Synthesis of (−)-Warburganal and 4α-methoxycarbonyl congener from 1-abietic acid

Synthesis of Mono‐ and Sesquiterpenoids, XV Synthesis of (‐)‐Warburganal, an Insect Antifeedant

“…Although (*)warburganal has repeatedly been synthesi~ed to date6- ',), there are only two partial syntheses of (-)-warburganal from naturally occurring terpenoids 14,15). Ohno and coworkers converted (-)-abietic acid into (-)-warburganal (1) in 7.7% overall yield in 14 steps14), while CortCs et al prepared (-)-1 from (+)-confertifolin in 13% overall yield in 4 steps15).…”

Complementarity of electronic and vibrational circular dichroism based on stereochemical studies of vic-diols

“…In the hydroxylation reaction (Scheme 1, step 2), the osmium-tetroxide approach to the double bond can occur from both α and β sites of the skeleton. According to the literature and depending on the reaction conditions, the process can result in obtaining either of them, or a mixture of both diols (α and β) [29,[55][56][57][58]. There is no conformity regarding the stereochemistry of the diol product resulting from this reaction.…”

“…Our synthesis strategy was slightly different from those described [55][56][57][58][59][60][61]. As shown in Scheme 1, methyl ester of abietic acid, obtained quantitatively in the first step, was next treated with catalytic amounts of osmium tetroxide in the presence of morpholine N-oxide (NMO) as a co-oxidant in a mixture of tert-butanol/water.…”

Synthetic Transformations of Abietic Acid IV [1]. B- and C-Ring Oxidation

“…By Jones oxidation of 3 we obtained two products: 12 (23%) and 13 (44%). 12 has already been synthesized by cleavage of 3 with NaIO 4 [5] and Pb(OAc) 4 [7,14]. 13 has a carbonyl function in conjugation to the double bond in ring B. Michael addition [15] of methyl cyanoacetate introduces a side chain in position 7.…”

“…To induce selective cleavage of ring B or C it is important that only one of the two double bonds of 1 is oxidized by the reagent. It has been shown that osmium tetroxide attacks selectively the double bond of ring C yielding 3 [7]. In this paper we describe reactions which introduce oxygen functions selectively in ring B or C and subsequent transformations which lead to chiral synthons useful for the synthesis of terpene derivatives.…”