70424-09-8Relevant articles and documents
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.
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 (2018/11/10)
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).
The Synthesis and Absolute Configuration of the Novel Ichthyotoxic Diacylglycerols, Umbraculumin A and Umbraculumin C
Medeiros, Edna Faria De,Herbert, John M.,Taylor, Richard J. K.
, p. 2725 - 2730 (2007/10/02)
The total syntheses of umbraculumin A 1 and umbraculumin C 2 in homochiral form are described.Noteworthy steps involve (i) the preparation of the key Z,E-acid 10 by organolithium addition to pyrylium salts, (ii) the use of the 4-methoxyphenylmethyl protecting group for the preparation of 1,2-diacyl glycerols and its removal using trifluoroacetic acid-anisole without significant acyl migration (DDQ removal having proved inefficient) and (iii) a new procedure for the stereoselective preparation of (Z)- and (E)-3-methylthiopropenoic acid.
