2-Substituted 2,3-Dihydro-4H-1,3-benzoxazin-4-ones: Novel Auxiliaries for Stereoselective Synthesis of 1-beta-Methylcarbapenems(1).
The dihydrobenzoxazone 9e, which is easily prepared from salicylamide 11 and cyclohexanone, serves as an efficient auxiliary in the synthesis of the 1-beta-methylcarbapenem key intermediate 10. The stereocontrolled Reformatsky-type reactions of the acetoxyazetidinone 2 with the carboximides 6 gave the intermediates 7 with high diastereoselectivities in high chemical yields. The auxiliary 9e also acts as a good leaving group in the TMSCl-promoted Dieckmann-type cyclization leading to a 1-beta-methylcarbapenem skeleton. By using this auxiliary, 10 was synthesized in 58% overall yield and four steps from 2.
Kondo
Kazuhiko
K
Research Laboratory of Applied Biochemistry, Tanabe Seiyaku Co. Ltd., 3-16-89, Kashima, Yodogawa-ku, Osaka 532, Japan.
Seki
Masahiko
M
Kuroda
Tooru
T
Yamanaka
Takeshi
T
Iwasaki
Tameo
T