*3.1. Anhydrous Forms*

Three anhydrous forms of BL have been identified. According to their melting points (Figure 2), forms I, II and III correspond to polymorphs 1, 2 and 3 previously reported in patent WO03089425. The DSC of the lowest melting form III shows its melting and simultaneous crystallization and melting of form I followed by the crystallization and melting of form II, the highest melting form.

High quality single crystals suitable for crystal structure determination have been obtained only for Form I, while the crystal structure of form III was determined from PXRD data obtained in Synchrotron. Regarding form II, only its unit cell and space group could be determined. The X-ray powder diffractograms of the three anhydrous forms are shown in Figure 3.

**Figure 2.** DSC analysis of the different anhydrous forms of BL, showing the melting of form I at 200 ◦C, form II at 202 ◦C and form III at 197 ◦C followed by simultaneous crystallization and melting of form I and subsequent crystallization and melting of form II.

**Figure 3.** PXRD patterns of the different anhydrous forms of BL.
