Erschienen in:
Helvetica Chimica Acta, 63 (1980) 7, Seite 1960-1970
Sprache:
Englisch
DOI:
10.1002/hlca.19800630724
ISSN:
0018-019X;
1522-2675
Entstehung:
Anmerkungen:
Beschreibung:
Synthesis of Optically Active 2‐Methyl‐ and 2‐Ethyl‐1, 6‐dioxaspiro [4.4]nonane‐ and ‐[4.5]decane Pheromones from a Common Chiral PrecursorThe versatility of the bromoepoxide6as chiral building block, which is readily available in both enantiomeric forms from malic acid, and which has previously been used for a vermiculine synthesis, is further demonstrated by the preparation of the title compounds1, 3, 4and5. Alkylation of 1,3‐dithiane, first with the 1‐ethoxyethyl‐protected ω‐chloroalcohols8bor9band then with the (S)‐(−)‐bromoepoxide6, followed by oxirane opening withSelectrideor methylGilman‐reagent creates the desired carbon skeletons and functionality patterns14–17, in overall yields of 60–80%. Acetal and thioacetal hydrolyses directly furnish the spiroacetal target structures1and3–5as 3:2‐diastereomeric mixtures; theE/Z‐epimers3are separated by preparative GC.(Fig.).