I have not tested this, but the code that translates F# quotations to LINQ expressions (and compiles them) has now moved from F# PowerPack into the F# Core library, so I think that is the most up-to-date version:
open Microsoft.FSharp.Linq.RuntimeHelpers
LeafExpressionConverter.EvaluateQuotation <@ 1 + 2 @>
and to use it for lambdas
let d=LeafExpressionConverter.EvaluateQuotation <@ fun y -> y+1.0 @>
:?> ( double -> double )
Console.WriteLine(d 10)
outputs
11
Note the cast at the end to convert the ''obj'' to a lambda of the correct type