2. Reboxitine is used to treat depression and is a norepincphrinc uptake inhibit

Question

2. Reboxitine is used to treat depression and is a norepincphrinc uptake inhibitor (NRI). Norepinephrine is a neurotransmitter. Much like low levels of scrotonin, low levels of norepinephrine are linked to depression. Uptake inhibitors increase the concentration of norepincphrine in the brain and can treat depression. While reboxitine is marketed as the raccmate (i.e, racemic mixture) the (S.S)-enantiomer is much more active and thus the enantioselective synthesis was pursued. In 2007 an industrial scale synthesis of (S,S)-reboxitine was reported (Org. Proc. Res. & Devel. 2007, 11,354). The chiral centers can be established in the first step of the synthesis using an asymmetric epoxidation reaction called the "Sharpless Asymmetric Epoxidation." Using the paper to help you (the paper can be found on the ACS website) fill in structures of intermediates 3-7 in the reaction pathway below. Note that I have slightly changed the reagents in the reactions to produce compounds 4-7 from the reagents that are reported in the paper! All of the reagents shown below are ones you are familiar with and work in the same way (at least in theory) to those reported in the paper. In the boxes draw the products that would result from use of the reagents I've shown. (Hint in the TBS protection reaction the least sterically hindered alcohol can be protected sclectively) a Fill in the structures of intermodiates 3-7 0184 L-DIPT, TKOPr NaOH Sharpless Asymmetric TBSCI TsC Im Py OH 1. NaNH2 Intermedlate 6 In the reference Intermediate 5 in the reference b. Draw the structure of (S,S)-reboxetine.

Explanation / Answer

All the three mechanism are written absolutely correct.

Well done

In the first mechanism , attack of basic substrate takes place on less hindered site of epoxide ring and hence opening of ring takes place.

Stereo is correct.

In the 2nd mechanism we have used a de protecting group for TBS and hence it gets removed and then O- gains H+ from hydronium ion.

And finally in last step ring closing occurs in presence of base NaNH2 and again u have marked the correct stereo.

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