7-Hydroxymethyl-6-methyl-1-oxa-4-thiaspiro[4.5]dec-6-ene. Exceptionally High Anti to Sulfur Diastereoselectivity under Conditions of Johnson Ortho Ester Claisen Rearrangement Favors Cieplak Mode of Diastereoselection<sup>†</sup>

7-Hydroxymethyl-6-methyl-1-oxa-4-thiaspiro[4.5]dec-6-ene. Exceptionally High Anti to Sulfur Diastereoselectivity under Conditions of Johnson Ortho Ester Claisen Rearrangement Favors Cieplak Mode of Diastereoselection<sup>†</sup>