198. Muscopyridin, eine Base C₁₆H₂₅N aus natürlichem Moschus

Synthesis of (±)-muscopyridine analogue using ring-expansion reaction of cyclic β-keto ester via conjugate addition to alkynyl imine

“…The solvents were evaporated in vacuo. The residue was purified by reprecipitation (CH 2 Cl 2 and hexane) twice and then the further residue was purified by preparative TLC on silica gel (hexane/EtOAc = 1/1 as an eluent) to give the deprotected bicyclo-2-pyridone 11 as a white solid (141 mg, 79 %); Mp 179-181 °C; 1 …”

“…The resultant mixture was stirred under a hydrogen atmosphere at room temperature for 1 h. The reaction mixture was filtered through a Celite pad to remove the catalyst. The solvents were evaporated in vacuo and then the residue was purified by preparative TLC on silica gel (first hexane/EtOAc = 1/1, and then hexane/EtOAc = 1/2 as an eluent) to give the hydroxy muscopyridine analogue 15 as a colorless oil (6.7 mg, 81% yield): 1 …”

“…Infrared spectra were recorded on a JASCO FT/IR-460 Plus spectrometer. 1 H NMR spectra were recorded on a JEOL ECX-400 spectrometer (400 MHz) with tetramethylsilane as an internal standard. 13 C NMR spectra were recorded on a JEOL ECX-400 spectrometer (101 MHz) or a JEOL JNM a-500 spectrometer (126 MHz).…”

“…The solvents were evaporated in vacuo and then the residue was dried under reduced pressure to give imine 14a as a dark orange oil (1.11 g, 94% yield, E/Z = 60/40). The imine 14a was used without further purification: E/Z = 60/40; 1 …”

“…(R)-(+)-Muscopyridine 1 is one of the odoriferous constituents of natural musk from the musk deer Moschus moschiferus and a [10](2,6)-pyridinophane analogue (meta-pyridinophane). 1 Since the total synthesis of racemic-1 was reported by Biemann et al in 1957, 2a several groups reported total synthesis of racemic-1 2 and (R)-(+)-1 using several key reactions. 3 Synthesis of muscopyridine analogue 2 having a 4-methyl group at a pyridine ring was also reported (Scheme 1).…”