TY - JOUR
T1 - Highly stereocontrolled synthesis of the 1β-methylcarbapenem key intermediate by the reformatsky reaction of 3-(2-bromopropionyl)-2-oxazolidone derivatives with a 4-acetoxy-2-azetidinone
AU - Ito, Yoshio
AU - Sasaki, Akira
AU - Tamoto, Kastumi
AU - Sunagawa, Makoto
AU - Terashima, Shiro
PY - 1991
Y1 - 1991
N2 - The key synthetic intermediate (4) of 1β-methylcarbapenems (1-3) was efficiently synthesized by employing highly stereocontrolled Reformatsky reaction (C4-alkylation) of 3-(2-bromopropionyl)-2-oxazolidone derivatives (6) with (3R,4R)-4-acetoxy-3-[(R)-1-(t-butyldimethylsilyloxy)ethylJ-2-azetidinone (5) in the presence of zinc dust followed by removal of 2-oxazolidone moieties. The best diastereoselectivity (β:α=95:5) could be realized by uses of sterically crowded achiral 2-oxazolidone derivatives such as 4,4-dimethyl-, 4,4,5,5-tetramethyl, and 4,4-dibutyl-5,5-pentamethylene-2-oxazolidone and higher reaction temperatures (refluxing tetrahydrofuran). The remarkable diastereoselectivities observed for the Reformatsky reactions could be explained by means of the weakly chelating transition state models.
AB - The key synthetic intermediate (4) of 1β-methylcarbapenems (1-3) was efficiently synthesized by employing highly stereocontrolled Reformatsky reaction (C4-alkylation) of 3-(2-bromopropionyl)-2-oxazolidone derivatives (6) with (3R,4R)-4-acetoxy-3-[(R)-1-(t-butyldimethylsilyloxy)ethylJ-2-azetidinone (5) in the presence of zinc dust followed by removal of 2-oxazolidone moieties. The best diastereoselectivity (β:α=95:5) could be realized by uses of sterically crowded achiral 2-oxazolidone derivatives such as 4,4-dimethyl-, 4,4,5,5-tetramethyl, and 4,4-dibutyl-5,5-pentamethylene-2-oxazolidone and higher reaction temperatures (refluxing tetrahydrofuran). The remarkable diastereoselectivities observed for the Reformatsky reactions could be explained by means of the weakly chelating transition state models.
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U2 - 10.1016/S0040-4020(01)87086-1
DO - 10.1016/S0040-4020(01)87086-1
M3 - Article
AN - SCOPUS:0026083149
VL - 47
SP - 2801
EP - 2820
JO - Tetrahedron
JF - Tetrahedron
SN - 0040-4020
IS - 16-17
ER -