Process for the production of specific isomer mixtures from oxindole alkaloids

A method of preparing a mixture of isomers of a spiro oxindole alkaloid, said mixture having a definable isomer pattern, said method comprising:

• defining said isomer pattern of said mixture of isomers,
• selecting an organic solvent being able to dissolve said oxindole alkaloid and being heterogeneously miscible with water,
• preparing a heterogeneous solvent mixture comprising water and said organic solvent, and
• dissolving said oxindole alkaloid in said heterogeneous solvent mixture, said oxindole alkaloid being isomerized into said mixture of isomers according to said isomer pattern.

A method of preparing an isomer of a spiro oxindole alkaloid, said method comprising:

• selecting a first solvent being able to dissolve said oxindole alkaloid and being miscible with water,
• preparing a solvent mixture containing water and said first solvent,
• dissolving said oxindole alkaloid in said solvent mixture, said oxindole alkaloid being isomerized into said mixture of isomers,
• removing said solvent mixture from said mixture of isomers,
• selecting a second solvent having different solvating abilities for each isomer of said mixture of isomers,
• selecting the solvating ability of said second solvent corresponding to said isomer of said oxindole alkaloid,
• re-dissolving said mixture of isomers in said second solvent, and
• altering said second solvent to precipitate said isomer of said oxindole alkaloid.