Natural Science Forum / Chemistry / Organic Synthesis / November 2006

Andy,

Okay, I spent quite a few hours on this and I know it's wrong, but I did the
work and I'm going to post it.

Let me make it clear, I'm an undergrad finishing my first semester of
organic, so this is WAY out of my league. This is a 13 step synthesis (down
to the first thing I could find from Aldrich) and I'll point out what I
think are some pretty obvious problems with it along the way (besides the
fact that it's 13 steps)...

1: With but-2-yn-1-ol, do a reduction with lithium and ammonia to get
(E)-but-2-en-1-ol
2: You want to perform the Sharpless Epoxidation using diethyl (2S,
3S)-tartrate to get ((2R, 3R)-3-methyloxiran-2-yl)methanol
3: React this with HCl for epoxide ring opening to get (2R,
3S)-3-chlorobutane-1,2-diol

Okay, at this point, I'm not sure if the HCl is going to dehydrate that
original hydroxyl or not and that's basically where things get shakey the
rest of the way. We want to keep the 2 hydroxyl all the way and I don't
think it's going to survive the next 10 steps...

4: React with KOH to form the alkene, (S)-but-3-ene-1,2-diol
5: React with PBr3 in ether. This should brominate the 1-hydroxyl and
hopefully not too much of the 2-hydroxyl. Again, on shakey ground here. This
will hopefully leave (S)-1-bromobut-3-en-2-ol
6: React with magnesium  and then acid to debrominate it (and somehow keep
the hydroxyl????) leaving, (S)-but-3-en-2-ol
7: React with bromine to get (2S, 3S)-3,4-dibromobutan-2-ol
8: React with 2 eq. KOH to get  (S)-but-3-yn-2-ol
9: React with HCl (I'm sure that hydroxyl is hanging on for dear life) to
get (S)-3-chlorobut-3-en-2-ol
10: React with OsO4 to get (3S)-2-chlorobutane-1,2,3-triol
11: React with HIO4 in H2O and THF to get (S)-2-Hydroxypropanoyl chloride
12: React with 2 eq NH3 (and I have no idea what I'm doing here, I don't
think this'll work) to aminate the chlorine and the carbonyl oxyigen (2
steps in 1) to get your product, 2R-2-Hydroxypropionamidine.

I'm sure this will be of absolutely no use to you, but it was a great way to
pass my day....

"andytang" <graingerntang@aol.com> wrote in message
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