selective Schmidt reaction to give the the 3-azabicyclo[4.3.0]noanmine buildingblock 3b which was employed in a short synthesis of (±)-tecomanine 4. AsymmetricSchmidt reaction on 1, employing (2S,4R)-2-azido-4-hydroxypentane 14 as a chiral inducer, showed encouraging levels of enantiotopic methylene group stereo differentiation.
Conjugate addition of cyclohexanone lithium enolate to 2-nitro-2-butene and the Nef reaction on the resulting nitronate gave 2-(2-oxopropyl)cyclohexanone in good yield. Treatment of the 2-(2-oxopropyl)cyclohexanone thus obtained with potassium phosphate tribasic (K3PO4) in isopropanol gave 2, 3, 4, 5, 6, 7-hexahydro-3-methyl-3aH-inden-2-one (8). Application of the procedure to 1, 3-dimethyl-4-piperidone (11) gave the 1, 3, 4, 6, 7, 7a-hexahydro-6-oxo-2, 4, 7-trimethyl-2H-2-pyrindine (12). Epimerization of 12 with basic alumina gave (±)-tecomanine (1). The short synthesis of the alkaloid demonstrates the usefulness of K3PO4 as a base for cyclopentenone annulation of 1, 4-diketones without migration of the double bond.
1,6-dihydro-3(2H)-pyridinones as synthetic intermediates. Total synthesis of (±)-tecomanine
作者:Takeshi Imanishi、Noriyuki Yagi、Miyoji Hanaoka
DOI:10.1016/s0040-4039(01)92518-3
日期:1981.1
The first and stereoselective totalsynthesis of (±)-tecomanine (1) has been achieved from ethyl 1,6-dihydro-3(2H)-pyridinone-1-carboxylate (2) as a synthon.