A question recently asked here whether compounds know to be chiral can have non-measurable optical rotations: Are there chiral compounds that don't rotate plane-polarized light?.
Apparently they exist and the phenomenon is known as cryptochirality.
This prompted me to think of the opposite end of the spectrum of optical rotation. Which known compound shows the largest known optical rotation?
NB when I say "known compound" I mean something that has actually been synthesised in large enough quantities to be well characterised. So no theoretical-only compounds or esoteric systems.