Synthesis and conformational analysis of a type VIb β-turn mimetic based on an eight-membered lactam

Systematic Study of the Synthesis of Macrocyclic Dipeptide β-Turn Mimics Possessing 8-, 9-, and 10- Membered Rings by Ring-Closing Metathesis

“…Although the type VI β-turn did not possess proline, the eight-membered macrocycle forced the amide between the i + 1 and i + 2 residues to adopt the cis-isomer geometry, as illustrated by X-ray structural analysis, which also revealed a cis -olefin in a folded twist-boat-boat conformation . The saturated analogue of eight-membered lactam ( R , R )- 5 possessed a cis -amide geometry and type VIb β-turn conformation; however, dimerization took place over time in solution and in the solid state, as revealed by NMR dilution experiments and X-ray crystallographic studies. , Their cis -amide geometry and their propensity to favor type VI β-turns makes eight-membered lactams ( 5 ) structurally comparable to other type VI β-turn mimics, such as 5- tert -butylproline-containing peptides …”

Effects of i and i+3 residue identity on Cis–Trans isomerism of the aromatici+1–prolyli+2 amide bond: Implications for type VI β‐turn formation

“…The prevalence of type VI β‐turns in protein molecular recognition has stimulated the development of simple peptidic and nonpeptidic motifs with this secondary structure 19, 21–23, 26, 35, 40, 52–116. The determination of parameters to understand the local effects on cis – trans isomerization and type VI β‐turn formation would allow improved prediction, design, and interpretation of sequences containing these elements.…”

An unusual silicon mediated transannular cyclopropanation

“…NMR spectroscopy of this compound shows significantly broadened peaks, presumably due to slow conformational exchange as observed for related compounds. 10 The identity of the 6-trimethylsilyl-5,6-dihydroazocinone 3 was confirmed by X-ray crystallography (Fig. 1).…”