How to convert -OH to terminal -SH group in nucleolipids:
An alcohol can be converted to a corresponding thiol using Lawesson's reagent (LR; 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide). However, the reaction is messy and could give you a mixture of products in addition to intended thiol, including eliminated product, alkene (Ref.1). For example, treatment of acyclic 1,4-diols with LR gives the 1,3-dienes (Ref.1).

However, the substitution versus elimination outcome with LR is depends on the structural features of the substrate (Ref.2), and hence, worth considering. The computational mechanism is depicted below:



Alternatively, you can use highly efficient Mitsunabu type reaction with diisopropyl azodicarboxylate (Ref.3). The abstract summerize the reaction as:


  Various alcohols were converted to their corresponding thiolacetates by treatment with triphenylphosphine and diisopropyl azodicarboxylate in the presence of thiolacetic acid. The overall conversion was both highly efficient (89–99% yields) and stereoselective (99.5% inversion).




References:


T. Nishio, “Direct conversion of alcohols into thiols,” J. Chem. Soc., Perkin Trans. 1 1993, (10), 1113–1117 (DOI: 10.1039/P19930001113).
M. A. Chiacchio,  L. Legnani,  P. Caramella,  T. Tejero,  P. Merino, “Pivotal Neighboring‐Group Participation in Substitution versus Elimination Reactions – Computational Evidence for Ion Pairs in the Thionation of Alcohols with Lawesson's Reagent,” Eur. J. Org. Chem. 2017, (14), 1952–1960 (https://doi.org/10.1002/ejoc.201700127).
R. P. Volante, “A new, highly efficient method for the conversion of alcohols to thiolesters and thiols,” Tetrahedron Letters 1981, 22(33), 3119–3122 (https://doi.org/10.1016/S0040-4039(01)81842-6).