SYNTHESIS OF DL-PENTALENOLACTONE DL-PENTALENOLACTONE-F
SYNTHESIS OF DL-PENTALENOLACTONE DL-PENTALENOLACTONE-F
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DOI：
10.1021/ja00330a044
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发表时间：
1984-01-01
影响因子：
15
通讯作者：
THOMAS, PJ
中科院分区：
文献类型：
--
作者：
CANE, DE;THOMAS, PJ
（。+-。）的甲酯-戊烯内酯E （5-Me）和F （6-Me）是通过分子内插入α的途径合成的。-酰基碳变成一个未活化的C-H键，以关闭关键融合的三角洲-内酯环体系。由二甲基3,3-二甲基戊二酸酯经7步合成了7,7-二甲基双环[3.3.0]辛烷-3-酮（10）。通过一系列的碳甲氧基化、酮化、侧链还原、与乙氧酰氯甲酰腙的酰化和碱催化消除对甲苯磺酸，将必需的（重氮乙酰氧基）甲基侧链附加到10上。用Rh2(OAc)4催化剂回流氟利昂TF，可使所需的- δ -内酯31环闭合，产率为43-47%。内酯还原，脱氢和选择性缩醛的衍生乳提供34作为外显体的混合物。利用Paquette先前描述的方法，34被转化为戊烯内酯E甲酯（5-Me）。立体选择性环氧化5-Me外亚甲基双键得到戊烯内酯F甲酯（6-Me）。使用。alpha。重氮度量。还探索了用于制备双环[3.3.0]辛酮的-酮酯作为合成戊烯内酯本身的一种方法。因此，38在回流氟利昂TF中暴露于Rh2(OAc)4，得到相应的双环[3.3.0]辛烷-3- 1 39和螺环丁酮40的3:2混合物。然而，在相同的环化条件下，53只生成了螺环丁酮加合物54，没有任何证据表明生成了所需的双环[3.3.0]辛烷-3- 1 55。
The methyl esters of (.+-.)-pentalenolactone E (5-Me) and F (6-Me) were synthesized by a route based on the intramolecular insertion of an .alpha.-acylcarbene into an unactivated C-H bond to effect closure of the key fused .delta.-lactone ring system. Thus 7,7-dimethylbicyclo[3.3.0]octan-3-one (10) was assembled in 7 steps from dimethyl 3,3-dimethylglutarate. The requisite (diazoacetoxy)methyl side chain was appended to 10 by a sequence of carbomethoxylation, ketalization, side-chain reduction, acylation with glyoxalyl chloride tosylhydrazone and base-catalyzed elimination of p-toluenesulfinate. Ring closure to the desired .delta.-lactone 31 was effected in 43-47% yield by using Rh2(OAc)4 catalyst in refluxing Freon TF. Lactone reduction, deketalization and selective acetalization of the derived lactol provided 34 as a mixture of epimers. By use of the method previously described by Paquette, 34 was converted to pentalenolactone E methyl ester (5-Me). Stereoselective epoxidation of the exomethylene double bond of 5-Me provided pentalenolactone F methyl ester (6-Me). The use of .alpha.-diazo .beta.-keto esters for the elaboration of bicyclo[3.3.0]octanones was also explored as an approach to the synthesis of pentalenolactone itself. Thus exposure of 38 to Rh2(OAc)4 in refluxing Freon TF gave a 3:2 mixture of the corresponding bicyclo[3.3.0]octan-3-one 39 and the spirocyclobutanone 40. When 53 was subjected to the identical cyclization conditions, however, only the spirocyclobutanone adduct 54 was formed, without any evidence for the generation of the desired bicyclo[3.3.0]octan-3-one 55.