简要解答网友的问题：so much as  用于否定句，意思等于even（甚至）。

He doesn't so much as invite his best friends.

他甚至连他最好的朋友都没邀请。

如果深入分析，可以看出：这是一个省略结构，不定式也是一个省略to 的结果状语：

He doesn't do so much as to invite his best friends.

句式结构：

so...as to... 如此...以至于。

not so...as to... 没有如此... 远未到达怎样。

字面：他做的事还达不到邀请他最好朋友的程度。

【补充解答】

之前，有位网友提出了一个有趣的句子：She left without so much as a word.

句子虽短， without so much as 是一种什么结构？什么含义？

without so much as 的结构和意义

so much as 实际是一种比较结构，是as much as 用于否定时的变式。因此，so much as 与not 连用或类似not的否定词without 等连用，意思是：“还不如；甚至不；甚至没；连...也没；连...都没”。例如：

She didn’t know so much as a three-year-old child. 她还不如三岁的小孩懂得多。

He never spoke so much as a word.  他甚至连一句话也没说。

He left without so much as a nod.  他连头也不点一下就离开了。

She walked away without so much as a thank-you.  她走时连句感谢话都没说。

She left without so much as saying “good-bye”.  她甚至连“再见“都没说就走了。

He is poor without so much as a place to live in.  他穷得连住的地方都没有。