1.4- cyclohexanedione monoethylene ketal

Camps et al. developed a route to ( )-HA from a keto capamate 7, which was obtained in 22% overall yield from 1,4-cyclohexanedione monoethylene ketal (3) (Scheme 4-5). ° This new approach to racemic HA features the elaboration of the pyridone moiety of HA in a late stage. In this way, we can access the different heterocyclic analogs instead of the pyridone moiety in HA. However, the total yield of HA was not markedly improved, compared with that of other approaches, and the purification of the isomers proved to be a tedious and difficult task. 

The structure of huperzine A was confirmed by total synthesis. There are several reports on total synthesis [27]. The following described was recently accomplished by Kozikowski s group [28,29]. The monoprotected diketone, 1,4-cyclohexanedione monoethylene ketal 5-4 was used as starting material. The pyrrolidine enamine of 5-5 was heated with acrylamide followed by hydrolysis to provide an 85 15 mixture of the lactam 5-6 and 5-7. After protection of the lactam nitrogen by benzylation, dehydrogenation of the latter mixtures afforded pyridone 5-8, then hydrogenolysis of its N-benzyl group, followed by O-methylation with methyl iodide and silver carbonate which yielded methoxypyridine 5-... 

In this original and imaginitive approach, a rapid assembly of the phenanthrene core of morphine, containing a novel non-aromatic A ring, was achieved in an intermolecular Diels-Alder reaction between quinone 173 (prepared from 3-methoxy-2-hydroxy benzaldehyde in 7 steps and an overall yield of 35%) and diene 174 (from 1,4-cyclohexanedione monoethylene ketal in 2 steps with an overall yield of 30%), Scheme 20. In one of several unsuccesful attempts to aromatize ring A, an unexpected tandem... 

Chiral nonracemic enamines formed in situ by reaction of aldehydes and ketones with proline-based organocatalysts also undergo stereoselective a-oxygenation. MacMillan and coworkers have achieved enantioselective a-oxidation of a range of aliphatic aldehydes such as (5.87) with 97-99% ee using proline in combination with nitrosobenzene (5.85). This method can be applied to the aminoxylation of six-membered cyclic ketones such as 1,4-cyclohexanedione monoethylene ketal (5.88). 59... 

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