Abstract

In our previous research, we obtained more than 20 cocrystal structures between anti-malarial 11-Azaartemisinin (11-Aza) and different substituted salicylic acids (SalA-Xs)1. Small perturbations in the functional group of cocrystal coformers could result in drastic changes in crystal structures since we’ve found the parent 11-Aza:SalA and 11-Aza:4-BrSalA crystallized in polar 21 stacks, 11-Aza:4-FSalA having a tetragonal spatial arrangement, while 11-Aza:4-ClSalA and 11-Aza:4-ISalA have orthorhombic structures with 1-D translational stacks2. Using the heteroseeding method, phase pure polymorphs of 11-Aza:4-ClSalA, 11-Aza4-ISalA, and 11-Aza:4-MeoxySalA were obtained using 11-Aza:SalA or 11-Aza:4-FSalA as seed crystals. The results show the flexibility in the lactam:acid heterosynthons and the possibilities of applying heteroseeding to engineer the cocrystal polymorphism.

reference

1. Roy, M., Li, K., Nisar, M., Wong, L. W.-Y., Sung, H. H.-Y., Haynes, R. K. & Williams, I. D. Acta Cryst, 2021, C77, 262-270.
2. Williams, I. D., Li, K., Sung, H. H-Y., Roy, M. & Nisar, M. 70th Annual American Crystallographic Association Meeting, 2-7 August 2020.