Solid-Phase Total Synthesis and Structure Proof of Callipeltin B

Abstract

The cytotoxic, cyclic heptadepsipeptide, natural product callipeltin B was synthesized on a solid-phase support in 15% overall yield. Comparison of the 1H NMR spectra of three synthetic isomers with those of callipeltin B confirmed the configurational reassignment of its threonine residues as d-allothreonine and the assignment of the configuration of its beta-methoxytyrosine residue as (2R,3R).

The first total synthesis of the cyclodepsipeptide pipecolidepsin A

“…Despite the bulky D-allo-AHDMHA side chain, a rapid O-to-N transacylation occurred (up to 50%) during the removal of its Fmoc group. This O-to-N transacylation occurs even when the deprotection is performed by means of a single 3-min treatment 35 . Performing the macrolactamization step after ester bond formation over intermediate 20 and before exocyclic arm elongation did not prevent the occurrence of this severe side reaction.…”

Amino Acid-Protecting Groups

“…308 Due to the clean removal of the nitro group by hydrogenolysis and its low cost, nitro protection is still used for large-scale solution synthesis of peptides 309,310 and even for SPS, where the nitro group is removed by hydrogenolysis after the cleavage from the resin. 311 Create PDF files without this message by purchasing novaPDF printer (http://www.novapdf.com) …”

Synthesis of Bioactive Natural Products as Protein Inhibitors

“…22,23) Like the related cyclic depsipeptide callipeltin A, 24) the first natural peptide reported to have anti-HIV activity and cytotoxicity various tumor cell lines, callipeltin B possesses a 22-member macrolactone composed of -methoxy tyrosine ( -MeOTyr), (3S,4R)-3,4-dimethylpyroglutamic acid (diMePyroGlu), and several N-methylated D-amino acids. The configuration of -MeOTyr in callipeltins has not been determined due to its lability to acid.…”