From Magic to Medicine: Synthesis of Psilocybin for Therapeutics

Psilocybin is a naturally occurring psychedelic compound, and its clinical relevance, along with that of other psychedelics, has grown significantly in recent years. A renewed wave of interest and research has led to the clinical investigation of multiple psychedelic agents for a variety of health conditions. Notably, Australia and Canada have recently approved the clinical use of select psychedelic therapies under regulated and restricted conditions.1

Psilocybin is currently the most extensively studied psychedelic compound for the treatment of mental health conditions.2 It has likely been consumed by humans for millennia and is well tolerated over a range of doses.3 It also has a reasonable activity time, minimal abuse profile, and clinically acceptable duration of effects.2, 10 Ongoing clinical investigations are evaluating its efficacy across a range of indications, including major depressive disorder (MDD), treatment-resistant depression (TRD), alcohol and other substance use disorders, smoking cessation, and obsessive-compulsive disorder (OCD).2 It has shown such promise that the FDA granted breakthrough therapy designation to psilocybin-based therapies in 2018 for TRD and again in 2019 for MDD.4

Psilocybin has also been explored as an adjunct to individual and group psychotherapy in alleviating psychological distress associated with serious illnesses, such as cancer-related mood and anxiety disorders.2

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A proof-of-concept phase 2 trial recently demonstrated the significant and sustained efficacy of psilocybin, in combination with psychotherapy, for the treatment of alcohol use disorder (AUD).5 In another recent double-blind phase 2 study for TRD, a dose-dependent reduction in depression scores was observed in the weeks following administration of a single psilocybin dose.6 Similarly, a separate trial investigated the effects of two psilocybin-assisted therapy sessions for individuals with MDD. A significant reduction in depression scores was measured at the primary endpoint and at the four-week follow-up, and effects persisted for several months after administration.7 With noticeable effects after just one or two doses, the reduced administration frequency (compared to daily anti-depressants) improves treatment adherence leading to more successful patient outcomes.2

In addition, a growing number of phase 2 trials are currently underway to evaluate psilocybin’s potential across a broad spectrum of other conditions, including post-traumatic stress disorder (PTSD), OCD, bipolar II depression, anorexia nervosa, fibromyalgia, phantom limb pain, migraine, and distress associated with serious medical illnesses.2 It is also being investigated for its neuroplastic ability which has implications for neurodegenerative diseases like Alzheimer’s.8

 

Synthesis of Psilocybin

While psilocybin is naturally occurring in almost all mushrooms of the psilocybe genus (and in some other genera), isolating psilocin and psilocybin from mushrooms on gram scale is difficult. Additionally, the chemical content of the mushrooms can vary based on genetics, growing conditions, soil profile, and age. In clinical trials, both dose and purity must be precisely defined, as regulatory standards and scientific rigor demand strict control. In order to meet these demands, a robust synthesis is required. Recent clinical activities have gained momentum, and research interest in psilocybin is rapidly increasing, with several notable reports on its synthesis. Numerous synthetic methods for psilocybin have been reported to date,9 with the common approach involving the use of a benzyl-protected phosphorylating reagent, followed by deprotection. Kargbo and colleagues at the Usona Institute in Madison, Wisconsin, have worked extensively on the large-scale synthesis of psilocybin. They first developed a multi-gram scale, first-generation synthesis of psilocybin based on published methods.10 However, this initial approach encountered several challenges for scale-up. In response, they developed a second-generation synthesis, which involved the direct phosphorylation of psilocin on a kilogram scale.11

To demonstrate Veranova’s capabilities as a supplier of psychedelics, we performed a successful trial of the improved second-generation synthesis of psilocybin as reported by Kargbo et al.11 As shown in Scheme 1, psilocybin was synthesized in four steps starting from commercially available 4-acetoxyindole 1. Acylation of 4-acetoxyindole 1 in the presence of oxalyl chloride yielded compound 2. Treatment of 2 with dimethylamine provided ketoamide 3 as a solid. LAH reduction of intermediate 3 yielded psilocin 4. The direct phosphorylation of psilocin 4 was accomplished by treatment with POCl3 resulting in crude psilocybin. The crude psilocybin was further purified by re-slurrying in methanol and water, affording crystalline psilocybin in high purity (≥ 99.9%).

Scheme 1. Synthesis of Psilocybin.

Challenges involved in the scale-up of psilocybin synthesis

Kargbo and co-workers’ procedure is highly robust and scalable, but nevertheless presents several practical challenges.

1. The addition of oxalyl chloride to indole 1 is exothermic, so slow addition is required to avoid temperature excursions. The indole acyl chloride 2 is quite unstable and can degrade easily in the presence of moisture, so it was typically used for the next step within one day after isolation. Because compound 2 is designated as Veranova control band 4, appropriate safety measures must be observed when handling the dry solid. All handling must be conducted within an isolator, with personnel wearing a respirator mask, Tyvek sleeves, and appropriate personal protective equipment (PPE).

