Synthesis of 5-Azacytidine

Abstract

The present invention provides a method for the preparation of 5-azacytidine, wherein 5-azacytidine is represented by the structure: The method involves the silylation of 5-azacytosine, followed by the coupling of silylated 5-azacytosine to a protected β-D-ribofuranose derivative. The coupling reaction is catalyzed by trimethylsilyl trifluoromethanesulfonate (TMS-Triflate).

Description

RELATED APPLICATIONS [0001] This application is a continuation of U.S. application Ser. No. 10 / 390,526, filed Mar. 17, 2003, entitled “Synthesis of 5-Azacytidine,” now U.S. Pat. No. 7,038,038. The foregoing reference is hereby incorporated by reference in its entirety.FIELD OF THE INVENTION [0002] The invention relates to the synthesis of 5-azacytidine (also known as azacitidine and 4-amino-1-β-D-ribofuranosyl-S-triazin-2(1H)-one). 5-azacytidine may be used in the treatment of disease, including the treatment of myelodysplastic syndromes (MDS). BACKGROUND OF THE INVENTION [0003] 5-azacytidine (also known as azacitidine and 4-amino-1-β-D-ribofuranosyl-S-triazin-2(1H)-one; Nation Service Center designation NSC-102816; CAS Registry Number 320-67-2) has undergone NCI-sponsored trials for the treatment of myelodysplastic syndromes (MDS). See Kornblith et al., J. Clin. Oncol. 20(10): 2441-2452 (2002) and Silverman et al., J. Clin. Oncol. 20(10): 2429-2440 (2002). 5-azacytidine may be defi...

AI Technical Summary

Benefits of technology

"The present invention provides a method for synthesizing 5-azacytidine, which is suitable for use in humans and can be produced in large scales. The method involves reacting 5-azacytosine with a silylating reagent to yield a compound, which is then coupled with another compound to form 5-azacytidine. The method is carried out in a dry organic solvent and avoids the use of tin catalysts and other metal ions. The resulting 5-azacytidine is purified and can be recrystallized for further use."

Problems solved by technology

The s-triazine ring of 5-azacytidine has a particular sensitivity to water (see J. A. Beisler, J. Med. Chem., 21, 204 (1978)); this characteristic has made the synthesis of 5-azacytidine a challenge, especially in manufacturing at commercial scale.

A number of prior art methods have been developed in order to avoid the use of water; however, these methods all have additional problems that render them undesirable for the production of large-scale batches of 5-azacytidine.

The drawbacks of this scheme include the presence of steps that are difficult to scale-up, the use of benzene as solvent in one step, and the requirement for a deprotection step performed in a closing pressure vessel using dry ammonia.

Furthermore, the final 5-azacytidine product was isolated from the reaction mixture by filtration with no further purification; this is not acceptable for the synthesis of an Active Pharmaceutical Ingredient (API) for human use.

The addition of further purification steps will further reduce the overall yield.

There are many significant weaknesses in this procedure.

The low recovery during purification can be correlated with the poor anomeric ratio and with the known low stability of 5-azacytidine in water.

This procedure is difficult to scale-up with plant equipment due to the special handling requirements of gaseous HCl.

The lack of control of the tin level means that the procedure is not suitable for producing an API for human use.

Second, emulsions developed during the workup of the coupling mixture.

The phase separation of the emulsion is slow, so the water-sensitive protected 5-azacytidine was exposed to water for variable periods of time leading to variable amounts of decomposition.

These problems mean that the process is not conveniently amenable to scale-up.

Moreover, this one step / one pot reaction is not suitable for the synthesis of 5-azacytidine because the extraction is done is the presence of acetonitrile.

As a consequence, the protected 5-azacytidine in the acetonitrile is exposed during extraction to the aqueous phase for variable amounts of time, which in turn leads to variable amounts of decomposition of the protected 5-azacytidine.

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