Question

Challenge question: Opiorphin is a natural painkiller present in human saliva. Determine the absolute (R, S) configuration for each stereocenter in Opiorphin.

Answer 1

Well I see 5 stereo centers

Answer 2

I'm also seeing 5 stereocentres
R was clockwise, S is counterclockwise
From left to right I got R, S, R, S, R
I don't have a clue if I did this right though, I didn't grasp the complete concept when I learned it at school.

Answer 3

I see 7.

Answer 4

I'm pretty sure there is 5 just looked it up
http://pubchem.ncbi.nlm.nih.gov/compound/25195667#section=Chemical-and-Physical-Properties
Under 4.1 computed properties
In the table it says 5 as well for defined atom stereocentre count

Answer 5

I will just answer it without even looking at the structure:
Opiorphin being a non-glycine penta-peptide hormone means there must be 5 asymmetric carbon, usually we name peptides after the super old l and d convention. Almost all natural occurring amino acids are on l form which is the equivalent of the S form, making my guess (2S, 5S, 8S, 11S, 14S) named according peptide backbone after biochemical convention.
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@aaronq
Cheater to use a peptide and not link me!

Answer 6

5 is right, and yes they're all S.

@Frostbite great deduction ..but you're not allowed to think before answering a question, you're supposed to just do as you're told lol jk you clever mofo

knowing that all natural amino acids are L (or S) and all sugars are D (or R) comes in handy.

Answer 7

Nature never screw up in terms of stereochemistry (thank you enzymes), while the chemists tend to do! :D (R and S thalidomid,,, I rest my case!)