 14; R3 and R4 are each, independently, H or the remainder -   CO-R 'of a fatty acid HOOC-R' o R 'is a hydrocarbon radical, linear or branched, saturated or ethylenically unsaturated Cs to C17, with the proviso that only one group R3 and R4 is a residue -CO-R '.   2. Use according to claim 1, characterized in that R1 is a butyl radical.   3. Prodrogues corresponding to the general formula (II): ## STR2 ## is a linear or branched C 2 to C 18 alkyl radical; A is H, -CO-R "o R" is a linear or branched, saturated or ethylenically unsaturated C 1 -C 17 hydrocarbon-based radical, or the -CO-X residue of a HOOC-X active compound having a reactive carboxyl group ; B is a residue -CO-R 'of a fatty acid HOOC-R' o R 'is a hydrocarbon radical, linear or branched, saturated or ethylenically unsaturated C5 to C17, or a -CO- (CH2) n group -COO-W on = 4 to 14 and W is the residue of an active compound having a primary amino group or primary hydroxyl; D and E are each, independently, H or a residue -CO-X or -CO-R '; with the provisos that (i) when B is -CO-R ', at least two of groups A, D and E are -CO-X, and (ii) when B is -CO- (CH2) n-COO-W , A, D and E are H, -CO-R 'or -CO-R ".   4. Prodrugs according to claim 3, characterized in that R1 is a butyl radical.   5. Precursors of prodrugs of the formula II, which correspond to the general formula III CH20C-R ' / O-C-Z \ (III) OR1 X'-C-O "0 C - Z O .. 0   where R 1 is as defined above, the group -CO-X 'is the residue of an amino acid or a peptide whose amino group (s) are protected, -CO-Z is a group -CO-X 'or a group -CO-R' as defined above, at least one of -CO-Z being -CO-X '.   6. Precursors according to claim 5, characterized in that the amino group of the amino acid is protected by a t-butyloxy-carbamate group.   Precursors according to claim 5 or 6,   characterized in that R 1 is a butyl radical.   8. Process for preparing a compound of the formula   (I) defined in claim 1, characterized in that it comprises (a) the enzymatic esterification of an α-D-alkyl-   suitable glucopyranoside with a C6-C18 fatty acid in a non-polar solvent in the presence of a lipase to obtain mainly a monoester, and then (b) optionally, esterifying the monoester to a diester under conditions   similar to those of step (a).