Design, iterative synthesis and structure of novel optically active trispiro-dendritic melamines incorporating ‘ open-chain ’ versus ‘ closed-chain ’ serinolic peripheral units

Starting from commercial C-2-substituted 2-aminopropane-1,3-diols (serinols, ‘open-chain’ peripheral units) and optically active amino-1,3-dioxanes (‘closed-chain’ peripheral units) as cycloacetals of (1S,2S)-2-amino-1-(4-nitrophenyl)propane-1,3-diol (p-nitrophenylserinol) or its 2-dimethylamino analogue, we herein report a new series of di- and trimeric G-1 trispiro-dendritic melamines, they were synthesised convergently by iterative chemoselective amination of cyanuric chloride. Depending on the number of hydroxymethyl groups in the ‘open-chain’ peripheral unit and the type of the rigid amino-anchorage (axial or equatorial) of the ‘closed-chain’ counterpart, the classic restricted rotation about the C(s-triazine)–N(exocyclic) partial double bonds induced, progressively, specific spatial arrangements in angularly connected G-0 and G-1 dendrons, including axial chirality in G-1 dimeric or G-1 trimeric melamines.