Methods for the purification of L-glufosinate
Compositions and methods for isolating L-glufosinate from a composition comprising L-glufosinate and glutamate are provided. The method comprises converting the glutamate to pyroglutamate followed by the isolation of L-glufosinate from the pyroglutamate and other components of the composition to obtain substantially purified L-glufosinate. The composition comprising L-glufosinate and glutamate is subjected to an elevated temperature for a sufficient time to allow for the conversion of glutamate to pyroglutamate, followed by the isolation of L-glufosinate from the pyroglutamate and other components of the composition to obtain substantially purified L-glufosinate. The glutamate alternatively may be converted to pyroglutamate by enzymatic conversion. The purified L-glufosinate is present in a final composition at a concentration of 90% or greater of the sum of L-glufosinate, glutamate, and pyroglutamate. In some embodiments, a portion of the glutamate in the starting composition may be separated from the L-glufosinate using a crystallization step. Solid forms of L-glufosinate materials, including crystalline L-glufosinate ammonium, are also described.
1. An L-glufosinate crystalline form, the crystalline form characterized by an X-ray powder diffraction (XRPD) pattern comprising at least three peaks selected from 10.0, 11.4, 12.5, 16.5, 17.4, 18.1, 19.6, 20.0, 21.8, 22.9, 23.6, 24.0, 25.1, 25.5, 26.1, 26.3, 26.4, 27.9, 28.2, 28.4, 28.7, 29.2, 30.2, 30.9, 31.6, 31.7, 32.7, 33.0, 33.3, 34.3, 35.2, 36.7, 37.2, 37.4, 37.8, 38.3, 38.7, and 39.3° 2θ, ±0.2° 2θ, as determined on a diffractometer using Cu-Kα radiation, wherein the XRPD pattern comprises at least one peak at 10.0, 11.4, or 12.5° 29±0.2° 2θ, as determined on a diffractometer using Cu-Kα radiation.
2. The L-glufosinate crystalline form according to claim 1 , wherein the XRPD pattern comprises at least six peaks selected from 10.0, 12.5, 16.5, 17.4, 18.1, 19.6, 20.0, 21.8, 22.9, 23.6, 24.0, 25.5, 26.3, 26.4, 29.2, 34.3, 35.2, and 37.4° 2θ, ±0.2° 2θ.
3. The L-glufosinate crystalline form according to claim 1 , wherein the XRPD pattern comprises at least ten peaks selected from 10.0, 12.5, 16.5, 17.4, 18.1, 19.6, 20.0, 21.8, 22.9, 23.6, 24.0, 25.5, 26.3, 26.4, 29.2, 34.3, 35.2, and 37.4° 2θ, ±0.2° 2θ.
4. The L-glufosinate crystalline form according to claim 1 , wherein the form has the XRPD pattern of FIG. 3 .