Synthesis of enantiopure 7-[3-azidopyl]indolizidin-2-one amino acid. A constrained mimic of the peptide backbone geometry and heteroatomic side-chain functionality of the ala-lys dipeptide.
Enantiopure N-(BOC)amino-7-[3-azidopropyl]indolizidin-2-one acid 1 has been synthesized by displacement of the methanesulfonate of its 7-hydroxypropyl counterpart 11 with sodium azide and subsequent ester hydrolysis. N-(BOC)Amino-7-[3-hydroxypropyl]indolizidin-2-one ester 11 was obtained from a sequence commencing with the alkylation of (2S,8S)-di-tert-butyl 5-oxo-2,8-di-[N-(PhF)amino]azelate 5 (PhF = 9-(9-phenylfluorenyl)). Stereoselective allylation of 5, regioselective olefin hydroboration, selective primary alcohol protection as a silyl ether, and oxidation of the secondary alcohol gave (2S,4R,8S)-di-tert-butyl 4-[3-tert-butyldimethylsiloxypropyl]-5-oxo-2,8-di-[N-(PhF)amino]azelate 9 as a pure diastereomer in 33% overall yield. Linear ketone 9 was then converted into the indolizidinone heterocycle by a route featuring reductive amination, lactam cyclization, and isolation by way of a silyl ether which provided the (6S,7R)-isomer of 11.
Feng
Z
Z
Département de Chimie, Université de Montréal, C. P. 6128, Succursale Centre Ville, Montréal, Québec, Canada H3C 3J7.
Lubell
W D
WD
D000596:Amino Acids / Q000138:chemical synthesis* / Q000737:chemistry; D004151:Dipeptides / Q000737:chemistry*; D007212:Indolizines / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry / Q000379:methods; D018716:Molecular Mimicry; D015394:Molecular Structure; D013237:Stereoisomerism
D000596:Amino Acids; D004151:Dipeptides; D007212:Indolizines