[PKa]

HI I am new to this forum and am looking to get some answers from chiral chemistry experts.
I am curious to know if one can predict the optical rotation of a compound if we know the optical rotation of individual components that are part of the molecule. for example, can we predict or use a formula to predict the optical rotation of Boc-Cys-Ala-OMe if we know the optical rotations of Boc-Cys-OH and H-Ala-OMe?
As far as I know, it is not possible to predict the optical rotation of any compound unless it is a reported compound with a known specific rotation. I would appreciate any leads or links to read more on he topic.

[phth]

It can be done with DFT, but it is complicated.  Do you forget about the S-cis/S-trans isomerism that only exists between Cys-Ala not Cys+Ala

[PKa]

Thanks for the reply. I do not remember having read anywhere about this kind of calculation . Yes S-cis and S-trans would make it little more complicated. It would be interesting to find out that somebody had already done this kind of study.