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To a solution of LiHMDS in THF (72.9 mL of a 1 M solution, 72.9 mmol, 2.2 eq) at −78° C. under Ar was added a solution of (1R,4S)-methyl 4-((t-butoxycarbonyl)amino)cyclopent-2-enecarboxylate (prepared according to the procedure of US 20050101628 A1 (see page 31, column 1, Procedure B, step B)), 8.00 g, 33.2 mmol, 1 eq) in THF (40 mL) dropwise over 1 hr. After stirring for 30 min, a solution of t-butyl(2-iodoethoxy)dimethylsilane (13.29 g, 46.4 mmol, 1.4 eq) in THF (20 mL) was added. The solution was kept at −78° C. for 15 min, then gradually warmed to 0° C. over 2 hrs, and kept at 0° C. for 1 hr. 1 N HCl and water were added, the solution extracted with DCM, the organics combined, dried over MgSO4, and concentrated. Purification by chromatography (400 g column) eluting with 5 to 20% EtOAc/heptane afforded the title compound of Step A. 1H NMR (CHLOROFORM-d) δ: 5.76-5.85 (m, 2H), 4.90 (d, J=9.0 Hz, 1H), 4.72-4.82 (m, 1H), 3.69 (s, 3H), 3.57-3.64 (m, 2H), 2.24 (dd, J=13.9, 8.0 Hz, 1H), 2.14 (dd, J=14.1, 3.5 Hz, 2H), 1.71-1.82 (m, 1H), 1.40-1.50 (m, 9H), 0.84-0.90 (m, 9H), 0.03 (s, 6H). ESI-MS (m/z): Calculated for C20H37NO5Si: 422.2 (M+23). found: 422.2.

1. customprepared
2. customdropwise over 1 hr
3. waitThe solution was kept at −78° C. for 15 min
4. waitkept at 0° C. for 1 hr
5. extractionthe solution extracted with DCM
6. dry with materialdried over MgSO4
7. concentrationconcentrated
8. customPurification by chromatography (400 g column)
9. washeluting with 5 to 20% EtOAc/heptane