如何使用正则表达式解析句子

I need to parse a sentence like: "Alice is a boy." into ['Alice', 'boy'] and and "An elephant is a mammal." into ['elephant', 'mammal']. Meaning I need to split the string by 'is' while also remove 'a/an'. Is there an elegant way to do it?I need to parse a sentence like: "Alice is a bo