[Black Mage]

This is for my own self study, and I was reading through Warren's "Organic Synthesis: The Disconnection Approach" (pgs. 196-197) they discuss the synthesis of (11R,17S)-11.17-dimethylhentriacontane an example of a kind of disconnection where you can break it into two fragments then can then be reconnected "with the right steriochemistry" yet in the example the pre-LiAlH4/NaH, Pd H2 reduction intermediate it is not the correct steriochemistry. Am I missing something here how this reaction gives the 11R,17S steriochemistry as opposed to a mix? I'm sure I am missing some glaringly obvious point so please try to help illuminate that for me.

The original paper can be found here:

D. Pempo, J. Viala, J.-L. Parrain and M. Santelli, Tetrahedron: Assymmetry, 1996, 7, 1951

[Dan]

in the example the pre-LiAlH4/NaH, Pd H2 reduction intermediate it is not the correct steriochemistry. Am I missing something here how this reaction gives the 11R,17S steriochemistry as opposed to a mix? I'm sure I am missing some glaringly obvious point so please try to help illuminate that for me.

The stereochemistry is correct. You are missing a rotation. See attachment for an example.

[Black Mage]

Oh wow  , thank you very much!