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The synthesis of two new A‐ring precursors, useful for the convergent assembly of 2α‐ethyl and 2β‐ethyl derivatives of 19‐nor‐1α,25‐dihydroxyvitamin D3, is described. These building blocks were prepared in 14 steps from quinic acid, which led to a new and practical synthesis of 2α‐ethyl‐14‐epi‐19‐nor‐20‐epi‐23‐yne‐1,25(OH)2D3, an analog that shows a remarkably low calcemic effect in mice, while retaining the ability to promote cell differentiation and to inhibit cell proliferation in a number of human cancer cell lines.

Organo-phosphorus compounds S 0080Catalyst-Free Alcoholysis of Phosphane-Boranes: A Smooth, Cheap, and Efficient Deprotection Procedure. -Phosphane-borane complexes bearing at least one aromatic substituent are readily deprotected either in pure refluxing MeOH or EtOH or at more elevated temperature in a mixture of MeOH and toluene. Microwave irradiation accelerates the deboronation reaction dramatically. Phosphite-borane complexes and phosphane-borane complexes bearing three aliphatic substituents fail to react. -(VAN OVERSCHELDE, M.; VERVECKEN, E.; MODHA, S. G.; COGEN, S.; VAN DER EYCKEN, E.; VAN DER EYCHEN*, J.; Tetrahedron 65 (2009) 32, 6410-6415; Dep. Org. Chem., Fac. Biosci. Eng., Univ. Gent, B-9000 Gent, Belg.; Eng.) -Klein 47-153