Isolation of callipeltins A–C and of two new open-chain derivatives of callipeltin A from the marine sponge Latrunculia sp. A revision of the stereostructure of callipeltins

Synthesis of Bioactive Natural Products as Protein Inhibitors

“…These observations permitted the assignment of the absolute configuration of -MeOTyr in callipeltins as 2R,3R. 25) This finding matched D'Auria's conclusion obtained by the degradative procedure. 26) In addition, the non-proteinogenic amino acids in callipeltins, diMePyroGlu and D-allothreonine (D-alloThr), were synthesized from Gerner's aldehyde.…”

“…In the course of our studies on callipeltins, I estimated the absolute configuration of -MeOTyr in callipeltin E by a synthetic procedure 25) instead of a degradative one. 26) We achieved asymmetric syntheses of all stereoisomers of protected -MeOTyr from the cinnamyl derivative using Sharpless asymmetric aminohydroxylation 27) and dihydroxylation methodogies.…”

Quantum Mechanical Calculation of NMR Parameters in the Stereostructural Determination of Natural Products

“…[51] Initially, for these potent antiviral marine peptides isolated from the sponges Callipelta sp. [52,53] and Latrunculia sp., [54] the configuration [52] of nine amino acid residues of callipeltin A was proposed as -Ala, (2R,3R,4S)-4-amino-7-guanidino-2,3-dihydroxyheptanoic acid (AGDHE), (3S,4R)-3,4-dimethyl--glutamine (diMeGln), -Thr (two residues), -Arg, -Leu, -NMeAla. In 2002, [54] the -Ala was reassigned as -Ala, and -Thr-1 as -Thr-1.…”

“…In particular, the relative and absolute configuration of the β-OMeTyr residue remained unassigned due to the chemical degradation of this residue under acidic hydrolysis conditions; the relative configuration of AGDHE, except for C4, proposed on the basis of homonuclear J coupling analysis [52] was not confirmed by subsequent synthetic studies; [55] the presence of two -aThr residues in neamphamide, [56] a marine peptide that shows high structural homology with 15, was in disagreement with previous identification as -aThr1 and -Thr2. [54] Following our procedure, [18] for a molecule containing more than a single pair of stereocenters, like callipeltin A, each C2 fragment is examined independently from the rest of the whole molecule, comparing the calculated and experimental 3 J H,H and 2,3 J C,H coupling values. According to the above rational, we designed five C2 fragments for callipeltin A, namely, AGDHE 2,3 , AGDHE 3,4 , -aThr1, -aThr2, and β-OMeTyr (Scheme 12).…”

Quantum Mechanical Calculation of Coupling Constants in the Configurational Analysis of Flexible Systems: Determination of the Configuration of Callipeltin A

“…[1,2] and Latrunculia sp. [3] Callipeltin A shows both antiviral activity against HIV-1-infected CEM4 lymphocytes and antifungal activity against Fusarium oxysporum, Helminthosporium sativum, Phytophtora hevea, and Candida albicans. More recently, callipeltin A was found to be a selective and powerful inhibitor of the cardiac sodium/calcium exchanger and eliciting interest as a potential regulator of myocardial contractility.…”