Diastereo- and Enantioselective Synthesis of Fluorinated Threonines

Natural and Synthetic Halogenated Amino Acids—Structural and Bioactive Features in Antimicrobial Peptides and Peptidomimetics

“…Many biosynthetic pathways relying on the reaction of fluoroacetaldehyde and glycine under the catalysis of threonine transaldolases have been reported for producing 4-fluorothreonine ( 28 ) [ 115 ]. A synthesis has been published by Scolastico ( Scheme 3 ) [ 116 ] starting from epoxide ( 37 ). Oxidation of the alcohol using periodate as the terminal oxidant under the catalysis of Ru(III) provided carboxylic acid ( 38 ) which was then reacted with concentrated ammonia to give regioisomers ( 39 ) and ( 40 ) in a 9:1 ratio.…”

“…Subsequent debenzylation using Pd/C and methanol provided compound ( 42 ), which was then used as the starter for the electrophilic deoxyfluorination to give carbamate-protected 4-fluorotheonine ( 43 ). Final deprotection to ( 28 ) was achieved via treatment with 6N HCl [ 116 ]. Potenti et al recently reported another synthetic route avoiding the use of Ru(III) [ 117 ].…”

Fluoroalkyl substituted (Z)-dehydro α-amino ester as a building block for the fluorine-containing cyclopropyl α-amino esters and dihydrooxazole

“…The route to the b-fluoroalkyl substituted (Z)-a,b-dehydro amino ester (7 and 9) was started from fluorinated syn-N,Ndibenzyl threonine ethyl ester 4, which were stereoselectively synthesized according to the reported procedures for trifluoromethyl substituent (4a) [2]. Protection of hydroxyl group of 4a with Tos group led to the formation of syn-8, which was further transformed into N-dibenzyl protected (Z)-a,b-dehydro amino ester (9) in excellent yield via a b-elimination of TsOH in the presence of NaH.…”

Liposidomycins − Synthetic Studies Towards the Ribosyldiazepanone Moiety

“…The latter was derived from D ‐ribose in two steps involving concomitant protection of the anomeric hydroxy group and secondary alcohols9 followed by oxidation of the primary alcohol 10. Both synthetic pathways involve the formation of a heterocyclic compound, an oxazolidinone or an oxazoline, which can be isomerized to give the thermodynamically more stable trans isomer so as to ensure predominant formation of the threo isomer 11. In the first route, aldehyde 9 was condensed with the anion of tert ‐butyl N ‐benzyloxysarcosinate ( 11 ), generated at −78 °C using lithium diisopropylamide in THF,12 as outlined in path A 13.…”