A new and unusually flexible route to cyclopentanoids synthesis of sarkomycin and prostaglandins

✍ Scribed by Akihiro Misumi; Kyoji Furuta; Hisashi Yamamoto

• Publisher: Elsevier Science
• Year: 1984
• Tongue: French
• Weight: 220 KB
• Volume: 25
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)99968-4

✦ Synopsis

In the foregoing paper we described an efficient coupling of a-bromomethylacrylate and the doubly charged succinate ion.' Our approach characterized by the successful regiospecific cyclization after the initial alkylation step. In view of the inefficiency of condensation of /3-halopropionate with reagents of succinate dianion, 1 the behavior of certain dianions having unsymmetrical intermediates after the " initial alkylation was studied. Gratifyingly, the dianion r," prepared by reaction of diisopropyl 3-hexenedioate with 2.2 equiv of LDA in THF-HMPA at -78°C for 30 min was found to be satisfactory. Thus, the reaction of ,& with ethyl 3-bromopropionate (0.67 equiv) at -78°C for 1 h and -20°C for 3 h produced cyclopentanone 2 as a mixture of olefinic isomers, id from which the ketal 3 was isolated as a sole product in 52% over-all yield.

3 Of special significance is the regio-and stereoselective shift of the double bond of 2 to the /3, y-position during ketalization. 4 I, Furthermore, the E-double bond in 3 could be cleaved ^_ cleanly to the aldehyde ,4_5 with 'NaI04-OS04 (87%).