Facile Syntheses of Valiolamine and Its Diastereomers from (-)-Quinic Acid. Nucleophilic Substitution Reactions of 5-(Hydroxymethyl)cyclohexane-1,2,3,4,5-pentol

摘要

Valiolamine (1), 1-epz-valiolamine (2), 2-epi-valiolamine (3), (1R,2R)-valiolamine (4), and 2-amino regioisomer 17 have been prepared from (-)-quinic acid (6) in 14 (8.4% overall yield), 13 (9.0%), 15 (4.3%), 17 steps (2.5%), and 12 steps (13%), respectively. Charged nucleophilic ring-openings of cyclic sulfate (1R,2S,3S,4S,5S)-4,5-di-O-acetyl-3-O-benzyl-5-(benzyloxymethyl)-1,2-O,O-sulfonyl-cyclohexane-1,2,3,4,5-pentol (11) occurred regioselectively at C-2, whereas the corresponding ring-openings of its (1S,2R)-diastereomer 34 proceeded preponderantly at C-1. (1R,2S,3R,4S,5S)-2,4,5-Tri-O-acetyl-3-O-benzyl-5-((benzyloxy)methyl)-1-O-(trifluoromethanesulfonyl)cyclohexane-1,2,3,4,5-pentol (24) underwent novel internal displacement spontaneously to form (1S,2S,3R,4S,5S)-1,2,4-tri-O-acetyl-3-O-benzyl-5-((benzyloxy)methyl)cyclohexane-1,2,3,4,5-pentol (25), whereas its 2-epimer was inert under the same conditions. Ruthenium-catalyzed dihydroxylation of alkene, (3R,4S,5S)-4,5-O-acetyl-3-O-benzyl-5-((benzyloxy)methyl)-1-cyclohexene-3,4,5-triol (31), gave the desired β-1,2-diol 32 in higher yield and stereoselectivity than the osmium tetraoxide protocol. The regioselectivity. of charged nucleophilic ring-openings of cyclic sulfates 11, 34, and 38 is discussed.