Synthesis 2020; 52(22): 3378-3388
DOI: 10.1055/s-0040-1707994
special topic
Synthesis in Industry
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Fused Oxepane HIV Integrase Inhibitor MK-1376

Department of Process Research and Development, Merck & Co., Inc., Kenilworth, NJ 07033, USA   Email:
Zhiguo Jake Song
Neil A. Strotman
Jinquin Yin
Tao Pei
Hallena R. Strotman
Tetsuji Itoh
Edward C. Sherer
Guy R. Humphrey
› Author Affiliations
Further Information

Publication History

Received: 22 January 2020

Accepted after revision: 20 February 2020

Publication Date:
16 March 2020 (online)

Published as part of the Special Topic Synthesis in Industry


Controlling the absolute and relative stereochemistry of a seven-membered oxepane in the formation of HIV integrase inhibitor MK-1376 was accomplished through a strategy involving the use of asymmetric allylation and stereoconvergent, substrate-directed installation of an amine fragment. Surprising reactivity was demonstrated during the asymmetric allylation in which the allyl-pyrimidone product was formed reversibly. The stereoconvergent amine addition was accomplished through an elimination/addition sequence involving a quinone methide reactive intermediate, and nucleophilic trapping of the reactive quinone methide intermediate with methylamine. This novel approach delivered MK-1376, offering 100-fold greater productivity and 50-fold less waste than the initial synthetic chemistry route.

Supporting Information

  • References

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  • 10 Even under these optimized conditions for the π-allyl cyclization, Boc-methylamine species 6 still gave only racemic trans-product.
  • 11 Interestingly, when 1 equiv K2CO3 was added to the asymmetric allylation reaction, the rate increased and the sense of enantioselectivity completely switched from 96% ee (R) to –45% ee (S). This reversal in selectivity could signal a change in mechanism from one involving attack of the pyrimidone on Pd followed by reductive elimination to one involving intermolecular attack of the pyrimidone anion directly on the Pd-bound allyl fragment.
  • 12 No hydrogenation reaction was observed in dichloromethane.
  • 13 During this oxidation screen an interesting unprecedented oxidation was discovered using Tl(NO3)3 in HOAc, which oxidized the oxepane to the olefin (Scheme 11). This olefin could then be converted into the dibromide, which gave the vinyl bromide regioselectively upon base-mediated elimination. Further pursuit of this method was not attempted due to the toxicity of thallium; but, it was encouraging to note traces of the desired C-10 halogenated compound were observed after halogenations in the presence of Tl(NO3)3 using NBS, NCS and t-BuOCl. At this point, evidence from the thallium(III) catalyzed and Pyr2INO3 halogenations indicated an auxiliary oxidant may be beneficial in driving the halogenation to completion.
  • 14 Process mass intensity (PMI) was decreased from >60,000 to 1200.
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