Nuclear magnetic resonance spectra were recorded on 400 MHz spectrometers. Chemical shifts for automatically by direct measurement of the absolute frequency of the deuterium lock signal by the spectrometer hardware. Melting points were recorded using an Optimelt MPA100 apparatus and are uncorrected. The high-resolution mass spectrometry (HRMS) analyses were performed using electrospray ion source (ESI) or pneumatically assisted atmospheric pressure chemical ionization (APCI) using an atmospheric solids analysis probe (ASAP). ESI was performed using a Waters LCT Premier equipped with an ESI source operated in positive or negative ion mode. The software used was MassLynx 4.1. This software does not account for the electron and all the calibrations/references are calculated accordingly, i.e. [M+H]+ is detected and the mass is calibrated to output . APCI was performed using an Orbitrap XL or Xevo G2S using an ASAP to insert samples into the APCI source. The sample was introduced at ambient temperature and the temperature increased until the sample vaporised. In mass spectrometry for thietan-3-ols, in some instances the ionization method fragmented the substrate to generate a carbocation, whereby [M-OH] + was often found instead of [M+H] + .