Indanomycin synthesis

An early study of the allylation reactions of oxocarbenium systems has been described by Danishefsky for synthesis efforts directed towards indanomycin. The reactions of ( )-and (Z)-2-butenylsilanes silanes are the focus for this report. However, the study also examined reactions of the (E,Z)-mixture of 2-butenyl-tri-n-butylstannanes with tri-o-acetyl-o-galactal 132 at -30 °C, in the presence of BF3 OEt2... 

Scheme 13. Reductive lithiation in the total synthesis of indanomycin...

Most applications of the intramolecular Diels-Alder reaction use 1-substituted butadienes and these reactions often form a key step in the synthesis of polycyclic natural products. Substituents in the connecting chain may influence the facial selectivity of the cycloaddition reaction, as well as the endo. exo selectivity. For example, in a synthesis of the antibiotic indanomycin, the triene 83 gave, on heating. 

Other natural products has been made only within the past few years. Consequently, it has not yet been widely utilized. Although more circuitous, Protocols II and IV have been more widely exploited in the synthesis of a variety of natural products, such as rapamycin, caUculin indanomycin, sangUfehrin vitamin restrictinol, ... 

This tremendous substrate tolerance is very significant for natural-product synthesis. In a synthesis of rapamycin 2.160, a double Stille coupling was used to close the macrocycle in the last step after all of the deprotections had been carried out (Scheme 2.51). Other no protecting group Stille couplings are in syntheses of manumycin 2.163 (Scheme 2.52) " and indanomycin (Scheme 2.53). ... 

Having thus established the main stereochemical features, the Claisen rearrangement of glycal esters could be further utilized to provide key intermediates for a number of natural product syntheses Carbohydrates served as starting materials in the total synthesis of the ionophore antibiotics lasalocid A 43 by Ireland et al. [15] and indanomycin 46 by Ley et al. [16] (Scheme 8), as well as the 3-acyl tetramic acid antibiotics tirandamycic acid 49 [17] and (+)-streptolic acid 52 [18] (Ireland et al.. Scheme 9). Several further examples have been reported in the literature [19-21]. 

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