Novel S-Xanthenyl Protecting Groups for Cysteine and Their Applications for the Nα-9-Fluorenylmethyloxycarbonyl (Fmoc) Strategy of Peptide Synthesis1-3
摘要:
The 9H-xanthen-9-yl (Xan) and 2-methoxy-9H-xanthen-9-yl (2-Moxan) groups can be introduced onto sulfhydryl functions by S-alkylation reactions involving the corresponding xanthydrols, plus trifluoroacetic acid (TFA) as catalyst. Conversely, these groups are removed rapidly by acid in the presence of appropriate silane or thiol scavengers. The 3-methoxy-9H-xanthen-9-yl (3-Moxan) derivative was also studied, but abandoned for several reasons including challenging synthesis, excessive lability to acid, and insufficient stability in the presence of base. The N-alpha-9-fluorenyl-methyloxycarbonyl (Fmoc), S-Xan or 2-Moxan-protected cysteine derivatives were prepared and applied to the solid-phase syntheses of several model peptides. Selective removal of S-Xan and S-2-Moxan groups, while retaining tris(alkoxybenzyl)amide (PAL) anchoring, is best accomplished with TFA-CH2Cl2-Et3SiH (1:98.5:0.5), 25 degrees C, 2 h. Alternatively, oxidative deprotection of S-Xan or S-2-Moxan with iodine (10-20 equiv) or thallium(III) tris(trifluoroacetate) [Tl(tfa)(3)] (1-3 equiv) to provide disulfides can be carried out on peptide substrates both in solution and while polymer-bound. Compared to established chemistries with the acid-labile and oxidizable S-triphenylmethyl (Trt) group, S-Xan and S-2-Moxan gave equal or superior results in terms of peptide purities (including no detectable tryptophan alkylation) and overall yields.
Iodine-catalyzed efficient synthesis of xanthene/thioxanthene-indole derivatives under mild conditions
作者:Weihang Miao、Pingting Ye、Mengjiao Bai、Zhixin Yang、Suyue Duan、Hengpan Duan、Xuequan Wang
DOI:10.1039/d0ra05217e
日期:——
xanthen-9-ol and thioxanthen-9-ol with indoles has been developed, providing an efficient procedure for the synthesis of xanthene/thioxanthene-indole derivatives with good to excellent yields. This protocol offers several advantages, such as short reaction times, green solvent, operational simplicity, easily available catalyst and mild reaction conditions. Moreover, this method showed good tolerance of functional
Gastric antisecretory agents. 2. Antisecretory activity of 9-[(aminoalkyl)thio]-9H-xanthenes and 5-[(aminoalkyl)thio]-5H-[1]benzopyrano[2,3-b]pyridines
作者:James A. Bristol、Elijah H. Gold、Irwin Gross、Raymond G. Lovey、James F. Long
DOI:10.1021/jm00140a020
日期:1981.8
A series of 9-[(aminoalkyl)thio]-9H-xanthenes (3-6) and 5-[(aminoalkyl)thio]-5H-[1]benzopyrano[2,3-b]pyridines (7-10) possessing gastricantisecretory activity in the rat and dog is described Many of the compounds possessed good activity in the pylorus-ligated rat and several inhibited histamine-stimulated gastric acid secretion in the dog. The mechanism of acid secretion inhibition is not related