Wednesday, November 23, 2011

Process Wednesday: R.B. Woodward on scale-up

From my wanderings online, I found a hilarious story about a grad student burning all of his material on a 200X scale-up of a successful 50 milligram reaction:
Wasserman's project concerned the synthesis of artificial penicillin, and at one juncture he needed to convert S-benzylpenicillamine, an incredibly precious compound of which Eli Lilly had given Woodward 25 g, into a 5,5 fused-ring thiazolidinelactam. Wasserman had tried the reaction on a 50 mg sample, and it worked like a charm. So Woodward suggested that Wasserman scale the reaction up over the weekend. On Saturday he confidently scaled up by a factor of 200, reacting 10 g of the S-benzylpenicillamine, almost half of the remaining supply. Instead of colorless crystals, he recovered only a deep yellow, intractable oil. 
He was devastated and conflicted. Should he wait until Woodward came to lab, or should he bite the bullet and telephone to announce that his naive blunder in using so much material had resulted in a catastrophe? No one who has known Prof. Wasserman would be surprised that he chose the proper course and decided to telephone. 
Reaching Prof. Woodward at home, Wasserman reported that he had attempted the reaction on a larger scale, but that it was an utter failure, and that precious starting material had been destroyed.
Woodward asked, "How much of the S-benzylpenicillamine did you use?" Wasserman gulped and answered, "10 grams." 
There was a pause. Then Woodward admonished, "Ten grams! Harry! Even I don't know all the things that could go wrong in that kind of reaction."
 I feel Wasserman's pain. I guess he managed to do all right by himself.

P.S. You gotta love the Woodward line "Even I."

7 comments:

  1. I wonder what he'd have said if it had worked.

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  2. Yeah, I've done the same thing and it's awfully embarrassing. Nowadays, I usually hold to the rule of 5 in scale up. In this case, 50mg ---> 250mg. That usually gives you just enough difference for you to deal with any changes that may be coming to light or that you hadn't noticed in the first run.

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  3. I probably would have gone 500 mgs, but I'm nuts like that.

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  4. @gyg3s: He would've said nothing because it worked.

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  5. http://memegenerator.net/instance/11609255

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  6. are you a redditor?

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  7. Not sure what you mean. Do I read the chemistry reddit? Yeah, once or twice a week. Do I participate actively? Not really. That's about it for my reddit exposure.

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looks like Blogger doesn't work with anonymous comments from Chrome browsers at the moment - works in Microsoft Edge, or from Chrome with a Blogger account - sorry! CJ 3/21/20