Diels-Alder reaction retrosynthetic analysis, using

Retrosynthetic Analysis and Solution Devising this synthesis will help you see how a Diels-Alder reaction can be used to impart specific stereochemistry in a synthesis. It will also help you review some other reactions you have just learned. Here is our retrosynthetic scheme ... 

Diels-Alder reactions are widely used for making carbon-carbon bonds, and retrosynthetic analysis can reveal opportunities for their application. If a synthetic target contains a cyclohexene ring, start with the double bond and use curved arrows to disconnect the bonds to be formed in the sought-for cycloaddition. For example ... 

CHAllEHGtl Propose an efficient synthesis of the cyclohex-enol below, beginning exclusively with acychc starting materials and employing sound retrosynthetic analysis strategy. [Hint A Diels-Alder reaction may be useful, but take note of structural features in dienes and dienophiles that permit Diels-Alder reactions to work well (Section 14-8).]... 

In many cases, fragmentations corresponding to the retroreaction of a powerful reaction (sec. lO.S.B.vi) can be identified and used retrosynthetically. Retro-mass spectral analysis has been applied to total synthesis by Kametani. The mass spectra of tetrahydroisoquinoline alkaloids show fragmentations by the three major pathways shown in Scheme 10.24.1 Kametani observed that path c (a retro Diels-Alder reaction) was the major fragmentation pathway (sec. ll.S.B). Xylopinene (274) gave this specific fragmentation (to 275 and... 

SCHEME 10 Retrosynthetic analysis using the sequential Diels-Alder and Claisen reactions. 

Finally, Kibayashi used aqueous versions of the intramolecular acyl-nitroso Diels-Alder reaction to good effect in his stereocontrolled syntheses of (-)-swainsonine (6.28) [78] and (-)-pumiliotoxin C (6.34) [79] (Schemes 1.13 and 1.14). In each case, oxazinolactam cycloadducts (cf. 6.32 and 6.38) served as key functional chiral building blocks for the remaining synthetic operations. For example, retrosynthetic analysis of the trihydroxy-indohzidine system of swainsonine (6.28) reveals that the pyrrolidine ring of this target can be formed by amine alkylation (cf. 6.29) while the vicinal diol can be installed via substrate-controlled cw-hydroxylation of a (Z)-allyl... 

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