Table 1.

Reduction of ketones containing the furanyl ring and using spiroborate ester 1 in 10 and 1 mol %^a

Entry	Substrate	Cat. 1 (%)	Yieldb (%)	Eec (%)
1		10	63	95
2		1	65	95
3		10	87 d	91
4		1	91	85
5		10	88d	96
6		1	95	96
7		10	86d	92
8		5	78d	92
9		10	82	>99e

^aThe reaction was carried out using 0.7 equiv of borane DMS in THF at room temperature.

^bYield after distillation in a Kugelrohr apparatus.

^cDetermined by GC of the acetate on a CP-Chirasil-Dex CB column.

^dYield after column chromatography.

^aDetermined by ³¹P NMR of a phosphonate (CDA) derivative.¹⁵