 |
ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 12, Number 5
BKCSDE 12(5)
May 20, 1991 |
|
| |
Title |
Enantioselective Synthesis of 1-Substituted 1,2,3,4-Tetrahydroisoquinoline Alkaloids via Asymmetric Reduction |
Author |
Byung Tae Cho*, Cheol Kyu Han |
Keywords |
|
Abstract |
Enantioselective synthesis of 1-substituted tetrahydroisoquinoline alkaloids (1) via asymmetric reduction of 1-substituted 3,4-dihydroisoquinolines (2) and the corresponding iminium salts (3) with the selected chiral hydride reagents, such as K glucoride (5), Itsuno's reagent (6), and Mosher's reagent (7) were examined. In these reactions, dihydroisoquinolines were not reduced by the hydride reagents, whereas the iminium salts were easily reduced under the same reaction conditions found in successful reduction of ketones. Thus, the reduction of 6,7-dimethoxy-3,4-dihydroisoquinolium iodide(3a) with 5, 6 and 7 provided the product 1a with 52.3 % ee, 18 % ee, and 66.4 % ee, respectively. For 1-benzyl derivatives (3b-3d), syntheses of 1b-1d with 0.7-6.2 % ee, 5.9-21 % ee, and 1.4-2.7 % ee were achieved with chiral reducing agents 5, 6 and 7, respectively. For 1-aryl derivatives, use of 5, 6 and 7 resulted in optical inductions in the range of 25.2-43 % ee, 13-21.1 % ee, and 6.3-16 % ee, respectively. |
Page |
565 - 569 |
Full Text |
PDF
|
|
|
