The scarlet letter: Reichstein's substance S. A comparison of the angiostatic properties of 5α-tetrahydro S and 5β-tetrahydro S

Article abstract of DOI:10.1016/0039-128X(95)00080-A

5β-Tetrahydro-Reichtein's Substance S (3α, 5β-THS) from different sources yielded variable bioassays activity in the chick chorio-allantoic membrane assay system. Physical characterization showed impure products. Synthesis of this compound by two different routes yielded active and inactive 3α,5β-THS. Of the other two epimers, 3β,5β-THS (epi-THS) and 3α,5α-THS (allo-THS), only the latter was active. These results suggest that the impurities present in 3α,5β-THS synthesized by reduction of the α,β-unsaturated ketone of Substance S might be either or both the epi- lallo-epimers (3β,5β-THS and 3α,5α-THS, respectively), with only the latter contributing the positive angiostatic activity to the mixture. Of the two synthetically derived compounds, only the latter was shown to maintain the activity, whereas 3α,5β-THS was not antiangiogenic.