Analogues of amphibian alkaloids: total synthesis of (5R,8S,8aS)-(−)-8-methyl- 5-pentyloctahydroindolizine (8-epi-indolizidine 209B) and [(1S,4R,9aS)-(−)-4-pentyloctahydro- 2H-quinolizin- 1-yl]methanol

• Joseph P. Michael,
• Claudia Accone,
• Charles B. de Koning and
• Christiaan W. van der Westhuyzen

Beilstein J. Org. Chem. 2008, 4, No. 5, doi:10.1186/1860-5397-4-5

• (−)-39 in 70% yield. In order to introduce the remaining stereogenic centres of the target system, the alkene bond of the bicyclic vinylogous urethane 39 needs to be reduced stereoselectively. Based on our previous success with the indolizidine analogue 19, we opted for catalytic hydrogenation, which is

• through bicyclic enaminone intermediates in which the alkene bond is located between the bridgehead position and the adjacent site, we have a convenient and dependable method for introducing the correct relative stereochemistry at these two sites by means of catalytic hydrogenation. However, the

Knorr- Rabe partial reduction of pyrroles: Application to the synthesis of indolizidine alkaloids

• Brendon S. Gourlay,
• John H. Ryan and
• Jason A. Smith

Beilstein J. Org. Chem. 2008, 4, No. 3, doi:10.1186/1860-5397-4-3

• -alkylindolizidines and the stereoselectivity obtained is opposite to that of catalytic hydrogenation. Conclusion An efficient stereoselective synthesis of indolizidine alkaloids has been developed from α-ketopyrrole intermediates using a modified version of Knorr and Rabe's pyrrole reduction. Background The Birch

• to the facile and rapid reaction of the α-ketopyrrole 8 we explored the potential tandem α-ketopyrrole reduction/catalytic hydrogenation as an alternative to catalytic hydrogenation. The catalytic hydrogenation of 5-substituted tetrahydroindolizidines proceeds with high diastereoselectivity [14][15

• as a 9:1 mixture of diastereomers. The volatility of the compound meant that for practical purposes it was isolated as the hydrochloride salt by adding concentrated HCl to the organic extract before evaporation. Catalytic hydrogenation of the hydrochloride salt of the pyrroline gave a corresponding

A convenient allylsilane- N-acyliminium route toward indolizidine and quinolizidine alkaloids

• Roland Remuson

Beilstein J. Org. Chem. 2007, 3, No. 32, doi:10.1186/1860-5397-3-32

• with one equivalent of stannic chloride resulted in the formation of 10 via the acyliminium ion intermediate 11. Subsequent oxidation of alcohol 10 with pyridinium dichromate, then catalytic hydrogenation (H2 over Pd/C) of ketone 12 induced hydrogenolysis of the CBz group, reduction of the double bond

• by reduction with LiAlH4 of indolizidinones 26. Access to (-)-dendroprimine by catalytic hydrogenation of indolizidinones 26. Synthesis of (±)-myrtine and (±)-epimyrtine. Enantioselective synthesis of (+)-myrtine and (-)-epimyrtine. Synthesis of (±)-lasubines I and II and (±)-2-epilasubine II

Diastereoselective synthesis of some novel benzopyranopyridine derivatives

• Pradeep K. Mohakhud,
• Sujeet M. R. Kumar,
• Vasanth M. R. Kumar,
• Ravi M. R. Kumar,
• Moses D. R. Babu,
• Vyas D. R. K and
• Om D. R. Reddy

Beilstein J. Org. Chem. 2006, 2, No. 25, doi:10.1186/1860-5397-2-25

• derivative was also obtained from the N-benzylated-1,2,3,4-tetrahydro[1,3]-dioxolo-[6,7]-5H-[1]benzopyrano [3,4-c]pyridine via catalytic hydrogenation. The resolution of the enantiomers was carried out using D-(-)-mandelic acid as chiral reagent. The absolute configuration of the S,S-mandelate salt

The vicinal difluoro motif: The synthesis and conformation of erythro- and threo- diastereoisomers of 1,2-difluorodiphenylethanes, 2,3-difluorosuccinic acids and their derivatives

• David O'Hagan,
• Henry S. Rzepa,
• Martin Schüler and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2006, 2, No. 19, doi:10.1186/1860-5397-2-19

• -difluorosuccinic acids 19. The preparation of stereoisomers of 2,3-difluorosuccinic acids, has involved conversions of tartaric acids (esters) [6][7], as described above in Scheme 1. Other approaches have involved the direct fluorination of fumaric acid [16] and the catalytic hydrogenation of 2,3-difluoromaleic

Multiple hydride reduction pathways in isoflavonoids

• Auli K. Salakka,
• Tuija H. Jokela and
• Kristiina Wähälä

Beilstein J. Org. Chem. 2006, 2, No. 16, doi:10.1186/1860-5397-2-16

• isoflavans 9, which however are obtained by catalytic hydrogenation [10][16][20]). Incidentally, it is appropriate to point out that flavones do not undergo similar reductive metabolism in mammals as described above for isoflavones. We will nevertheless present at a later date certain findings on the hydride

• study clears this issue by 2D NMR work on a natural 2-isoflavene, [54] establishing that the H-2 and H-4 protons appear at δ 6.87 and 3.61, respectively, much as expected by correlation data shift calculations. Isoflavans (9) have not been prepared by hydride reductions, but by catalytic hydrogenation

Hydrogenation of aromatic ketones, aldehydes, and epoxides with hydrogen and Pd(0)EnCat™ 30NP

• Steven V. Ley,
• Angus J. P. Stewart-Liddon,
• David Pears,
• Remedios H. Perni and
• Kevin Treacher

Beilstein J. Org. Chem. 2006, 2, No. 15, doi:10.1186/1860-5397-2-15

• effectively be reduced using Pd(0)EnCat™ 30NP under conventional catalytic hydrogenation conditions of H2 (atmospheric pressure) with good selectivity and conversions [20]. Results and discussion The results obtained using different conditions for the carbonyl reduction of 4-methoxybenzaldehyde and 4