Photoinduced addition of methanol to 5(S)-5-triisopropylsiloxymethyl-N-boc-dihydropyrrole-2(5H)-one: A new route to 4(S), 5(S)-disubstituted pyrrolidin-2-ones

Synthesis of (2S,3S)-3′-fluoroisoleucine

“…Because of the problems associated with reduction of the aldehyde 6, we investigated application of a direct photochemical addition of methanol to the enone 4 discovered by Mann et al 8 Irradiation of a solution of the dihydropyrrolone 4 in methanol containing benzophenone as photoexitant gave a 68% yield of the alcohol 7, identical in all respects with the sample prepared by reduction of the aldehyde 6. The alcohol was now treated with diethylaminosulfur trifluoride in dichloromethane which had been passed through a column of basic alumina prior to use, to give the fluoride 13 in 61% yield.…”

“…The organic layer was dried (MgSO 4 ) and the solvents were removed in vacuo. The product was purified by flash column chromatography on silica gel using petroleum ether : ethyl acetate (3 : 1) as eluent to afford 8.5, H-5A), 3.94 (1H, dd, J 5B,5A 8.6, J 5B,4 8.5, H-5B), 3.77 (1H, m, H-6), 3.67 (1H, dd, J 7A,7B 10.6, J 7A,5 4.3, H-7A), 3.56 (1H, dd, J 7B,7A 10.6, J 7B,5 3.5, H-7B), 2.84 (1H, m, H-4), 2.52 (1H, dd, J 3A,3B 17.7, J 3A,4 8.7, H-3A), 2.47 (1H, dd, J 3A,3B 17.7, J 3B,4 9.8, H-3B), 1.44 (9H, s, C(CH 3 ) 3 ) and 1.07 (9H, s, OSiC(CH 3 ) 3 ).…”

Garner's aldehyde

“…When the reaction was performed in methanol, poor E/Z ratios were observed, while in THF or benzene, high stereoselectivity was observed (Table 2). 141, [143][144][145][146][147][148][149] Taylor and coworkers have developed a one pot procedure for the preparation of 106. The corresponding alcohol 10 was oxidised using manganese dioxide in the presence of the ylide and the aldehyde (1) so formed was trapped as formed to produce the α,β-unsaturated ester 106 directly.…”

Development of 2′-Substituted (2S,1′R,2′S)-2-(Carboxycyclopropyl)glycine Analogues as Potent N-Methyl-d-aspartic Acid Receptor Agonists

“…The intermediates 6a and 6b was cyclized into the lactones 7a and 7b using TFA in DCM or p -TsOH in MeOH as previously reported. 22, 23 …”