A facile and efficient synthesis of 4-hydroxy-2,6-cis-tetrahydropyrans via tandem cross-metathesis/thermal S(N)2' reaction: protecting-group-free synthesis of (+/-)-diospongin A.

The tandem cross-metathesis/thermal S(N)2' reaction was explored for the facile and efficient synthesis of 4-hydroxy-2,6-cis-tetrahydropyrans. The mildness of the thermal conditions allowed for the synthesis of 4-hydroxy-2,6-cis-tetrahydropyrans from base-sensitive substrates without the use of protecting groups. The tandem reaction enabled a protecting-group-free synthesis of (+/-)-diospongin A.