Deprotection hydrogen fluoride

The trimethylsilyl protecting group can be removed by routine deprotection with triethylamine -hydrogen fluoride complex. 

The popular acids for deprotection by acidolysis are hydrogen fluoride for benzyl-based protectors and trifluoroacetic acid for rerr-butyl-based protectors. The use of hydrogen fluoride for deprotection emerged from the observation that it is a good solvent for dissolving enzymes (because of the N-to-0 acyl shift see Section 6.6), and that the enzymatic activity is recovered (O-to-N acyl shift) in saline solution. Two different approaches are employed for removal of benzyl-based... 

Conversely, exposure to hydrogen fluoride at 0 °C over short periods of time leads to almost quantitative hydrolysis.[37-39] In aprotic organic solvents, decomposition takes place unless the sulfate hemi-ester is neutralized with strong counterions.[37,381 The results of a detailed study are summarized in Figures 1 and 2t4°l which show the effect of various acids used in peptide chemistry in deprotection and in cleavage from the resin as well as the effect of temperature on the hydrolysis of tyrosine 0-sulfate as a sodium salt. 

A newly developed stable dimethyl ether-HF complex (1 15),668 which can be stored at room temperature, is highly effective for the deprotection and cleavage of peptides from Merrifield resins (isolated peptide yields = 88-94%). It can easily be handled, and it is a very useful and convenient hydrogen fluoride equivalent. 

The free amide peptide was synthesized on 4-methylbenzhydrylamine-substituted polystyrene resin, and the resin-bound peptide for antibody production was prepar on aminomethyl polystyrene. Cleavage/deprotection was done with hydrogen fluoride/anisole at 0 C. The free amide was not active in either bioassay. However, polyclonal antibody prepared against the resin-bound (22 24) sequence was immunologically reactive to EDNH reverse phase column fractions. We are now attempting to determine if the sequence represents an inactive fragment of authentic EDNH. 

Mitsunobu reaction as well as by mesylation and subsequent base treatment failed, the secondary alcohol was inverted by oxidation with pyridinium dichromate and successive reduction with sodium borohydride. The inverted alcohol 454 was protected as an acetate and the acetonide was removed by acid treatment to enable conformational flexibility. Persilylation of triol 455 was succeeded by acetate cleavage with guanidine. Alcohol 456 was deprotonated to assist lactonization. Mild and short treatment with aqueous hydrogen fluoride allowed selective cleavage of the secondary silyl ether. Dehydration of the alcohol 457 was achieved by Tshugaejf vesLCtion. The final steps toward corianin (21) were deprotection of the tertiary alcohols of 458 and epoxidation with peracid. This alternative corianin synthesis needed 34 steps in 0.13% overall yield. 

Final Deprotection of Protected Eglin c Using Hydrogen Fluoride... 

In the tert-butoxycarbonyl (Boc) strategy for solid-phase peptide synthesis, cleavage from the solid-phase and side-chain deprotection is performed with strong acids such as hydrogen fluoride. Treatment of a glycopeptide with strong acid results in partial or, in most cases, complete cleavage... 

There is no simple way to selectively deprotect secondary TBS ethers in the presence of primary TBS ethers. The solution here is a strategy in which all TBS groups are first cleaved and then the primary alcohol groups are selectively reprotected with TBSCl. Common reagents for deprotection of silyl protection groups are fluoride sources such as CsF, TBAF or, as here, hydrogen fluoride in solution in NEts. 

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