Designing oscillating circuit for DIY DC -DC converter
You have shown an N Channel MOSFET, whose gate must be driven positive relative to its source to turn it on.
The MOSFET gate must be driven ABOVE source by typically 5V or more. This value varies with device. 

To use an N Channel MOSFET in that circuit you need to reference the 5V gate drive to +32V so it swings 32/37V.
 Vout here ~+ Dutycycle x Vin = 70% x 32V ~= 22V.

As David Kessner says, a P Channel MOSFET may be an easier-to-use choice here.
 Connect source to Vcc = +32V, drain to L1 and drive gate negative going relative to source and to +32V to turn the FET on.