They all have a form of the prefix syn- (which also appears as sym-, syl-, sys-, and sy-), but the rest is unrelated.
Bol comes from a Greek root meaning 'throw' and is found in words like parabola and ballistic. Biosis is from the Greek bio 'life', and posium comes from the Greek poton 'drink', which means it's related to potable. A sympotes was a fellow drinker, and a symposium was originally a drinking party (where there was often intellectual entertainment). It then came to mean an intellectual meeting or conference.