574. Synthetical studies of terpenoids. Part V. A new synthesis of (±)-6β-acetoxy-5,5,9β-trimethyl-trans-2-decalone

Abstract

Narang a d Dutta : 574. Synthetical Studies of Terpenoids. Part V.l A New Synthesis of ( & ) -6 p -Acetox y-5,5,9 ptrimethyltrans -2 -decalone.By SARAN ADHAR NARANG and PHANINDRA CHANDRA DUTTA.A new synthesis of the compound named in the title begins with preparation of the ketone (11) and its condensation with 2-chloroethyl ethyl ketone,

Enantioselective Synthesis of the C1−C11 Fragment of Bafilomycin A1Using Non-Wittig and Desymmetrization Strategies

“…Interestingly, the yield of the reaction was improved from 49% (literature) to 73% from 13 using two modifications: the intermediate acetal was not purified and the Dieckmann reaction was conducted in refluxing tetrahydrofuran instead of diethyl ether. For the subsequent dimethylation reaction, we addressed a one-pot dianion approach which, in our hands, gave better results than the two-step procedure described by Narang and Dutta . The dianion approach required strong basic conditions (1 equiv of NaH, then t -BuLi/HMPA in THF at −78 °C), and the reaction was clean on a 1-g scale.…”

Synthesis of cuauhtemone

“…Ketal olefin 6 (7.64 g, 0.034 mol) was dissolved in 100 ml of 85% aqueous acetic acid and the solution was heated at 100 °C for 1.5 h. Water and acetic acid were removed in vacuo and the product taken up in ether. Washing of the ether with saturated sodium bicarbonate solution followed by drying (NaaSO-i) and solvent removal yielded an oil which was chromatographed on silica gel to afford 6.0 g (95%) of 7: ir (CHCI3) 1705,1655 cm"1; NMR (CDClg) 0.79 (s, 3 H), 1.69 (s, 3 H), 5.37 ppm (m, 1 H). Hydroxylation of 7.…”

“…The primary requirement for activity in vitamin D analogues appears to be the presence of a -hydroxyl, or, as in 5,6-trans-cholecalciferol (4), a hydroxyl in the same position, relative to the transoid diene system, as the -hydroxyl.la•4 Synthetic la-hydroxycholecalciferol ( 5) is now being used in the clinical treatment of nephritic bone disease in humans. 5 With the foregoing facts in mind, we and many others6,7 have been studying synthetic routes to the preparation of hydroxylated (or otherwise modified) vitamin D analogues, particularly compounds 2 and 5. All studies reported to date, with the exception of a total synthesis8 of 5 have involved the synthesis of steroidal precursors convertible into A5,7-steroids, from which the vitamins can be obtained by the usual photochemical-thermal isomerization process.…”

Synthesis of cis-9-Cyano-l,10-dimethyl-6-ethylenedioxy-1-octalin and its Conversion into an Intermediate for a Synthesis of Thelepogine

“…Because of this we undertook a synthesis of 2 as part of some work directed towards the total synthesis of thelepogine (3). We now wish to describe a synthesis of 2 through the intermediacy of 1.…”