2. Synthesis of ketoamide 3 involves the addition of dimethylamine to compound 2. This condensation evolves HCl, which can form a solid salt in the reactor headspace, slowing the reaction and preventing thorough mixing. Therefore, subsurface addition of dimethylamine in THF is recommended to avoid any condensation. Moreover, getting good purity of ketoamide 3 is important. The presence of a small amount of oxalyl chloride in compound 2 can lead to formation of downstream impurities.

3. The LAH reduction of ketoamide 3 to psilocin 4 involves the simultaneous reduction of two ketone functionalities and an acetoxy group. This transformation presents significant challenges, particularly on a large scale, due to the requirement of excess lithium aluminum hydride (LAH) under reflux conditions. LAH is pyrophoric in nature and reacts violently with water, generating substantial heat and releasing hydrogen gas. Consequently, quenching the reaction with water at scale poses a notable safety risk. These hazards can be mitigated through appropriate safety measures, including the slow addition of a THF/water (100:27) mixture followed by dilution with DCM/MeOH (9:1) and maintaining efficient cooling of the reaction mixture throughout the quenching process. After the addition of water, giving sufficient time to quench the LAH completely can avoid eruptions.

4. The preparation of psilocybin via direct phosphorylation of psilocin 4 is a moisture sensitive reaction. The presence of moisture can lead to the re-formation of starting material 4, psilocin. Formation of psilocin can be avoided by maintaining inert reaction conditions and efficient cooling. During the addition of POCl3, a sticky precipitate forms that could inhibit efficient stirring on scale. Prolonged agitation of the reaction can lead to the formation of unknown impurities and known impurity pyrophosphate psilocybin. It is critical to stop the reaction within two hours of completing POCl3 addition.

5. Isolation of crude psilocybin from aqueous solution presents a significant challenge due to high solubility of the crude mixture in water. Failure to maintain an optimal water:IPA ratio during the isolation step can result in reduced yields. Furthermore, the subsequent isolation of pure active pharmaceutical ingredient (API) from hot water on scale presents an additional complication, as psilocybin is prone to degradation to its precursor, psilocin, at elevated temperatures.

Conclusion

Realizing the promise and healing potential of psilocybin requires reliable synthesis driven by an effective chemical processing team. Overcoming significant operational challenges, we successfully synthesized multi-gram quantities of psilocybin via direct phosphorylation of psilocin, achieving a 38% yield and high purity (NLT 99.9%, area), in comparison to reported purity of 99.7% in the final step. This high level of purity was achieved at the methanol reslurry stage, with no methanol solvate detected by ¹H NMR. Minor modifications to the final isolation procedure, namely cooling the psilocybin-methanol and psilocybin-water slurries to 5–10 °C prior to filtration, led to a modest increase in yield relative to the literature reported 31% yield. The process chemistry team at Veranova is able to overcome all the above challenges and develop a cost effective, robust, scalable process for the synthesis of psilocybin on a multi-kilogram scale to meet our customers’ needs.

 

