Chemistry of L-Ascorbic Acid: Regioselective and Stereocontrolled 2-C- and 3-C-Allylation via Thermal Claisen Rearrangement
摘要:
We report the convenient preparation of 3-O- and 2-O-allylated derivatives of 5,6-O-isopropylidene-L-ascorbic acid (1) with various allyl substituents in high yield and their quantitative thermal Claisen rearrangement to the corresponding 2-C- and 3-C-allylated derivatives with high regio- and stereoselectivity under relatively mild conditions. This reaction will now allow the synthesis of heretofore unknown 3-C-allylated derivatives of L-ascorbic acid in high yield. The high chiral induction at the substituents of the allylic carbon, especially in the case of the 3-O-methyl-2-O-crotyl derivative, is intriguing. This general method of preparation of 2-C- and 3-C-allylated derivatives of ascorbic acid may have important applications in synthetic organic and pharmaceutical chemistry.
A study on a general chemoselective method for the preparation of 3-O-alkyl and differentially protected 2.3-di-O-alkyl derivatives of 5,6-O-isopropylidene-L-ascorbic acid is described.
l-Ascorbic acid in organic synthesis: DBU-catalysed one-pot synthesis of tetramic acid derivatives from 5,6-O-isopropylidene ascorbic acid
作者:Biswajit K. Singh、Shyam S. Verma、Namrata Dwivedi、Rama P. Tripathi
DOI:10.1016/j.tetlet.2006.01.098
日期:2006.3
Reaction of 5,6-O-isopropylidene-2,3-bis-O-alkyl ascorbic acid with different amines in the presence of DBU at ambient temperature resulted in the formation of 3,4-bis-O-alkyl-l-alkyl-5-(2-hydroxy ethyl)-5-hydroxy-1,5-dihydropyrrol-2-ones in moderate yields. (c) 2006 Elsevier Ltd. All rights reserved.
Diastereoselective transannular [2+2] photocycloaddition of ascorbic acid derivatives
作者:Sébastien Redon、Olivier Piva
DOI:10.1016/j.tetlet.2005.11.102
日期:2006.1
Ring-closing metathesis of bis-O,O-alkenyl ascorbic acid derivatives affords cyclic ethers in good yields which can be further converted by irradiation at 254 nm into new polyoxacyclic structures according to a diastereoselective transannular [2+2] photocycloaddition. (c) 2005 Elsevier Ltd. All rights reserved.
Regio- and Chemoselective Alkylation of <scp>l</scp>-Ascorbic Acid under Mitsunobu Conditions