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A chemical investigation of the Arctic-derived fungus <i>Eutypella</i> sp. D-1 based on the OSMAC (one strain many compounds) approach resulted in the isolation of five cytosporin polyketides (compounds <b>1</b>–<b>3</b> and <b>11</b>–<b>12</b>) from rice medium and eight cytosporins (compounds <b>2</b> and <b>4</b>–<b>11</b>) from solid defined medium. The structures of the seven new compounds, eutypelleudesmane A (<b>1</b>), cytosporin Y (<b>2</b>), cytosporin Z (<b>3</b>), cytosporin Y₁ (<b>4</b>), cytosporin Y₂ (<b>5</b>), cytosporin Y₃ (<b>6</b>), and cytosporin E₁ (<b>7</b>), were elucidated by analyzing their detailed spectroscopic data. Structurally, cytosporin Y₁ (<b>4</b>) may be a key intermediate in the biosynthesis of the isolated cytosporins, rather than an end product. Compound <b>1</b> contained a unique skeleton formed by the ester linkage of two moieties, cytosporin F (<b>12</b>) and the eudesmane-type sesquiterpene dihydroalanto glycol. Additionally, the occurrence of cyclic carbonate moieties in compounds <b>6</b> and <b>7</b> was found to be rare in nature. The antibacterial, immunosuppressive, and cytotoxic activities of all compounds derived from <i>Eutypella</i> sp. D-1 were evaluated. Unfortunately, only compounds <b>3</b>, <b>6</b>, <b>8</b>, and <b>10</b>–<b>11</b> displayed immunosuppressive activity, with inhibitory rates of 62.9%, 59.5%, 67.8%, 55.8%, and 68.7%, respectively, at a concentration of 5 μg/mL.