Converting Open-Drain to Active-High (low voltage, low power)
The circuit simulator isn't working for me today (grr).

PNP.  Emitter to +V, base to RTC through a resistor (100k\$\Omega\$?).  Collector to boost converter, with resistor to ground (same as base resistor).  Size the resistor for a happy medium between turning on &amp; off reliably, and not consuming too much current.  It should consume very little current when off.