Stereocontrolled Transformation of Nitrohexofuranoses into Cyclopentylamines via 2-Oxabicyclo[2.2.1]Heptanes. Iv: Synthesis of Enantiopure Methyl (1S,2R,3R,4R,5S)-5-Benzyloxycarbonylamino-2,3-Isopropylidenedioxy-4-Methoxycyclopentanecarboxylate