Enantiospecific Syntheses of Valienamine and 2-epi-Valienamine(1).
Cyclic sulfite 10, readily available from (-)-quinic acid (3) in 10 steps, was ring opened regio- and stereospecifically with azide anion to give (1S,2R,3R,4R)-1-azido-3,4-di-O-benzyl-5-(benzyloxymethyl)cyclohex-5-ene-2,3,4-triol (11). Deprotection of 11 afforded, for the first time, 2-epi-valienamine (2), which was isolated as penta-N,O-acetyl-2-epi-valienamine (14). The configuration of the free hydroxy group in 11 was inverted by a two-step sequence to give the blocked valienamine 19 that was deprotected to give valienamine (1), isolated as penta-N,O-acetylvalienamine (21). This approach furnished (+)-valienamine (1) in 16 steps (7% overall yield) and recorded the first synthesis of 2-epi-valienamine (2) in 13 steps (11% overall yield).
Shing
Tony K. M.
TK
Department of Chemistry, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
Li
Tin Y.
TY
Kok
Stanton H.-L.
SH