Can a benzyl ether be removed in the presence of an ester?

I'd like to deprotect a benzyl group for a [Fráter–Seebach alkylation](https://en.wikipedia.org/wiki/Fr%C3%A1ter%E2%80%93Seebach_alkylation). Would it be possible to do this with a Birch reduction using Li/NH3 (or Na/NH3), without also reducing the ester carbonyl group?


[![Selective debenzylation of methyl (S)-3-(benzyloxy)butanoate](https://i.stack.imgur.com/vv8cW.png)](https://i.stack.imgur.com/vv8cW.png)


If not, hydrogenation over Pd/C seems to be a plausible alternative. How else can I remove the benzyl group on oxygen?




In Wutz's book on protecting groups,[1] I found an example of almost instantaneous reductive debenzylation which leaves an ester untouched:[2]


[![Debenzylation example with Na/NH3](https://i.stack.imgur.com/O4Apr.png)](https://i.stack.imgur.com/O4Apr.png)


The use of BCl3 is also possible:[3]


[![Debenzylation with BCl3](https://i.stack.imgur.com/EX5xp.png)](https://i.stack.imgur.com/EX5xp.png)




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**References:**


1. Wuts, P. G. M. *Greene's Protective Groups in Organic Synthesis*, 5th ed.; Wiley: Hoboken, NJ, 2014, p 131.
2. Sulikowski, M. M.; Davies, G. E. R. E.; Smith, A. B., III. Avermectin–milbemycin synthetic studies. Part 7. An approach to the southern hemisphere of milbemycin α1. *J. Chem. Soc., Perkin Trans. 1* **1992,** 979–989. [DOI: 10.1039/P19920000979](https://doi.org/10.1039/P19920000979).
3. Williams, D. R.; Brown, D. L.; Benbow, J. W. Studies of Stemona alkaloids. Total synthesis of (+)-croomine. *J. Am. Chem. Soc.* **1989,** *111* (5), 1923–1925. [DOI: 10.1021/ja00187a081](https://doi.org/10.1021/ja00187a081).


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