It is stated that routes to biologically active polypropionates, carbohydrates, and related natural products are proposed and that approaches to these compounds utilize recent findings (1) that allenyl stannanes and gamma-(alkoxy)allyl stannanes of greater than 95% ee can be readily prepared, and (2) that these reagents condense with aldehydes by highly selective SE' pathways. It is noted that the allenylstannanes undergo Cram or chelation controlled additions to alpha-chiral aldehydes leading to syn,syn; anti,syn; syn, anti; or anti,anti products depending on reaction conditions. This reaction is said to have potential applications to polypropionate antibiotic synthesis. The principal investigator notes that the proposed route to simple and complex monosaccharides is based on observations that gamma- (alkoxy)allylstannanes undergo diastereo- and enantioselective additions to aldehydes affording monoprotected homoallylic 1,2-diols of greater than 95% optical purity. He indicates that with nonracemic alpha-alkoxy aldehydes considerably enhanced, diastereoselectivities are realized through reagents/substrate matching. This methodology is said to be particularly attractive because it allows the preparation of differentially protected complex monosaccharides of 5-10 carbons from readily available chiral pool starting materials. It is noted that such intermediates are precursors to glycoconjugates and oligomers with potential antibiotic and antitumor properties. It is finally indicated that the methodology is also applicable to alpha-amino aldehydes and certain imines, thus allowing for the synthesis of various biologically active amino sugars with high stereochemical control.