References

  1. (a) Department of Neurology, University of California San Francisco, San Francisco, CA, USA. (b) Department of Psychiatry and Behavioral Sciences, University of California San Francisco, San Francisco, CA, USA.
  2. Mitchell J. M.; Anderson B. T. Psychedelic therapies reconsidered: compounds, clinical indications, and cautious optimism. Neuropsychopharmacology 2024, 49, 96. https://doi.org/10.1038/s41386-023-01656-7
  3. Brown, R.T.; Nicholas, C.R.; Cozzi, N.V.; Gassman, M.C.; Cooper, K.M.; Muller, D.; Thomas, C.D.; Hetzel, S.J.; Henriquez, K.M.; Ribaudo, A.S.; Hutson, P.R. Pharmacokinetics of Escalating Doses of Oral Psilocybin in Healthy Adults. Clinical Pharmacokinetics 2017, 56(12), 1543. https://doi.org/10.1007/s40262-017-0540-6
  4. (a) U.S. Food and Drug Administration. (2025, Jan 13). Breakthrough Therapy Designation Approvals: Previous Cumulative CY CDER BT Approvals. FDA. Retrieved June 16, 2025, from https://www.fda.gov/media/95302/download (b) COMPASS Pathways. (2018, October 23). COMPASS Pathways receives FDA Breakthrough Therapy designation for psilocybin therapy for treatment resistant depression [Press release]. PR Newswire. Retrieved June 16, 2025, from https://www.prnewswire.com/news-releases/compass-pathways-receives-fda-breakthrough-therapy-designation-for-psilocybin-therapy-for-treatment-resistant-depression-834088100.html (c) Brooks, M. (2019, November 25). FDA grants psilocybin second breakthrough therapy designation for resistant depression. Medscape Medical News. Retrieved June 16, 2025, from https://www.medscape.com/viewarticle/921789
  5. Bogenschutz, M.P.; Ross, S.; Bhatt, S.; Baron, T.; Forcehimes, A.A.; Laska, E.; Mennenga, S.E.; O’Donnell, K.; Owens, L.T.; Podrebarac, S.; Rotrosen, J.; Tonigan, J.S.; Worth, L. Percentage of Heavy Drinking Days Following Psilocybin-Assisted Psychotherapy vs Placebo in the Treatment of Adult Patients With Alcohol Use Disorder: A Randomized Clinical Trial. JAMA Psychiatry 2022, 79(10), 953. https://doi.org/10.1001/jamapsychiatry.2022.2096
  6. Goodwin, G.M.; Aaronson, S.T.; Alvarez, O.; Arden, P.C.; Baker, A.; Bennet, J.C.; Bird, C.; Blom, R.E.; Brennan, C.; Brusch, D.; Burke, L.; Campbell-Coker, K.; Carhart-Harris, R.; Cattell, J.; Daniel, A.; DeBattista, C.; Dunlop, B.W.; Eisem, K.; Feifel, D.; Forbes, M.; …Malievskaia, E. Single-Dose Psilocybin for a Treatment-Resistant Episode of Major Depression. N Engl J Med 2022, 387, 1637. https://doi.org/10.1056/NEJMoa2206443
  7. Davis, A.K.; Barret, F.S.; May, D.G.; Cosimano, M.P.; Sepeda, N.D.; Johnson, M.W.; Finan, P.H.; Griffiths, R.R. Effects of Psilocybin-Assisted Therapy on Major Depressive Disorder: A Randomized Clinical Trial. JAMA Psychiatry 2021, 78, 481. https://doi.org/10.1001/jamapsychiatry.2020.3285
  8. Zheng, S.; Ma, R.; Yang, Y.; Li, G. Psilocybin for the treatment of Alzheimer’s disease. Front. Neurosci. 2024, 18:1420601. https://doi.org/10.3389/fnins.2024.1420601
  9. (a) Hofmann, A.; Heim, R.; Brack, A.; Kobel, H.; Frey, A.; Ott, H.; Petrzilka, T.; Troxler, F. Helv. Chim. Acta 1959, 42, 1557. (b) Speeter, M. E.; Anthony, W. C. The Action of Oxalyl Indoles: A New Approach to Tryptamines. J. Am. Chem. Soc. 1954, 76, 6208. https://doi.org/10.1021/ja01652a113 (c) Hofmann, A.; Frey, A.; Ott, H.; Petrzilka, T.; Troxler, F. [Elucidation of the structure and synthesis of psilocybin] Experientia 1958, 14, 397. https://doi.org/10.1007/BF02160424 (d) Ono, M.; Shimamine, M.; Takahashi, K. Bull. Nat. Inst. Hygienic Sci. 1973, 91, 39.
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  11. Kargbo, R. B.; Sherwood, A,; Walker, A.; Cozzi,N.V.; Dagger, R. E.; Sable,J.; Kaylo,K.; Patterson, T.; Tarpley, G.; Meisenheimer,P. Direct Phosphorylation of Psilocin Enables Optimized cGMP Kilogram-Scale Manufacture of Psilocybin. ACS Omega 2020, 5, 16959. https://doi.org/10.1021/acsomega.0c02387

About the authors

Cale WeatherlyCale Weatherly is Associate Director of Chemical Development at Veranova’s West Deptford, NJ site. He earned a PhD in Chemistry from the University of Wisconsin-Madison, developing synthetic organic methodologies under Prof. Jennifer M. Schomaker, and conducted postdoctoral research in natural products synthesis at the University of Pennsylvania under Prof. Amos B. Smith, III. Cale joined Veranova as a scientist in 2021, with prior work as a process chemist at Exemplify Biopharma and Abzena.

Headshot of Sanjeev Vernekar

Sanjeev Vernekar is an Associate Principal Scientist in Chemical Development at Veranova’s West Deptford, NJ site. He earned a Ph.D. in Organic Chemistry from the University of Muenster, Germany, where he focused on the synthesis of carba analogue of the natural product N-Acetylneuraminic acid under the guidance of Prof. Hartmut Redlich. Following his doctoral studies, he pursued postdoctoral research in Chemical Biology at the University of Warwick, UK. After moving to the United States, Sanjeev began his career as a Senior Researcher at the Center for Drug Design in Minnesota and subsequently worked as a Process Chemist at Thermo Fisher in South Carolina. He joined Veranova in 2021, bringing with him deep expertise in synthetic route development, process scale-up, and technology transfer.

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