Concise chemoenzymatic synthesis of gabosine A, ent-epoformin and ent-epiepoformin

Enantioselective Synthesis of a New Non-Natural Gabosine

“…Initially, we used IBX, a reagent routinely employed by our group for these transformations [ 40 ] ( Table 2 , entry 1). However, we were surprised to observe the formation of the diene-dione 14 along with the target product 13 .…”

“…Although toluene is the most suitable aromatic substrate, as it bears the methyl side chain of some gabosines, in 2001, Banwell and co-workers failed in their attempt to use it, and reported the preparation of gabosine A from iodobenzene derived diol 1 [ 39 ], introducing the methyl group in one of the lasts steps, as shown in Figure 2 . In 2011, we were able to prepare the same target from toluene [ 40 ] and in 2017 we reported the synthesis of gabosine H and two non-natural methylgabosines [ 41 ] from the same starting material ( Figure 2 ).…”

Total Synthesis of Gabosine H and Two Non-natural Gabosines

“…A few years back, we reported the chemoenzymatic synthesis of (-)-gabosine A along with the synthesis of ent-epoformin and ent-epiepoformin. 20 The synthetic avenue for the construction of non-natural gabosines (NNGs) was initiated with a procedure previously reported by our lab, that produces 2 as the major product (Scheme 1). 21 Epoxidation of compound 2 with 1,8diazabicyclo [5.4.0]undec-7-ene (DBU) in CH 2 Cl 2 for 24 hours at room temperature generated cis-epoxide 3 in 60% yield.…”

“…In this context, we have developed a novel method for the synthesis of gabosine H (Scheme 5) via cis-diol 10, which was prepared by our research group 26 (in two simple steps form the biotransformation diol 1) and previously used for the synthesis of gabosine A. 20 Oxidation of diol 10 with IBX in a mixture of ethyl acetate and DMF (9:1) proved to be moderately selective, providing mono-oxidized product 9 with 54% yield, along with…”

Crystal structure and absolute configuration of (3aS,4S,5R,7aR)-2,2,7-trimethyl-3a,4,5,7a-tetrahydro-1,3-benzodioxole-4,5-diol

“…1) which is used as a precursor in enantioselective syntheses of epoxycyclohexenone compounds. Model compounds of the central core of ambuic acid (Labora et al, 2008), (+)-and (À)bromoxone (Labora et al, 2010), an epoxyquinol analog (Heguaburu et al, 2010), gabosine A, ent-epoformin and entepiepoformin (Labora et al, 2011) have been prepared starting from the same precursor. The title compound, diol (3) (see Fig.…”