The antepenult, if accented, can have the acute only (ἄνθρωπος, βασίλεια
a. Some nouns in -εως and -εων admit the acute on the antepenult. Thus, the genitive of nouns in -ις and -υς (πόλεως, πόλεων, ἄστεως), the forms of the Attic declension, as ἵ_λεως ( cross289). So the Ionic genitive in -εω (πολί_τεω); also some compound adjectives in -ως, as δύσερως
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].