Ring-opening of the compound 6.

Entry	Solvent	Temperature	Reagents	Yield
1	DCM	−5 °C	TMSOTf	7, 16%
2	DCM	r.t.	TMSOTf, Et3N	n.r.
3	DCM	−78 °C to −10 °C	TMSOTf	Complex
4	MeOH	r.t. ∼ reflux	NaOMe	n.r.
5	THF	−78 °C	LDA	n.r.
6	THF	0 °C	LDA	Complex
7	THF	0 °C	DIBAL-H	Decom.
8	DCM	0 °C	TIPSOTf	n.r.