Isaac Barrow, Newtons teacher, had already discovered the rudiments of calculus:
http://en.wikipedia.org/wiki/Isaac_Barrow
Hooke played a significant role in establishing the law of universal gravitation:
http://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gra...
Newtons first law comes from Galileo's principle of inertia:
http://en.wikipedia.org/wiki/Newton%27s_laws_of_motion#Newto...
And so on and so forth, lookup Kepler, Galileo, Huygens, Hooke, Barrow, Descartes, Fermat and so on in the Wikipedia, or better read any serious scholarly history of physics about this period, this is only scratching the surface of people whose work Newton very directly built upon. There is no synthesis to be done without a period of establishing a great many of particular results.