Preparation of THP-ester-derived pyridinium-type salts and their reactions with various nucleophiles.
Nucleophilic substitution at the anomeric positions of tetrahydropyranyl (THP) and related carbohydrate-derived esters that proceeded through pyridinium-type salt intermediates have been developed. Treatment of the 6-substituted α-acetoxy-tetrahydropyrans with TMSOTf (TMS=trimethylsilyl) and 2-substitutited pyridines, such as 2-p-tolylpyridine and 2-methoxypyridine, led to the efficient generation of cis-pyridinium-type salts. These salts reacted with various nucleophiles, such as alcohols, azides, and organozinc reagents, to form nucleophilic-substitution products. A characteristic feature of these processes was that they took place under mild conditions, which did not affect acid-labile protecting groups. Furthermore, the reactions that employed azides and C-nucleophiles generated 2,6-trans products with high degrees of stereoselectivity.
Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka, 565-0871 Japan. fujioka@phs.osaka-u.ac.jp
Hiromichi
H
Fujioka
Yutaka
Y
Minamitsuji
Takahiro
T
Moriya
Kazuhisa
K
Okamoto
Ozora
O
Kubo
Tomoyo
T
Matsushita
Kenichi
K
Murai
D000143:Acids / Q000737:chemistry; D001386:Azides / Q000737:chemistry; D004952:Esters; D011725:Pyridines / Q000737:chemistry; D011726:Pyridinium Compounds / Q000737:chemistry*; D012492:Salts / Q000737:chemistry*; D013237:Stereoisomerism
D000143:Acids; D001386:Azides; D004952:Esters; D011725:Pyridines; D011726:Pyridinium Compounds; D012492:Salts