Absolute configurations of the p-menthane-2,5-diones and p-menthane-2,5-diols

Abstract

The eight diastereoisomeric p-menthane-2,5-diols (1-8), the four diastereoisomeric p-menth-l-ene-3,6-diols (9-12), and the two (+ )-p-menthane-2,5-diones (13 and 14), which all have the same absolute configuration at the isopropyl group as (-)-a-phellandrene (15), have been prepared, characterized, and interrelated. Absolute configurations have been established for 1-14 by stereoselective chemical interconversions, including hydrogenation of diols 9-12, Jones oxidation of diols 1-6, lithium aluminum hydride reduction of diones 13 and 14, and displacements by formate and hydride ions on monotosylates of diol 4.

Absolute Configuration of Menthene Derivatives by Vibrational Circular Dichroism

“…The authors assumed the (+)-(3 S ,4 S ,6 R )-3,6-dihydroxy-1 - menthene ( 10 ) structure by comparison of the specific rotation with that of (−)- ent - 10 , which was prepared from (−)-( R )-α-phellandrene . The same reaction sequence was also used to define the configuration of several menthene derivatives. − Nonetheless, in a chemical study of Mikania saltensis , ent - 10 was reported with a dextrorotatory specific rotation of +114 (at unspecified wavelength), contrasting with the results from the study of 10 from Chenopodium multifidum . In more recent papers on the medicinal plants Brickellia rosmarinifolia , Ligularia muliensis , Ligularia sagitta , and Lindera strychnifolia and on the mixture of Amomum tsao-ko, Artemisia scoparia , Chrysanthemum indicum , Eupatorium fortunei , and Houttuynia cordata contained in a Chinese multiherb remedy, the AC of the 3,6-dihydroxy-1-menthene 10 was defined on the basis of the data given in the chemical study of Mikania saltensis …”

“…In the COSY spectrum of 1, H-3 (δ H 4. 19) displayed correlations with H-2 (δ H 5.69) and H-4 (δ H 1.84), while H-5 (δ H 3.55) showed a correlation with H-6 (δ H 3.81) (Figure S2, Supporting Information). The HSQC spectrum allowed the unambiguous assignment of all the protonated carbons as listed in Table 1.…”

Sustainable catalytic rearrangement of terpene-derived epoxides: towards bio-based biscarbonyl monomers

“…In the literature, biscarbonyl 14 has already been reported in 1964 and 1971, but was not synthesized from renewable resources or in a sustainable fashion. The authors used a pathway starting from 2,5-dimethoxy-p-cymene applying lithium and ammonia in ethanol [44] or the oxidation of the corresponding diols via Jones oxidation applying highly toxic and carcinogenic chromium trioxide [45]. To the best of our knowledge, this is the first reported synthesis via a double rearrangement starting from bio-based γ-terpinene dioxide.…”