The first total synthesis of the potent antifungal and cytotoxic agent (+)-crocacin D in optically pure form following a convergent strategy is described here. The regioselective ringopening of a silyl-substituted epoxide with an azide ion, based on a method developed by us earlier, and subsequent subjection of the resulting α-azido-β-hydroxyalkylsilane intermediate to a Peterson elimination reaction
In the presence of catalytic amounts of PtCl 2 and AgX (X = OTf or SbF b ), (Z)-6-trimethylsilyl-5-hexen-1-ol and (Z)-5-trimethylsilyl-4-penten-1-ol reacted smoothly with aldehydes to give 2,3-disubstituted tetrahydropyransand tetrahydrofurans, respectively, in good to high yields. The reaction mechanism involves the isomerization of the starting vinylsilanes to the corresponding allyl-silanes and
An approach to total synthesis of (+)-lycoricidine
作者:Matthias C. McIntosh、Steven M. Weinreb
DOI:10.1021/jo00070a016
日期:1993.8
A convergent synthesis of a protected version of (+)-lycoricidine has been accomplished in 13 steps from L-arabinose. Preparation of the aminocyclitol moiety 50 employed a novel vinylsilane-terminated N-sulfonyliminium ion cyclization of vinylsilane aldehyde 42. Closure of the B-ring using an intramolecular Heck reaction afforded lycoricidine derivative 58. An unexpected cyclization of vinylsilane aldehyde 42 allowed for the stereodivergent preparation of semiprotected conduritols 43 and 45.
Platinum-catalyzed allylation of carbon electrophiles with alkenylsilanes
In the presence of catalytic amounts of PtCl2 and AgSbF6, (Z)-alkenylsilanes react with various carbon electrophiles at the gamma-position to give allylation products. A plausible mechanism for the Pt-catalyzed allylation involves alkene migration of alkenylsilanes to allylsilanes and subsequent allylation of carbon electrophiles. (C) 2014 Elsevier Ltd. All rights reserved.
Anti-hydroalumination of Homo- and bishomopropargyl alcohols
作者:Shengming Ma、Fang Liu、Ei-ichi Negishi
DOI:10.1016/s0040-4039(97)00764-8
日期:1997.6
The reaction of omega-Me3Si- or omega-Me3Ge-substituted 3-butyn-1-ol, 4-pentyn-1-ol, and their derivatives with DIBAL-H and a small trialkylalane, e.g., Me3Al or Et3Al, at 23 degrees C gives, after iodinolysis, the corresponding (Z)-4-iodo-3-buten-1-ols and (Z)-5-iodo-4-penten-1-ols in a highly stereo- and regioselective manner, most probably via endo-dig mode cyclic anti-hydroalumination, while treatment of omega-carbosubstituted 3-butyn-1-ols with Red-Al or LiAlH4 at high temperatures followed by iodinolysis can give the corresponding (Z)-4-iodo-3-buien-1-ols also in a highly regio- and stereoselective manner. (C) 1997 Elsevier Science Ltd.