[ClH:1].[NH2:2][C:3]([CH3:12])(/[CH:7]=[CH:8]\[CH2:9][C:10]#[N:11])[C:4]([OH:6])=[O:5].[BH4-].[Na+].Cl>CO>[ClH:1].[ClH:1].[NH2:2][C:3]([CH3:12])(/[CH:7]=[CH:8]\[CH2:9][CH2:10][NH2:11])[C:4]([OH:6])=[O:5]The (3Z)-2-amino-5-cyano-2-methylpent-3-enoic acid hydrochloride product of Example 1k is taken up in MeOH. To this is added Co(II)Cl2.6H2O in one portion with stirring under argon during which the reaction mixture is expected to turn purple. This is followed by the cautious addition of NaBH4 in 6 portions over 15 min. at 25° C. during which the reaction mixture is expected to turn black. HCl is then added carefully and the reaction mixture is stirred until the reaction becomes a light purple color. It is then concentrated under reduced pressure and the residue is subjected to BioRad ‘H’ form ion exchange resin. Elution with 1% NH4OH/H2O gives the desired fraction. This is concentrated to drive off excess NH3 at <55° C. on a rotary evaporator and then acidified to pH 4.5 with conc. HCl before it is concentrated to dryness to afford the desired title product.
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