Exceptions to the recessive accent of compound verbs.—a. The accent cannot precede the augment or reduplication: ἄπειμι
N.—A long vowel or diphthong not changed by the augment receives the accent: ὑπ-εῖκε
b. The accent cannot precede the last syllable of the preposition before the simple verb nor move back to the first of two prepositions: περίθες
c. When compounded with a monosyllabic preposition, monosyllabic second aorist middle imperatives in -οῦ from μι-verbs retain the circumflex: προδοῦ
d. The accent of uncompounded infinitives, participles, aorist passive, perfect passive, and of the second aorist middle imperative (2. p. sing., but see cross426 c) is retained in composition.
f. Compound subjunctives are differently accentuated in the Mss.: ἀποδῶμαι and ἀπόδωμαι, ἐπιθῆται and ἐπίθηται; the aorist of ἵ_ημι has προῶμαι and πρόωμαι. ἀπέχω has ἀπόσχωμαι. Compound optatives retain the accent of the primitives: ἀποδοῖτο, as δοῖτο. For συνθοῖτο, προσθοῖσθε ( cross746 c) the Mss. occasionally have σύνθοιτο, πρόσθοισθε; and so πρόοιτο.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].