646518-16-3Relevant articles and documents
A systematic study of the solid state and solution phase conformational preferences of β-peptides derived from C(3)-alkyl substituted transpentacin derivatives
Abraham, Elin,Claridge, Timothy D.W.,Davies, Stephen G.,Odell, Barbara,Roberts, Paul M.,Russell, Angela J.,Smith, Andrew D.,Smith, Lorna J.,Storr, Helen R.,Sweet, Miles J.,Thompson, Amber L.,Thomson, James E.,Tranter, George E.,Watkin, David J.
, p. 69 - 100 (2011/04/18)
The solid state and solution phase conformational preferences of a homologous series of β-peptides derived from a range of 2-amino-3-alkylcyclopentanecarboxylic acid residues have been investigated using a variety of spectroscopic and crystallographic techniques. These studies indicate that C(3)-alkyl substitution trans to the amino group on the cyclopentane backbone is tolerated by the established 12-helix secondary structural preference of the parent pentamer and hexamer derived from 2-aminocyclopentanecarboxylic acid (transpentacin) residues in both the solid state and solution phase. Evidence for the alternative turn type conformation identified for the C(3)-unsubstituted tetramer was not observed in the C(3)-alkyl substituted derivatives, consistent with the alkyl substituent anti to the amino functionality destabilising this motif. These results suggest that oligomers based around the transpentacin scaffold may be amenable to further elaboration at C(3) anti to the amino group with retention of the secondary structure.
Asymmetric synthesis of (1R,2S,3R)-3-methylcispentacin and (1S,2S,3R)-3-methyltranspentacin by kinetic resolution of tert-butyl (±)-3-methylcyclopentene-1-carboxylate
Bunnage, Mark E.,Chippindale, Ann M.,Davies, Stephen G.,Parkin, Richard M.,Smith, Andrew D.,Withey, Jonathan M.
, p. 3698 - 3707 (2007/10/03)
Conjugate addition of lithium dibenzylamide to tert-butyl (±)-3-methylcyclopentene-1-carboxylate occurs with high levels of stereocontrol, with preferential addition of lithium dibenzylamide to the face of the cyclic α,β-unsaturated acceptor anti- to the 3-methyl substituent. High levels of enantiorecognition are observed between tert-butyl (±)-3-methylcyclopentene-1-carboxylate and an excess of lithium (±)-N-α-methylbenzylamide (10 eq.) (E > 140) in their mutual kinetic resolution, while the kinetic resolution of tert-butyl (±)-3-methylcyclopentene-1-carboxylate with lithium (S)-N-benzyl-N-α-methylbenzylamide proceeds to give, at 51% conversion, tert-butyl (1R,2S,3R,αS)-3-methyl-2-N-benzyl-N-α-methylbenzylaminocyclopentane- 1-carboxylate consistent with E > 130, and in 39% yield and 99 ± 0.5% de after purification. Subsequent deprotection by hydrogenolysis and ester hydrolysis gives (1R,2S,3R)-3-methylcispentacin in >98% de and 98 ± 1% ee. Selective epimerisation of tert-butyl (1R,2S,3R,αS)-3-methyl-2-N-benzyl-N-α-methylbenzylaminocyclopentane- 1-carboxylate by treatment with KOtBu in tBuOH gives tert-butyl (1S,2S,3R,αS)-3-methyl-2-N-benzyl-N-α-methylbenzylaminocyclopentane- 1-carboxylate in quantitative yield and in >98% de, with subsequent deprotection by hydrogenolysis and ester hydrolysis giving (1S,2S,3R)-3-methyltranspentacin hydrochloride in >98% de and 97 ± 1% ee.
