ACR X SAME ALT ASSIGNED HAD LTSS FROM ACR Y. SYS ERROR.

Narrative

I WAS WORKING AN ARR SECTOR FOR BOSTON LOGAN ARPT; PVD SECTOR. I WAS PROVIDING EXTENDED INTRAIL FOR BOS ARRS. BDL DEPS TFC HAVE A SPECIFIC RTE; COASTAL 1 DEP SID; WHICH CONFLICTS VERTLY WITH BOS INBOUNDS. I HAD AN ACR X; FL210; BEING HANDED OFF FROM THE INITIAL BOSTON ARTCC SECTOR; EBOUND TO BOS. DURING THIS TIME; I WAS WORKING ACR Y COASTAL DEP SBOUND; CLBING TO FL220. THE PRECEDING SECTOR WAS SEQUENCING ACR X BEHIND AN ACR Z TO BOS. ACR Z WAS TURNED OVER TO MY SECTOR FREQ WITHOUT A HDOF; WHICH CAUSED SOME CONFUSION BRIEFLY. NOT BEING AWARE THAT ACR Z WAS PRECEDING ACR X I BASED CLB CTL AND TURNS ON THE FACT THAT ACR X SHOULD NOT BE TURNED; SINCE I ASSUMED HE WAS THE ONLY ARR TO BOS. THE PRECEDING SECTOR; HOWEVER; TURNED ACR X TO ACHIEVE INTRAIL WITH ACR Z AND; BY DOING SO; ACR X WAS PLACED IN CONFLICT WITH ACR Y. BOTH ACFT WERE TURNED; BUT SEPARATION WAS STILL LOST; 4 MI. I BELIEVE THIS ERROR WOULD HAVE NOT OCCURRED IF I WAS INFORMED OF ACR Z INBOUND WITH THE PROPER PROCS FROM THE PRECEDING SECTOR. MY CTL ACTIONS WERE BASED ON ONLY THE 1 ACFT XING ACR Y.