The use of enantiomerically pure ketene dithioacetal bis(sulfoxides) in highly diastereoselective intramolecular nitrone cycloadditions. Application in the total synthesis of the β-amino acid (–)-cispentacin and the first asymmetric synthesis of cis-(3R,4R)-4-amino-pyrrolidine-3-carboxylic acid

Abstract

Intramolecular 1,3-dipolar nitrone cycloaddition onto an enantiomerically pure ketene dithioacetal dioxide using a three-carbon tether gave the corresponding 5,5-disubstituted isoxazolidine as a single diastereomer in good yield. This reaction has been used as the key step in an asymmetric synthesis of the naturally occurring antibiotic, (-)-cispentacin. An asymmetric synthesis of 4-amino-pyrrolidine-3-carboxylic acid has also been carried out using the intramolecular nitrone cycloaddition as the stereocontrolling step.

Efficient Gold‐Catalyzed Hydroamination of 1,3‐Dienes

“…For example, (2,2-dimethoxyethyl)carbamic acid benzyl ester (6) [15] retains its dimethyl acetal in the reaction with diene 1 a. (Scheme 4).…”

Efficient Gold‐Catalyzed Hydroamination of 1,3‐Dienes

“…This reaction also tolerates certain functional groups. For example, (2,2‐dimethoxyethyl)carbamic acid benzyl ester ( 6 )15 retains its dimethyl acetal in the reaction with diene 1 a . (Scheme ).…”

Amino Acid Metabolism and Transport Mechanisms as Potential Antifungal Targets

“…Icofungipen, formerly known as PLD-118 (which was formerly known as BAY 10-8888), was isolated from the culture broth of a strain of Bacillus cereus , and is water-soluble and amphoteric ( Figure 1 ) [ 20 , 21 ]. The mode of action is due to an active transport of the molecule via proline and other amino acid permeases into fungal cells, where it inhibits the isoleucyl-tRNA synthase and protein synthesis [ 22 , 23 , 24 , 25 ].…”