1H NMR and crystallographic evidence for tolerance of bulky electron withdrawing methanesulfonyl group on robustness of the U-motif in pyrazolo[3,4-d]pyrimidine core based ‘Leonard linker’ compounds and formation of plus (+) motif

X-ray crystallographic analysis of two new ‘Leonard/trimethylene linker’ compounds; 1,3-bis(4-methoxy-6-methylsulfonyl-lH-pyrazolo[3,4-d]pyrimidin-1-yl)propane (4a) and 1,3-bis(4-ethoxy-6-methylsulfonyl-lH-pyrazolo[3,4-d]pyrimidin-1-yl)propane (4b) not only confirm robustness of the unusual U-motif conformation seen in earlier related compounds (1 and 2) but in addition reveal novel chain motif formed due to intermolecular CH⋯O and CH⋯N interactions resulting in novel plus (+) motif.