Chemical shifts were reported in ppm downfield from the peak of Me4Si (TMS) used as the internal standard. Splitting patterns are designed as "br, s, d, t, q, and m," indicating "broad, singlet, doublet, triplet, quartet, and multiplet," respectively. The IR spectra were recorded on a SHIMADZU IRPrestige-21 FT-IR spectrophotometer using a KBr disk or a NaCl cell. Mass spectra were obtained on a JEOL JMS-700 or a JEOL JMS-T100CS.
High-resolution mass spectra were obtained on a JEOL JMS-700 or a JEOL JMS-T100CS.
Column chromatography was performed on silica gel (Kanto Chemical Co.). Thin-layer chromatography was performed on pre-coated plates (0.25 mm, silica gel Merck 60 F254).
Reaction mixtures were stirred magnetically. Preparation of ku-76 and 2d were reported previously (Abe et al., 2012) (link).