Table 3. Tunable diastereoselectivity in accessing a stereoisomeric family of bicyclic-γ-lactones through chiral Lewis base catalyst and Brønsted base permutations in the DAL organocascade.

Entry	Catalyst	Base	(R)-(–)-14e a (%)	(R)-(+)-14e′ a (%)	(S)-(+)-14e′′ a (%)	(S)-(–)-14e′′′ a (%)
1	A	I	27	22	25	18
2	A	II	24	—	23	15
3	A	III	27	—	—	21
4	A	IV	29	—	20	—
5	B	V	—	—	26	19
6	B	IV	—	—	18	—
7	C	IV	22	—	—	—

^aYields and diastereomeric ratios are based on isolated, purified cycloadducts. Enantiomeric excess was determined by chiral phase-HPLC. *Employed in free-base form. Inset is a single crystal X-ray structure in ORTEP format of adduct (R)-(+)-14′′ following ring opening with 4-bromobenzylamine (50% probability; TIPS and 4-bromobenzyl groups are removed for clarity, see ESI Fig. S1). ^a4-BrC₆H₄CH₂NH₂, THF, 23 °C, 36 h (46%).