Table 3.

Cores synthesised by the sequence of olefination, reduction, and deprotection, and the corresponding starting alcohols and aldehydes.^a

Entry	Alcohol	Aldehyde	Product	Yield
1	18	19	20	82%b
2	21	22	23	83%b
3	–	24	25	79%c
4	–	26	27	63%d

^aConditions: ^b(i) IBX (3 equiv), EtOAc, reflux, 2.25–3 h; (ii) KOt-Bu (1.5–2.3 equiv), THF, 0 °C, 7–40 min; K₂CO₃ (4 equiv), PhSO₂NHNH₂ (3 equiv), DMF, 100 °C, 70–80 min; (iv) 7.4 M HCl, 100 °C, 2 h; ^c(ii) KOt-Bu (1.8 equiv), THF, 0 °C, 5 min; (iii) K₂CO₃ (4 equiv), PhSO₂NHNH₂ (3 equiv), DMF, 100 °C, 75 min; (iv) 7.4 M HCl, 100 °C 3.5 h; ^d(ii) NaH (2.4 equiv), THF, 0 °C, 70 min; (iii) K₂CO₃ (4 equiv), PhSO₂NHNH₂ (3 equiv), DMF, 100 °C, 2 h; (iv) 7.4 M HCl, 100 °C, 2 h.