Studies toward the synthesis of sesquiterpenes bakkanes

Author(s)

Tiago de Oliveira Vieira

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2005-09-30

Examining board members

Helena Maria Carvalho Ferraz; Ursula Brocksom; Silvio do Desterro Cunha; Jose Ricardo Romero; Hans Viertler

• Advisor: Helena Maria Carvalho Ferraz

Abstract

In this thesis, we have developed studies towards the synthesis of sesquiterpenes bakkanes, which key step consisted on the construction of the cis-hydrindanic system through a thallium(III) mediated ring contraction reaction of cis-decalins and 2-octalones. Only the cis-octalins, such as the 1,2,3,4,4a,5,8,8a-octahydro-4a-methylnaphthalene and the 1,2,3,4,4a,5,8,8a-octahydro-4a,7-dimethylnaphthalene, were able to be ring contracted in satisfactory yields; the 4,4a,5,6,7,8-hexahydro-4a,5-dimethylnaphthalen-2(3H)-one, however, furnished the ring contraction product in low yield. We tried to use the reaction of 1,2,3,4,4a,5,8,8a-octahydro-4amethylnaphthalene with TTN in the synthesis of nor-bakkenolide-A, but we could not accomplish the synthesis because it was not possible to make the last step of the sequence, in all tested approaches. Great efforts were made in the diastereoselective preparation of the 4,4a,5,6, 7 ,8-hexahydro-4a,5-dimethylnaphthalen-2(3H)-one, through three different approaches that were investigated, being two of them with profit. However, the low yield (38%) of the ring contraction reaction of 4,4a,5,6, 7,8-hexahydro-4a,5-dimethylnaphthalen-2(3H)-one, precluded the continuation of the synthetic rout proposed to the bakkenolide-A. We have also performed the kinetic resolution of three different cis-octalols that were prepared through Diels-Alder reaction followed by diastereoselective reduction - with the Novozym 435 lipase, and the resolved products were isolated in excellent yields (≥ 40% for each enantiomer) and excellent ee\'s (≥ 98%). (AU)