A new stereoselective total synthesis of (+/-)-swainsonine is described. Successive treatment of cis-3,4-epoxy-7-(p-toluenesulfonamido)-1-heptyne with dicobalt octacarbonyl, Lewis acid, and cerium(IV) ammonium nitrate effected stereoselective formation of the trans-2-ethynyl-3-hydroxypiperidine skeleton with retention of configuration at the propynyl center. The piperidine derivative thus prepared was converted into the title compound efficiently.

The rat hearts preserved in a variable magnetic field at -3°C showed better hemodynamic and metabolic performance than those preserved using conventional storage at 4°C.

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Recent studies performed in our laboratory 1,2) disclosed that the epoxy-alkyne derivatives 1 (nϭ1-3; R 1 ϭH) underwent endo mode cyclization upon successive treatment with dicobaltoctacarbonyl [Co 2 (CO) 8 ], Lewis acids such as boron trifluoride-diethyl ether (BF 3 · OEt 2 ), and cerium (IV) ammonium nitrate (CAN), ending up with the exclusive formation of the corresponding oxygen-containing heterocycles 2 (nϭ 1-3; R 1 ϭH). Thus the tetrahydrofuran and tetrahydropyran frameworks 2 (nϭ1,2; R 1 ϭH) 1a-d) possessing the 2-ethynyl-3-hydroxy functionality could be prepared with high stereoselectivity as well as in a stereospecific manner. Although stereoselective but not stereospecific formation of the oxepane 2 (nϭ3; R 1 ϭH) 1e) could also be realized, this novel endo mode procedure was found not to be applicable to the construction of larger ring-sized oxacycles like oxocane.1e)The fact that many natural occurring polyether species 3) have the methyl group at the ring junction prompted us to investigate if this endo mode cyclization method could be used for the preparation of oxacycles 2 (R 1 ϭMe) having the methyl substitutent at C-2 or C-3 position. This paper reports the results of the cyclization reaction of the cobalt complexes of 4,5-epoxy-5-methyl-7-trimethylsilyl-6-heptyne-1-ol (10) and 4,5-epoxy-4-methyl-7-trimethylsilyl-6-heptyne-1-ol (11) in the presence of a Lewis acid where the corresponding endo mode cyclized products were exclusively formed. Results and DiscussionThe starting epoxy derivatives 10 and 11 for the endo mode cyclization were synthesized as follows. The monotert-butyldimethylsilyl (TBDMS)-protected alcohol 3 4) was oxidized under Swern conditions to give the labile aldehyde, which was consecutively exposed to Horner-Emmons conditions with ethyl 2-(diethylphosphono)propionate and to diisobutylaluminum hydride (DIBAL-H) affording the allylic alcohol (E)-4 in 74% yield. Transformation of the alcohol moiety of (E)-4 to an ethynyl group was realized by oxidation then use of the Ramirez-Corey dibromoolefination 5) and base treatment to provide the acetylide. The anion at the triple bond terminus was then quenched by trimethylsilyl (TMS) chloride and the resulting product was hydrolyzed with 1% hydrochloric acid to produce (E)-5 in a 50% overall yield. On the other hand, (Z)-5 was prepared as a major product from 6. The Swern oxidation and methyllithium addition of 6 1e) gave the secondary alcohol (64%), which was subsequently oxidized under Swern conditions and treated with lithium TMS-acetylide to provide 7 in 86% yield. Dehydration of 7 with thionyl chloride was followed by acidic hydrolysis to afford (Z)-5 (52%) along with (E)-5 (15%). The stereochemistry of 5 was determined on the basis of an NOE experiment. An NOE experiment with (Z)-5 revealed a 3.2% enhancement between the methyl group and the vinylic proton, whereas no enhancement was observed between these protons of (Z)-5 thus strongly supporting the assigned structures as shown in Chart 2. Upon exposure to m-chloroperbenzoic acid...

The case involved a 26-year-old woman with Marfan syndrome (MFS) and severe mitral valve regurgitation who hoped to bear a child. Anticipating future surgery to treat cardiovascular disease via a median sternotomy, we performed mitral annuloplasty via a right anterior thoracotomy. Mitral valve repair for mitral valve regurgitation via a right anterior thoracotomy is one of the most beneficial procedures for patients with MFS.