862996-27-8

Upstream product

• 71432-55-8 2-tert-butyl-1,3-diisopropylisourea 
• 147266-92-0 (2R,4S )-1-(tert-butoxycarbonyl)-4-hydroxypyrrolidine-2-carboxylic acid 
• 71432-55-8 2-tert-butyl-1,3-diisopropylisourea 
• 77450-00-1 (2R,4R)-4-hydroxyproline-1,2-dicarboxylic acid 1-tert-butyl 2-ethyl ester 
• 862996-26-7 (2R)-N-Boc-trans-4-acetoxy-D-proline ethyl ester 

Relevant academic research and scientific papers

Triggering activity of catalytic rod-like supramolecular polymers

Supramolecular polymers based on benzene-1,3,5- tricarboxamides (BTAs) functionalized with an L- or D-proline moiety display high catalytic activity towards aldol reactions in water. High turnover frequencies (TOF) of up to 27 × 10-4 s-1/

Locked conformations for proline pyrrolidine ring: Synthesis and conformational analysis of cis- and trans-4-tert-butylprolines

The motional restrictions of the proline pyrrolidine ring allow this secondary amine amino acid to act as a turn inducer in many peptides and proteins. The pyrrolidine ring is known to exhibit two predominant pucker modes (i.e., C-4 (Cγ) exo and endo envelope conformers whose ratio can be controlled by proper substituents in the ring). In nature, the exo puckered 4(R)-hydroxy-L-proline plays a crucial role as a building block in collagen and collagen-like structures. It has been previously concluded that the electronegativity of the 4-cis-substituent increases the endo puckering while the electronegativity of the 4-trans-substituent favors the exo puckering. Here, we have introduced a sterically demanding tert-butyl group at C-4 in trans- and cis-configurations. In the case of trans-substitution, the induced puckering effect on the pyrrolidine ring was studied with X-ray crystallography and 1H NMR spectral simulations. Both cis- and trans-4-tert-butyl groups strongly favor pseudoequatorial orientation, thereby causing opposite puckering effects for the pyrrolidine ring, cis-exo and trans-endo for L-prolines, in contrast to the effects observed in the case of electronegative C-4 substituents. The syntheses and structural analysis are presented for the conformationally constrained 4-tert-butylprolines. The prolines were synthesized from 4-hydroxy-L-proline, substitution with t-BuCuSPhLi being the key transformation. This reaction gave N-Boc-trans-4-tert-butyl-L-proline tert-butyl ester in 94% ee and 57% de. Enantioselectivity was increased to 99.2% ee by crystallization of N-Boc-trans-4-tert-butyl-L-proline in the final step of the synthesis.