Click on a link to retrieve supplementary data submitted for this article:

• Crystal structure data
• (CIF format, 24 KB)

• Synthesis of 1–4 and COSY, NOESY, HMQC and HMBC spectra for 1
• (PDF format, 314 KB)

• Chemical shift data tables for 1 and 2, COSY spectra for 2–4, NOE, HMQC and HMBC spectra for 3 and NOE spectra for 3
• (PDF format, 525 KB)

• Chemical shift data tables for 3 and 4, NOESY, HMQC and HMBC spectra for 4, cell packing for 3 and UV-vis absorption spectra for 1–4
• (PDF format, 394 KB)