{
  "abstract": "Many natural products isolated from Rubiaceae plants, such as mollugin and rubioncolin B, contain 1-hydroxy-2-methoxycarbonylnaphthohydropyran skeletons. To access this framework, we developed a novel method for the preparation of highly functionalized ortho-naphthoquinone methides (o-NQMs) and subsequent intermolecular [4 + 2]-cycloaddition reactions with olefins. o-NQM precursors were prepared via Hauser-Kraus annulation of cyanophthalides with an α,β-unsaturated ester. Treatment of these precursors with a Lewis acid generated the corresponding o-NQMs, which underwent intermolecular [4 + 2]-cycloaddition with olefins to afford polycyclic compounds bearing the 1-hydroxy-2-methoxycarbonylnaphthohydropyran skeleton. This approach provides efficient access to the frameworks found in natural products and facilitates structural derivatization. The present methodology was further applied to synthetic studies toward rubioncolin B.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 4,
  "authors": [
    {
      "name": "Takaaki Aijima"
    },
    {
      "name": "Jin Tokunaga"
    },
    {
      "name": "Haru Igusa"
    },
    {
      "name": "Yoshinari Sawama"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/9v60qyd1w4q0k.bib",
  "cited_by": 0,
  "doi": "10.1248/cpb.c26-00375",
  "fulltext_url": "https://www.jstage.jst.go.jp/article/cpb/74/9/74_c26-00375/_article",
  "id": "9v60qyd1w4q0k",
  "issns": [
    "1347-5223",
    "0009-2363"
  ],
  "landing_url": "https://www.jstage.jst.go.jp/article/cpb/74/9/74_c26-00375/_article",
  "language": null,
  "licence": "CC-BY-NC",
  "licence_label": "CC BY-NC",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by-nc/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "jstage-journal",
      "chemistry/medicinal"
    ],
    [
      "openalex",
      "1605|Organic Chemistry Synthesis Methods"
    ]
  ],
  "openalex": "W7212307493",
  "pdf_url": "https://www.jstage.jst.go.jp/article/cpb/74/9/74_c26-00375/_pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-12",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/9v60qyd1w4q0k.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:34Z",
      "native_id": "10.1248/cpb.c26-00375",
      "source": "jstage",
      "url": "https://www.jstage.jst.go.jp/article/cpb/74/9/74_c26-00375/_article"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "openalex:1605|Organic Chemistry Synthesis Methods",
      "subfield": "organic"
    }
  ],
  "title": "Preparation of Highly Functionalized ortho-Naphthoquinone Methides and Their Subsequent Intermolecular [4 + 2]-Cycloadditions with Olefins",
  "title_text": "Preparation of Highly Functionalized ortho-Naphthoquinone Methides and Their Subsequent Intermolecular [4 + 2]-Cycloadditions with Olefins",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:17:34Z",
  "url": "https://research.draconitic.com/paper/9v60qyd1w4q0k",
  "venue": "Chemical and Pharmaceutical Bulletin",
  "versions": []
}