Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: Acetanilide on December 28, 2014, 12:52:17 PM
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Hi,would someone help me?
I have tried to synthesize the 6-bromo-6-deoxy- α,α’- trehalose (TH-Br) using procedure reported in literature: N-bromosuccinimide was added to a solution of trehalose anhydrous in DMF (anhydrous too) in a molar ratio of 2:1. Trehalose didn't solubilize so I firstly used 40 °C and then the reaction was cooled to 0°C under stirring. After 45 min. triphenylphospine in a equimolar ratio of N-bromosuccinimide was added and the reaction was carried out at room temperature for 2 days. During this period I monitored the reaction doing TLC (BuOH/ EtOH/ H2O 5:3:2 ) but I didn’t see any product (only trehalose was present), so I left the reaction carry on for another 2 days, with no results. I know important parameters are temperature and anhydrous environment, so I took care of these. I thought – maybe I’m wrong with calculations - so I rewised them but they were correct.
What may I have wrong? ???
Thanks to everyone will help me.
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Could you please link the literature reference.
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I have used many sources (PhD thesis) with this Work reference:
S. Hannessian, P. Lavallèe Carbohydrate Research 1973, 28, 303-311.
In every works, procedure is always the same, as I did.
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Hi,would someone help me?
I have tried to synthesize the 6-bromo-6-deoxy- α,α’- trehalose (TH-Br) using procedure reported in literature: N-bromosuccinimide was added to a solution of trehalose anhydrous in DMF (anhydrous too) in a molar ratio of 2:1. Trehalose didn't solubilize so I firstly used 40 °C and then the reaction was cooled to 0°C under stirring. After 45 min. triphenylphospine in a equimolar ratio of N-bromosuccinimide was added and the reaction was carried out at room temperature for 2 days. During this period I monitored the reaction doing TLC (BuOH/ EtOH/ H2O 5:3:2 ) but I didn’t see any product (only trehalose was present), so I left the reaction carry on for another 2 days, with no results. I know important parameters are temperature and anhydrous environment, so I took care of these. I thought – maybe I’m wrong with calculations - so I rewised them but they were correct.
What may I have wrong? ???
Thanks to everyone will help me.
S. Hannessian, P. Lavallèe Carbohydrate Research 1973, 28, 303-311.
In every works, procedure is always the same, as I did.
The immediately obvious deviation is TLC analysis conditions (highlighted in red).
The authors' TLC eluent is 10:3 chloroform/methanol. It is possible that the the product coelutes with the starting material in the eluent system you used (i.e. that product was formed, but you did not detect it).
Did you proceed with the peracetylation step? The product may be very difficult to purify otherwise.
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Eluents I've used are the same reported in these thesis, more recent, where there are two bands (relative of two products, I know :) )
I have original thesis for references of this kind, so I can't put link here, but I have scanned the page where all this is written.. I know it can't be considered as reference, but it's what I have to follow.. I've asked to the author too, but she replied the things reported here, wondering why for me it's not the same. I've tried many times (I know it's not a good thing :-[ ), but always no result.. (https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fmedia-cache-ak0.pinimg.com%2Foriginals%2Fc3%2F72%2F14%2Fc37214be2b12ad3e471b7f38c2d84fab.jpg&hash=b3aa9e62e6a88faae0e7ce1fdc0b714b8018caea)