Opener Michael Davidson played numerous pull shots to the mid-wicket boundary in his knock of 79 and was ably assisted by Ben Cant (38), Dean van Deventer (28) and Scott Duggan (26*), who along with 35 extras provided the backbone to their total.
Sydenham's reply never really recovered after a disastrous start, with van Deventer (4-32) capping a fine all-round performance by ripping through their top order.
Old Boys-Collegians produced a stunning turnaround to defeat opening-round winners East Shirley by 65 runs at Burwood Park.
OBC set a modest 144, which was propped up by Matt McEwan (44) and Todd Astle (35), before they produced a disciplined bowling performance to rout Easts for 79.
Canterbury trio Ed Nuttall (4-19), McEwan (2-23) and Logan van Beek (2-24) were the chief destroyers for OBC, with Nuttall picking up his second four-wicket haul from as many games this season