[democanarchis]

Hi all,

Was doing a boc deprotection to (S)-3-amino-2,4-dimethylpentan-2-ol using literature conditions (stirring in 3M aq HCL: EtOAc at room temp for 16h, then removal of volatiles in vacuo, diluting with EtOAc and 4 x sat. NaHCO3 washes, drying over MgSO4 and conc in vacuo). Lit procedure for exact compound gave 99%. On concentration of the org layer, only recovered about 50 mg of a brown oil, equating to about 0.1% of the total mass of compound expected. Saturated some of the aq washes with NaCL and extracted with 3:1 Chloroform:Ethanol, nothing. Concentrated a small portion of the aqueous on rotavap and got back what looked like a salt, NMR in D2O came back blank for organic material. TLC of aqueous showed no movement, looked just like salt, various stains tried.

So, any ideas where my 5g of amino alcohol has gone? Isn't volatile so that isn't it. 

[Doc Oc]

In my experience, free amines are quite difficult to extract.  I would go back to the NaHCO3 washes and extract those many times with ethyl acetate (many times = at least 5, maybe as many as 15), chloroform/EtOH is probably too nonpolar to grab it.  I've extracted amino acids from basic aqueous phases this way and you can track your extractions by TLC (stain with ninhydrin, it binds to amines nicely).

[democanarchis]

Well, your procedure worked a lot better than the chloroform/ethanol mix! I recovered about 50% mass balance, unfortunately the expected amino alcohol was not present. On further inspection of the literature it seems likely that I misinterpreted 3M HCL: EtOAc as 1:1 3M aq HCl:EtOAc, as opposed to anh EtOAc saturated to 3M with HCl gas, although i'm still not sure exactly what kind of side reactions might have taken place. Thanks for the suggestion anyhow, definately will keep that procedure in mind in future.

[chonfusion]

How about simply drying it up with rotovap and extract the powder into CHCl3/MeOH?

[argirisha]

In the present method, after basifying aquoes portion with NaOH, then product can be extracted in to THF.
As an alternative:
It is always good to deprotect Boc in an aminol system using 4M Dioxane-HCl. After completion of reaction, by adding diethyl ether compound can be precipitated and filtered or by just concentration of solvents yields almost quantitative yield.