The possibility of displacing the phenol substituent (introduced in the first step) on 53 by means of a second substitution with a different Grignard reagent was then probed, as this would allow access to yet another class of P(V) compounds, namely tertiary phosphine oxides. To our delight, when 53 was treated with an excess of Grignard reagent in THF the para-cresol substituent on phosphorus could indeed be displaced, affording compound 57 and 58 in 70% yield and 95:5 e.r. (98% e.s.) (Scheme 5, left). Interestingly, and in contrast to when Grignard reagents were employed to displace the thiazolidinone leaving group, this substitution was found to proceed with inversion of configuration at P (see Supporting Information for further details). Encouraged by the successful displacement of the para-cresol substituent on phosphorus with Grignard reagents, we considered if the products derived from substitution with alkyl alcohols in the second step could be converted to enantioenriched bis-alkyl phosphonate esters by means of another stereospecific substitution with biologically relevant alcohols. Indeed, employing glucose bearing phosphonate ester 39 as a substrate, the para-cresol substituent could be swiftly exchanged with a variety of alkyl alcohol nucleophiles with high levels of enantiospecificity (with inversion of configuration at P). Phosphonate 59, derived from (±)-citronellol was obtained in 63% yield and 97:3 d.r. while 60, which bears an alkyne handle for further functionalization through click chemistry 184 could be obtained in 33% yield and 98:2 d.r. Finally, 61, derived from 3-phenoxy benzyl alcohol (a common motif in agrochemicals) was obtained in 70% yield and 97:3 d.r. (Scheme 5, right).