26398-93-6Relevant articles and documents
Lepadins I-K, 3- O-(3′-Methylthio)acryloyloxy-decahydroquinoline Esters from a Bahamian Ascidian Didemnum sp. Assignment of Absolute Stereostructures
ómarsdóttir, Sesselja,Wang, Xiao,Liu, Hong-Bing,Duggan, Brendan M.,Molinski, Tadeusz F.
, p. 13670 - 13677 (2018)
Three decahydroisoquinoline alkaloids, lepadins I-K, were isolated from a specimen of Didemnum sp. collected in the Bahamas. The structures of the new compounds were assigned by an integrated analysis of MS, IR, and 1H, 13C, and 2D NMR spectra. Like previously reported lepadins, the structures of the new compounds contain a decahydroquinoline heterocyclic core in lepadin I, and a new variation, an octahydroquinoline in lepadin J, but differ from earlier reported compounds by acylation of the 3-hydroxyl group by a rare 3′-methylthioacrylate. The absolute configuration of lepadin I was solved by interpretation of NOE measurements, and exciton coupled circular dichroism (ECCD) of the corresponding N-p-bromobenzoyl derivative. The latter constitutes a general method for determination of absolute configuration of the entire lepadin family. The configuration of the remote side-chain secondary carbinol was solved by the modified Mosher's esters method. Lepadin I inhibited butyrylcholineesterase (BuChE, IC50 3.1 μM), but only weakly inhibited acetylcholineesterase (AChE) (10% at 100 μM).
N-Methylated Peptide Synthesis via Generation of an Acyl N-Methylimidazolium Cation Accelerated by a Br?nsted Acid
Fuse, Shinichiro,Hayashi, Yoshihiro,Kawauchi, Susumu,Nakamura, Hiroyuki,Otake, Yuma,Shibata, Yusuke
supporting information, p. 12925 - 12930 (2020/06/04)
The development of a robust amide-bond formation remains a critical aspect of N-methylated peptide synthesis. In this study, we synthesized a variety of dipeptides in high yields, without severe racemization, from equivalent amounts of amino acids. Highly reactive N-methylimidazolium cation species were generated in situ to accelerate the amidation. The key to success was the addition of a strong Br?nsted acid. The developed amidation enabled the synthesis of a bulky peptide with a higher yield in a shorter amount of time compared with the results of conventional amidation. In addition, the amidation can be performed by using either a microflow reactor or a conventional flask. The first total synthesis of naturally occurring bulky N-methylated peptides, pterulamides I–IV, was achieved. Based on experimental results and theoretical calculations, we speculated that a Br?nsted acid would accelerate the rate-limiting generation of acyl imidazolium cations from mixed carbonic anhydrides.
SYNTHESIS AND CORRECTED STRUCTURES OF SULPHUR-CONTAINING AMIDES FROM GLYCOSMIS SPECIES: SINHARINES, PENIMIDES, AND ILLUKUMBINS
Hinterberger, Sabine,Hofer, Otmar,Greger, Harald
, p. 6279 - 6286 (2007/10/02)
The structures of sinharine and methylsinharine isolated from Glycosmic cyanocarpa, penimide A and penimide B from G. chlorosperma, and methylillukumbin A, illukumbin B and methylillukumbin B from G. mauritiana were revised on the basis of synthesis and additional spectroscopic evidence.The methylthio group and the aromatic moiety have to change their positions in the molecules.Thus the compounds represent amides of 3-(methylthio)-propenoic acid and not cinnamides as described previously.