Complex sentence: This dissenting group of students and professors disagreed with the system prevalent on UNMSM at that time, however some analysts believe most of them where in an arrangement for establish their own university outside the control of medical board that existed in the 1960s at San Marcos University.
Split into simpler sentences: This dissenting group of students and professors disagreed with the system prevalent in UNMSM at the time. However, some analysts believe most of them where already under a prior arrangement to establish their own university outside the control of the medical board that existed in the 1960s at San Marcos University.