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ChemicalBook CAS DataBase List Entecavir
142217-69-4

Entecavir synthesis

11synthesis methods
Entecavir is synthesized from 4-trimethylsilyl-3-butyn-2-one and acrolein. The key features of its preparation are: (1) a stereoselective boron–aldol reaction to afford the acyclic carbon skeleton of the methylenecylopentane moiety; (2) its cyclization by a Cp2TiCl-catalyzed intramolecular radical addition of an epoxide to an alkyne; and (3) the coupling with a purine derivative by a Mitsunobu reaction.142217-69-4.png
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Yield:142217-69-4 60%

Reaction Conditions:

Stage #1: ((1 R,3S,5S)-5-acetoxy-3-(2-amino-6-chloro-9H-purin-9-yl)-2-methylenecyclopentyl)methyl acetatewith sodium hydroxide at 80; for 2 h;
Stage #2: with hydrogenchloride in water at 0; pH=7;

Steps:

14

Example 14 Preparation of entecavir To (II) (0.4 g, 1.05 mmol) at room temperature, a 2.5 M solution of NaOH (10 mL) was added. The reaction mixture was heated to 80 °C for 2 h. The reaction mixture was cooled to 0 °C and neutralized with HCl to pH = 7. Decolorizing carbon (0.5 g) was added and the mixture was heated at 90 °C for 1 h. The hot mixture was filtered through Celite. The filtrate was cooled under stirring to effect crystallization. The estimated yield was 60 % approximately.

References:

EP2474548,2012,A1 Location in patent:Page/Page column 19

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