L-Proline tert-butyl ester
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L-Proline tert-butyl ester

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L-Proline tert-butyl ester is a tert-butyl ester of L-Proline which is an amino acid and precursor (with vitamin C) for collagen, the building block of the structure of tendons, ligaments, arteries, veins and muscles. It is important in wound healing.

Cyclic Amino Acids
Catalog number
CAS number
Molecular Formula
Molecular Weight
L-Proline tert-butyl ester
tert-butyl (2S)-pyrrolidine-2-carboxylate
L-Pro-OtBu; (S)-Pyrrolidine-2-carboxylic acid tert-butyl ester; L-Proline tert-butyl ester; L-Proline t-Butyl Ester; tert-butyl pyrrolidine-2-carboxylate; (S)-tert-Butyl pyrrolidine-2-carboxylate
Colorless liquid
≥ 98% (HPLC)
0.995±0.06 g/cm3
Melting Point
98-103 °C
Boiling Point
219.2±33.0 °C
Store at 2-8 °C
InChI Key
Canonical SMILES
1. Locked conformations for proline pyrrolidine ring: synthesis and conformational analysis of cis- and trans-4-tert-butylprolines
Ari M P Koskinen, Juho Helaja, Esa T T Kumpulainen, Jari Koivisto, Heidi Mansikkamäki, Kari Rissanen J Org Chem. 2005 Aug 5;70(16):6447-53. doi: 10.1021/jo050838a.
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 (Cgamma) 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.
2. Pentanidium-catalyzed enantioselective phase-transfer conjugate addition reactions
Ting Ma, Xiao Fu, Choon Wee Kee, Lili Zong, Yuanhang Pan, Kuo-Wei Huang, Choon-Hong Tan J Am Chem Soc. 2011 Mar 9;133(9):2828-31. doi: 10.1021/ja1098353. Epub 2011 Feb 11.
A new chiral entity, pentanidium, has been shown to be an excellent chiral phase-transfer catalyst. The enantioselective Michael addition reactions of tert-butyl glycinate-benzophenone Schiff base with various α,β-unsaturated acceptors provide adducts with high enantioselectivities. A successful gram-scale experiment at a low catalyst loading of 0.05 mol % indicates the potential for practical applications of this methodology. Phosphoglycine ester analogues can also be utilized as the Michael donor, affording enantioenriched α-aminophosphonic acid derivatives and phosphonic analogues of (S)-proline.
3. Synthesis of glycopeptides with phytoalexin elicitor activity--III. Syntheses of hexaglycosyl hexapeptides and a nonaglycosyl hexapeptide
T Takeda, T Kanemitsu, Y Ogihara Bioorg Med Chem. 1996 Nov;4(11):1873-80. doi: 10.1016/s0968-0896(96)00170-8.
A block synthesis of the model compound for the phytoalexin elicitor-active glycoprotein is described. Combination of the C-terminus free compounds, N-(9-fluorenylmethoxycarbonyl)-O-(tert-butyl)-L-seryl-L-proline (1) or N-(9-fluorenylmethoxycarbonyl)-(2,3,4,6-tetra-O-acetyl-beta-D-g luc opyranosyl) -(1-->6)-(2,3,4-tri-O-acetyl-alpha-D-mannopyranosyl)-(1-->6) -(2,3,4-tri-O-acetyl-alpha-D-mannopyranosyl)-L-seryl-L-proline (2) with the N-terminus free compounds, 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl -(1-->6)-(2,3,4-tri-O-acetyl-alpha-D-mannopyranosyl)-(1-->6)-(2,3,4-tri- O -acetyl-alpha-D-mannopyranosyl)-L-seryl-L-prolyl-L-seryl-L-proline methyl ester (4), O-(tert-butyl)-L-seryl-L-prolyl-(2,3,4,6-tetra-O-acetyl-beta-D -glucopyranosyl)-(1-->6)-(2,3,4-tri-O-acetyl-alpha-D-mannopyranosyl) -(1-->6)-(2,3,4-tri-O-acetyl- alpha-D-mannopyranosyl)-L-seryl-L-proline methyl ester (6) or 2,3,4,6-tetra-O-acetyl-beta-D- glucopyranosyl -(1-->6)-(2,3,4-tri-O-acetyl-alpha-D-mannopyranosyl)-(1-->6) -(2,3,4-tri-O-acetyl-alpha-D-mannopyranosyl)-L-seryl-L-prolyl -(2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl)-(1-->6) -(2,3,4-tri-O-acetyl-alpha-D-mannopyranosyl)-(1-->6) -(2,3,4-tri-O-acetyl-alpha-D-mannopyranosyl)-L-seryl-L-proline methyl ester (8), by use of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) gave three hexaglycosyl hexapeptides and a nonaglycosyl hexapeptide derivatives (9, 11, 14, and 17). These N-terminus free compounds were derived from triglycosyl tetrapeptides (3 and 5) or a hexaglycosyl tetrapeptide (7) on selective deblock reaction by morpholine. The hexaglycosyl hexapeptides (10, 13, and 16) and the nonaglycosyl hexapeptide (18) have been prepared by the convergent block synthesis.
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