Macrolides syntheses

The intramolecular coupling of organostannanes is applied to macrolide synthesis. In the zearalenone synthesis, no cyclization was observed between arylstannane and alkenyl iodide. However, intramolecular coupling take.s place between the alkenylstannane and aryl iodide in 706. A similar cyclization is possible by the reaction of the alkenylstannane 707 with enol triflate[579]. The coupling was applied to the preparation of the bicyclic 1,3-diene system 708[580]. 

Intramolecular 1,4-addition is useful for macrolide synthesis. An unusual molecule of punctaporonin B (272) has been synthesized by this 1,4-addition of 271(160]. Cyclization to form the seventeen-membered ring macrolide 273 was carried out at 0.1-0.5 vi concentration[161. The choice of ligands seems to be important in the macrocyclization. The 26-membered ring model 274 for a synthesis of the ring system of tetrin A was obtained in 92% yield by using triisopropyl phosphite as a ligand[162]. 

Macrolides, synthesis of 632 Mannich-type reactions 641 Mass spectrometry... 

General Procedure for the Silylformaltion/Sakurai Allylation. Synthesis of Polyol Fragments for Polyketide and Macrolide Synthesis. In a magnetically stirred stainless-steel Parr bomb the substrate (1 eq) is dissolved in benzene. The solution is cooled to - 78 °C until frozen. Rh(acac)(CO)2 (3 mol %) is then added and the Parr bomb is assembled and pressurized with CO (60 bar) and vented. This purge is repeated twice and the Parr bomb is pressurized with CO (60 bar) at - 78 °C. The apparatus is then immersed in an oil bath and heated at 60 °C for 22-24 h. After cooling to 0 °C, the bomb is vented. The solution... 

Inverse type hetero-Diels-Alder reactions between p-acyloxy-a-phenylthio substituted a, p-unsaturated cabonyl compounds as 1-oxa-1,3-dienes, enol ethers, a-alkoxy acrylates, and styrenes, respectively, as hetero-dienophiles result in an efficient one step synthesis of highly functionalized 3,4-dihydro-2H-pyrans (hex-4-enopyranosides). These compounds are diastereospecifically transformed into deoxy and amino-deoxy sugars such as the antibiotic ramulosin, in pyridines having a variety of electron donating substituents, in the important 3-deoxy-2-gly-culosonates, in precursors for macrolide synthesis, and in C.-aryl-glucopyranosides. 

A General Method for the Preparation of 9-, 10-, and 11-Membered Unsaturated Macrolides Synthesis of 8-Prop1onyl-E-5-nonenol1de... 

An application of the regiocontrol for ozonide decomposition by an allylic methoxy group (donor) is a macrolide synthesis [247]. 

Ten years have passed since the first edition of this book appeared. Most of the new citations refer to newly developed stereoselective reactions a stunning macrolide synthesis by S.L. Schreiber (p. 324ff.) demonstrates successful applications of the new methods. The most surprising, even dramatic, development, however, has occurred in the field of new organic materials and machineries. This is exemplified with a few outstanding examples in a new chapter called Nanometer Size Architecture . 

A GENERAL METHOD FOR THE PREPARATION OF 9-, 10-, AND 11-MEMBERED UNSATURATED MACROLIDES SYNTHESIS OF 8-PROPIONYL-(E)-5-NONENOLIDE (2H-Oxecin-2-one, 3,4,5,8,9,10-hexahydro>9-(1 -oxopropyl)-, (E)-)... 

This is a simple example for a macrolide synthesis from an to-hydroxyaldehyde andylideH. 

For a review, in English, of computer-aided conformational design in macrolide synthesis (including carbonolides) see O. Yonemitsu, Yuki Gosei Kagaku Kyokaishi, 1994, 52, 946. 

Regarding the temperature dependence of the formation of oligomers in the macrolide synthesis under Yamaguchis conditions for macrocycles, Seebach et al. 

Macrolide synthesis has been extensively reviewed by several authors in the last few years [7]. Synthesis of macrocyclic compounds, most being unnatural, via ring closure reactions by high dilution techniques was discussed by Rossa and Vogtle... 

Despite that it is named as such quite often in the literature, the radical -scission or -cleavage is not a fragmentation in the sense considered in this chapter. The flrst example of a macrolide synthesis through such a reaction type was achieved by Ohloff ° and resulted in an industrial synthesis of exal-tolide (134 Scheme 70). Schteiber has described iron-copper-promoted fragmentation reactions of a-al-koxy hydroperoxides as a route to macrolides. Two recent informative publications which cover the prior literature have been written by Suginome and Macdonald. ... 

Macrolides, synthesis of 86YGK206 85T3569, 85YZ619 84YGK876. Maitansinoids, synthesis of 83YGK51. 

Although a number of syntheses of this important degradation product have been described, coverage of this aspect of macrolide synthesis is beyond the scope of this chapter. For details, the reader is directed to existing reviews and the citations therein. Although 52 is a common starting material for many of the synthetic studies in this area, its synthesis is not described. However, where an analog of 52 was used as a synthetic intermediate, as in the case of 80 (Scheme 2.9), the synthesis of that compound is discussed. 

Organotin alkoxides are employed for the etherification and esterification of alcohols, the latter of which is also applied to the macrolide synthesis (eq (117)) [112]. 

RCO2H, R OH, (a) 2,4,6-Cl3C6H2COCl, EtjN, THF, (b). R OH, DMAP, >95% yield. This method is best suited to the preparation of relatively unhindered esters otherwise some esterification of the benzoic acid may occur at the expense of the acid to be esterified. This method has also been used extensively for macrolide synthesis. 

Scheme 7 Pd-catalyzed intramolecular allylic acetoxylation for macrolides synthesis...

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