No abstract

Additionen der aus den Sulfoxiden (II) unter der Einwirkung von Li‐diisopropylamid entstehenden Anionen verlaufen regio‐ und stereospezifisch unter Bildung der trans‐1,4‐Addukte (III).

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Starting with the racemic aldehyde 4, prepared from the tris(trimethylsilyl) ether 3, the possibility was demonstrated of converting a trimethylsilylated primary hydroxy group with high selectivity into an aldehyde group in the presence of two trimethylsilylated secondary hydroxy groups employing oxalyl chloride and dimethyl sulfoxide (Swern reagent) as oxidant. The alkynylation of this aldehyde with 1‐metalated hept‐1‐yne afforded a chromatographically separable mixture of two diastereomeric alcohols, both being suitable intermediates for the synthesis of PGF2α. The diastereofacial selectivity of the addition strongly depends on the metal employed. Hept‐1‐yn‐1‐yllithium afforded a 67:33 mixture of (13 R*)‐ and (13 S*)‐alcohol, hept‐1‐yn‐1‐yltriisopropoxytitanium, however, a 30:70 mixture.