Methanesulfonic acid (2R,3R,3aR,9aR)-2-(5-bromo-2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-3-hydroxy-5,5,7,7-tetraisopropyl-tetrahydro-1,4,6,8-tetraoxa-5,7-disila-cyclopentacycloocten-3-ylmethyl ester