Exegesis:

autos de ‘but he,’ emphatic as contrasted with ochloi polloi.

ēn hupochōrōn en tais erēmois ‘retired (and stayed) in the wilderness.’ The imperfect may be iterative or durative, preferably the former: from time to time Jesus slipped away to the desert for prayer (cf. The Four Gospels – a New Translation, New English Bible, Translator’s New Testament). en tais erēmois (locative, not indicating a direction) anticipates the result of the retiring.

hupōchoreō (also 9.10) ‘to retire.’

kai proseuchomenos ‘and was praying,’ goes also with ēn.

Translation:

To make explicit the locative force of the preposition one may say, ‘having withdrawn, he stayed and prayed in the wilderness (or, stayed in the wilderness and prayed there).’

To withdraw, or, ‘to go away (from them),’ ‘to isolate oneself’ (Bahasa Indonesia RC).

Wilderness and prayed, see references on 1.80 and 1.10.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.