Novel Spiroheterocycles by Aziridination of α‐Methylene‐γ‐ and ‐δ‐lactams

Abstract

New potentially bioactive α‐spiroaziridino‐γ‐ and ‐δ‐lactams have been prepared by treatment of α‐methylene‐γ‐ and ‐δ‐lactams with ethyl N‐{[(4‐nitrophenyl)sulfonyl]oxy}carbamate (NsONHCO2Et) in the presence of CaO. These compounds, through reductive aziridine ring opening, can be intermediates for the synthesis of α‐ and β‐aminolactams, which are useful as conformational constraints in peptides. The above procedure has been successfully extended to one α‐methyleneoxindole to obtain a new spirooxindole derivative, a potential precursor of natural alkaloids. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Ethyl Nosyloxycarbamate: A Chameleonic Aminating Agent

“…In the case of -alkylidene -and -lactams the initially produced potentially bioactive spiroaziridines (Scheme 37), were easily opened by a reductive procedure to -and -amino butyro-and valerolactams [70].…”

Stereochemical implications in the synthesis of 3,3′-spirocyclopropyl oxindoles from β-aryl/alkyl-substituted alkylidene oxindoles

“…All reactions were carried out in oven-dried glassware under nitrogen unless otherwise specified. Alkylidene oxindoles 3a 25 3c-f, 26 3h, 25 and 3i, 26 methylbenzoylformate derivatives 1b-1c, 27 N-methyl isatin 10, 28 hydrate 12, 29 and β-silanol 14 30 were prepared according to the literature and spectral data ( 1 H NMR and 13 C NMR) were consistent with reported data. 1 H nuclear magnetic resonance (NMR) spectra were obtained at either 300, 400, 500 or 600 MHz.…”

Applications of NHC-mediated O- to C-carboxyl transfer: synthesis of (±)-N-benzyl-coerulescine and (±)-horsfiline

“…29 As an alternative strategy, selective reduction of the ester functionality within 18 was attempted. Treatment of 18 with LiAlH 4 at rt resulted in over-reduction, generating N-benzyl-3-allylindole 21 in 44% isolated yield, while selective reduction was achieved through treatment with sodium borohydride and calcium chloride in methanol, 30 giving alcohol 20 in 80% yield (Scheme 2). At the moment we cannot distinguish between the over-reduction process to give 21 proceeding either via direct reductive retro-Claisen reaction of the ester, or retro-aldol reaction of in situ formed alcohol 20.…”

“…Following the method described by Loreto et al, 30 sodium borohydride (163 mg, 4.30 mmol) was added to a suspension of 18 (550 mg, 1.43 mmol) and calcium chloride (239 mg, 2.15 mmol) in MeOH (3.5 mL) at 0 C and the resulting mixture stirred for 4 h then warmed to rt and stirred overnight before concentration in vacuo. 3 N citric acid was added dropwise until reaching pH 2-3 before extracting with CH 2 Cl 2 (25 mLÂ3 CDCl 3 ) 179.3, 143.7, 136.0, 132.3, 129.8, 129.2, 128.8, 128.0, 127.6, 123.7, 123.1, 119.7, 109.8, 67.2, 54.7 À3.3 ppm)).…”