- Total synthesis of natural and unnatural lamellarins with saturated and unsaturated D-rings
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(Chemical Equation Presented) Twenty-eight natural and unnatural lamellarins with either a saturated or an unsaturated D-ring were synthesized according to our developed synthetic route. The key step involved the Michael addition/ring closure (Mi-RC) of the benzyldihydroisoquinoline and α-nitrocinnamate derivatives, which provided the 2-carboethoxypyrrole intermediates in moderate to good yields (up to 78% yield). Subsequent hydrogenolysis/lactonization furnished lamellarins with a saturated D-ring in excellent yields (up to 93% yield). DDQ oxidation of the saturated lamellarin acetates led directly to the corresponding unsaturated analogues in 54-95% yield. In addition, only two steps in our developed strategy require column chromatography.
- Ploypradith, Poonsakdi,Petchmanee, Thaninee,Sahakitpichan, Poolsak,Litvinas, Nichole D.,Ruchirawat, Somsak
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p. 9440 - 9448
(2007/10/03)
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- Synthesis of (±)-Glaucine and (±)-Neospirodienone via an One-Pot Bischler-Napieralski Reaction and Oxidative Coupling by a Hypervalent Iodine Reagent
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Condensation of 3,4-dimethoxybenzeneethanamine (3d) and various benzeneacetic acids, i.e., 4a-e, via a practical and efficient one-pot Bischler-Napieralski reaction, followed by NaBH4 reduction, produced a series of 1-benzyl-1,2,3,4-tetrahydroisoquinolines, i.e., 5a-e, in satisfactory yields (Scheme 3). Oxidative coupling of the N-acyl and N-methyl derivatives 6a-e of the latter with hypervalent iodine ([IPh(CF 3COO)2]) yielded products with two different skeletons (Scheme 4). The major products from N-acyl derivatives 6a-c were (±)-N-acylneospirodienones 2a-c, while the minor was the 3,4-dihydroisoquinoline 7. (±)-Glaucine (1), however, was the major product starting from N-methyl derivative 6e. Possible reaction mechanisms for the formation of these two types of skeleton are proposed (Scheme 5).
- Huang, Wei-Jan,Singh, Om V.,Chen, Chung-Hsiung,Lee, Shoei-Sheng
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p. 167 - 174
(2007/10/03)
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