P 1010

Optical rotation was measured in CHCl₃ solution by a P-1010 digital polarimeter (Jasco, Tokyo, Japan). ¹H and ¹³C NMR spectra were recorded at 400 and 100 MHz in CDCl₃ by Bruker spectrometers (Karlsruhe, Germany). ESIMS were recorded using LC/MS ESIMS-TOF system (Agilent 6230B, HPLC 1260 Infinity) (Milan, Italy). The HPLC separation was performed using a Phenomenex LUNA (C18 (2) 5u 150 mm × 4.6 mm) (Torrance, CA, USA). Analytical, preparative, and reverse-phase TLCs were carried out on silica gel (Merck, Kieselgel 60, F254, 0.25, 0.5 mm, and RP-18 F254s respectively) plates (Merck, Darmstadt, Germany). The spots were visualized by exposure to UV radiation, or by spraying first with 10% H₂SO₄ in MeOH, and then with 5% phosphomolybdic acid in EtOH, followed by heating at 110 °C for 10 min. Column chromatography was performed using silica gel (Kieselgel 60, 0.063–0.200 mm) (Merck, Darmstadt, Germany).

Structural elucidation of the new compound by NMR spectra (¹H NMR, ¹³C NMR, gHSQC (heteronuclear single quantum correlation) and heteronuclear multiple bond correlation (gHMBC)) were performed using a Varian Unity INOVA AS 400 FT-NMR spectrometer (Varian, Palo Alto, CA, USA), and chemical shifts were expressed in δ (ppm), with tetramethylsilane (TMS) used as an internal standard. The dimethyl sulfoxide-d₆ (DMSO-d₆) was used as a solvent. Melting points were obtained using a Fisher-John’s melting point apparatus. Optical rotations were measured on a JASCO P-1010 digital polarimeter. Infrared spectra were obtained on a Perkin Elmer Spectrum One FTIR spectrometer (Perkin-Elmer, Walthanm, MA, USA). High resolution fast-atom bombardment mass spectrometry (HR-FAB/MS) were recorded using a JEOL JMS-700 (JEOL, Tokyo, Japan) mass spectrometer.

Optical rotations were measured in a CH₃Cl solution on a Jasco (Tokyo, Japan) P-1010 digital polarimeter. The UV and ECD spectra were recorded at room temperature on a Jasco (Tokyo, Japan) J815 spectropolarimeter, using 0.1 mm cells and concentrations of about 1 × 10⁻³ M in CH₃CN solution. During measurement, the instrument was thoroughly purged with N₂. ¹H NMR spectra were recorded at 400 MHz in CDCl₃ on either Bruker (Karlsruhe, Germany) or Varian (Palo Alto, CA, USA) Inova spectrometers. Analytical and preparative thin-layer chromatography (TLC) was performed on silica gel (Kieselgel 60, F₂₅₄, Merck, Darmstadt, Germany) 0.25 mm and 0.5 mm plates, respectively. The compounds spots were visualized on TLC plates by exposure to UV light and/or by spraying them, first with 10% H₂SO₄ in MeOH, and then with 5% phosphomolybdic acid in EtOH, followed by heating at 110 °C for 10 min. Column chromatography (CC) was carried out on silica gel (Kieselgel 60, 0.063–0.200 mm, Merck, Darmstadt, Germany). The dimethyl acetal 2 was obtained as previously described [25 (link),32 (link)]. CHCl₃ was distilled from P₂O₅ prior its use and stored under nitrogen atmosphere. All solvent and reagents were purchased from Merck (Darmstadt, Germany) and used without further purification unless otherwise stated.