First synthesis of segetalin A and analogous cyclohexapeptides

The cyclization of peptides and depsipeptides

“…Segetalin A, cyclo (Gly-Val-Pro-Val-Trp-Ala) from Vaccaria segetalis seeds has been synthesized [101] by macrocyclization between C-terminal Ala and Gly. Ring closure using the pentafluorophenyl ester gave no results, but DPPA with a linear precursor at 10 −4 M gave a 45% yield (PyBrop registered a 10% yield).…”

Inverse γ‐Turn‐Inspired Peptide: Synthesis and Analysis of Segetalin A Indole Hemi­aminal

“…[11] The structure of native segetalin A has been well studied by crystal-structure analysis and in solution by NMR spectroscopy. [12,13] In the solid state, segetalin A is characterized by two β turns, one type I (Trp 4 and Ala 5 ) and one type VI (Val 1 and Pro 2 ) with a cis-Pro bond. [12] The structure is fixed by two transannular hydrogen bonds formed between Gly 6 and Val 3 , which results in an overall antiparallel β-sheet structure.…”

“…[12] It is known that it adopts a rigid main conformation without the formation of a second set of NMR signals for the trans-Pro rotamer. [13] The 1 H NMR spectrum of the linear peptide aldehyde 1 shows instead only the trans conformer. The configuration of the Val-trans-Pro rotamer was assigned on the basis of the chemical shift of the β-and γ-CH 2 groups (δ = 29.0 and 24.5 ppm, respectively) of the proline by HSQC.…”

“…In the 1 H NMR spectrum, the resonance for the NH protons is found at δ = 0.78 ppm; this is quite low relative to the same signal for the cyclic peptide (δ = 1.61 ppm). [12,13] Increasing the pH value stepwise to 6.5 should lead to head-to-tail cyclization of the macrocyclic 18-membered imine. Indeed, the ring that is formed could not be assigned to the expected macrocycle 2a.…”

Doubled haploid production in nutraceutical species: a review

“…One of the species investigated in our research was Saponaria vaccaria L., a herbaceous, dicotyledonous annual commonly known as cow cockle. This and related species contain saponins, fine quality starch, and cyclopeptides (Mazza et al 1992;Biliaderis 1993;Sonnet et al 2001). Saponins have traditionally been used as natural detergents and foaming agents, but also have potential to be used as drugs, healthcare products, vaccine adjuvants, or drug delivery products (Hostettmann and Marston 1995).…”