「」。
"Cleopatra" has become synonymous with beautiful women.
Literal
"Cleopatra" [topic-は] beautiful-woman [genitive-の] synonym [target-に-become-ている].
~になっている is the resultative form of ~になる: 'has become and is now.' Describes a state that was arrived at in the past and persists now. 代名詞 literally 'substitute-name-word' = 'pronoun' grammatically, but metaphorically 'synonym, byword for, poster child of.' This metaphorical use is common: XはYの代名詞 = 'X is the go-to example of Y.'