Novel synthetic approaches to aza heterocycles oxo 945 amino acids and e 945 946 unsaturated carboxylic acids esters

Abstract

A two step on pot synthesis of disubstituted piperidone and piperidines only trans configuration starting from 945 946 unsaturated ketoesters has been developed Cascade type reaction using BF3 OEt2 or one pot deprotection of tBoc group by TFA then TEA facilated the intramolecular aza Michael addition of 945 946 unsaturated ketoesters to afford trans 2 3 disubstituted piperidines Also initial synthetic study of 5 membered heterocyclic 946 enamino esters has been established using catalytic amount of B C6F5 3 Few 5 membered heterocyclic 946 enamino esters have synthesized by optimizing the reaction conditions This procedure gives an easy access to the chiral and non chiral 5 membered heterocyclic 946 enamino esters in good yields under mild reaction condition Further a Short and concise synthesis of enantiopure side chain modified 945 amino acids such as 4 oxo L norvaline 6 oxo L homonorleucine and 5 cis alkyl prolines is described Meldrum 8217 s acid has been employed for the preparation of aminocarboxylate derived 946 ketoesters Knoevenagel condensation of L aminocarbo xylate derived 946 ketoesters with aldehydes followed by reductive decarboxylation afforded unnatural 945 amino acids Application of the method has been illustrated by the synthesis of a fluorescent amino acid In another study novel and expedient syntheses of 945 946 unsaturated carboxylic acids esters has been described by exploring the reactivity of alkylidene Meldrum 8217 s acids with water alcohols in presence of FeCl3 8226 6H2O Application of this method has been extended to biomass derived aldehydes and synthesis of sunscreen filters newline newline