proline analogue???

[pjh]

Would someone tell me this answer?

I'm looking for proline analogues.
Of course, I know a few of  proline analogues, for example,
L-azetidine-2-carboxylate, 3,4-dehydro-DL-proline, and
L-thiazolidine-4-carboxylate.

This is all I know of proline analogues.

Would you let me answer any other proline analogue other than above if
you know.

Thanks in advance