[phth]

yeah you're right excess water equivalents; HPLC is equilibration conditions.  Needs to be for the separation to work.

[clarkstill]

Is no one going to mention the anomeric effect??

[Babcock_Hall]

The reason for the anomeric effect was controversial the last time I checked in.  However, empirically the methyl pyranosides prefer one diastereomer over the other.  https://books.google.com/books?id=RT_zCAAAQBAJ&pg=PA245&lpg=PA245&dq=methylglucoside+isomers&source=bl&ots=ANQiUdQQyo&sig=wFdqLTL_0JckBzfCRhhLkOC2j-g&hl=en&sa=X&ved=0CCAQ6AEwAGoVChMIw8iS3_PVxwIVAZMNCh2y0g2-#v=onepage&q=methylglucoside%20isomers&f=false

[clarkstill]

There are several schools of thought. For a recent discussion...

http://onlinelibrary.wiley.com/doi/10.1002/anie.201411185/abstract

[phth]

This is exactly why I stated I couldnt come up with the answer;  It needs to be modeled to really tell.  The anomeric effect really is proposed in undergrad textbooks as stuff not interacting with the solvent.  I agree with the authors of the paper that Clarkstill posted; it's all about dipoles and hydrogen bonding/solvation effects.  Another example is β-D-glycopyranose/α-D-glucopyranose is 64/36 in H₂O and for mthe same book
Solvents and Solvent Effects in Organic Chemistry, Fourth Edition. Edited by Christian Reichardt and Thomas Welton
Copyright 8 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 978-3-527-32473-6