Phenylisoserine: A versatile amino acid for the construction of novel beta-peptide structures

The N-Boc O-tert-butyldimethysilyi-substituted hexa-beta -peptide methyl es ter 18 was constructed from the O-TBS ether of (-)-(2R, 3S)-phenylisoserine . By NMR, it was determined that this home beta -peptide adopts a highly st able beta -strand-type secondary structure in chloroform solution, which is stabilized by both hydrophobic interactions involving the OTBS methyl grou ps of residues i and i + 2, and inter-(five-membered)/intra (six-membered)- residue H-bonding interactions. These interactions are systematically repea ted along the peptide chain and, thereby, operate in concert to stabilize t he observed conformation of 18.