A Diversity-Oriented Approach to Large Libraries of Artificial Macrocycles

Diversity-oriented approach to large artificial macrocycle libraries with a ring size of 13—18 atoms relying on the “build-couple-pair” strategy is disclosed. The “couple” phase included three one-pot steps including consequent amide coupling of N-Boc-monoprotected vicinal diamines with two alkenyl carboxylic acids, followed by ring-closing metathesis as the key “pair” step. The scope and limitations of the method were established for all three reagents. In particular, various acyclic, mono- and bicyclic aliphatic diamine derivatives with the N−C−C−N dihedral angle less than ca. 130° appeared to be suitable substrates. The proposed approach was used to construct a virtual library of 1.8 ⋅ 10⁵ macrocycles derived from 12,283 different scaffolds. More than 40 % of members of this library contained a protected amino function and hence can be suitable for the post-pairing modification, thus giving rise to at least a billion-size chemical space based on the REAL-type synthetic methodology. Validation of the approach under parallel synthesis conditions on a 383-member subset showed a 61 % success rate over the whole 4–5-step reaction sequence. Finally, the synthetic approach also worked on a gram scale (up to 8.0 g).