Jnm eca600

Specific rotations were measured using a P-2200 digital polarimeter (l = 5 cm; JASCO, Tokyo, Japan). IR spectra were measured using a JASCO FT/IR-4600 typeA spectrometer; ECD spectroscopy was performed using a JASCO J-1500 spectrometer. ESI and high-resolution ESI mass spectra were recorded on a Shimadzu LCMS-IT-TOF instrument. FAB and HRFABMS data were recorded using a JASCO SX-102A mass spectrometer. ¹H NMR spectra were recorded on JEOL ECS400 (400 MHz) and JNM-ECA 600 (600 MHz) spectrometers (JEOL). ¹³C NMR spectroscopy was performed on a JEOL JNM-ECA 600 (150 MHz) spectrometer. 2D-NMR experiments were carried out on a JEOL JNM-ECA 600 (600 MHz) spectrometer (JEOL).
Normal-phase silica-gel column chromatography was performed using silica gel 60 (63–210 μm; Kanto Chemical Co., Tokyo, Japan). Reverse-phase silica-gel column chromatography was performed using C18-OPN gel (140 μm; Nacalai Tesque, Kyoto, Japan). HPLC was performed using an SPD-M10Avp UV-vis detector (Shimadzu, Kyoto, Japan).

The following instruments were used to obtain spectroscopic data: specific rotations, Horiba SEPA-300 digital polarimeter (l = 5 cm); UV spectra, Shimadzu UV-1600 spectrometer; IR spectra, Shimadzu FTIR-8100 spectrometer; FAB-MS and high-resolution MS, JEOL JMS-SX 102A mass spectrometer; ESIMS and HRESIMS, Exactive Plus mass spectrometer (Thermo Fisher Scientific Inc., MA, USA); ¹H-NMR spectra, JEOL JNM-ECA600 (600 MHz) and JNM-ESC400 (400 MHz) spectrometers; ¹³C-NMR spectra, JEOL JNM-ECA600 (150 MHz) and JNM-ESC400 (100 MHz) spectrometers, with tetramethylsilane as an internal standard; HPLC detector, Shimadzu SPD-10Avp UV-VIS detectors; and HPLC column, Cosmosil 5C₁₈-MS-II (Nacalai Tesque Inc.). The following experimental conditions were used for column chromatography (CC): ordinary-phase silica gel CC, silica gel 60N (Kanto Chemical Co., Tokyo, Japan; 63–210 mesh, spherical, neutral), normal-phase thin-layer chromatography (TLC), pre-coated TLC plates with silica gel 60F₂₅₄ (Merck, Darmstadt, Germany; 0.25 mm), with detection achieved by spraying with 1% Ce(SO₄)₂–10% aqueous H₂SO₄, and followed by heating.

Optical rotations were measured on a PerkinElmer 341 automatic polarimeter (PerkinElmer, Inc., Waltham, MA, USA). NMR spectra were obtained on JEOL JNM-ECA600 (600 MHz for ¹H) or JEOL JNM-AL300 (300 MHz for ¹H) spectrometers (JEOL Ltd, Tokyo, Japan). Chemical shifts are reported in parts per million relative to the internal standards [tetramethylsilane (0.00 ppm) for ¹H; CD₃OD (49.00 ppm) for ¹³C]. High performance liquid chromatography (HPLC) was carried out using a Shimadzu LC-10AT VP HPLC system and SPD-10A VP UV detector (Shimadzu Corp., Kyoto, Japan) with CHIRALPAK AD or OD (4.6Φ × 250 mm; Daicel Corporation, Osaka, Japan; detection: UV 254 nm, eluent: n-hexane/ethanol, flow rate: 1.0 ml/min, temperature: 30°C).
Thin layer chromatography was carried out using silica gel plates (Merck 5715, 0.25 mm; Merck KGaA, Darmstadt, Germany). Silica gel flash column chromatography was carried out using a Biotage Isolera One chromatograph (Biotage AB, Uppsala, Sweden) with Biotage SNAP Ultra cartridges (silica gel, 25 μm). Methyl (R)-lactate and benzyl (S)-lactate were purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan). Both the stereoisomers of 1-(tert-butoxycarbonyl)piperidine-3-carboxylic acid were purchased from Alfa Aesar, A Johnson Matthey Company (Heysham, Lancashire, UK). The outline of synthesis of the S-isomer of CCG-1423 is summarized in Fig 2.